DYE SENSITIZED PHOTOVOLTAIC CELLS

Abstract

Provided herein are improvements to dye-sensitized photovoltaic cells that enhance the ability of those cells to operate in normal room lighting conditions. These improvements include printable, non-corrosive, nonporous hole blocking layer formulations that improve the performance of dye-sensitized photovoltaic cells under 1 sun and indoor light irradiation conditions. Also provided herein are highly stable electrolyte formulations for use in dye-sensitized photovoltaic cells. These electrolytes use high boiling solvents, and provide unexpectedly superior results compared to prior art acetonitrile-based electrolytes. Also provided herein are chemically polymerizable formulations for depositing thin composite catalytic layers for redox electrolyte-based dye-sensitized photovoltaic cells. The formulations allow R2R printing (involves coating, fast chemical polymerization, rinsing of catalytic materials with methanol) composite catalyst layers on the cathode. In situ chemical polymerization process forms very uniform thin films, which is essential for achieving uniform performance from every cell in serially connected photovoltaic module.

Claims

1-28. (canceled)

29. A dye-sensitized photovoltaic cell comprising: a cathode: an electrolyte; a porous dye-sensitized titanium dioxide film layer; and an anode; wherein the electrolyte comprises two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary/tertiary/quaternary mixtures of these solvents.

30. The dye-sensitized photovoltaic cell of claim 29, wherein the electrolyte comprises at least 50% sulfolane or dialkyl sulfone.

31. The dye-sensitized photovoltaic cell of claim 29, wherein the electrolyte comprises up to 50% of 3-alkoxypropionitrile, cyclic and acyclic lactones, cyclic and acyclic carbonates, low viscosity ionic liquids, or binary/tertiary/quaternary mixtures thereof.

32. The dye-sensitized photovoltaic cell of claim 29, wherein the electrolyte comprises up to 0.6 M N-methylbenzimidazole and up to 0.1 M lithium bis(trifluorosulfon)imide as additives.

33-49. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a schematic diagram illustrating the general architecture of a dye-sensitized photovoltaic cell as described herein.

DETAILED DESCRIPTION

Definitions

[0014] Unless specifically noted otherwise herein, the definitions of the terms used are standard definitions used in the art of organic chemistry. Exemplary embodiments, aspects and variations are illustrated in the figures and drawings, and it is intended that the embodiments, aspects and variations, and the figures and drawings disclosed herein are to be considered illustrative and not limiting.

[0015] While particular embodiments are shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art. It should be understood that various alternatives to the embodiments described herein may be employed in practicing the methods described herein. It is intended that the appended claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.

[0016] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art. All patents and publications referred to herein are incorporated by reference.

[0017] As used in the specification and claims, the singular form “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.

[0018] Abbreviations and acronyms used herein: [0019] ACN - Acetonitrile. [0020] DSPC - Dye-Sensitized Photovoltaic Cell. [0021] DI - deionized. [0022] EDOT - 3,4-ethylenedioxythiophene. [0023] FF - Fill Factor. [0024] FTO - Fluoride-doped Tin Oxide. [0025] GBL - Gamma-butyrolactone. [0026] Jsc - Short-circuit current density. [0027] MPN - 3-methoxypropionitrile [0028] PEDOT - Poly(3,4-ethyelenedioxythiophene) [0029] PEN - polyethylene napthalate [0030] PET - polyethylene terephthalate [0031] PSS - poly(4-styrene sulfonic acid) [0032] SDS - sodium dodecyl sulfate. [0033] TBHFP - Tetra-n-butylammonium hexafluorophosphate. [0034] Voc - Open circuit voltage. [0035] VOC - Volatile Organic Compound.

[0036] “Graphene” is an allotrope of carbon consisting of a single layer of carbon atoms arranged in a hexagonal lattice.

[0037] A “hole-blocking” layer in a photovoltaic cell is a nonporous layer disposed between the cathode and anode which reduces and/or inhibits back-transfer of electrons from the electrolyte to the anode.

[0038] The dye-sensitized photovoltaic cells described herein comprise: [0039] a cathode; [0040] an electrolyte; [0041] a porous dye-sensitized titanium dioxide film; and [0042] an anode.

