The following specification particularly describes the nature of the invention and the manner in which it is to be performed
The present invention relates to an improved Solid-State Polymer composition, a process for its preparation and an.improved Dye-sensitized Solar Cell. The invention more particularly relates to a Solid-State Polymer composition containing Azino-bis- (3-ethyl benzo thiazoline-6-sulphonate) ion [ABTS] as dopant. Polyethylene oxide (PEO) and iodine/iodide redox couple. The performance of the Dye-sensitized Solar Cell has been observed to be very high.
Introduction
Solar power has a great potential as a source of renewable energy, and hence intense research activity takes place in this field. In photoelectrochemical (PEC) solar cells, light energy may be converted into electrical energy. In 1991, O' Regan and Gratzel presented an efficient dye sensitized (PEC) cell containing highly porous nanocrystalline titanium dioxide electrode, sensitized with a monolayer of a ruthenium complex wherein these modules contain organic electrolytes with dissolved iodine/iodide as redox couple. These nanocrystalline dye-sensitized solar cells (nc-DSSCs), also known as "Gratzel cells" exhibited current conversion efficiency of over 10% [B. O' Regan and Gratzel, Nature 353 (1991) 737]. These devices utilize an iodine-iodide redox mediator dissolved in acetonitrile to transport holes. For long-term operation, the usage of liquid electrolytes containing organic solvents is sensitive to negative stability effects like evaporation and decomposition due to atmosphere [Peng Wang et al, Chem. Commun,, (2002)2972].
Operative principle of the dye-sensitized solar cells
The operating principle of the DSSC is shown in Fig.l of the drawing accompanying this specification. . At the heart of the system is a mesoporous oxide layer composed of nanometer-sized particles, which have been sintered together to allow for electronic conduction to take place (2). The material of choice has been Ti02 (anatase) (1) although alternative wide band gap oxides such as ZnO and Nb205 have also been investigated. Attached to the surface of the nanocrystalline film is a monolayer of the charge transfer dye (3). Photoexcitation of the latter results in the injection of an electron

into the conduction band of the oxide. The original state of the dye is subsequently restored by electron donation from the electrolyte, usually an organic solvent containing redox system (4), such as the iodine/iodide couple. The regeneration of the sensitizer by iodide intercepts the recapture of the conduction band electron by the oxidized dye. The iodide is regenerated in turn by the reduction of triiodide at the counter electrode (5) the circuit being completed via electron migration through external load. The voltage generated under illumination corresponds to the difference between the Fermi level of the electron in the solid and the redox potential of the electrolyte. Overall the device generates electric power from light without suffering any permanent chemical transformation.
The best photovoltaic performance both in terms of conversion yield and long-term stability has so far been achieved with polypyridyl complexes of ruthenium. Sensitizers having the general structure ML2(X)2, where L stands for 2,2' -bipyridyl -4,4' -dicarboxylic acid M is Ru and X represents a halide, cyanide, thiocyanate, acetyl acetonate, thiacarbamate or water substituent, are particularly promising. Thus, the ruthenium complex cis-RuL2(NCS)25 known as N3 dye, has become paradigm of heterogeneous charge transfer sensitizer for mesoporous solar cells [Nazeeruddin et al, 1 Am. Chem, Soc, 115 (1993) 6382],
It would be observed from the above, that the major disadvantage for using iodine/iodide liquid electrolyte lies in the long-term operation process, since the usage of liquid electrolytes containing organic solvents would have poor long-term stability due to leakage of electrolyte and sublimation of Iodine, [Kay. A, Gratzel, M, Sol. Energy, Mater. Sol. Cells, 44 (1996) 99].
Several attempts have been made to find a suitable substitute for the liquid electrolytes by introducing p-type inorganic semiconductors, organic hole-conductors etc. A number of solutions have been proposed to solve this problem. They are given as follows:
The Dye-sensitized solar cells or Gratzel cells have low cost raw materials and high efficiency to convert solar energy. These cells achieve about 11 % solar power efficiencies. These cells employ a liquid electrolyte (iodine/iodide redox couple dissolved in an organic solvent). While selecting the electrolyte in a DSSC, it is worthwhile to

