Anthra[2,3-b]benzo[d]thiophene Derivatives and their Use as Organic
Semiconductors
Field of the Invention
The invention relates to novel anthra[2,3-b]benzo[d]thiophene derivatives,
methods of their preparation, their use as semiconductors in organic
electronic (OE) devices, and to OE devices comprising these derivatives.
Background and Prior Art
In recent years, there has been development of organic semiconducting
(OSC) materials in order to produce more versatile, lower cost electronic
devices. Such materials find application in a wide range of devices or
apparatus, including organic field effect transistors (OFETs), organic light
emitting diodes (OLEDs), photodetectors, organic photovoltaic (OPV)
cells, sensors, memory elements and logic circuits to name just a few. The
organic semiconducting materials are typically present in the electronic
device in the form of a thin layer, for example less than 1 micron thick.
The performance of OFET devices is principally based upon the charge
carrier mobility of the semiconducting material and the current on/off ratio,
so the idea! semiconductor should have a low conductivity in the off state,
combined with a high charge carrier mobility (> 1 x 10"3 cm2 V1 s"1). In
addition, it is important that the semiconducting material is relatively stable
to oxidation i.e. it has a high ionisation potential, as oxidation leads to
reduced device performance. Further requirements for the semiconducting
material are a good processability, especially for large-scale production of
thin layers and desired patterns, and high stability, film uniformity and
integrity of the organic semiconductor layer.
In prior art various materials have been proposed for use as OSCs in
OFETs, including small molecules like for example pentacene, and
polymers like for example polyhexylthiophene.
A promising class of conjugated small molecule semiconductors has been
based upon the pentacene unit.[1j When deposited as a thin film by
vacuum deposition, it was shown to have carrier mobilities in excess of 1
cm2 V"1 s"1 with very high current on/off ratios greater than 106.[2]
However, vacuum deposition is an expensive processing technique that is
unsuitable for the fabrication of large-area films. Initial device fabrication
was improved by adding solubilising groups, such as trialkylsilylethynyl,
allowing mobilities >0.1 cm2 V1 s"1 [3]. It has also been reported that
adding further substituents to the pentacene core unit can improve its
semiconducting performance in field-effect transistor (FET) devices.[1]
However, the OSC materials of prior art, and devices comprising them,
which have been investigated so far, do still have several drawbacks, and
their properties, especially the solubility, processibility, charge-carrier
mobility, on/off ratio and stability still leave room for further improvement.
Therefore, there is still a need for OSC materials that show good
electronic properties, especially high charge carrier mobility, and good
processibilty, especially a high solubility in organic solvents. Moreover, for
use in OFETs there is a need for OSC materials that allow improved
charge injection into the semiconducting layer from the source-drain
electrodes. For use in OPV cells, there is a need for OSC materials having
a low bandgap, which enable improved light harvesting by the photoactive
layer and can lead to higher cell efficiencies.
It was an aim of the present invention to provide compounds for use as
organic semiconducting materials that do not have the drawbacks of prior
art materials as described above, and do especially show good
processibility, good solubility in organic solvents and high charge carrier
mobility. Another aim of the invention was to extend the pool of organic
semiconducitng materials available to the expert. Other aims of the
present invention are immediately evident to the expert from the following
detailed description.
It was found that these aims can be achieved by providing compounds as
claimed in the present invention. In particular, the inventors of this
invention have found that compounds derived from anthra[2,3-
b]benzo[d]thiophene,
which is disubstituted by ethynyl groups in 7- and 12-position, are suitable
as semiconductors, exhibit very good solubility in most organic solvents,
and show high performance when used as semiconducting layer in
electronic devices like OFETs. It was found that OFET devices comprising
such compounds as semiconductors show good mobility and on/off ratio
values and can easily be prepared using solution deposition fabrication
methods and printing techniques.
The asymmetrical anthra[2,3-6]benzo[d]thiophene unit has been
previously prepared [4,5] and it was shown to have mobilities as high as
0.41 cm W1.[4] The high mobility was achieved by preparation of the
device at room temperature allowing the possible use of plastic flexible
substrates. Furthermore, according to single-crystal X-ray diffraction
studies, the anthra[2,3-6]benzo[d]thiophene unit exhibits a herringbone
arrangement [4], which is similar to that of pentacene[6].
However, the herringbone arrangement reported for the anthra[2,3-
ib]benzo[d]thiophene unit is not optimal for charge transport in FET
devices. Another disadvantage of anthra[2,3-b]benzo[d]thiophene as
reported in prior art is that the material is only moderately soluble in
common organic solvents, which means that the compound is not ideal for
solution processing by mass-production printing techniques such as ink-
jet, gravure and flexo printing.
However, prior art does neither disclose nor suggest how anthra[2,3-b]
benzo[d]thiophene could be modified to improve its properties in the way
described above. In particular, prior art does not provide any hint that this
could be solved by adding subtituents to the anthra[2,3-
b]benzo[d]thiophene core, or to the type or exact position of possible
substituents.
Summary of the Invention
The invention relates to compounds of formula I
wherein
R1 and R2 are independently of each other halogen, -CN, -NC, -
NCO, -NCS, -OCN, -SCN, -C(=O)NR0R00, -C(=O)X0, -
C(=O)R0, -NH2, -NR°R0G, -SH, -SR°, -S03H, -S02R°, -OH,
-N02, -CF3, -SF5, optionally substituted silyl or germanyl
groups, or optionally substituted carbyl or hydrocarbyl
groups that optionally comprise one or more hetero
atoms,
R3"6 are independently of each other H, halogen, -CN, -NC, -
NCO, -NCS, -OCN, -SCN, -C(=O)NR0R00, -C(=0)X°, -
C(=O)R0, -NH2, -NR0R°°, -SH, -SR°, -SO3H, -S02R°, -OH,
-N02, -CF3, -SF5, optionally substituted silyl groups, or
optionally substituted carbyl or hydrocarbyl groups that
optionally comprise one or more hetero atoms,
neighboured pairs of groups R3 and R4 or R5 and R6 may
also form a ring system with each other or with the
benzene ring to which they are attached,
X° is halogen,
R° and R00 are independently of each other H or an optionally
substituted aliphatic or aromatic hydrocarbyl group having
1 to 20 C atoms,
and wherein the benzene rings may also be substituted by
one or more additional groups R6.
The invention further relates to a formulation comprising one or more
compounds of formula I and one or more solvents, preferably selected
from organic solvents.
The invention further relates to an organic semiconducting formulation
comprising one or more compounds of formula I, one or more organic
binders, or precursors thereof, preferably having a permittivity e at 1,000
Hz of 3.3 or less, and optionally one or more solvents.
The invention further relates to the use of compounds and formulations
according to the present invention as charge transport, semiconducting,
electrically conducting, photoconducting or light emitting material in an
optical electrooptical, electronic, electroluminescent or photoluminescent
components or devices.
The invention further relates to the use of compounds and formulations
according to the present invention as charge transport, semiconducting,
electrically conducting, photoconducting or light emitting material in
optical, electrooptical, electronic, electroluminescent or photoluminescent
components or devices.
The invention further relates to a charge transport, semiconducting,
electrically conducting, photoconducting or light emitting material or
component comprising one or more compounds or formulations according
to the present invention.
The invention further relates to an optical, electrooptical or electronic
component or device comprising one or more compounds, formulations,
components or materials according to the present invention.
The optical, electrooptical, electronic electroluminescent and
photoluminescent components or devices include, without limitation,
organic field effect transistors (OFET), thin film transistors (TFT),
integrated circuits (IC), logic circuits, capacitors, radio frequency
identification (RFID) tags, devices or components, organic light emitting
diodes (OLED), organic light emitting transistors (OLET), flat panel
displays, backlights of displays, organic photovoltaic devices (OPV), solar
cells, laser diodes, photoconductors, photodetectors, electrophotographic
devices, electrophotographic recording devices, organic memory devices,
sensor devices, charge injection layers, charge transport layers or
interlayers in polymer light emitting diodes (PLEDs), organic plasmon-
emitting diodes (OPEDs), Schottky diodes, planarising layers, antistatic
films, polymer electrolyte membranes (PEM), conducting substrates,
conducting patterns, electrode materials in batteries, alignment layers,
biosensors, biochips, security markings, security devices, and
components or devices for detecting and discriminating DNA sequences.
Brief Description of the Drawings
Figure 1 and Figure 2 show the UV vis spectrum and the DSC curve,
respectively, of the compound prepared according to example 1.
Detailed Description of the Invention
The anthra[2,3-b]benzo[d]thiophenes of the present invention are easy to
synthesize and exhibit several advantageous properties, like a low
bandgap, a high charge carrier mobility, a high solubility in organic
solvents, a good processability for the device manufacture process, a high
oxidative stability and a long lifetime in electronic devices. In addition, they
show the following advantageous properties:
i) The addition of two ethynyl groups, preferably trialkylsilylethynyl groups,
in 7- and 12 position of the anthra[2,3-b]benzo[d]thiophene core helps
solubilising the molecular material in common organic solvents allowing
the material to be easily solution processed. The addition of the
(trialkylsilyl) ethynyl substituents also promotes the material to exhibit n-
stacking order and thus to form highly organized crystalline films after
deposition from solution.
ii) The size of the (trialkylsilyl) ethynyl groups strongly influences the n-
stacking interactions in the solid state. For small substituent groups, where
the diameter of the trialkylsilyl group is significantly smaller than half the
length of the acene core, a one-dimensionalrc-stack or "slipped stack"
arrangement is formed. However, when the size of the trialkylsilyl group is
approximately the same as half the length of the acene core, a two-
dimensional 7t-stack or "bricklayer" arrangement is favoured, which has
been found to be the optimal for charge transport in FET devices.
Therefore, by adding two trialkylsilyl groups of the correct size and in the
correct position to the anthra[2,3-b]benzo[(/]thiophene unit, the packing
arrangement in the solid state is affected and a preferential 71-stacking can
be obtained with a suitably sized trialkylsilyl group.
iii) The HOMO energy level of trialkylsilylethynyl substituted anthra[2,3-
jb]benzo[dJthiophene is lower than that of anthra[2,3-£>]benzo[cQthiophene
due to the electron-withdrawing nature of the trialkylsilylethynyl groups.
