TECHNICAL FIELD
This invention relates to photoelectrochemical
photovoltaic cells (PPC). More particularly, the invention
relates to photoelectrochemical photovoltaic modules of
large size (both flexible and rigid) that include
plurality of the PEC integrated in one photovoltaic
source.
Examples of the PEC are disclosed in the following patent
specifications:
US4927721, Photoelectrochemical cell; Michael Graetzel and
Paul Liska, 1990.
US5350644, Photovoltaic cells; Michael Graetzel, Mohammad
K Nazeeruddin and Brian 0'Regan, 1994.
US5525440, Method of manufacture of photo-electrochemical
cell and a cell made by this method; Andreas Kay, Michael
Graetzel and Brian 0'Regan, 1996.
US5728487, Photoelectrochemical cell and electrolyte for
this cell; Michael Graetzel, Yordan Athanassov and Pierre
Bonhote, 1998.
WO 98/05084, Photoelectrochemical cell, S. Brodie et all.
US6297900- Electrophotochromic Smart Windows and Methods,
Gavin Tulloch and Igor Skryabin, 2000.
US6555741- Methods to Implement Interconnects in Multicell
Regenerative Photovoltaic Photoelectrochemical
Devices, G.Phani, I.Skryabin and J.Hopkins, 2001
US6664623 - Methods to Implement Sealing and Electrical
Connections to Single Cell and Multi-cell Regenerative
Photovoltaic Photoelectrochemical Devices, G.Phani,
J.Hopkins, D.Vittorio, I.Skryabin, 2002
BACKGROUND OF THE INVENTION
Photoelectrochemical Photovoltaic Cells (PPC), as of
the type disclosed in the above patents, are typically
fabricated in a laminate arrangement between two
substrates. In a typical arrangement, at least one
substrate is transparent to visible light and comprises a
transparent support (typically glass for rigid modules and
plastic - for flexible modules) to which a transparent
electrically conductive (TEC) coatings is applied. Another
substrate is not necessarily transparent to visible light.
Various materials suitable for non-transparent substrate
are described in the prior art, including:
• Thin metallic films supported by glass, ceramic or
polymer,
• Metallic foils,
• Metallic mesh,
• Carbon based conductors.
However, the TEC coatings, which usually comprise a metal
oxide(s), have high resistivity when compared with normal
metal conductors, resulting in high resistive losses for
large area cells. Thus, in practical application, these
cells are combined in modules.
Dimensions of the modules are limited, however, by
necessity to maintain uniform thickness of a module
(typically 20-50 micrometers). In, order to make a large
photovoltaic photoelectrochemical panel (PPP) the modules
are electrically connected and laminated between two
additional large panes, one of which is being transparent.
(see, for example, Australian design No2093/2002) .
Manufacture of such panels, however, requires additional
manufacturing equipment and procedures.
OBJECTIVE OF THE INVENTION
'Objective of this invention is to provide cost
effective large size . photovoltaic Photoelectrochemical
panel.
SUMMARY OF THE INVENTION
Generally the present invention provides for a
Photoelectrochemical Photovoltaic Panel (PPP) comprising
one shared substrate and a number of individual
substrates. The shared substrate is an electrical
conductor or is at least partially coated by an
electrically conducting material. Similarly, individual
substrates are all electrical conductors or at least
partially coated with an electrically conducting material.
In one embodiment the shared substrate is transparent
to at least a part of solar radiation.
In another embodiment at the individuals substrates
are all transparent to at least a part of solar radiation.
In further embodiment the individual substrates and
the shared substrate (hereafter - the substrates) are all
transparent to.at least a part of solar radiation.
In yet a further embodiment said electrically
conducting material is a transparent electronic conductor
(TEC), for example fluorine doped tin oxide or indium-tin
oxide.
Photoelectrochemical photovoltaic cells (PPC) are
formed between the shared substrate and the individual
substrates. Each PPC includes a photosensitive electrode,
a counter electrode and an electrolyte dispensed between
the photosensitive electrode and the counter electrode.
The photosensitive electrode typically comprises nanoparticulate
wide band semiconductor (for example
titanium dioxide), photosensitised by a thin layer of dye.
. In one embodiment the photosensitive electrodes of
the PPC are supported by the shared substrate whereas the
counter electrodes of the PPC - by the individual
substrates.
In another embodiment only some of the
photosensitive electrodes are supported by the shared
substrate and the remaining photosensitive electrodes are
supported by the individual substrates.