consider the sealing that is necessary to prevent the loss of the liquid electrolyte by leakage and / or evaporation of the solvent. Thus, the presence of organic liquid electrolytes in such cells may result in some practical limitations with sealing and long-term operation. [B. O'Regan and Gratzel, Nature 353 (1991) 737, P. Wang et al., Chem, Commun., (2002) 2972, Kubo, W, et al., J. Phys. Chem, B, 105 (2001) 12809, A, F. Nogueira et al.. Coord Chem, Rev. 248 (2004) 1455]. The efficiency of the cell also has to be improved apart from the high temperature performance.
In order to overcome the above mentioned defects, solid-state hole conductors have been incorporated in the form of molecular and polymeric hole conductors in DSSCs including polypyrrole [K. Murakoshi et al., Chem. Lett, (1997) 471], copper salts such as Cul and CuSCN [K. Tennakone et al., Semicond. SclTechnol. 11 (1996) 1737, B. O' Reagan et al.. Adv. Mater, 12 (2000) 1263] and the amorphous organic hole conductor 2,2',7,7' - tetrakis (N,N-di"p-methoxyphenyl-amine) 9,9'- spirobifluorene [U. Bach et al.. Nature 395 (1998) 583]. Hov^ever, device efficiencies with such materials remained relatively low in all these cases (< 1. 5 %).
An alternative approach to electronic hole conductors is the use of polymer gel electrolytes. In this case, plasticizers are used as additives during the preparation of the electrolyte in order to increase chain mobility and the ionic conductivity of the electrolyte. Furthermore, these efforts led to the development of "quasi-solid-state" dye-sensitized cells having energy conversion efficiencies similar to that of liquid electrolytes. However, in this also the sealing of such cells remains a problem. [A.F, Nogueira et al.. Adv. Mater, 13, No.l 1, (2001) 826].
A modified quasi-solid electrolyte system involved using 3-methoxypropionitrile based liquid electrolyte having l-methyl-3-propylimidazolium iodide as the iodide resource. These new quasi-solid electrolyte were used in regenerative photoelectrochemical cells that yielded about 6.7 % efficiency under simulated full sunlight. Though such a fabricated device showed a good thermal stability for 30 days, the efficiency was less compared to that of liquid electrolyte cells [P. Wang et al., J. Flourine Chem. 125 (2004) 1241],

The use of polymer electrolytes without addition of any polymeric agent or plasticizer in such dye-sensitized photovoltaic cells is known to exploit both the efficiency advantage of ionic conduction employed in the case of liquid electrolyte devices and the stability advantage of an all-solid-state device having no volatile components.
The major advantage of replacing liquid junction with polymer electrolyte is that the ionic conducting polymers incorporating the redox couple can easily penetrate into the porous network by solution casting technique and show good wet-ability with the nano-structured electrode. Desirable effects like high electrical conductivity, non-volatility, good ionic mobility and electrochemical stability make them preferable to organic solvent-based electrolytes.
In the present invention, we demonstrate for the first time the use of Iodine-ABTS [Azino-bis- (3-ethyl benzo thia2oline-6-sulphonate)] ion in a polymer composition which forms a charge transfer complex and hence useful as an electrolyte for device fabrication
thus yielding an appreciably high efficiency.
Accordingly, the main objective of the present invention is to provide an improved solid-state polymer composition useful as an efficient electrolyte for dye-sensitized, photoelectrochemical solar cells having very high conversion efficiency.
According to another objective of the present invention is to provide a process for the preparation of an improved solid-state polymer composition useful as electrolyte for dye-sensitized, photoelectrochemical solar cells having high conversion efficiency.
According to yet another objective of the present invention is also to provide an improved dye-sensitized solar cell having high performance.
The above objectives have been achieved by us by fabricating a suitable dye-sensitized solar cell with charge transfer complex reaction mechanism in an appropriate solid polymer composition. In the context of development of new cathode material for all-solid-state electrochemical power sources in general and silver-anode solid-state-batteries in particular, our earlier study dealt with the use of iodine -