This enhances the oxidative stability of the material, which is particularly
important for when it is applied as a semiconducting layer in an FET
device. For reference, the HOMO energy level of the anthra[2,3-
b]benzo[c/]thiophene core is already measured as being 0.75 eV lower
than that of pentacene.[4]
Especially preferred are compounds of formula I wherein one or more of
R3"6 denote aryl or heteroaryl optionally substituted by L, or straight chain,
branched or cyclic alkyl with 1 to 20 C-atoms, which is unsubstituted or
mono- or polysubstituted by F, CI, Br or I, and wherein one or more non-
adjacent CH2 groups are optionally replaced, in each case independently
from one another, by -0-, -S-, -NR0-, -SiT^R00-, -CY1=CY2- or -feC- in
such a manner that O and/or S atoms are not linked directly to one
another, or denotes optionally substituted aryl or heteroaryl preferably
having 1 to 30 C-atoms, with
R and R being independently of each other H or alkyl with 1 to 12 C-
atoms,
Y1 and Y2 being independently of each other H, F, CI or CN, and
L being selected from F, CI, Br, I, -CN, -N02 , -NCO, -NCS, -
OCN, -SCN, -C(=O)NR0R00, -C(=O)X0, -C(=O)R0, -NR°R00,
optionally substituted silyl, or aryl or heteroaryl with 4 to 40,
preferably 6 to 20 ring atoms, and straight chain or branched
alkyl, alkoxy, oxaalkyl, thioalkyl, alkenyl, alkynyl,
alkylcarbonyl, alkoxycarbonyl, alkylcarbonlyoxy or
alkoxycarbonyloxy with 1 to 20, preferably 1 to 12 C atoms,
wherein one or more H atoms are optionally replaced by F or
CI, wherein R°, R00 and X° are as defined above.
Further preferred are compounds of formula I wherein one or more groups
R3"6 are selected of formula -(A-B)a, wherein, in case of multiple
occurrence independently of one another, A is selected from -
CY1=CY2- or -C=C- and B is selected from aryl or heteroaryl optionally
substituted by L as defined above, with Y1 and Y2 being as defined above,
and a being 1, 2 or 3.
Further preferred are compounds of formula I wherein one or more groups
R3"6 denote Ci-C20-alkyl that is optionally substituted with one or more
fluorine atoms, Ci-C2o-alkenyl, Ci-C2o-alkynyl, Ci-C2o-alkoxy or-oxaalkyl,
CrC2o-thioalkyl, CrC2o-silyl, Ci-C20-amino or CrC2(rfluoroalkyl, in particular
from alkenyl, alkynyl, alkoxy, thioalkyl or fluoroalkyl, all of which are straight-
chain and have 1 to 12, preferably 5 to 12 C-atoms, most preferably pentyl,
hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl.
If two or more of the substituents R36form a ring system with each other
and/or with the benzene ring to which they are attached, this is preferably
a 5-, 6- or 7-membered aromatic or heteroaromatic ring, preferably
selected from pyrrole, pyridine, pyrimidine, thiophene, selenophene,
thiazole, thiadiazole, oxazole and oxadiazole, especially preferably
thiophene or pyridine, all of which are optionally substituted by L as
defined above.
Especially preferred are compounds of formula I, wherein one or both
groups R1 and R2 denote a silyl group, or an optionally substituted aryl or
heteroaryl group, preferably optionally substituted by L as defined above.
The silyl group is optionally substituted and is preferably selected of the
formula -AR'R"R"\ wherein A is Si or Ge, preferably Si, and R\ R" and R'"
are identical or different groups selected from H, a Ci-C40-alkyl group,
preferably CrC4-alkyl, most preferably methyl, ethyl, n-propyl or isopropyl,
a C2-C40-alkenyl group, preferably C2-C7-alkenyl, a C6-C4o-aryl group,
preferably phenyl, a C6-C40-arylalkyl group, a C-i-C40-alkoxy or -oxaalkyl
group, or a C6-C40-arylalkyloxy group, wherein all these groups are
optionally substituted with one or more groups L as defined above.
Preferably, R', R" and R'" are each independently selected from optionally
substituted Ci.io-alkyl, more preferably CWalkyl, most preferably Ci.3-alkyl,
for example isopropyl, and optionally substituted Ce-io-aryl, preferably
phenyl. Further preferred is a silyl group wherein one or more of R\ R" and
R"' form a cyclic silyl alkyl group together with the Si or Ge atom, preferably
having 1 to 8 C atoms.
In a preferred embodiment, R', R" and R'" are identical groups, for
example identical, optionally substituted, alkyl groups, as in
triisopropylsilyl. Very preferably the groups R", R" and R"' are identical,
optionally substituted CM0, more preferably C-m, most preferably C^3 alkyl
groups. A preferred alkyl group in this case is isopropyl.
A group of formula -AR'R"R"' or -AR'R"" as described above is a preferred
optional substituent for the C-|-C4o-carbyl or hydrocarbyl group.
Preferred groups -SiR'R"Rm include, without limitation, trimethylsilyl,
triethylsilyl, tripropylsilyl, dimethylethylsilyl, diethylmethylsilyl,
dimethylpropylsilyl, dimethylisopropylsilyl, dipropylmethylsilyl,
diisopropylmethylsilyl, dipropylethylsilyl, diisopropylethylsilyl,
diethylisopropylsilyl, triisopropylsilyl, trimethoxysilyl, triethoxysilyl,
trimethoxyrnethylsilyl, trivinylsilyl, triphenylsilyl, diphenylisopropylsilyl,
diisopropylphenylsilyl, diphenylethylsilyl, diethylphenylsilyl,
diphenylmethylsilyl, triphenoxysilyl, dimethylmethoxysilyl,
dimethylphenoxysilyl, methylmethoxyphenylsilyl, etc., wherein the alkyl,
aryl or alkoxy group is optionally substituted.
Especially preferred are the compounds of the following subformulae:
wherein R3"11, R'( R" and R'" are as defined above, and Y3, Y4 and Y5 are
independently of each other selected from CH, (CH)2, S, O, N and Se,
such that S and/or O atoms are not directly linked to each other.
Especially preferred are compounds of formula I, !1 and 12 wherein
R3'6 denote H, F or alkyl or fluoroalkyi having from 1 to 12 C.atoms, and/or
Y3-Y5-Y4 denotes CH-S-CH, CH-Se-CH, CH-O-CH, N-S-N, CH-IM=CH or
CH=N-CH, and/or R', R" and R'" denote Cwo alkyl.
The term "carbyl group" as used above and below denotes any
monovalent or multivalent organic radical moiety which comprises at least
one carbon atom either without any non-carbon atoms (like for example
-OsC-), or optionally combined with at least one non-carbon atom such as
N, O, S, P, Si, Se, As, Te or Ge (for example carbonyl etc.). The term
"hydrocarbyl group" denotes a carbyl group that does additionally contain
one or more H atoms and optionally contains one or more hetero atoms
like for example N, O, S, P, Si, Se, As, Te or Ge.
A carbyl or hydrocarbyl group comprising a chain of 3 or more C atoms
may also be straight-chain, branched and/or cyclic, including spiro and/or
fused rings.
Preferred carbyl and hydrocarbyl groups include alkyl, alkoxy,
alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy,
each of which is optionally substituted and has 1 to 40, preferably 1 to 25,
very preferably 1 to 18 C atoms, furthermore optionally substituted aryl or
aryloxy having 6 to 40, preferably 6 to 25 C atoms, furthermore
alkylaryloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and
aryloxycarbonyloxy, each of which is optionally substituted and has 6 to
40, preferably 7 to 40 C atoms, wherein all these groups do optionally
contain one or more hetero atoms, preferably selected from N, O, S, P, Si,
Se, As, Te and Ge.
The carbyl or hydrocarbyl group may be a saturated or unsaturated acyclic
group, or a saturated or unsaturated cyclic group. Unsaturated acyclic or
cyclic groups are preferred, especially aryl, alkenyl and alkynyl groups
(especially ethynyl). Where the CrC4o carbyl or hydrocarbyl group is
acyclic, the group may be straight-chain or branched. The C1-C40 carbyl
or hydrocarbyl group includes for example: a C1-C40 alkyl group, a C1-C40
alkoxy or oxaalkyl group, a C2-C40 alkenyl group, a C2-C40 alkynyl group, a
C3-C40 allyl group, a C4-C40 alkyldienyl group, a C4-C40 polyenyl group, a
Cs-Ci8 aryl group, a C6-C4o alkylaryl group, a C6-C40 arylalkyl group, a C4-
C40 cycloalkyl group, a C4-C40 cycloalkenyl group, and the like. Preferred
among the foregoing groups are a C1-C20 alkyl group, a C2-C20 alkenyl
group, a C2 -C2o alkynyl group, a C3-C20 allyl group, a C4-C2o alkyldienyl
group, a C6-Ci2 aryl group and a C4-C20 polyenyl group, respectively. Also
included are combinations of groups having carbon atoms and groups
having hetero atoms, like e.g. an alkynyl group, preferably ethynyl, that is
substituted with a silyl group, preferably a trialkylsilyl group.
Aryl and heteroaryl preferably denote a mono-, bi- or tricyclic aromatic or
heteroaromatic group with up to 25 C atoms that may also comprise
condensed rings and is optionally substituted with one or more groups L
as defined above.
Very preferred substituents L are selected from halogen, most preferably
F, or alkyl, alkoxy, oxaalkyl, thioalkyl, fluoroalkyl and fluoroalkoxy with 1 to
12C atoms or alkenyl, alkynyl with 2 to 12 C atoms.
Especially preferred aryl and heteroaryl groups are phenyl in which, in
addition, one or more CH groups may be replaced by N, naphthalene,
thiophene, selenophene, thienothiophene, dithienothiophene, fluorene
and oxazole, all of which can be unsubstituted, mono- or polysubstituted
with L as defined above. Very preferred rings are selected from pyrrole,
preferably N-pyrrole, pyridine, preferably 2- or 3-pyridine, pyrimidine,
thiophene preferably 2-thiophene, selenophene, preferably 2-
selenophene, thieno[3,2-b]thiophene, thiazole, thiadiazole, oxazole and
oxadiazole, especially preferably thiophene-2-yl, 5-substituted thiophene-
2-yl or pyridine-3-yl, all of which can be unsubstituted, mono- or
polysubstituted with L as defined above.
An alkyl or alkoxy radical, i.e. where the terminal CH2 group is replaced by
-0-, can be straight-chain or branched. It is preferably straight-chain, has
2, 3, 4, 5, 6, 7 or 8 carbon atoms and accordingly is preferably ethyl,
propyl, butyl, pentyl, hexyl, heptyl, octyl, ethoxy, propoxy, butoxy, pentoxy,
hexoxy, heptoxy, or octoxy, furthermore methyl, nonyl, decyl, undecyl,
dodecyl, tridecyl, tetradecyl, pentadecyl, nonoxy, decoxy, undecoxy,
dodecoxy, tridecoxy or tetradecoxy, for example.
An alkenyl group, wherein one or more CH2 groups are replaced by -
CH=CH- can be straight-chain or branched. It is preferably straight-chain,
has 2 to 10 C atoms and accordingly is preferably vinyl, prop-1-, or prop-
2-enyl, but-1-, 2- or but-3-enyl, pent-1-, 2-, 3- or pent-4-enyl, hex-1-, 2-, 3-,
4- or hex-5-enyl, hept-1-, 2-, 3-, 4-, 5- or hept-6-enyl, oct-1-, 2-, 3-, 4-, 5-,
6- or oct-7-enyl, non-1-, 2-, 3-, 4-, 5-, 6-, 7- or non-8-enyl, dec-1-, 2-, 3-, 4-
, 5-, 6-, 7-, 8- or dec-9-enyl.