[0043] Also provided herein are dye-sensitized photovoltaic cells which comprise a nonporous hole-blocking layer interposed between the anode and the dye-sensitized titanium dioxide film. The nonporous “hole-blocking” layer may comprise an organotitanium compound, such as a titanium alkoxide. The organotitanium compound may be polymeric, such as a polymeric titanium alkoxide. An exemplary polymeric titanium alkoxide is poly(n-butyl titanate). The nonporous or compact hole-blocking layer may also comprise titanium in the form of an oxide, such as compact anatase or rutile film. The thickness of the hole blocking layer may be from about 20 nm to about 100 nm.

[0044] The anode may comprise a transparent conducting oxide (TCO)-coated glass, a TCO coated transparent plastic substrate, or a thin metal foil. Exemplary transparent conducting oxides include fluorine-doped tin oxide, indium-doped tin oxide, and aluminum-doped tin oxide. Exemplary transparent plastic substrates may comprise PET or PEN.

[0045] Also provided herein is a method of preparing a dye-sensitized photovoltaic cell as described above, comprising the step of applying the nonporous blocking layer on the anode. The nonporous blocking layer may be applied to the anode using art-known techniques, such as gravure, silkscreen, slot, spin or blade coating.

[0046] The dye-sensitized photovoltaic cell described herein comprises an electrolyte. In some embodiments the electrolyte may comprise a redox couple. In some embodiments the redox c couple comprises organocopper (I) and organocopper (II) salts. Suitable organocopper salts include copper complexes comprising bi- and polydentate organic ligands with counterions. Suitable bidentate organic ligands include, but are not limited to, 6,6'-dialkyl-2,2'-bipyridine; 4,4',6,6'-tetralkyl-2,2'-bipyridine; 2,9-dialkyl-1,10-phenathroline; 1,10-phenathroine; and 2,2'-bipyridine. Suitable counterions include, but are not limited to, bis(trifluorosulfon)imide, hexafluorophosphate, and tetrafluoroborate. The ratio of organocopper(l) to organocopper(II) salts may be from about 4:1 to about 12:1. Alternatively, the ratio of organocopper(i) to organocopper(ll) salts may be from about 6:1 to about 10:1.

[0047] The redox couple may comprise copper complexes with more than one ligand. For example, the redox couple may comprise a copper (I) complex with 6,6'-dialkyl-2,2'-bipyridine and a copper (II) complex with a bidentate organic ligand selected from the group consisting of 6,6'-dialkyl-2,2'-bipyridine; 4,4',6,6'-tetralkyl-2,2'-bipyridine; 2,9-dialkyl-1,10-phenathroline; 1,10-phenathroine; and 2,2'-bipyridine. Alternatively, the redox couple may comprise a copper (I) complex with 2,9-dialkyl-1,10-phenathroline and a copper (II) complex with a bidentate organic ligand selected from the group consisting of 6,6'-dialkyl-2,2'-bipyridine; 4,4',6,6'-tetralkyl-2,2'-bipyridine; 2,9-dialkyl-1,10-phenathroline; 1,10-phenathroine; and 2,2'-bipyridine.

[0048] The dye-sensitized photovoltaic cell described herein comprises an electrolyte, which may comprise two or more solvents. Suitable solvents include, but are not limited to, sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids and binary/tertiary/quaternary mixtures of these solvents. In an exemplary embodiment, the electrolyte comprises at least 50% sulfolane or dialkyl sulfone. Alternatively, the electrolyte may comprise up to about 50% of 3-alkoxypropionitrile, cyclic and acyclic lactones, cyclic and acyclic carbonates, low viscosity ionic liquids, or binary/tertiary/quaternary mixtures thereof. The electrolyte may also comprise up to about 0.6 M N-methylbenzimidazole and up to about 0.2 M lithium bis(trifluorosulfon)imide as additives.

[0049] In some embodiments, the dye-sensitized photovoltaic cell described herein further comprises a cathode catalyst disposed on the cathode. A suitable cathode catalyst may comprise a mixture of 2D conductor and electronic conducting polymer. A “2D conductor” is a molecular semiconductor with thickness in atomic scale. Exemplary 2D conductors include graphenes, transition metal dichalcogenides (ex., molybdenum disulfide or diselenide), or hexagonal boron nitride. For use in the cathode catalysts described herein, the graphene may comprise a molecular layer or nano/micro crystal. The graphene may be derived from reduced graphene oxide. Suitable conducting polymers include but are not limited to polythiophene, polypyrrole, polyaniline, and derivatives thereof. An exemplary polythiophene for use in the photovoltaic cell described herein is PEDOT.