2, 2'Azino-bis-(3-ethylbenzothiazoline-6"Sulphonate) ion [ABTS] as cathode in a silver-iodine cell based on Ag6l4W04 as a stable silver ion conducting solid electrolyte [Maruthamuthu et aL, Bull Chem. Soc. Jpn. 60 (1987) 1113 and Austin et al., Bull Mater. Sci. 12, No. 2 (1989) 147].
The above findings paved the way, to use the iodine-ABTS mixture for preparing the polymer composition of the present invention. The molecular iodine (I2) forms a charge transfer complex with ABTS; thereby the problems of sealing and the stability of the liquid electrolyte encountered in DSSCs have been over come to a greater extent.
Accordingly, the present invention provides an improved solid-state polymer composition useful as an efficient electrolyte for dye-sensitized, photoelectrochemical solar cells which comprises Azino-bis-(3-ethyl benzo thiazoline-6-sulphonate) ion [ABTS], as a dopant, along with Polyethylene oxide (PEO) and iodine/iodide redox couple.
According to another embodiment of the present invention there is provided an improved solid-state polymer composition useful as an efficient electrolyte for dye-sensitized, photoelectrochemical solar cells, which comprises Azino-bis- (3-ethyl benzo thiazoline-6-sulphonate) ion [ABTS], as a dopant, in an amount in the range of 0. 026 to 0.104 % by weight. Iodine in the range of 0.012 to 0.06 % by weight, KI 0.12 % by weight and Polyethylene oxide (PEO) 0.8 to 1.2 % by weight.
According to yet another embodiment of the present invention there is provided a process for the preparation of the improved solid-state polymer composition useful as an efficient electrolyte for dye-sensitized, photoelectrochemical solar cells which comprises mixing appropriate amounts of Azino-bis-(3-ethyl benzo thiazoline-6-sulphonate) ion [ABTS], as a dopant, Polyethylene oxide (PEO) and iodine/iodide redox couple using a polar solvent having boiling point in the temperature range greater than 85 °C, heating the resulting mixture in the temperature in range of 80 - 85°C for a period in the range of 2 to 3 hrs and cooling the resulting solution to room temperature.

The amount of Azino-bis- (3-ethyl benzo thiazoline-6-sulphonate) ion [ABTS] as dopant used may be in the range of 0.026 to 0.104 % by weight preferably in the range of 0.052 to 0.104 % by weight and more preferably in the range of 0.078 % by weight.
The amounts of Polyethylene oxide (PEO) of 1.2 % by weight and KI 0.12 % by weights were taken as reported earlier [A.F. Nogueira et al., Adv. Mater. 13, No.ll, (2001)826].
The amount of iodine used may be in the range of 0.012 to 0.06 % by weight preferably in the range of 0.036 to 0.06 % by weight and more preferably in the range of 0.048 % by weight.
This electrolyte can also be prepared in different compositions by varying the concentrations of I2 and ABTS like 0.012 to 0.06 % by weight of Iodine and 0.026 to 0,104 % by weight of ABTS. With the above concentrations, different electrolytes were prepared and studied. The polymer compositions were dried by solution casting technique and used for characterization studies.
According to still another objective of the present invention there is provided an improved dye-sensitized solar cell which consists of an anode comprising a dye adsorbed Ti02 nanoparticles coated on FTO (fluorine doped tin oxide [F: SnO2]) conducting glass having a coating of a solid-state polymer composition containing Azino-bis-(3-ethyl benzo thiazoline-6-sulphonate) ion [ABTS], as a dopant along with Polyethylene oxide (PEO) and iodine/iodide redox couple, the cathode being FTO (fluorine doped tin oxide [F: Sn02]) conducting glass coated with platinum or carbon and placed over the anode in such a way that the polymer composition is sandwiched between the two electrodes and held tightly together by means of alligator clips.
In a preferred embodiment of the present invention there is provided an improved dye-sensitized solar cell which consists of an anode comprising a dye adsorbed Ti02 nanoparticles coated on FTO (fluorine doped tin oxide [F: Sn02]) conducting glass having a coating of a solid-state polymer composition containing Azino-bis-(3-ethyl benzo thiazoline-6-sulphonate) ion [ABTS], as a dopant, in an amount in the range of 0. 026 to 0.104 % by weight, Iodine in the range of 0.012 to 0.06 % by weight, Kl 0.12 %

by weight and Polyethylene oxide (PEO) in the range of 0,8 to 1.2 % by weight, the cathode being FTO (fluorine doped tin oxide [F: Sn02]) conducting glass coated with platinum or carbon and placed over the anode in such a way that the polymer composition is sandwiched between the two electrodes and held tightly together by means of alligator clips.
In another embodiment of the present invention there is provided an improved dye-sensitized solar cell which consists of an anode comprising a dye adsorbed Ti02 nanoparticles coated on FTO (fluorine doped tin oxide [F: Sn02]) conducting glass having a coating of a solid-state polymer composition containing Azino-biS-(3-ethyl benzo thiazoline-6-sulphonate) ion [ABTS], as a dopant, in an amount of 1.2 % by weight of Polyethylene oxide, 0.12 % by weight of KI, 0.048 % by weight of Iodine and 0.078 % by weight of ABTS , the cathode being FTO (fluorine doped tin oxide [F: SnO2) conducting glass coated with platinum or carbon and placed over the anode in such a way that the polymer composition is sandwiched between the two electrodes and held tightly together by means of alligator clips.
The details of the invention are presented in the Examples given below which are given to illustrate the invention only and therefore should not be construed to limit the scope of the invention.
Preparation of the polymer compositions
Materials and Methods
Polyethylene oxide and ABTS were purchased from Aldrich. Iodine, KI and Dimethyl Formamide (DMF) were used as received from Merck. Nanoporous TiOs [P 25, Degussa] semiconductor thin films on FTO (fluorine doped tin oxide [F: Sn02]) conducting glasses of sheet resistance 10 Q/sq. cm [BHEL, India]) were prepared using previously reported procedure [Sirimanne et al, J, Sol Chem. 66 (2003) 142]. These thin films were coated with N3 dye [(cis-dithiocyanato)-N, N'- bis(2,2'-bipyridyl -4,4'-dicarboxylic acid)-ruthenium(II) dihydrate)] as reported in the literature [Nazeeruddin et al, 1993 J. Am. Chem. Soc, 115 (1993) 6382].