Especially preferred alkenyl groups are C2-C7-1E-alkenyl, C4-C7-3E-
alkenyl, C5-C7-4-alkenyl, C6-C7-5-alkenyl and C7-6-alkenyl, in particular
C2-C7-1E-alkenyl, C4-C7-3E-alkenyl and C5-C7-4-alkenyl. Examples for
particularly preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl,
1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl,
3E-hexenyl, 3E-heptenyl, 4-pentenyI, 4Z-hexenyl, 4E-hexenyl,
4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groups having up to 5 C
atoms are generally preferred.
An oxaalkyl group, i.e. where one CH2 group is replaced by -O-, is
preferably straight-chain 2-oxapropyl (=methoxymethyl), 2-
(=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl), 2-, 3-, or 4-oxapentyl, 2-,
3-, 4-, or 5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-
oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-,7-, 8- or 9-
oxadecyl, for exam pie. Oxaalkyl, i.e. where one CH2 group is replaced by -
0-, is preferably straight-chain 2-oxapropyl (=methoxymethyl), 2-
(=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl), 2-, 3-, or 4-oxapentyl, 2-,
3-, 4-, or 5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-
oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-,7-, 8- or 9-
oxadecyl, for example.
In an alkyl group wherein one CH2 group is replaced by -O- and one by -
CO-, these radicals are preferably neighboured. Accordingly these
radicals together form a carbonyloxy group -CO-O- or an oxycarbonyl
group -O-CO-. Preferably this group is straight-chain and has 2 to 6 C
atoms. It is accordingly preferably acetyloxy, propionyloxy, butyryloxy,
pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl,
butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxy-
ethyl, 2-butyryloxyethyl, 3-acetyloxypropyI, 3-propionyloxypropyl,
4-acetyloxybutyI, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl,
butoxycarbonyl, pentoxycarbony!, methoxycarbonylmethyl, ethoxy-
carbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl,
2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(propoxy-
carbonyl)ethyl, 3-(methoxycarbonyl)propyl, 3-(ethoxycarbonyl)propyl,
4-(methoxycarbonyi)-butyl.
An alkyl group wherein two or more CH2 groups are replaced by -O-
and/or -COO- can be straight-chain or branched. It is preferably straight-
chain and has 3 to 12 C atoms. Accordingly it is preferably bis-carboxy-
methyl, 2,2-bis-carboxy-ethyl, 3,3-bis-carboxy-propyl, 4,4-bis-carboxy-
butyl, 5,5-bis-carboxy-pentyl, 6,6-bis-carboxy-hexyl, 7,7-bis-carboxy-
heptyl, 8,8-bis-carboxy-octyl, 9,9-bis-carboxy-nonyl, 10,10-bis-carboxy-
decyl, bis-(methoxycarbonyl)-methyl, 2,2-bis-(methoxycarbonyl)-ethyl,
3,3-bis-(methoxycarbonyl)-propyl, 4,4-bis-(methoxycarbonyl)-butyl, 5,5-bis-
(methoxycarbonyl)-pentyl, 6,6-bis-(methoxycarbonyl)-hexyl, 7,7-bis-
(methoxycarbonyl)-heptyl, 8,8-bis-(methoxycarbonyl)-octyl, bis-
(ethoxycarbonyl)-methyl, 2,2-bis-(ethoxycarbonyl)-ethyl, 3,3-bis-
(ethoxycarbonyl)-propyl, 4,4-bis-(ethoxycarbonyl)-butyl, 5,5-bis-
(ethoxycarbonyl )-hexyl.
A thioalkyl group, i.e where one CH2 group is replaced by -S-, is
preferably straight-chain thiomethyl (-SCH3), 1-thioethyl (-SCH2CH3), 1-
thiopropyl (= -SCH2CH2CH3), 1-(thiobutyl). 1-(thiopentyl), l-(thiohexyl), 1-
(thioheptyl), l-(thiooctyl), l-(thiononyl), l-(thiodecyl), l-(thioundecyl) or 1-
(thiododecyl), wherein preferably the CH2 group adjacent to the sp2
hybridised vinyl carbon atom is replaced.
Afiuoroalkyl group is preferably straight-chain perfluoroalkyl CiF2i+1,
wherein i is an integer from 1 to 15, in particular CF3, C2F5, C3F7, C4F9,
C5Fn, C6F13, C7F15 or C8Fi7, very preferably C6F13.
R1"6 and R', R", R"' can be an achiral or a chiral group. Particularly preferred
chiral groups are 2-butyl (=1-methylpropyl), 2-methylbutyl, 2-methylpentyl,
3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, in particular 2-methylbutyl, 2-
methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1 -
methylhexoxy, 2-octyloxy, 2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl, 4-
methylhexyl, 2-hexyl, 2-octyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methoxyoctoxy,
6-methyloctoxy, 6-methyloctanoyloxy, 5-methylheptyloxycarbonyl, 2-
methylbutyryloxy, 3-methylvaleroyloxy, 4-methylhexanoyloxy, 2-
chlorpropionyloxy, 2-chloro-3-methylbutyryloxy, 2-chloro-4-methylvaleryloxy,
2-chloro-3-methylvaleryloxy, 2-methyl-3-oxapentyl, 2-methyl-3-oxahexyl, 1-
methoxypropyl-2-oxy, 1-ethoxypropyl-2-oxy, 1 -propoxypropyl-2-oxy, 1-
butoxypropyl-2-oxy, 2-fluorooctyloxy, 2-fluorodecyloxy, 1,1,1-trifluoro-2-
octyloxy, 1,1,1-trifluoro-2-octyl, 2-fluoromethyloctyloxy for example. Very
preferred are 2-hexyl, 2-octyl, 2-octyloxy, 1,1,1-trifluoro-2-hexyl, 1,1,1-
trifluoro-2-octyl and 1,1,1-trifluoro-2-octyloxy.
Preferred achiral branched groups are isopropyl, isobutyl (=methylpropyl),
isopentyl (=3-methylbutyl), tert. butyl, isopropoxy, 2-methyl-propoxy and 3-
methylbutoxy.
-CY^CY2- is preferably -CH=CH-, -CF=CF- or -CH=C(CN)-.
Halogen is F, CI, Br or I, preferably F, CI or Br.
The compounds of formula I may also be substituted with a polymerisable
or reactive group, which is optionally protected during the process of
forming the polymer. Particular preferred compounds of this type are
those of formula I wherein one or more of R36 or L denotes P-Sp, wherein
P is a polymerisable or reactive group and Sp is a spacer group or a
single bond. These compounds are particularly useful as semiconductors
or charge transport materials, as they can be crosslinked via the groups P,
for example by polymerisation in situ, during or after processing the
polymer into a thin film for a semiconductor component, to yield
crosslinked polymer films with high charge carrier mobility and high
thermal, mechanical and chemical stability.
Preferably the polymerisable or reactive group P is selected from
, CH2=CW2-(0)kr, CH3-CH=CH-0-, (CH2=CH)2CH-
OCO-, (CH2=CH-CH2)2CH-OCO-, (CH2=CH)2CH-0-, (CH2=CH-CH2)2N-,
(CH2=CH-CH2)2N-CO-, HO-CW2W3-, HS-CW2W3-, HW2N-, HO-CW2W3-
NH-, CH2=CW1-CO-NH-, CH2=CH-(COO)k1-Phe-(0)k2-, CH2=CH-(CO)kr
PhQ-{0\2-, Phe-CH=CH-( HOOC-, OCN-, and W4W5W6Si-, with W1 being
H, F, CI, CN, CF3, phenyl or alkyl with 1 to 5 C-atpms, in particular H, CI or
CH3, W2 and W3 being independently of each other H or alkyl with 1 to 5
C-atoms, in particular H, methyl, ethyl or n-propyl, W4, W5and W6 being
independently of each other CI, oxaalkyl or oxacarbonylalkyl with 1 to 5 C-
atoms, W7 and W8 being independently of each other H, CI or alkyl with 1
to 5 C-atoms, Phe being 1,4-phenylene that is optionally substituted by
one or more groups L as defined above, and k, and k2 being
independently of each other 0 or 1.
Alternatively P is a protected derivative of these groups which is non-
reactive under the conditions described for the process according to the
present invention. Suitable protective groups are known to the ordinary
expert and described in the literature, for example in Green, "Protective
Groups in Organic Synthesis", John Wiley and Sons, New York (1981),
like for example acetals or ketals.
Especially preferred groups P are CH2=CH-COO-, CH2=C(CH3)-COO-,
CH2=CH-, CH2=CH-0-, (CH2=CH)2CH-OCO-, (CH2=CH)2CH-G >r protected derivatives
Polymerisation of group P can be carried out according to methods that are
known to the ordinary expert and described in the literature, for example in
D. J. Broer; G. Challa; G. N. Mol, Macromol. Chem, 1991,192, 59.
The term "spacer group" is known in prior art and suitable spacer groups
Sp are known to the ordinary expert (see e.g. Pure Appl. Chem. 73(5),
888 (2001). The spacer group Sp is preferably of formula Sp'-X', such that
P-Sp- is P-Sp'-X'-, wherein
Sp' is alkylene with up to 30 C atoms which is unsubstituted or
mono- or polysubstituted by F, CI, Br, I or CN, it being also
possible for one or more non-adjacent CH2 groups to be
replaced, in each case independently from one another, by -
O-, -S-, -NH-, -NR0-, -SiF^R00-, -CO-, -COO-, -OCO-, -OCO-
O-, -S-CO-, -CO-S-, -CH=CH- or -CsC- in such a manner
that O and/or S atoms are not linked directly to one another,
X' is -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR0-, -NR°-
CO-, -NR°-CO-NR00-, -OCH2-, -CHzO-, -SCH2-, -CH2S-, -
CF20-, -OCF2-, -CF2S-, -SCF2-, -CF2CH2-, -CH2CF2-, -
CF2CF2-, -CH=N-, -N=CH-, -N=N-, -CH=CR0-, -CY1=CY2-, -
C=C-, -CH=CH-COO-, -OCO-CH=CH- or a single bond,
R° and R00 are independently of each other H or alkyl with 1 to 12 C-
atoms, and
Y1 and Y2 are independently of each other H, F, CI or CN.
X" is preferably -O-, -S-, -OCH2-, -CH20-, -SCH2-, -CH2S-, -CF20-, -OCF2-,
-CF2S-, -SCF2-. -CH2CH2-, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-, -
N=CH-, -N=N-, -CH=CR0-, -CY1=CY2-, -C=C- or a single bond, in particular
-O-, -S-, -C=C-, -CY1=CY2- or a single bond. In another preferred
embodiment X' is a group that is able to form a conjugated system, such
as -C=C- or -CY1=CY2-, or a single bond.
Typical groups Sp' are, for example, -(CH2)P-, -(CH2CH20)q -CH2CH2-, -
CH2CH2-S-CH2CH2- or-CH2CH2-NH-CH2CH2- or-(SiR°R00-O)p-, with p
being an integer from 2 to 12, q being an integer from 1 to 3 and R° and
R00 having the meanings given above.
Preferred groups Sp' are ethylene, propylene, butylene, pentylene,
hexylene, heptylene, octylene, nonylene, decylene, undecylene,
dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene,
ethylene-thioethylene, ethylene-N-methyl-iminoethylene, 1-
methylalkylene, ethenylene, propenylene and butenylene for example.