[0050] In one alternative embodiment, the present application provides a dye-sensitized photovoltaic cell comprising a cathode; an electrolyte; a porous dye-sensitized titanium dioxide film layer; an anode; and a nonporous hole-blocking layer interposed between the anode and the dye-sensitized titanium dioxide film layer; wherein the electrolyte comprises a redox couple comprising organocopper (I) and organocopper (II) salts, and wherein the ratio of organocopper (I) to organocopper (II) salts is from about 4:1 to about 12:1.

[0051] In another alternative embodiment, the present application provides a dye-sensitized photovoltaic cell comprising a cathode; an electrolyte; a porous dye-sensitized titanium dioxide film layer; an anode; and a nonporous hole-blocking layer interposed between the anode and the dye-sensitized titanium dioxide film layer; wherein the electrolyte comprises two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary/tertiary/quaternary mixtures of these solvents.

[0052] In another alternative embodiment, the present application provides a dye-sensitized photovoltaic cell comprising a cathode; a cathode catalyst disposed on the cathode, wherein the cathode catalyst comprises a 2D conductor and an electronic conducting polymer; an electrolyte; a porous dye-sensitized titanium dioxide film layer; an anode; and a nonporous hole-blocking layer interposed between the anode and the dye-sensitized titanium dioxide film layer.

[0053] In another alternative embodiment, the present application provides a dye-sensitized photovoltaic cell comprising a cathode; an electrolyte; a porous dye-sensitized titanium dioxide film layer; and an anode; wherein the electrolyte comprises a redox couple comprising organocopper (I) and organocopper (II) salts, and wherein the ratio of organocopper (I) to organocopper (II) salts is from about 4:1 to about 12:1; and wherein the electrolyte comprises two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary/tertiary/quaternary mixtures of these solvents.

[0054] In another alternative embodiment, the present application provides a dye-sensitized photovoltaic cell comprising a cathode; a cathode catalyst disposed on the cathode, wherein the cathode catalyst comprises a 2D conductor and an electronic conducting polymer; an electrolyte; a porous dye-sensitized titanium dioxide film layer; and an anode; wherein the electrolyte comprises a redox couple comprising organocopper (I) and organocopper (II) salts, and wherein the ratio of organocopper (I) to organocopper (II) salts is from about 4:1 to about 12:1.

[0055] In another alternative embodiment, the present application provides a dye-sensitized photovoltaic cell comprising a cathode; a cathode catalyst disposed on the cathode, wherein the cathode catalyst comprises a 2D conductor and an electronic conducting polymer; an electrolyte; a porous dye-sensitized titanium dioxide film layer; and an anode; wherein the electrolyte comprises two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary/tertiary/quaternary mixtures of these solvents.

[0056] In another alternative embodiment, the present application provides a dye-sensitized photovoltaic cell comprising a cathode; an electrolyte; a porous dye-sensitized titanium dioxide film layer; an anode; and a nonporous hole-blocking layer interposed between the anode and the dye-sensitized titanium dioxide film layer; wherein the electrolyte comprises a redox couple comprising organocopper (I) and organocopper (II) salts, and wherein the ratio of organocopper (I) to organocopper (II) salts is from about 4:1 to about 12:1; and herein the electrolyte comprises two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary/tertiary/quaternary mixtures of these solvents.

[0057] In another alternative embodiment, the present application provides a dye-sensitized photovoltaic cell comprising a cathode; a cathode catalyst disposed on the cathode, wherein the cathode catalyst comprises a 2D conductor and an electronic conducting polymer; an electrolyte; a porous dye-sensitized titanium dioxide film layer; an anode; and a nonporous hole-blocking layer interposed between the anode and the dye-sensitized titanium dioxide film layer; wherein the electrolyte comprises a redox couple comprising organocopper (I) and organocopper (II) salts, and wherein the ratio of organocopper (I) to organocopper (II) salts is from about 4:1 to about 12:1.