Example 1
The polymer composition was prepared by dissolving 1.2 % by weight of PEO, 0.12 % by weight of KI, 0.012 % by weight of I2 and 0.026 % by weight of ABTS in 25 mL of DMF by heating at a temperature of 80 °C. After heating for a period of two and a half hours, it was cooled to room temperature.
Example 2
Another composition was prepared by dissolving 1.2 % by weight of PEO, 0.12 % by weight of KI, 0.012 % by weight of I2 and 0.052 % by weight of ABTS in 25 mL of DMF by heating at a temperature of 80 °C. After heating for a period of two and a half hours, it was cooled to room temperature.
Example 3
Another composition was prepared by dissolving L2 % by weight of PEO, 0.12 % by weight of KI, 0.024 % by weight of I2 and 0.026 % by weight of ABTS in 25 mL of DMF by heating at a temperature of 80 °C. After heating for a period of two and a half hours, it was cooled to room temperature.
Example 4
Another composition was prepared by dissolving 1.2 % by weight of PEO, 0.12 % by weight of KI, 0.036 % by weight of I2 and 0.052 % by weight of ABTS in 25 mL of DMF by heating at a temperature of 80 °C. After heating for a period of two and a half hours, it was cooled to room temperature.
Example 5
Another composition was prepared by dissolving L2 % by weight of PEO, 0,12 % by weight of KI, 0.048 % by weight of I2 and 0.078 % by weight of ABTS in 25 mL of DMF by heating at a temperature of 80 °C. After heating for a period of two and a half hours, it was cooled to room temperature.

Example 6
Another composition was prepared by dissolving 1.2 % by weight of PEO, 0J2 % by weight of KI, 0.036 % by weight of I2 and 0.104 % by weight of ABTS in 25 mL of DMF by heating at a temperature of 80 °C. After heating for a period of two and a half hours, it was cooled to room temperature.
Example 7
Another composition was prepared by dissolving 1.2 % by weight of PEO, 0.12 % by weight of KI, 0.06 % by weight of I2 and 0.078 % by weight of ABTS in 25 mL of DMF by heating at a temperature of 80 °C. After heating for a period of two and a half hours, it was cooled to room temperature.
Characterization
The more preferable polymer composition of Example 5 has been investigated using the following characterizations techniques. The FT-IR spectra of the polymer composition prepared in the case of Example 5 were recorded using a Perkin-Elmer RXl spectrophotometer and the XRD patterns were studied using a Siefert Model SF 60 X-ray diffraction system with Cu-Ka1 radiation. A Hewlett-Packard Precision LCR meter 4284A model was employed to measure the conductivities of the samples at room temperature over the frequency range of 20Hz to 1 MHz. The micrographs were taken by using a Jeol-JSM 6362 model high resolution Scanning Electron Microscope (SEM).

Fabrication of the photoelectrochemical cell employing Platinum cathode
Example 8
For the fabrication of solar cell according to the present invention, the dye adsorbed TiO2 nanoparticles coated on the FTO [F: Sn02] conducting glasses were used as anode and the platinum coated FTO [coated by sputtering technique] as photocathode respectively. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 1 (500 µL) was cast and evaporated to dryness. This was placed on the face of the platinum coated FTO glass (photocathode) in such a way that the polymer composition was sandwiched between the two electrodes (2 x 2 cm ) and held tightly together by means of alligator clips.
Example 9
For the fabrication of another solar cell according to the present invention, the dye adsorbed Ti02 nanoparticles coated on the FTO [F: Sn02] conducting glasses were used as anode and the platinum coated FTO [coated by sputtering technique] as photocathode respectively. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 2 (500 µL) was cast and evaporated to dryness. This was placed on the face of the platinum coated FTO glass (photocathode) in such a way that the polymer composition was sandwiched between the two electrodes (2 x 2 cm ) and held tightly together by means of alligator clips.
Example 10
For the fabrication of yet another solar cell according to the present invention, the dye adsorbed Ti02 nanoparticles coated on the FTO [F: Sn02] conducting glasses were used as anode and the platinum coated FTO [coated by sputtering technique] as photocathode respectively. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 3 (500 µL) was cast and evaporated to dryness. This was placed on the face of the platinum coated FTO glass (photocathode) in such a way that the polymer composition was sandwiched between the two electrodes (2x2 cm^) and held tightly together by means of alligator clips.