In the practical realisation of the invention the
shared substrate is substantially larger than each of the
individual substrates allowing for a significant number of
PPC to be formed in one panel. Although the invention has
no specific restrictions on the shape of the shared
substrate, rectangular shape is advantageous for the
purpose of use and manufacture, especially - for roll-toroll
manufacture, which is preferable when the shared
substrate and all the individual substrates are made of
flexible material.
In'one aspect of the invention, the shared substrate
is divided into electrically isolated regions; each region
opposes at least one adjacent individual substrate and the
PPC are formed between the individual substrate and the
opposing isolated region of the shared substrate.
In one embodiment in accordance with this aspect of
the invention at least one of the substrates is made of
glass coated by Transparent Electronic Conductor (TEC).
In another embodiment in accordance with this aspect
of the invention, at least one of the substrates is made
of polymeric material coated by TEC.
In still another embodiment, at least one of the
substrates is made of metal or metal alloy. Preferential
metals include titanium, tungsten, nickel, zinc or alloys
such as stainless steel.
In yet another embodiment at least one of the
substrates is made of metal coated by impermeable nitride
(e.g. TiN). .
In a further embodiment, at least one of the
substrates comprises metal foil or metallic mesh.
In still a further embodiment, at least one of the
substrates comprises polymeric sheet coated by metal or
laminated with metallic foil.
In yet a further embodiment the shared substrate
comprise polymeric material coated by TEC and all the
individual substrates comprise metal foil.
In the preferred embodiment the shared substrate is
made of polymeric material coated by TEC and all the
individual substrates comprise metallic foil, wherein said
photosensitive electrodes of said PPC are formed on the
individual substrates and counter electrodes - on the
shared substrate.
The invention provides for various shapes and
dimensions of the individual substrates, it is
preferential, however, to .utilise the individual
substrates (and PPC electrodes) of circular shape in order
to minimise resistive losses. Another advantage of the
circular shape is in minimisation of perimeter for a given
area of the PPC electrodes, since each of the PPC needs to
be sealed along the perimeter of the individual substrate.
Dimensions of each PPC depend on the type of conductor.
Dimensions of the individual substrate depend on
resistivity of selected TEC material. It has been
established that for full sun operations diameter of each
PPC must not exceed 10-15 mm if resistivity of the TEC
material is around 10 Ohms/square.
In the preferred embodiment the individual substrates
are. electrically connected to selected electrically
isolated regions of the common substrate. This allows for
electrical connections between the PPC to form two
terminal power source of the PPP. It is advantageous to
connect the PPC in such a way that both negative and
positive terminals of the power source are located on the
shared substrate.
. In another aspect of the invention a pattern of a
second electrically .conductive material is created on at
least one substrate. This material is selected to have
conductivity higher than that of the first electrically
conductive material. The second electrically conductive
material enhances conductivity of the substrate without
significant . reduction of its optical transparency.
Examples of the secondary conductive material include
metal (for example, Ag, Cu, Au) tracks deposited on the
substrate using screen-printing, vacuum mask deposition,
electroplating, etc.
In one embodiment, the electrically conductive
material is protected by an impermeable protective layer
of glazing or polymeric material. This protection is
especially important when said electrically conductive
material is exposed to said electrolyte of PPC.
In another embodiment the pattern of the second
electrically conductive material is created by varying the
thickness of the first conducting material in such a way
that regions of the substrate where high optical
trarismittance is required (under or opposite the
photosensitive electrodes) are coated by the relatively
thin TEC (the first electrically conductive material),
whereas other regions of the substrates, where high
electrical conductance is required, are coated by a thick
electrically conductive material or (the second
electrically conductive material).
According to another aspect of the invention, small
holes are prepared either in the shared substrates or in
the common substrate. The holes are used for filling the
cells with said electrolyte. The holes are further sealed
with a polymeric material, preferably by the laminate that
comprises a hot melt polymeric material and a metal foil.
From yet a further aspect of the invention, at least one
isolated, region of the shared substrate is further
subdivided into electrically isolated subregions and the
opposing individual substrate is also divided into
electrically isolated subregions, with each said PPC being
formed between parts of two opposing subregions (one on
the shared substrate and another on the indvidual
substrate) and said adjacent PPC are electrically
interconnected in series by an interconnecting material.
To enable connections of cells in series, the
interconnecting material is placed between a separate part
of the sub region adjacent to the photosensitive
electrode of n-th said PPC and a separate part of the sub
region adjacent to said counterlectrode of (n+l)-th PPC.