[0058] In another alternative embodiment, the present application provides a dye-sensitized photovoltaic cell comprising a cathode; a cathode catalyst disposed on the cathode, wherein the cathode catalyst comprises a 2D conductor and an electronic conducting polymer; an electrolyte; a porous dye-sensitized titanium dioxide film layer; an anode; and a nonporous hole-blocking layer interposed between the anode and the dye-sensitized titanium dioxide film layer; wherein the electrolyte comprises two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary/tertiary/quaternary mixtures of these solvents.

[0059] In another alternative embodiment, the present application provides a dye-sensitized photovoltaic cell comprising a cathode; a cathode catalyst disposed on the cathode, wherein the cathode catalyst comprises a 2D conductor and an electronic conducting polymer; an electrolyte; a porous dye-sensitized titanium dioxide film layer; and an anode; wherein the electrolyte comprises a redox couple comprising organocopper (I) and organocopper (II) salts, and wherein the ratio of organocopper (I) to organocopper (II) salts is from about 4:1 to about 12:1; wherein the electrolyte comprises two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary/tertiary/quaternary mixtures of these solvents.

[0060] In another alternative embodiment, the present application provides a dye-sensitized photovoltaic cell comprising a cathode; a cathode catalyst disposed on the cathode, wherein the cathode catalyst comprises a 2D conductor and an electronic conducting polymer; an electrolyte; a porous dye-sensitized titanium dioxide film layer; an anode; and a nonporous hole-blocking layer interposed between the anode and the dye-sensitized titanium dioxide film layer; wherein the electrolyte comprises a redox couple comprising organocopper (I) and organocopper (II) salts, and wherein the ratio of organocopper (I) to organocopper (II) salts is from about 4:1 to about 12:1; wherein the electrolyte comprises two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary/tertiary/quaternary mixtures of these solvents.

[0061] Also provided herein is a method of producing a photovoltaic cell of claim comprising the step of polymerizing PEDOT on the cathode from monomeric EDOT. The PEDOT may be polymerized on the cathode by chemical polymerization or electrochemical polymerization. The PEDOT is may be polymerized on the cathode using ferric tosylate or ferric chloride as a catalyst. The ratio of EDOT to ferric chloride may be from about 1:3 to about 1:4. In one embodiment, EDOT is mixed with graphene before chemical polymerization. The EDOT/graphene/ferric catalysis may be deposited from n-butanol on the cathode using spin, gravure, blade or slot coating techniques and allowed to polymerize on the substrate.

[0062] Also provided herein is a method for forming composite catalytic layers on the cathode of a dye-sensitized photovoltaic cell, comprising the step of forming a composite graphene material with one or more conducting polymers. Suitable conducting polymers include, but are not limited to, polythiophenes, polypyrroles, and polyanilines. The ratio of graphene to conducting polymer may be from about 0.5:10 to about 2:10. A suitable polythiophene for use in this method is PEDOT. In one alternative embodiment of the method, the polymer and graphenes are polymerized prior to deposition on the cathode. The composite may be formed by the steps of depositing graphene on an electrode to form a graphene layer; and electrodepositing the polymer on the graphene layer.

EXADMPLES

Example 1 - Blocking Layer

[0063] Blocking layers were applied on a fluorine doped tin oxide (FTO) coated glass using 0.1 to 1% of Tyzor™ poly(n-butyl titanate) solution in n-butanol by spin or blade coating technique. An aqueous dispersion containing 20% by weight of TiO.sub.2 (Degussa P25 with a particle size of 21 ± 5 nm) and 5% by weight of poly(4-vinyl pyridine) was prepared and applied on the prepared electrodes with and without blocking layer using blade coating technique. The thickness of the TiO.sub.2 layer was ca. 6 microns. The TiO.sub.2 coating was sintered at 500° C. for 30 minutes, cooled to 80° C. and immersed in a 1:1 acetonitrile/t-butanol dye solution containing 0.3 mM D35 dye (Dyenamo, Stockholm, SE)(see structure at end of Examples) and 0.3 mM deoxycholic acid. The anodes were kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark. The dye-sensitized anode was sandwiched with pyrolytically deposited platinum catalyst on an FTO coated glass slide using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of 200 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of Lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine in acetonitrile was injected between anode and cathode using pinhole on the cathode. The pinhole was sealed using Meltonix/glass cover using heat sealing process. A conductive silver paint was applied on the contact areas of anode and cathode and dried to form electrical contact.