Example 11
For the fabrication of still another solar cell according to the present invention the dye adsorbed TiOi nanoparticles coated on the FTO [F: Sn02] conducting glasses were used as anode and the platinum, coated FTO [coated by sputtering technique] as photocathode respectively. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 4 (500 µL) was cast and evaporated to dryness. This was placed on the face of the platinum coated FTO glass (photocathode) in such a way that the polymer composition was sandwiched between the two electrodes (2x2 cm ) and held tightly together by means of alligator clips.
Example 12
For the fabrication of yet another solar cell according to the present invention, the dye adsorbed Ti02 nanoparticles coated on the FTO [F: Sn02] conducting glasses were used as anode and the platinum coated FTO [coated by sputtering technique] as photocathode respectively. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 5 (500 µL) was cast and evaporated to dryness. This was placed on the face of the platinum coated FTO glass (photocathode) in such a way that the polymer composition was sandwiched between the two electrodes (2 X 2 cm ) and was held tightly together by means of alligator clips.
Example 13
For the fabrication of still another solar cell according to the present invention, the dye adsorbed Ti02 nanoparticles coated on the FTO [F: Sn02] conducting glasses were used as anode and the platinum coated FTO [coated by sputtering technique] as photocathode respectively. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 6 (500 µL) was cast and evaporated to dryness. This was placed on the face of the platinum coated FTO glass (photocathode) in such a way that the polymer composition was sandwiched between the two electrodes (2x2 cm2) and held tightly together by means of alligator clips.

Example 14
For the fabrication of still another solar cell according to the present invention, the dye adsorbed Ti02 nanoparticles coated on the FTO [F: SnOi] conducting glasses were used as anode and the platinum coated FTO [coated by sputtering technique] as photocathode respectively. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 7 (500 |iL) was cast and evaporated to dryness. This was placed on the face of the platinum coated FTO glass (photocathode) by such a way that the polymer composition was sandwiched between the two electrodes (2x2 cm2) and held tightly together by means of alligator clips.
Fabrication of the photoelectrochemical cell employing Carbon cathode
A cell was also fabricated using carbon counter electrode. The dye adsorbed Ti02 nanoparticles coated on the FTO [F: Sn02] conducting glasses served as anode and the conducting carbon cement (Leit C, Neubauer Chemikalien) coated on FTO conducting glasses by doctor's blade technique was used as Carbon counter electrode. On the surface of this conducting glass (photoanode) the polymer composition solution of (500 µL) was cast and evaporated to dryness. This was placed on the face of the carbon coated FTO glass (photocathode) in such a way that the polymer composition was sandwiched between the two electrodes (2 x 2 cm ) and held tightly together by means of alligator clips.
Example 15
A cell was fabricated using carbon counter electrode. The dye adsorbed Ti02 nanoparticles coated on the FTO [F: Sn02] conducting glasses served as anode and the conducting carbon cement (Leit C, Neubauer Chemikalien) coated on FTO conducting glasses by doctor's blade technique was used as Carbon counter electrode. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 1 (500 |iL) was cast and evaporated to dryness. This was placed on the face of the carbon coated FTO glass (photocathode) in such a way that the polymer composition was sandwiched between the two electrodes (2 x 2 cm ) and held tightly together by means of alligator clips.