The compounds of formula I can be synthesized according to or in
analogy to methods that are known to the skilled person and are
described in the literature. Other methods of preparation can be taken
from the examples. Especially preferred and suitable synthesis methods
are further described below.
The synthesis of the anthra[2,3-b]benzo[c/]thiophene unit with added
trialkylsilylethynyl groups is shown in Scheme 1. Commercially available
dibenzothiophene undertakes a Friedel-Crafts reaction with phthalic
anhydride to give 2-(2'-carboxybenzoyl)dibenzothiophene. The acid is
then treated with aluminium chloride and phosphorus pentachloride to
yield anthra[2,3-b]benzo[cf]thiophene-7,12~dione. The dione is alkylated
with the lithium salt of the trialkylsilylacetylene reagent followed by
aromatisation utilising tin (II) chloride under acidic conditions to give 7,12-
bis(trialkylsiIylethynyl)anthra[2,3-b]benzo[djthiophene.
Scheme 1
wherein R is an alkyl group and wherein the bezene rings are optionally
substituted with one or more groups R6 as defined above and below.
The novel methods of preparing compounds as described above and
below are another aspect of the invention. Especially preferred is a
method of preparing a compound of formula I, comprising the following
steps:
a) subjecting an optionally substituted dibenzothiophene to a Friedel-
Crafts reaction with phthalic anhydride to give an optionally substituted
2-(2'-carboxybenzoyl)dibenzothiophene,
b) treating the acid group of the product of step a) with a dehydrating
agent, preferably aluminium chloride and phosphorus pentachloride, to
give an optionally substituted anthra[2,3-b]benzo[d]thiophene-7,12-
dione,
c) reacting the product of step b) with the lithium salt of a trisubstituted
silylacetylene reagent, preferably trialkylsilylacetylene, followed by
aromatisation, preferably utilising tin (II) chloride, under acidic
conditions to give 7,12-bis(trisubstituted silylethynyl)anthra[2,3-
b]benzo[d]thiophene.
The invention further relates to a formulation comprising one or more
compounds of formula I and one or more solvents, preferably selected
from organic solvents.
Preferred solvents are aliphatic hydrocarbons, chlorinated hydrocarbons,
aromatic hydrocarbons, ketones, ethers and mixtures thereof. Additional
solvents which can be used include 1,2,4-trimethylbenzene, 1,2,3,4-
tetramethyl benzene, pentylbenzene, mesitylene, cumene, cymene,
cyclohexylbenzene, diethylbenzene, tetralin, decalin, 2,6-lutidine, 2-fluoro-
m-xylene, 3-fluoro-o-xylene, 2-chlorobenzotrifluoride, dimethylformamide,
2-chloro-6fluorotoluene, 2-fluoroanisole, anisole, 2,3-dimethylpyrazine, 4-
fluoroanisole, 3-fluoroanisole, 3-trifluoro-methylanisoIe, 2-methylanisole,
phenetol, 4-methylansiole, 3-methylanisole, 4-fluoro-3-methylanisole, 2-
fluorobenzonitrile, 4-fluoroveratrol, 2,6-dimethylanisole, 3-
fluorobenzonitrile, 2,5-dimethylanisole, 2,4-dimethylanisole, benzonitrile,
3,5-dimethylanisole, N,N-dimethylaniline, ethyl benzoate, 1-fluoro-3,5-
dimethoxybenzene, 1-methylnaphthalene, N-methylpyrrolidinone, 3-
fluorobenzotrifluoride, benzotrifluoride, benzotrifluoride, diosane,
trifluoromethoxybenzene, 4-fluorobenzotrifluoride, 3-fluoropyridine,
toluene, 2-fluorotoluene, 2-fluorobenzotrifluoride, 3-fluorotoluene, 4-
isopropylbiphenyl, phenyl ether, pyridine, 4-fluorotoluene, 2,5-
difluorotoluene, 1-chloro-2,4-difiuorobenzene, 2-fluoropyridine, 3-
chlorofluorobenzene, 3-chlorofluorobenzene, 1-chloro-2,5-
difluorobenzene, 4-chlorofluorobenzene, chlorobenzene, o-
dichlorobenzene, 2-chlorofluorobenzene, p-xylene, m-xylene, o-xylene or
mixture of o-, m-, and p-isomers. Solvents with relatively low polarity are
generally preferred. For inkjet printing solvents with high boiling
temperatures and solvent mixtures are preferred. For spin coating
alkylated benzenes like xylene and toluene are preferred.
The invention further relates to an organic semiconducting formulation
comprising one or more compounds of formula I, one or more organic
binders, or precursors thereof, preferably having a permittivity e at 1,000
Hz of 3.3 or less, and optionally one or more solvents.
Combining specified soluble compounds of formula I, especially
compounds of the preferred formulae as described above and below, with
an organic binder resin (hereinafter also referred to as "the binder") results
in little or no reduction in charge mobility of the compounds of formula I,
even an increase in some instances. For instance, the compounds of
formula I may be dissolved in a binder resin (for example poly(a-
methylstyrene) and deposited (for example by spin coating), to form an
organic semiconducting layer yielding a high charge mobility. Moreover, a
semiconducting layer formed thereby exhibits excellent film forming
characteristics and is particularly stable.
If an organic semiconducting layer formulation of high mobility is obtained
by combining a compound of formula I with a binder, the resulting
formulation leads to several advantages. For example, since the
compounds of formula I are soluble they may be deposited in a liquid form,
for example from solution. With the additional use of the binder the
formulation can be coated onto a large area in a highly uniform manner.
Furthermore, when a binder is used in the formulation it is possible to
control the properties of the formulation to adjust to printing processes, for
example viscosity, solid content, surface tension. Whilst not wishing to be
bound by any particular theory it is also anticipated that the use of a binder
in the formulation fills in volume between crystalline grains otherwise being
void, making the organic semiconducting layer less sensitive to air and
moisture. For example, layers formed according to the process of the
present invention show very good stability in OFET devices in air.
The invention also provides an organic semiconducting layer which
comprises the organic semiconducting layer formulation.
The invention further provides a process for preparing an organic
semiconducting layer, said process comprising the following steps:
(i) depositing on a substrate a liquid layer of a formulation comprising
one or more compounds of formula I as described above and below,
one or more organic binder resins or precursors thereof, and
optionally one or more solvents,
(ii) forming from the liquid layer a solid layer which is the organic
semiconducting layer,
(Hi) optionally removing the layer from the substrate.
The process is described in more detail below.
The invention additionally provides an electronic device comprising the
said organic semiconducting layer. The electronic device may include,
without limitation, an organic field effect transistor (OFET), organic light
emitting diode (OLED), photodetector, sensor, logic circuit, memory
element, capacitor or photovoltaic (PV) cell. For example, the active
semiconductor channel between the drain and source in an OFET may
comprise the layer of the invention. As another example, a charge (hole or
electron) injection or transport layer in an OLED device may comprise the
layer of the invention. The formulations according to the present invention
and layers formed therefrom have particular utility in OFETs especially in
relation to the preferred embodiments described herein.
The semiconducting compound of formula I preferably has a charge
carrier mobility, (i, of more than 0.001 cm2V"V1, very preferably of more
than 0.01 cm2V1s"1, especially preferably of more than 0.1 cm W1 and
most preferably of more than 0.5 cm2V"V1.
The binder, which is typically a polymer, may comprise either an insulating
binder or a semiconducting binder, or mixtures thereof may be referred to
herein as the organic binder, the polymeric binder or simply the binder.
Preferred binders according to the present invention are materials of low
permittivity, that is, those having a permittivity s at 1,000 Hz of 3.3 or less.
The organic binder preferably has a permittivity s at 1,000 Hz of 3.0 or
less, more preferably 2.9 or less. Preferably the organic binder has a
permittivity e at 1,000 Hz of 1.7 or more. It is especially preferred that the
permittivity of the binder is in the range from 2.0 to 2.9. Whilst not wishing
to be bound by any particular theory it is believed that the use of binders
with a permittivity e of greater than 3.3 at 1,000 Hz, may lead to a
reduction in the OSC layer mobility in an electronic device, for example an
OFET. In addition, high permittivity binders could also result in increased
current hysteresis of the device, which is undesirable.
An example of a suitable organic binder is polystyrene. Further examples
of suitable binders are disclosed for example in US 2007/0102696 A1.
Especailly suitable and preferred binders are described in the following.
In one type of preferred embodiment, the organic binder is one in which at
least 95%, more preferably at least 98% and especially all of the atoms
consist of hydrogen, fluorine and carbon atoms.
It is preferred that the binder normally contains conjugated bonds,
especially conjugated double bonds and/or aromatic rings.
The binder should preferably be capable of forming a film, more preferably
a flexible film. Polymers of styrene and a-methyl styrene, for example
copolymers including styrene, a -methylstyrene and butadiene may
suitably be used.
Binders of low permittivity of use in the present invention have few
permanent dipoles which could otherwise lead to random fluctuations in
molecular site energies. The permittivity e (dielectric constant) can be
determined by the ASTM D150 test method.
It is also preferred that in the present invention binders are used which
have solubility parameters with low polar and hydrogen bonding
contributions as materials of this type have low permanent dipoles. A
preferred range for the solubility parameters ('Hansen parameter*) of a
binder for use in accordance with the present invention is provided in
Table 1 below.
Table 1
The three dimensional solubility parameters listed above include:
dispersive (5d). polar (5P) and hydrogen bonding (8h) components (CM.
Hansen, Ind. Eng. and Chem., Prod. Res. and Devi., 9, No3, p282., 1970).
These parameters may be determined empirically or calculated from
known molar group contributions as described in Handbook of Solubility
Parameters and Other Cohesion Parameters ed. A.F.M. Barton, CRC
Press, 1991. The solubility parameters of many known polymers are also
listed in this publication.
It is desirable that the permittivity of the binder has little dependence on
frequency. This is typical of non-polar materials. Polymers and/or
copolymers can be chosen as the binder by the permittivity of their
substituent groups. A list of suitable and preferred low polarity binders is
given (without limiting to these examples) in Table 2:
Table 2
Other polymers suitable as binders include poly(1,3-butadiene) or
polyphenylene.
Especially preferred are formulations wherein the binder is selected from
poly-a-methyl styrene, polystyrene and polytriarylamine or any copolymers
of these, and the solvent is selected from xylene(s), toluene, tetralin and
cyciohexanone.
Copolymers containing the repeat units of the above polymers are also
suitable as binders. Copolymers offer the possibility of improving
compatibility with the compounds of formula I, modifying the morphology
and/or the glass transition temperature of the final layer composition. It will
be appreciated that in the above table certain materials are insoluble in
commonly used solvents for preparing the layer. In these cases analogues
can be used as copolymers. Some examples of copolymers are given in
Table 3 (without limiting to these examples). Both random or block
copolymers can be used. It is also possible to add some more polar
monomer components as long as the overall composition remains low in
polarity.