In one embodiment the interconnecting material
comprises metallic particles, and/or graphite flakes.
In another embodiment the said interconnecting
material comprises metal wire, wire braid or wire plait.
In yet another embodiment the said electrically
interconnecting material comprises metallic mesh.
In a further embodiment electrically conducting
components of the interconnecting material are protected
from electrolyte of PPC by impermeable electrically
insulating material, preferably - polymeric material, in
which said conducting components are embedded.
In the preferred embodiment said polymeric material
is hot .melt material.
In one process the insulating hot melt material is
melted and adhered to both substrates due to the heat
generated in metallic interconnecting material. The
invention provides for passing electrical current through
the interconnecting material in order to generate heat
sufficient for. melting and adhesion of the hot melt
material. In preferred process the heat is generated by an
inductive action of an electromagnetic field.
.. Specific attention is given to the spaces that formed
between the individual substrates when they attached to
the common substrate.
In one embodiment these spaces are filled with an
hermetic sealant.
In another embodiment humidity absorbing material
(e.g. - molecular sieves) is . placed in these spaces; to
ensure long term stability of the photoelectrochemical
devices.
In yet another embodiment these spaces are fully or
partially filled with a solvent of the same chemical
nature as that used for an electrolyte in the
photoelectrochemical cells. This is to minimise long term
degradation effects caused by the loss of solvent in the
cells.
BRIEF DESCRIPTION OF DRAWINGS
Having broadly portrayed the nature of the present
invention, embodiments thereof will now be described by
way of example and illustration only. In the following
description, reference will be made to the accompanying
drawings in which:
Figure 1 is a 3D diagrammatic representation of a PPP
formed in accordance with the first example of the
invention.
Figure 2 is an enlarged partial cross- section of a
Photoelectrochemical Photovoltaic Panel formed in
accordance with the first example of the invention.
.Figure 3 is an enlarged partial cross-sectional view
of a PPP formed in accordance with the second example of
the invention.
Figure 4 is a partial plan representation of a PPP
formed in accordance with the second example of the
invention.
Figure 5 is a 3D diagrammatic representation of the
flexible shared substrate of PPP formed in accordance with
the third example of the invention.
Figure 6 is a 3D diagrammatic representation of the
flexible PPP formed in accordance with the third example
of the invention.
DBTAJLBD DESCRIPTION OF DRAWINGS
With reference to Figure 1, a 3D diagrammatic representation
of a PPP is shown. Itae panel comprises twelve individual
substrates l and a shared substrate i. The substrates are
coated by TEC (fluorine doped tin oxide) layer 3. The
electrically isolated regions of the transparent electrical
conductor 3 are formed by removing said conductor along the
isolation lines 4. This procedure utilizes laser radiation
and can be applied to all the substrates; 3D representation
in Pig. 1 allows visualisation of these lines only on the
shared substrate. The PPC are 'formed between parts of the
isolated regions 5 of the common substrate and opposing
isolated regions of the isolated substrate. The PPC are
interconnected to form 2 terminal power output of the PPP.
The terminals are created by depositing Ag bus-bars 6. Also
shown a plane A, cross-sectional representation in which is
shown in Figure 2.
With reference to figure 2, cross section that includes three
individual glass substrates is shown. The shared substrate 1
(also-glass) and the individual substrates 2 are coated by
TJSC layer 3. The electrically isolated regions are formed byremoving
TEC material along the lines 4. Counter electrodes
7 (ultra-thin layer of Pt based catalyst) is formed on parts
of the electrically isolated regions of the individual
substrates 2, using standard screen-printing technique. .
Photosensitized electrodes 8 are formed on parts of the
isolated regions
3a of the shared substrate 2. The photosensitized, electrodes
B comprise nano-particulate layer of titanium dioxide (15
microns thick) photosensitized by Ru-based dye. Formation
(by screen-printing followed by firing) and
photosensitization of the nano-particulate layer of titanium
dioxide was performed in accordance with standard procedures
well known in the prior art. The PPC were interconnected by
interconnecting material 9 that comprises W particles
embedded into silicons based matrix and filled by redox
electrolyte 10 through small filling holes in the shared
substrate (not shown)„ External negative and positive
terminals 6 are created by application of Ag bus-bars.
With reference to Fig. 3, cross-sectional representation of
the second example depicts only one individual substrate 2.
All the numbered elements in this figure are as per Fig. 1
and Fig. 2. This example is different from the first example
of the invention in that the photosensitized electrodes here
are formed on. the individual substrates and counter
electrodes - on the common substrate.