Example 16
Yet another cell was fabricated using carbon counter electrode. The dye adsorbed TiOa nanoparticles coated on the FTO [F: Sn02] conducting glasses served as anode and the conducting carbon cement (Leit C, Neubauer Chemikalien) coated on FTO conducting glasses by doctor's blade technique was used as Carbon counter electrode. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 2 (500 µL) was cast and evaporated to dryness. This was placed on the face of the carbon coated FTO glass (photocathode) in such a way that the polymer composition was sandwiched between the two electrodes (2x2 cm2) and held tightly together by means of alligator clips.
Example 17
Another cell was fabricated using carbon counter electrode. The dye adsorbed Ti02 nanoparticles coated on the FTO [F: SnO2] conducting glasses served as anode and the conducting carbon cement (Leit C, Neubauer Chemikalien) coated on FTO conducting glasses by doctor's blade technique was used as Carbon counter electrode. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 3 (500 [iL) was cast and evaporated to dryness. This was placed on the face of the carbon coated FTO glass (photocathode) in such a way that the polymer composition was sandwiched between the two electrodes (2 x 2 cm ) and held tightly together by means of alligator clips.
Example 18
Still another cell was fabricated using carbon counter electrode. The dye adsorbed TiO2 nanoparticles coated on the FTO [F: Sn02] conducting glasses served as anode and the conducting carbon cement (Leit C, Neubauer Chemikalien) were coated on FTO conducting glasses by doctor's blade technique was used as carbon counter electrode. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 4 (500 µL) was cast and evaporated to dryness. This was placed on the face of the carbon coated FTO glass (photocathode) in such a way that the polymer composition

was sandwiched between the two electrodes (2x2 cm ) and held tightly together by means of alligator clips.
Example 19
Another cell was fabricated, using carbon counter electrode. The dye adsorbed Ti02 nanoparticles coated on the FTO [F: SnOj] conducting glasses served as anode and the conducting carbon cement (Leit C, Neubauer Chemikalien) was coated on FTO conducting glasses by doctor's blade technique and were used as Carbon counter electrode. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 5 (500 µL) was cast and evaporated to dryness. This was placed on the face of the carbon coated FTO glass (photocathode) in such a way that the polymer composition was sandwiched between the two electrodes (2 x 2 cm ) and held tightly together by means of alligator clips.
Example 20
Still another cell was fabricated using carbon counter electrode. The dye adsorbed Ti02 nanoparticles coated on the FTO [F: Sn02] conducting glasses served as anode and the conducting carbon cement (Leit C, Neubauer Chemikalien) were coated on FTO conducting glasses by doctor's blade technique and was used as Carbon counter electrode. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 6 (500 µL) was cast and evaporated to dryness. This was placed on the face of the carbon coated FTO glass (photocathode) in such a way that the polymer composition was sandwiched between the two electrodes (2 x 2 cm ) and held tightly together by means of alligator clips.
Example 21
Another cell was fabricated using carbon counter electrode. The dye adsorbed Ti02 nanoparticles coated on the FTO [F: Sn02] conducting glasses served as anode and the conducting carbon cement (Leit C, Neubauer Chemikalien) were coated on FTO conducting glasses by doctor's blade technique and was used as Carbon counter electrode. On the surface of this conducting glass (photoanode) the polymer composition solution of Example 7 (500 µL) was cast and evaporated to dryness. This was placed on

the face of the carbon coated FTO glass (photocathode) in such a way that the polymer composition was sandwiched between the two electrodes (2 x 2 cm ) and held tightly together by means of alligator clips.
Photoelectrochemical measurements
The I-V characteristics of the solar cell fabricated with using the compositions described in Examples 1 to 7 employing both platinum and carbon cathodes have been measured in the dark and under illumination (area of 2 sq.cm with a tungsten halogen lamp [OSRAM, Germany] of intensity 172 mW/cm2 [EXTECH - 33, Light meter with memory] under AM 1.5 by masking the remaining area with Teflon) using a BAS lOOA electrochemical analyzer unit. The results are shown in the tables given below.



Results & Discussion
SEM studies
The high-resolution micrograph {SEM) picture of the solvent evaporated polymer composition of Example 5 is shown in Fig. 2 which showed uniformly distributed amorphous layers, as confirmed by XRD studies. Hence, the polymer composition when coated on Ti02 nanoparticles fits well into these pores that in turn form interconnected cavities where the polymeric composition acting as electrolyte is likely to flow freely as in the case of pure liquid phase, thus enhancing the electrical conduction.
It would be observed from the table given above that the more preferable solid polymer composition is of Example 5 as shown in Fig. 3. Though polymer solution was not expected to penetrate deeply into the Ti02 film due to its high molecular mass, it was found to spread uniformly on the dye surface.