Table 3
Other copolymers may include: branched or non-branched polystyrene-
block-polybutadiene, polystyrene-block(polyethylene-ran-butylene)-block-
polystyrene, polystyrene-block-polybutadiene-block-polystyrene,
polystyrene-(ethylene-propylene)-diblock-copolymers (e.g. KRATON®-
G1701E, Shell), poly(propylene-co-ethylene) and poly(styrene-co-
methylmethacrylate).
Preferred insulating binders for use in the organic semiconductor layer
formulation according to the present invention are poly(a-methylstyrene),
polyvinylcinnamate, poly(4-vinylbiphenyl), poly(4-methylstyrene), and
Topas™ 8007 (linear olefin, cyclo- olefin(norbornene) copolymer available
from Ticona, Germany). Most preferred insulating binders are poly(a-
methylstyrene), polyvinylcinnamate and poly(4-vinylbiphenyl).
The binder can also be selected from crosslinkable binders, like e.g.
acrylates, epoxies, vinylethers, thiolenes etc., preferably having a
sufficiently low permittivity, very preferably of 3.3 or less. The binder can
also be mesogenic or liquid crystalline.
As mentioned above the organic binder may itself be a semiconductor, in
which case it will be referred to herein as a semiconducting binder. The
semiconducting binder is still preferably a binder of low permittivity as
herein defined. Semiconducting binders for use in the present invention
preferably have a number average molecular weight (Mn) of at least 1500-
2000, more preferably at least 3000, even more preferably at least 4000
and most preferably at least 5000. The semiconducting binder preferably
has a charge carrier mobility, u, of at least 10"5cm2V"V1, more preferably
at least lO^cmVV.
A preferred class of semiconducting binder is a polymer as disclosed in
US 6,630,566, preferably an oligomer or polymer having repeat units of
formula 1:
wherein
Ar1, Ar2 and Ar3 which may be the same or different, denote,
independently if in different repeat units, an optionally
substituted aromatic group that is mononuclear or
polynuclear, and
m is an integer > 1, preferably £ 6, preferably > 10, more
preferably > 15 and most preferably > 20.
In the context of Ar1, Ar2 and Ar3, a mononuclear aromatic group has only
one aromatic ring, for example phenyl or phenylene. A polynuclear
aromatic group has two or more aromatic rings which may be fused (for
example napthyl or naphthylene), individually covalently linked (for
example biphenyl) and/or a combination of both fused and individually
linked aromatic rings. Preferably each Ar1, Ar2 and Ar3 is an aromatic
group which is substantially conjugated over substantially the whole group.
Further preferred classes of semiconducting binders are those containing
substantially conjugated repeat units. The semiconducting binder polymer
may be a homopolymer or copolymer (including a block-copolymer) of the
general formula 2:
A(C)B(d)...Z(Z) 2
wherein A, B,...,Z each represent a monomer unit and (c), (d),...(z) each
represent the mole fraction of the respective monomer unit in the polymer,
that is each (c), (d),...(z) is a value from 0 to 1 and the total of (c) + (d)
+...+ (z) = 1.
Examples of suitable and preferred monomer units A, B....Z include units
of formula 1 above and of formulae 3 to 8 given below (wherein m is as
defined in formula 1:
3
wherein
Ra and Rb are independently of each other selected from H, F, CN, N02, -
N(Rc)(Rd) or optionally substituted alkyl, alkoxy, thioalkyl, acyl,
aryl,
Rc and Rd are independently or each other selected from H, optionally
substituted alkyl, aryl, alkoxy or polyalkoxy or other
substituents,
and wherein the asterisk (*) is any terminal or end capping group including
H, and the alkyl and aryl groups are optionally fluorinated;
4
wherein
Y is Se, Te, O, S or -N(Re), preferably O, S or -N(Re)-,
Re is H, optionally substituted alkyl or aryl,
Ra and Rb are as defined in formula 3;
5
wherein Ra, Rb and Y are as defined in formulae 3 and 4;
6
wherein Ra, Rb and Y are as defined in formulae 3 and 4,
Z is -C(T1)=C(T2)-, -C=C-, -N(Rf)-, -N=N-, (Rf)=N-, -N=C(Rf)-,
T1 and T2 independently of each other denote H, CI, F, -CN or lower alkyl
with 1 to 8 C atoms,
Rf is H or optionally substituted alkyl or aryl;
7
wherein Ra and Rb are as defined in formula 3;
8
wherein Ra, Rb, R9 and Rh independently of each other have one of the
meanings of Ra and Rb in formula 3.
In the case of the polymeric formulae described herein, such as formulae
1 to 8, the polymers may be terminated by any terminal group, that is any
end-capping or leaving group, including H.
In the case of a block-copolymer, each monomer A, B....Z may be a
conjugated oligomer or polymer comprising a number, for example 2 to
50, of the units of formulae 3-8. The semiconducting binder preferably
includes: arylamine, fluorene, thiophene, spiro bifluorene and/or optionally
substituted aryl (for example phenylene) groups, more preferably
arylamine, most preferably triarylamine groups. The aforementioned
groups may be linked by further conjugating groups, for example vinylene.
In addition, it is preferred that the semiconducting binder comprises a
polymer (either a homo-polymer or copolymer, including block-copolymer)
containing one or more of the aforementioned arylamine, fluorene,
thiophene and/or optionally substituted aryl groups. A preferred
semiconducting binder comprises a homo-polymer or copolymer (including
block-copolymer) containing arylamine (preferably triarylamine) and/or
fluorene units. Another preferred semiconducting binder comprises a
homo-polymer or co-polymer (including block-copolymer) containing
fluorene and/or thiophene units.
The semiconducting binder may also contain carbazole or stilbene repeat
units. For example polyvinylcarbazole or polystilbene polymers or
copolymers may be used. The semiconducting binder may optionally
contain DBBDT segments (for example repeat units as described for
formula 1 above) to improve compatibility with the soluble compounds of
formula.
The most preferred semiconducting binders for use in the organic
semiconductor layer formulation according to the present invention are
poly(9-vinylcarbazole) and PTAA1, a polytriarylamine of the following
formula
wherein m is as defined in formula 1.
For application of the semiconducting layer in p-channel FETs, it is
desirable that the semiconducting binder should have a higher ionisation
potential than the semiconducting compound of formula I, otherwise the
binder may form hole traps. In n-channel materials the semiconducting
binder should have lower electron affinity than the n-type semiconductor
to avoid electron trapping.
The formulation according to the present invention may be prepared by a
process which comprises:
(i) first mixing a compound of formula I and an organic binder or a
precursor thereof. Preferably the mixing comprises mixing the two
components together in a solvent or solvent mixture,
(ii) applying the solvent(s) containing the compound of formula I and the
organic binder to a substrate; and optionally evaporating the
solvents) to form a solid organic semiconducting layer according to
the present invention,
(iii) and optionally removing the solid layer from the substrate or the
substrate from the solid layer.
In step (i) the solvent may be a single solvent or the compound of formula
I and the organic binder may each be dissolved in a separate solvent
followed by mixing the two resultant solutions to mix the compounds.
The binder may be formed in situ by mixing or dissolving a compound of
formula I in a precursor of a binder, for example a liquid monomer,
oligomer or crosslinkable polymer, optionally in the presence of a solvent,
and depositing the mixture or solution, for example by dipping, spraying,
painting or printing it, on a substrate to form a liquid layer and then curing
the liquid monomer, oligomer or crosslinkable polymer, for example by
exposure to radiation, heat or electron beams, to produce a solid layer. If
a preformed binder is used it may be dissolved together with the
compound of formula I in a suitable solvent, and the solution deposited for
example by dipping, spraying, painting or printing it on a substrate to form
a liquid layer and then removing the solvent to leave a solid layer. It will be
appreciated that solvents are chosen which are able to dissolve both the
binder and the compound of formula I, and which upon evaporation from
the solution blend give a coherent defect free layer.
Suitable solvents for the binder or the compound of formula I can be
determined by preparing a contour diagram for the material as described
in ASTM Method D 3132 at the concentration at which the mixture will be
employed. The material is added to a wide variety of solvents as
described in the ASTM method.
It will also be appreciated that in accordance with the present invention
the formulation may also comprise two or more compounds of formula I
and/or two or more binders or binder precursors, and that the process for
preparing the formulation may be applied to such formulations.
Examples of suitable and preferred organic solvents include, without
limitation, dichloromethane, trichloromethane, monochlorobenzene, o-
dichlorobenzene, tetrahydrofuran, anisole, morpholine, toluene, o-xylene,
m-xylene, p-xylene, 1,4-dioxane, acetone, methylethylketone, 1,2-
dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, ethyl
acetate, n-butyl acetate, dimethylformamide, dimethylacetamide,
dimethylsulfoxide, tetralin, decalin, indane and/or mixtures thereof.
After the appropriate mixing and ageing, solutions are evaluated as one of
the following categories: complete solution, borderline solution or
insoluble. The contour line is drawn to outline the solubility parameter-
hydrogen bonding limits dividing solubility and insolubility. 'Complete'
solvents falling within the solubility area can be chosen from literature
values such as published in "Crowley, J.D., Teague, G.S. Jr and Lowe,
J.W. Jr., Journal of Paint Technology, 38, No 496, 296 (1966)". Solvent
blends may also be used and can be identified as described in "Solvents,
W.H.Ellis, Federation of Societies for Coatings Technology, p9-10, 1986".
Such a procedure may lead to a blend of 'non' solvents that will dissolve
both the binder and the compound of formula I, although it is desirable to
have at least one true solvent in a blend.
Especially preferred solvents for use in the formulation according to the
present invention, with insulating or semiconducting binders and mixtures
thereof, are xylene(s), toluene, tetralin and o-dichlorobenzene.
The proportions of binder to the compound of formula I in the formulation
or layer according to the present invention are typically 20:1 to 1:20 by
weight, preferably 10:1 to 1:10 more preferably 5:1 to 1:5, still more
preferably 3:1 to 1:3 further preferably 2:1 to 1:2 and especially 1:1.
Surprisingly and beneficially, dilution of the compound of formula I in the
binder has been found to have little or no detrimental effect on the charge
mobility, in contrast to what would have been expected from the prior art.
In accordance with the present invention it has further been found that the
level of the solids content in the organic semiconducting layer formulation
is also a factor in achieving improved mobility values for electronic devices
such as OFETs. The solids content of the formulation is commonly
expressed as follows:
Solids content (%) = a + b xlOO
a + b + c
wherein
a = mass of compound of formula I, b = mass of binder and c = mass of
solvent.
The solids content of the formulation is preferably 0.1 to 10% by weight,
more preferably 0.5 to 5% by weight.
Surprisingly and beneficially, dilution of the compound of formula I in the
binder has been found to have little or no effect on the charge mobility, in
contrast to what would have been expected from the prior art.
The compounds according to the present invention can also be used in
mixtures or blends, for example together with other compounds having
charge-transport, semiconducting, electrically conducting,
photoconducting and/or light emitting semiconducting properties. Thus,
another aspect of the invention relates to a mixture or blend comprising
one or more compounds of formula I and one or more further compounds
having one or more of the above-mentioned properties. These mixtures
can be prepared by conventional methods that are described in prior art
and known to the skilled person. Typically the compounds are mixed with
each other or dissolved in suitable solvents and the solutions combined.