With reference to Figure 4 a partial' planar view of a PPP
depicting only 1 individual substrate is presented.
Additionally, sealing material 11 and filling holes 12 are
shown. The holes were used for'vacuum back filling of the
cells with an electrolyte.
With reference to Figure 5 a shared flexible substrate 1 ia
prepared in accordance with third example of the invention.
The substrate comprises plastic sheet coated by transparent
electronic conductor 3. The transparent
Electronic conductor 3 is divided into four electrically
isolated regions by the isolation lines 4. To enhance
electrical conductor of TEG material and to provide for
electrical connection four Ag bus-bars 6 are -deposited onto
the TEC as shown in the figure. On parts of three (out of
four) isolated regions of the shared substrate the circularly
shaped counter electrodes 7 are formed such as 8 equally
spaced counter electrodes belong to each of the three
isolated regions. This will provide for 8 PPC in each
isolated region of the shared substrate that will be
connected in parallel. Three groups of 8 PPC will be
connected in series as further demonstrated in Figure 6.
With reference to Figure 6 a flexible PPP is prepared in
accordance with the third example of the invention. The
patent utilizes pre-prepared shared substrate (shown in
details, in Fig. 5) and 24 individual substrates 2. Each
individual substrate comprises Ti foil, on which a
photosensitized electrode IB formed. The individual
substrates sealed with the shard substrate in such a way that
the photosensitive electrodes of the individual substrates
oppose counter electrodes of the shared substrates. The 24
PPC aire formed by filling spaces between the photosensitized
electrodes and opposing counter electrodes with a redox
electrolyte. The cells are connected in parallel in groups
of three by external electrical connectors 13 and in series
(in groups of 3) by electrical jumps 14. The positive and
negative electrical terminal of the PPP are also shown.

1. A photoelectrochemical Photovoltaic Panel (PPP)
comprising a number of individual substrates and a shared
substrate (the substrates), wherein
• the substrates are electrical conductors or at least
partially coated by an electrically conducting material/
at least one substrate is substantially transparent to
at least a part of solar radiation (optically
transparent),
• at least two of the individual substrates are provided
on a comifloia surface of the shared substrate,
• Photoelectrochemical Photovoltaic Cells (PPC), each
comprising a photosensitive electrode, a counter
electrode and an electrolyte dispensed between the
photosensitive electrode and the counter electrode are
formed between the shared substrate and the individual
substrates.
2. A PPP according to claim 1, wherein at least one
substrate cotrqpriaes optically transparent material coated
by a Transparent Electrical conductor (TEC).
3. A PPP according to claim 2, wherein said optically
transparent material comprise glass or plastic.
4. A PPP according to claim 2 and claim 3, wherein said TEC
•comprises fluorirxe doped tin oxide, indium tin oxide or
metallic mesh.
5. A PPP according to claim 1, wherein all the substrates
are optically transparent.
6. A PPP according to claim 1, wherein the shared substrate
comprises metal sheet or foil and all the individual
substrates are optically transparent.
7. A PPP according to claim 1, wherein the individual
substrates comprise metal sheet or foil and the shared
substrate is optically transparent,
8. A PPP in accordance with claim 1, wherein said
photosensitive electrode comprises nano-particulate wide
band semiconductor (for exainple - titanium dioxide),
photosensitised by a thin layer of dye and electrically
connected to one of the substrates or its electrically
conducting material.
9- A PPP in accordance with claim T, wherein said
photosensitive electrodes of PPC are supported by the
shared substrate.
10. A PPP in accordance with claim 1, wherein at least a pert
of said photosensitive electrodes of PPC are supported by
the shared substrate and photosensitive electrodes of
remaining PPC are supported by the individual substrates.
11. A PPP in accordance with claim 1,. wherein said shared
substrate is of rectangular shape.
12. A PPP in accordance with claim 1, wherein said individual
substrates are of rectangular or circular shape.
13. A PPP in accordance with claim 1, wherein, the shared
substrate is divided into electrically isolated regions;
each region opposes at least one adjacent individual
substrate and the PPC are formed between the individual
substrate and the opposing isolated region of the shared
substrate.
14. A PPP in accordance with any one of claim 13, claim * or
claim 7, wherein the shared substrate is made of
polymeric material coated by TEC and all the individual
substrates comprise metallic foil, wherein said
photosensitive electrodes of said PPC are formed on.
15. A Photoelectrochemical Photovoltaic Panel
(PPP) substantially as herein described with
reference to the accompanying drawings.