Conductivity measurements
The room temperature electrical conductivity (a) of the more preferable polymer composition of Example 5 was examined and found to be of the order of 2.71 X 10-6 S cm-1. It provides information on the mobility of ions, their interaction with the solvent and on ion pairing phenomena, which are expected to affect the photovoltaic performance and in particular the fill factor (ff) of DSSCs as shown in Fig. 4. The enhanced conductivity of the polymer composition as compared to that of the bare PEO membrane accounts for the observed high photocurrent and hence higher efficiency of the cell.
FT-IR Spectroscopy
The IR spectrum of the more preferable polymer composition of Example 5 showed the characteristic peaks of PEO as shown in Fig. 5. The absorption peak appearing weak at 1508 cm-1 is due to N=N stretching, whereas those bands at 1618 and 1581 cm-1 are due to the presence of benzene rings. The peak at 1570 cm-1 may be assigned to S-C-N. The frequency at 1104 cm-1 is assigned to SOB" groups. The peaks at 651 cm"* and 582 cm"* are due to the presence of disubstituted benzene rings. The bands at 2159 and 2234 cm"* belong to NCN-, SCN stretching vibrations. The peaks at 2956 and 2883 cm"* are due to -CH3 and -CH2 groups respectively. Therefore, these resuhs appear to confirm the presence of polyethylene oxide and ABTS in the polymer composition of Example 5.
XRD Diffraction analysis
The sharp intensity peaks of pure PEO are observed at scanning angles of 20 = 19.4 ° and 23,4 °. In addition, several other low intensity peaks corresponding to other phases of crystalline PEO are also observed, whereas the typical XRD pattern shows the presence of amorphous polyethylene oxide in the more preferable polymer composition Example 5.
On comparison with pure polyethylene oxide polymer, the XRD pattern corresponding to the polymer composition of Example 5 was found to exhibit an almost

peak free nature thus indicating the amorphous nature of the system as shown in Fig. 6. While the sharp intensity peaks at 2G = 19.4 ° and 23.4 "" appear with relatively low intensities all other low intensity peaks corresponding to pure PEO are absent in the case of the doped polymer system. This feature indicates that the degree of crystallinity decreases as a result of doping. The conductivity of the polymer composition of the more preferable composition of Example 5 increases by three orders, as confirmed by conductivity measurements and this is complemented by the amorphous nature of the polymer composition too. Thus, the XRD results have clearly shown that the polymer composition serves as an efficient electrolyte in order to enhance the performance of the solar cell.
Photoelectrochemical measurements
The current-voltage curve obtained under illumination for the DSSC fabricated using platinum electrode with the more preferable polymer composition of Example 5 investigated in this study is shown in Fig. 7, which exhibits a short circuit current density (Isc) of 14.54 mA/cm2, open circuit potential (Voc) of 672 mV with a fill-factor (ff) of 0.4 under irradiation, corresponds to an over-all conversion efficiency of 11.4 %, the highest in its kind. The short circuit current and open circuit potential values of the cells fabricated using Examples 1 to 7 are given in Table - 1 and their performance curves are shown in Fig, 8.
When the above cell was fabricated with carbon counter electrode it exhibited a short circuit current density (Isc) of 7.1 mA/cm and an open circuit potential (VQC) of 464 mV only. The performance characteristics of the other DSSCs fabricated using Examples 1 to 7 employing carbon electrodes are presented in Table - 2 and their current-voltage curves are shown in Fig. 9. The electron concentration in TiOa governs both the magnitude of the current and the position of the Fermi level or potential of Ti02. A higher Voc implies a larger electron concentration in TiO2, which in turn leads to a higher I3" concentration in solution. The poor ff may be due to the depletion of li concentration at the Pt cathode. The low 13" concentration at the Pt cathode increases the over-potential for reduction at the electrode. The current-induced shift of the redox potential at the Pt cathode may also decrease ff.

The result of the cell fabricated using the more preferable composition of Example 5 is significant because the use of solid-state polymer composition is found to overcome the major draw back of the liquid electrolyte (iodine/iodide redox couple in organic solvent) as the rate of evaporation is much less comparatively. Furthermore, the stability problem for long-term operation has also been overcome in view of the fact that I2 forms a charge transfer complex with ABTS that prevents the leakage of iodine to a greater extent.

The foresaid reactions would have effectively taken place between the dye and the charge transfer complex formed between ABTS and iodine in the polymer composition, thus, preventing the leakage of iodine and resulting in enhanced performance of the dye-sensitized solar cell
From the above results, we infer that I2 forms an effective charge transfer complex with ABTS that prevents considerably the loss of molecular iodine thereby increasing the stability comparatively. In addition, high charge separation created within the polymer avoids further electron-hole recombination. Thus, the stability of the fabricated dye-sensitized solar cell is enhanced and ultimately the over-all conversion efficiency (r\).