The formulations according to the present invention can additionally
comprise one or more further components like for example surface-active
compounds, lubricating agents, wetting agents, dispersing agents,
hydrophobing agents, adhesive agents, flow improvers, defoaming agents,
deaerators, diluents which may be reactive or non-reactive, auxiliaries,
colourants, dyes or pigments, sensitizers, stabilizers, nanoparticles or
inhibitors.
It is desirable to generate small structures in modern microelectronics to
reduce cost (more devices/unit area), and power consumption. Patterning
of the layer of the invention may be carried out by photolithography or
electron beam lithography.
Liquid coating of organic electronic devices such as field effect transistors
is more desirable than vacuum deposition techniques. The formulations of
the present invention enable the use of a number of liquid coating
techniques. The organic semiconductor layer may be incorporated into the
final device structure by, for example and without limitation, dip coating,
spin coating, ink jet printing, letter-press printing, screen printing, doctor
blade coating, roller printing, reverse-roller printing, offset lithography
printing, flexographic printing, web printing, spray coating, brush coating or
pad printing. The present invention is particularly suitable for use in spin
coating the organic semiconductor layer into the final device structure.
Selected formulations of the present invention may be applied to
prefabricated device substrates by ink jet printing or microdispensing.
Preferably industrial piezoelectric print heads such as but not limited to
those supplied by Aprion, Hitachi-Koki, InkJet Technology, On Target
Technology, Picojet, Spectra, Trident, Xaar may be used to apply the
organic semiconductor layer to a substrate. Additionally semi-industrial
heads such as those manufactured by Brother, Epson, Konica, Seiko
Instruments Toshiba TEC or single nozzle microdispensers such as those
produced by Microdrop and Microfab may be used.
In order to be applied by ink jet printing or microdispensing, the mixture of
the compound of formula I and the binder should be first dissolved in a
suitable solvent. Solvents must fulfil the requirements stated above and
must not have any detrimental effect on the chosen print head.
Additionally, solvents should have boiling points >100°C, preferably
>140°C and more preferably >150°C in order to prevent operability
problems caused by the solution drying out inside the print head. Suitable
solvents include substituted and non-substituted xylene derivatives, di-Ci_
2-alkyl formamide, substituted and non-substituted anisoles and other
phenol-ether derivatives, substituted heterocycles such as substituted
pyridines, pyrazines, pyrimidines, pyrrolidinones, substituted and non-
substituted /V,W-di-C-i_2-alkylanilines and other fluorinated or chlorinated
aromatics.
A preferred solvent for depositing a formulation according to the present
invention by ink jet printing comprises a benzene derivative which has a
benzene ring substituted by one or more substituents wherein the total
number of carbon atoms among the one or more substituents is at least
three. For example, the benzene derivative may be substituted with a propyl
group or three methyl groups, in either case there being at least three
carbon atoms in total. Such a solvent enables an ink jet fluid to be formed
comprising the solvent with the binder and the compound of formula I which
reduces or prevents clogging of the jets and separation of the components
during spraying. The solvent(s) may include those selected from the
following list of examples: dodecylbenzene, 1-methyl-4-tert-butylbenzene,
terpineol limonene, isodurene, terpinolene, cymene, diethylbenzene. The
solvent may be a solvent mixture, that is a combination of two or more
solvents, each solvent preferably having a boiling point >100°C, more
preferably >140°C. Such solvent(s) also enhance film formation in the layer
deposited and reduce defects in the layer.
The ink jet fluid (that is mixture of solvent, binder and semiconducting
compound) preferably has a viscosity at 20°C of 1 to 100 mPas, more
preferably 1 to 50 mPas and most preferably 1 to 30 mPas.
The use of the binder in the present invention also allows the viscosity of
the coating solution to be tuned to meet the requirements of the particular
print head.
The semiconducting layer of the present invention is typically at most 1
micron (=1 jam) thick, although it may be thicker if required. The exact
thickness of the layer will depend, for example, upon the requirements of
the electronic device in which the layer is used. For use in an OFET or
OLED, the layer thickness may typically be 500 nm or less.
In the semiconducting layer of the present invention there may be used
two or more different compounds of formula I. Additionally or alternatively,
in the semiconducting layer there may be used two or more organic
binders of the present invention.
As mentioned above, the invention further provides a process for
preparing the organic semiconducting layer which comprises (i) depositing
on a substrate a liquid layer of a formulation which comprises one or more
compounds of formula I, one or more organic binders or precursors
thereof and optionally one or more solvents, and (ii) forming from the
liquid layer a solid layer which is the organic semiconducting layer.
In the process, the solid layer may be formed by evaporation of the
solvent and/or by reacting the binder resin precursor (if present) to form
the binder resin in situ. The substrate may include any underlying device
layer, electrode or separate substrate such as silicon wafer or polymer
substrate for example.
In a particular embodiment of the present invention, the binder may be
alignable, for example capable of forming a liquid crystalline phase. In that
case the binder may assist alignment of the compound of formula I, for
example such that their aromatic core is preferentially aligned along the
direction of charge transport. Suitable processes for aligning the binder
include those processes used to align polymeric organic semiconductors
and are described in prior art, for example in US 2004/0248338 A1.
The formulation according to the present invention can additionally
comprise one or more further components like for example surface-active
compounds, lubricating agents, wetting agents, dispersing agents,
hydrophobing agents, adhesive agents, flow improvers, defoaming agents,
deaerators, diluents, reactive or non-reactive diluents, auxiliaries,
colourants, dyes or pigments, furthermore, especially in case crosslinkable
binders are used, catalysts, sensitizers, stabilizers, inhibitors, chain-
transfer agents or co-reacting monomers.
The present invention also provides the use of the semiconducting
compound, formulation or layer in an electronic device. The formulation
may be used as a high mobility semiconducting material in various devices
and apparatus. The formulation may be used, for example, in the form of a
semiconducting layer or film. Accordingly, in another aspect, the present
invention provides a semiconducting layer for use in an electronic device,
the layer comprising the formulation according to the invention. The layer or
film may be less than about 30 microns. For various electronic device
applications, the thickness may be less than about 1 micron thick. The layer
may be deposited, for example on a part of an electronic device, by any of
the aforementioned solution coating or printing techniques.
The compounds and formulations according to the present invention are
useful as charge transport, semiconducting, electrically conducting,
photoconducting or light mitting materials in optical, electrooptical,
electronic, electroluminescent or photoluminescent components or
devices. Especially preferred devices are OFETs, TFTs, ICs, logic circuits,
capacitors, RFID tags, OLEDs, OLETs, OPEDs, OPVs, solar cells, laser
diodes, photoconductors, photodetectors, electrophotographic devices,
electrophotographic recording devices, organic memory devices, sensor
devices, charge injection layers, Schottky diodes, planarising layers,
antistatic films, conducting substrates and conducting patterns. In these
devices, the compounds of the present invention are typically applied as
thin layers or films.
For example, the compound or formulation may be used as a layer or film,
in a field effect transistor (FET) for example as the semiconducting
channel, organic light emitting diode (OLED) for example as a hole or
electron injection or transport layer or electroluminescent layer,
photodetector, chemical detector, photovoltaic cell (PVs), capacitor
sensor, logic circuit, display, memory device and the like. The compound
or formulation may also be used in electrophotographic (EP) apparatus.
The compound or formulation is preferably solution coated to form a layer
or film in the aforementioned devices or apparatus to provide advantages
in cost and versatility of manufacture. The improved charge carrier
mobility of the compound or formulation of the present invention enables
such devices or apparatus to operate faster and/or more efficiently.
The compound, formulation and layer of the present invention are
especially suitable for use in an organic field effect transistor OFET as the
semiconducting channel. Accordingly, the invention also provides an
organic field effect transistor (OFET) comprising a gate electrode, an
insulating (or gate insulator) layer, a source electrode, a drain electrode
and an organic semiconducting channel connecting the source and drain
electrodes, wherein the organic semiconducting channel comprises an
organic semiconducting layer according to the present invention. Other
features of the OFET are well known to those skilled in the art.
OFETs where an organic semiconducting (OSC) material is arranged as a
thin film between a gate dielectric and a drain and a source electrode, are
generally known, and are described for example in US 5,892,244, US
5,998,804, US 6,723,394 and in the references cited in the background
section. Due to the advantages, like low cost production using the
solubility properties of the compounds according to the invention and thus
the processibility of large surfaces, preferred applications of these FETs
are such as integrated circuitry, TFT displays and security applications.
The gate, source and drain electrodes and the insulating and
semiconducting layer in the OFET device may be arranged in any
sequence, provided that the source and drain electrode are separated
from the gate electrode by the insulating layer, the gate electrode and the
semiconductor layer both contact the insulating layer, and the source
electrode and the drain electrode both contact the semiconducting layer.
An OFET device according to the present invention preferably comprises:
- a source electrode,
- a drain electrode,
- a gate electrode,
- a semiconducting layer,
- one or more gate insulator layers,
- optionally a substrate.
wherein the semiconductor layer preferably comprises a compound of
formula I, very preferably a formulation comprising a compound of formula
I and an organic binder as described above and below.
The OFET device can be a top gate device or a bottom gate device.
Suitable structures and manufacturing methods of an OFET device are
known to the skilled in the art and are described in the literature, for
example in US 2007/0102696 A1.
The gate insulator layer preferably comprises a fluoropolymer, like e.g. the
commercially available Cytop 809M® or Cytop 107M® (from Asahi Glass).
Preferably the gate insulator layer is deposited, e.g. by spin-coating,
doctor blading, wire bar coating, spray or dip coating or other known
methods, from a formulation comprising an insulator material and one or
more solvents with one or more fluoro atoms (fluorosolvents), preferably a
perfluorosolvent. A suitable perfluorosolvent is e.g. FC75® (available from
Acros, catalogue number 12380). Other suitable fluoropolymers and
fluorosolvents are known in prior art, like for example the
perfluoropolymers Teflon AF® 1600 or 2400 (from DuPont) or Fluoropel®
(from Cytonix) or the perfluorosolvent FC 43® (Acros, No. 12377).
Especially preferred are organic dielectric materials having a low
permittivity (or dielectric contant) from 1.0 to 5.0, very preferably from 1.8
to 4.0 ("low k materials"), as disclosed for example in US 2007/0102696
A1 or US 7,095,044.
An OPV device according to the present invention preferably comprises:
- a low work function electrode (for example Aluminum),
- a high work function electrode (for example ITO), one of which is
transparent,
- a biiayer of consisting of a hole transporting and an electron
transporting material; the biiayer can exist as two distinct layers, or as
a blended mixture, a so-called bulk heterjunction (BHJ) (see for
example Coakley, K. M. and McGehee, M. D. Chem. Mater. 2004, 16,
4533),
- an optional conducting polymer layer (such as for example
PEDOT:PSS) to modify the work function of the high work function
electrode to provide an ohmic contact for the hole,
- an optional coating on the high workfunction electrode (such as LiF) to
provide an ohmic contact for electrons.
The hole transporting material is constituted by a compound of the present
invention. The electron transporting material can be an inorganic material
such as zinc oxide or cadmium selenide, or an organic material such as a
fullerene derivate (for example PCBM, [(6,6)-phenyl C61-butyric acid
methyl ester] or a polymer see for example Coakley, K. M. and McGehee,
M. D. Chem. Mater. 2004, 16, 4533). For the blended mixture, an optional
annealing step may be necessary to optimize blend morpohology and
consequently OPV device performance.
In security applications, OFETs and other devices with semiconducting
materials according to the present invention, like transistors or diodes, can
be used for RFID tags or security markings to authenticate and prevent
counterfeiting of documents of value like banknotes, credit cards or ID
cards, national ID documents, licenses or any product with monetry value,
like stamps, tickets, shares, cheques etc..
Alternatively, the materials according to the invention can be used in
organic light emitting devices or diodes (OLEDs), e.g., in display
applications or as backlight of e.g. liquid crystal displays. Common OLEDs
are realized using multilayer structures. An emission layer is generally
sandwiched between one or more electron-transport and/ or hole-
transport layers. By applying an electric voltage electrons and holes as
charge carriers move towards the emission layer where their
recombination leads to the excitation and hence luminescence of the
lumophor units contained in the emission layer. The inventive compounds,
materials and films may be employed in one or more of the charge
transport layers and/ or in the emission layer, corresponding to their
electrical and/ or optical properties. Furthermore their use within the
emission layer is especially advantageous, if the compounds, materials
and films according to the invention show electroluminescent properties
themselves or comprise electroluminescent groups or compounds. The
selection, characterization as well as the processing of suitable
monomeric, oligomeric and polymeric compounds or materials for the use
in OLEDs is generally known by a person skilled in the art, see, e.g.,
Meerholz, Synthetic Materials, 111-112, 2000, 31-34, Alcala, J. Appl.
Phys., 88, 2000, 7124-7128 and the literature cited therein.
According to another use, the materials according to the present
invention, especially those which show photoluminescent properties, may
be employed as materials of light sources, e.g., of display devices such as
described in EP 0 889 350 A1 or by C. Weder et al., Science, 279, 1998,
835-837.
A further aspect of the invention relates to both the oxidised and reduced
form of the compounds according to this invention. Either loss or gain of
electrons results in formation of a highly delocalised ionic form, which is of
high conductivity. This can occur on exposure to common dopants.
Suitable dopants and methods of doping are known to those skilled in the
art, e.g. from EP 0 528 662, US 5,198,153 or WO 96/21659.
The doping process typically implies treatment of the semiconductor
material with an oxidating or reducing agent in a redox reaction to form
delocalised ionic centres in the material, with the corresponding
counterions derived from the applied dopants. Suitable doping methods
comprise for example exposure to a doping vapor in the atmospheric
pressure or at a reduced pressure, electrochemical doping in a solution
containing a dopant, bringing a dopant into contact with the semiconductor
material to be thermally diffused, and ion-implantantion of the dopant into
the semiconductor material.
When electrons are used as carriers, suitable dopants are for example
halogens (e.g., I2, Cl2, Br2, ICI, ICI3, IBr and IF), Lewis acids (e.g., PF5,
AsF5, SbF5, BF3, BCI3, SbCI5, BBr3 and S03), protonic acids, organic
acids, or amino acids (e.g., HF, HCI, HN03, H2S04, HCI04, FS03H and
CIS03H), transition metal compounds (e.g., FeCI3, FeOCI, Fe(CI04)3,
Fe(4-CH3C6H4S03)3, TiCI4, ZrCI4, HfCI4, NbF5, NbCI5, TaCI5, MoF5, MoCI5,
WF5, WCI6, UF6 and LnCI3 (wherein Ln is a lanthanoid), anions (e.g., CF,
Br\ l\ l3\ HS04", S042\ N03", CICV, BF4\ PF6", AsF6\ SbF6-, FeCI4",
Fe(CN)63~, and anions of various sulfonic acids, such as aryl-S03"). When
holes are used as carriers, examples of dopants are cations (e.g., H+, Li+,
Na+, K\ Rb+ and Cs+), alkali metals (e.g., Li, Na, K, Rb, and Cs), alkaline-
earth metals (e.g., Ca, Sr, and Ba), 02, XeOF4, (N02+) (SbF6"), (N02+)
(SbCI6"), (N02+) (BF4"), AgCI04, H2lrCI6, La(N03)3 6H20, FS0200S02F,
Eu, acetylcholine, R4N+, (R is an alkyl group), R4P+ (R is an alkyl group),
ReAs+ (R is an alkyl group), and R3S+ (R is an alkyl group).
The conducting form of the compounds of the present invention can be
used as an organic "metal" in applications including, but not limited to,
charge injection layers and ITO planarising layers in OLED applications,
films for flat panel displays and touch screens, antistatic films, printed
conductive substrates, patterns or tracts in electronic applications such as
printed circuit boards and condensers.
The compounds and formulations according to the present invention amy
also be suitable for use in organic plasmon-emitting diodes (OPEDs), as
described for example in Koller et al., Nature Photonics 2008 (published
online September 28, 2008).
According to another use, the materials according to the present invention
can be used alone or together with other materials in or as alignment
layers in LCD or OLED devices, as described for example in US
2003/0021913. The use of charge transport compounds according to the
present invention can increase the electrical conductivity of the alignment
layer. When used in an LCD, this increased electrical conductivity can
reduce adverse residual dc effects in the switchable LCD cell and
suppress image sticking or, for example in ferroelectric LCDs, reduce the
residual charge produced by the switching of the spontaneous polarisation
charge of the ferroelectric LCs. When used in an OLED device comprising
a light emitting material provided onto the alignment layer, this increased
electrical conductivity can enhance the electroluminescence of the light
emitting material. The compounds or materials according to the present
invention having mesogenic or liquid crystalline properties can form
oriented anisotropic films as described above, which are especially useful
as alignment layers to induce or enhance alignment in a liquid crystal
medium provided onto said anisotropic film. The materials according to
the present invention may also be combined with photoisomerisable
compounds and/or chromophores for use in or as photoalignment layers,
as described in US 2003/0021913.
According to another use the materials according to the present invention,
especially their water-soluble derivatives (for example with polar or ionic
side groups) or ionically doped forms, can be employed as chemical
sensors or materials for detecting and discriminating DNA sequences.
Such uses are described for example in L. Chen, D. W. McBranch, H.
Wang, R. Helgeson, F. Wudl and D. G. Whitten, Proc. Natl. Acad. Sci.
U.S.A. 1999, 96, 12287; D. Wang, X. Gong, P. S. Heeger, F. Rininsland,
G. C. Bazan and A. J. Heeger, Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 49;
N. DiCesare, M. R. Pinot, K. S. Schanze and J. R. Lakowicz, Langmuir
2002, 18, 7785; D. T. McQuade, A. E. Pullen, T. M. Swager, Chem. Rev.
2000, 100, 2537.
Unless the context clearly indicates otherwise, as used herein plural forms
of the terms herein are to be construed as including the singular form and
vice versa.
Throughout the description and claims of this specification, the words
"comprise" and "contain" and variations of the words, for example
"comprising" and "comprises", mean "including but not limited to", and are
not intended to (and do not) exclude other components.
It will be appreciated that variations to the foregoing embodiments of the
invention can be made while still falling within the scope of the invention.
Each feature disclosed in this specification, unless stated otherwise, may
be replaced by alternative features serving the same, equivalent or similar
purpose. Thus, unless stated otherwise, each feature disclosed is one
example only of a generic series of equivalent or similar features.
All of the features disclosed in this specification may be combined in any
combination, except combinations where at least some of such features
and/or steps are mutually exclusive. In particular, the preferred features of
the invention are applicable to all aspects of the invention and may be
used in any combination. Likewise, features described in non-essential
combinations may be used separately (not in combination).
It will be appreciated that many of the features described above,
particularly of the preferred embodiments, are inventive in their own right
and not just as part of an embodiment of the present invention.
Independent protection may be sought for these features in addition to or
alternative to any invention presently claimed.
References:
1. J. E. Anthony, Angew. Chem. Int. Ed., 2008, 47, 452.
2. S. F. Nelson, Y. Y. Lin, D. J. Gundlach and T. N. Jackson, Appl. Phys.
Lett., 1998, 72, 1854.
3. Maliakal, K. Raghavachari, H. Katz, E. Chandross and T. Siegrist,
Chem. Mater., 2004, 16, 4980.
4. Du, Y. Guo, Y. Liu, W. Qiu, H. Zhang, X. Gao, Y. Liu, T. Qi, K. Lu and
G. Yu, Chem. Mater., 2008, 20 (13), 4188.
5. M. L. Tedjamulia, Y. Tominaga and R. N. Castle, J. Heterocyclic
Chem., 1983, 20, 861. (b) F. Mayer, Ann. Chem., 488, 259.
6. S. T. Bromley, M. Mas-Torrent, P. Hadley and C. Rovira, J. Am.
Chem. Soc, 2004, 126, 6544.
7. M. L. Tang, M. E. Roberts, J. J. Lacklin, M. M. Ling, H. Meng and Z.
Bao, Chem. Mater., 2006,18, 6250.
The invention will now be described in more detail by reference to the
following examples, which are illustrative only and do not limit the scope of
the invention.
Example 1
7.12-Bis(triethvlsilvlethynvl)anthrar2,3-blbenzo[o1thiophene 1 is prepared
in three steps as follows:
2-(o-Carboxvbenzovl)dibenzothiophene
To a mixture of aluminium chloride (40.0 g, 300 mmol) in anhydrous
dichloromethane (1000 cm ) is added a suspension of phthalic anhydride
(14.8 g, 100 mmol) in anhydrous dichloromethane (200 cm3). The
suspension is stirred for 30 minutes, cooled to 5° C and then a solution of
dibenzothiophene (20.0 g, 110 mmol) in anhydrous dichloromethane (200
cm3) added drop wise under cooling with ice. After addition, the mixture is
allowed to stir at 23°C for 4 hours. The reaction mixture poured into a
solution of water (1000 cm3) and concentrated hydrochloric acid (400
cm3). The product extracted with dichloromethane (2 * 200 cm3) and the
organic extracted with aqueous sodium hydroxide (5%, 500 cm3). The
basic layer acidified and the oily precipitate is isolated by decanting away
the acidic solution. Water (200 cm3) is added, which solidified the oil and
the solid collected by filtration, washed with water (500 cm3) and dried
under vacuum to give 2-(o-carboxybenzoyl)dibenzothiophene as a pale
yellow solid (35.64 g, 99%). 1H NMR (300 MHz, CDCI3) 8.47-8.52 (m, 1
H), 7.99-8.15 (m, 2 H), 7.60-7.86 (m, 4 H), 7.35-7.57 (m, 4 H).