The maiden use of a polymer in conjunction with a charge transfer complex was found to result in stable device performance under 50 °C thermal stresses maintaining about 70 % of its initial value in the direct atmosphere with the raw fabricated dye-sensitized solar cell without sealing.
It would be observed that for the first time a charge transfer complex in doped solid polymer electrolyte in nanocrystalline dye-sensitized solar cell has been developed and the solid-state polymer electrolyte has been employed successfully in regenerative photoelectrochemical cells that yielded about 11.4 % over all power conversion efficiency in combination with the ruthenium polypyridyl photosensitizer.
Advantages of the invention:
1. An all-time high over-all conversion efficiency of 11.4 % has been recorded, for the dye-sensitized cell fabricated with platinum electrode using the polymer composition of the present invention , the highest in its kind of using polymer composition.
2. The sublimation of the iodine/iodide redox couple has been prevented thereby the sealing problems of the dye-sensitized solar cells have been overcome to a considerable extent.
3. Possibility to fabricate a more efficient, flexible, compact, reduced leakage effect and stable all solid-state dye-sensitized solar cells.
4. The cell of the present invention is attractive because of its efficiency and also
it is free from leakage.

We claim,
1. An improved solid state polymer composition useful as an efficient electrolyte for dye-sensitized, photoelectrochemical solar cells which comprises Azino-biS"(3-ethyl benzo thia2oUne-6-sulphonate) ion [ABTS], as a dopant, along with Polyethylene oxide (PEO) and iodine/iodide redox couple.
2. An improved solid-state polymer composition useful as claimed in Claim 1 wherein the amount of Azino-bis- (3-ethyl benzo thiazoline-6-sulphonate) ion [ABTS], as a dopant, is in the range of 0.026 to 0.104 % by weight, the amount of Iodine is in the range of 0.012 to 0.06 % by weight, the amount of KI is 0.12 % by weight and the amount of Polyethylene oxide (PEO) is \2 % by weight.
3. A process for the preparation of the improved solid-state polymer composition useful as an efficient electrolyte for dye-sensitized, photoelectrochemical solar cells which comprises mixing appropriate amounts of Azino-bis-(3-ethyl benzo thiazoline-6-sulphonate) ion [ABTS], as a dopant, Polyethylene oxide (PEO) and iodine/iodide redox couple using a polar solvent having boiling point in the temperature range greater than 85 ''C, heating the resulting mixture in the temperature in range of 80 - 85 °C for a period in the range of 2 to 3 hrs and cooling the resulting solution to room temperature.
4. A process as claimed in Claim 3 wherein the amount of Azino-bis- (3-ethyl benzo thiazoline-6-sulphonate) ion [ABTS] used is in the range of 0.026 to 0.104 % by weight preferably in the range of 0,052 to 0.104 % by weight and more preferably in the range of 0.078 % by weight, the amount of iodine used is in the range of 0.012 to 0.06 % by weight preferably in the range of 0,036 to 0.06 % by weight and more preferably in the range of 0.048 % by weight.
5. An improved dye-sensitized solar cell which comprises an anode comprising of a dye adsorbed Ti02 nanoparticles coated on FTO (fluorine doped tin oxide [F: SnO2]) conducting glass having a coating of a solid-state polymer composition comprising Azino-bis-(3-ethyl benzo thiazoline-6-sulphonate) ion [ABTS], as a dopant, along with Polyethylene oxide (PEO) and iodine/iodide redox couple, the cathode being FTO (fluorine doped tin oxide [F: Sn02]) conducting glass coated with platinum or carbon the cathode being placed over the anode in such a way that the polymer

composition is sandwiched between the two electrodes and held tightly together by means of alligator clips.
6. An improved dye-sensitized solar cell as claimed in Claim 5 wherein the
amount of Azino-bis-(3-ethyl benzo thiazoline-6-sulphonate) ion [ABTS] is in the range
of 0. 026 to 0.104 % by weight, Iodine in the range of 0.012 to 0.06 % by weight, KI
0.12 % by weight and Polyethylene oxide (PEO) in the range of 0.8 to 1.2 % by weight.
7. An improved dye-sensitized solar cell as claimed in Claim 6 wherein the
amount of Polyethylene oxide is 1.2 % by weight, KI 0.12 % by weight. Iodine
0.048 % by weight and 0.078 % by weight of Azino-bis-(3-ethyl benzo thiazoline-6-
sulphonate) ion [ABTS].
8. An improved solid-state polymer composition substantially as herein described
with reference to the Examples 1 to 7,
9. A process for preparing improved solid-state polymer composition substantially
as herein described.