Anthraf2,3-fo1benzorc/]thiophene-7.12-dione
To a mixture of 2-(o-carboxybenzoyl)dibenzothiophene (35.6 g, 107 mmol)
and phosphorus pentachloride (33.5 g, 161 mmol) in anhydrous 1,2-
dichlorobenzene (430 cm3) is added aluminium chloride (21.4 g, 161
mmol). The mixture is then heated at 140 °C for 17 hours. The reaction
mixture cooled to 23 °C and the solvent removed under vacuum to give a
black solid. Acetone (500 cm3) is added and the mixture filtered to give a
green/yellow solid which is dried under vacuum. To the solid is added
dichloromethane (1000 cm3) and the mixture heated. The hot mixture is
passed through a very short plug of silica (dichloromethane) to give
anthra[2,3-6]benzo[cQthiophene-7,12-dione as a yellow solid (5.43 g,
16%). MS m/z 314 (M+). 1H NMR (300 MHz, CDCI3) 9.04 (s, 1 H), 8.78 (s,
1 H), 8.31 - 8.41 (m, 3 H), 7.86 - 7.93 (m, 1 H), 7.78 - 7.85 (m, 2 H), 7.50 -
7.61 (m, 2 H); 13C NMR (75 MHz, CDCI3) 183.1, 182.8, 145.3, 141.3,
139.9, 134.7, 134.2, 134.1, 133.9, 133.8, 131.1, 129.9, 128.8, 127.4,
125.5, 123.2, 123.1, 122.4, 120.8.
7,12-Bis(triethvlsilvlethvnyl)anthrar2.3-fclbenzorQlthioDhene 1
To a solution of triethylsilyl acetylene (3.68 g, 25 mmol) in anhydrous 1,4-
dioxane (120 cm3) at room temperature is added n-butyllithium (2.5 M in
hexanes, 9.7 cm3, 24 mmol) dropwise. The reaction mixture is then stirred
for 1 hour at 23 °C before anthra(2,3-b]benzo[dlthiophene-7l12-dione
(2.00 g, 6.36 mmol) is added. The reaction mixture is then heated at reflux
for 6 hours, the heating turned off and the mixture allowed to cool in the
dark. Solid tin(ll) chloride(8.93 g, 47 mmol) is added piecewise over 5
minutes and then the reaction mixture allowed to stir for a further 5
minutes. Concentrated hydrochloric acid (20 cm3) added slowly, and the
mixture stirred for 1 hour in the dark. The mixture poured into water (200
cm3) and the product extracted with dichloromethane (2 x 100 cm3). The
combined organic extracts dried over anhydrous magnesium sulfate,
filtered and the solvent removed in vacuo to give a brown/purple solid.
The crude product is purified by column chromatography (40-60 petrol to
10% dichloromethane in petrol) followed by recrystallisation from 2-
butanone to give 7,12-bis(triethylsilylethynyl)anthra[2,3-
6]benzo[d]thiophene 1 as an orange/red crystalline solid (740 mg, 21%).
1H NMR (300 MHz, CDCI3) 9.39 (d, 1 H, J 0.76), 9.02 (d, 1 H, J 0.76),
8.58-8.67 (m, 2 H), 8.18-8.25 (m, 1 H), 7.73-7.49 (m, 1 H), 7.57-7.64 (m, 2
H), 7.43-7.49 (m, 2 H), 1.19-1.32 (m, 18 H), 0.84-0.97 (m, 12 H); 13C NMR
(75 MHz, CDCI3) 140.6, 139.4, 136.5, 134.9, 132.5, 131.9, 131.2, 129.9,
128.5, 127.3, 127.0, 126.6, 124.8, 122.9, 122.2, 119.8, 119.4, 119.0,
117.2, 106.5, 106.2,103.0, 102.9, 8.0, 7.9, 4.8, 4.7.
Example 2: Transistor Fabrication and Measurement
Top-gate thin-film organic field-effect transistors (OFETs) were fabricated
on glass substrates with photolithographically defined Au source-drain
electrodes. A 2 wt. % solution of compound 1 in a mixture of 4-
methylanisole:1-methylnaphthalene (97:3) was drop-cast ontop followed
by a spin-coated fluoropolymer dielectric material (D139). Finally a
photolithographically defined Au gate electrode was deposited. The
electrical characterization of the transistor devices was carried out in
ambient air atmosphere using computer controlled Agilent 4155C
Semiconductor Parameter Analyser. Charge carrier mobility in the
saturation regime (jj.sat) of 2 x 10"4 cm2A/s was calculated for compound 1
and a current on/off ratio of 1 x 103 was observed. Field-effect mobility
was calculated in the saturation regime (Vd > (Vg-V0)) using equation (1):
where W is the channel width, L the channel length, Cj the capacitance of
insulating layer, Vg the gate voltage, V0 the turn-on voltage, and nsat is the
charge carrier mobility in the saturation regime.Turn-on voltage (V0) was
determined as the onset of source-drain current.
Figure 1 shows the UVA/is absorption spectrum of 7,12-
bis(triethylsilylethynyl)anthra[2,3-b]benzo[d]thiophene in DCM solution,
with a maximum absorption wavelength ^max = 492 nm.
Figure 2 shows the DSC curve (1st cycle) at 10°C/min for 7,12-
bis(triethylsilylethynyl)anthra[2,3-b]benzo[d]thiophene, with a melting point
Tm (onset) =168°C.
Figure 3 shows the transfer characteristics and the charge carrier mobility
of compound 1 in an organic field-effect transistor.
Patent Claims
1. Compounds of formula I
I
wherein
R1 and R2 are independently of each other halogen, -CN, -NC, -
NCO, -NCS, -OCN, -SCN, -C(=O)NR0R00, -C(=0)X°, -
C(=0)R°, -NH2, -NR°R00, -SH, -SR°, -S03H, -SO2R0, -
OH, -N02, -CF3, -SF5, optionally substituted silyl or
germanyl groups, or optionally substituted carbyl or
hydrocarbyl groups that optionally comprise one or more
hetero atoms,
R3"6 are independently of each other H, halogen, -CN, -NC,
-NCO, -NCS, -OCN, -SCN, -C(=O)NR0R00, -C(=0)X°, -
C(=0)R°, -NH2, -NR°R00, -SH, -SR°, -S03H, -S02R°, -
OH, -N02, -CF3, -SF5, optionally substituted silyl
groups, or optionally substituted carbyl or hydrocarbyl
groups that optionally comprise one or more hetero
atoms, neighboured pairs of groups R3 and R4 or R5
and R6 may also form a ring system with each other or
with the benzene ring to which they are attached,
X° is halogen,
R° and R00 are independently of each other H or an optionally
substituted aliphatic or aromatic hydrocarbyl group
having 1 to 20 C atoms,
and wherein the benzene rings may also be substituted
by one or more additional groups R6.
2. Compounds according to claim 1, characterized in that they are
selected of the following formulae
wherein
R3"11 are as defined in claim 1,
R', R" and R'" are identical or different groups selected from H, a Cr
Cw-aikyl group, a C2-C40-a'kenyl group, a Ce-C^o-aryl group, a Cs-
C40-arylalkyi group, a C-i-Cso-alkoxy or -oxaalkyl group, or a C6-C40-
aryfaikyloxy group, wherein all these groups are optionally
substituted with one or more groups L,
L is selected from F, CI, Br, i, -CN, -H07, -NCO, -NCS, -OCN, -SCN,
-C(=O)NR0R00, -C(=0)X°, -C(=O)R0, -NR°R00, optionally substituted
silyl, or aryl or heteroaryl with 4 to 40, preferably 6 to 20 ring atoms,
and straight chain or branched alkyl, alkoxy, oxaalkyl, thioalkyl,
alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonlyoxy or
alkoxycarbonyloxy with 1 to 20, preferably 1 to 12 C atoms, wherein
one or more H atoms are optionally replaced by F or CI, wherein R°,
R00 and X° are as defined in claim 1,
Y3, Y4 and Y5 are independently of each other selected from CH,
(CH)2, S, O, N and Se, such that S and/or O atoms are not directly
linked to each other.
3. Compounds according to claim 1 or 2, characterized in that
R3"6 denote H, F or alkyl or fluoroalkyl having from 1 to 12 C.atoms,
Y3-Y5-Y4 denotes CH-S-CH, CH-Se-CH, CH-O-CH, N-S-N, CH-N=CH
or CH=N-CH, and R\ R" and R'" denote C,.10 alkyl.
4. Formulation comprising one or more compounds according to one or
more of claims 1 to 3 and one or more organic solvents.
5. Organic semiconducting formulation comprising one or more
compounds according to one or more of claims 1 to 3, one or more
organic binders or precursors thereof, having a permittivity e at
1,000 Hz of 3.3 or less, and optionally one or more solvents.
6. Use of compounds and formulations according according to one or
more of claims 1 to 5 as charge transport, semiconducting,
electrically conducting, photoconducting or light emitting material in
an optical, electrooptical, electronic, electroluminescent or
photoluminescent components or devices.
7. Charge transport, semiconducting, electrically conducting,
photoconducting or light emitting material or component comprising
one or more compounds or formulations according to one or more of
claims 1 to 5.
8. Optical, electrooptical, electronic, electroluminescent or
photoluminescent component or device comprising one or more
compounds, formulations, materials or components according to one
or more of claims 1 to 7.
9. Component or device according to claim 8, characterized in that it is
selected from the group consisting of organic field effect transistors
(OFET), thin film transistors (TFT), integrated circuits (IC), logic
circuits, capacitors, radio frequency identification (RFID) tags,
devices or components, organic light emitting diodes (OLED),
organic light emitting transistors (OLET), flat panel displays,
backlights of displays, organic photovoltaic devices (OPV), solar
cells, laser diodes, photoconductors, photodetectors,
electrophotographic devices, electrophotographic recording devices,
organic memory devices, sensor devices, charge injection layers,
charge transport layers or interlayers in polymer light emitting diodes
(PLEDs), organic plasmon-emitting diodes (OPEDs), Schottky
diodes, planarising layers, antistatic films, polymer electrolyte
membranes (PEM), conducting substrates, conducting patterns,
electrode materials in batteries, alignment layers, biosensors,
biochips, security markings, security devices, and components or
devices for detecting and discriminating DNA sequences.
10. Method of preparing a compound according to one or more of claims
1 to 3, comprising the following steps:
a) subjecting an optionally substituted dibenzothiophene to a Friedel-
Crafts reaction with phthalic anhydride to give an optionally
substituted 2-(2'-carboxybenzoyl)dibenzothiophene,
b) treating the acid group of the product of step a) with a dehydrating
agent, to give an optionally substituted anthra[2,3-
6]benzo[cf]thiophene-7,12-dione,
c) reacting the product of step b) with the lithium salt of a
trisubstituted silylacetylene reagent, followed by aromatisation,
preferably utilising tin (II) chloride, under acidic conditions to give
7,12-bis(trisubstituted silylethynyl)anthra[2,3-b]benzo[d]thiophene.

The invention relates to novel anthra[2,3-b]benzo[d]thiophene derivatives,
methods of their preparation, their use as semiconductors in organic electronic
(OE) devices, and to OE devices comprising these derivatives.