[0064] The photovoltaic performance of the fabricated cell was measured under AM 1.5 conditions at a light intensity of 97 mW/cm.sup.2. Two cells were fabricated for each set (denoted as cell 1 and cell 2). The photovoltaic performance of fabricated photovoltaic cells was characterized using open circuit voltage (V.sub.oc in mV), short circuit current density (J.sub.sc in milliamperes/square centimeter), fill factor and overall conversion efficiency (in %) and shown in Table 1. The fill factor (FF) is defined as the ratio of the maximum power from the photovoltaic cell to the product of V.sub.oc and J.sub.sc.

TABLE-US-00001 Photovoltaic characteristics of P25 based photovoltaic cells made with and without blocking layer under 1 sun irradiation conditions Sample Blocking layer deposited from Voc (mV) Jsc (mA/cm.sup.2) Fill factor Efficiency (%) No blocking layer- cell 1 0% Tyzor™ in n-butanol 1039.63 8.46 0.400 3.529 No blocking layer- cell 2 0% Tyzor™ in n-butanol 1029.82 8.90 0.406 3.733 Blocking layer 1- cell 1 0.15% Tyzor™ in n-butanol 1042.07 9.16 0.436 4.185 Blocking layer 1- cell 2 0.15% Tyzor™ in n-butanol 1036.02 8.84 0.446 4.101 Blocking layer 2- cell 1 0.3% Tyzor™ in n-butanol 1032.92 10.69 0.462 5.125 Blocking layer 2- cell 2 0.3% Tyzor™ in n-butanol 1035.38 10.60 0.443 4.881

Example 2 - Blocking Layer

[0065] Blocking layers were applied on a fluorine doped tin oxide (FTO) coated glass using 0.1 to 1% of Tyzor™ poly(n-butyl titanate) solution in n-butanol by spin or blade coating technique. Photoelectrodes were made with and without blocking layer on FTO coated glass using an aqueous colloidal TiO.sub.2 (18 nm particle size). The thickness of the TiO.sub.2 layer was ca. 6 microns. The TiO.sub.2 coating was sintered at 500° C. for 30 minutes, cooled to 80° C. and immersed in a 1:1 acetonitrile/t-butanol dye solution containing 0.3 mM D35 dye (Dyenamo, Sweden) and 0.3 mM deoxycholic acid. The anodes were kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark. The dye-sensitized anode was sandwiched with pyrolytically deposited platinum catalyst on an FTO coated glass slide using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of 200 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine in acetonitrile was injected between anode and cathode using pinhole on the cathode. The pinhole was sealed using Meltonix/glass cover using heat sealing process. A conductive silver paint was applied on the contact areas of anode and cathode and dried to form electrical contact. Two cells were fabricated for each set (denoted as cell 1 and cell 2).

[0066] The photovoltaic performance of the fabricated cell was measured under AM 1.5 conditions at a light intensity of 97 mW/cm.sup.2. The performance of fabricated photovoltaic cells was characterized using open circuit voltage (V.sub.oc in mV), short circuit current density (J.sub.sc in milliamperes/square centimeter), fill factor and overall photovoltaic conversion efficiency (in %) and shown in Table 2. The fill factor (FF) is defined as the ratio of the maximum power from the photovoltaic cell to the product of V.sub.oc and J.sub.sc.

TABLE-US-00002 Photovoltaic characteristics of 18 nm TiO2 based photovoltaic cells made with and without blocking layer under 1 sun irradiation conditions Blocking layer type Blocking layer deposited from Voc (mV) Jsc (mA/cm.sup.2) Fill factor Efficiency (%) No blocking layer- cell 1 0% Tyzor™ in n-butanol 1047.31 9.18 0.446 4.308 No blocking layer- cell 2 0% Tyzor™ in n-butanol 1082.60 9.34 0.436 4.419 Blocking layer 1- cell 1 0.15% Tyzor™ in n-butanol 1068.62 9.35 0.471 4.728 Blocking layer 1- cell 2 0.15% Tyzor™ in n-butanol 1071.24 9.06 0.469 4.572 Blocking layer 2- cell 1 0.3% Tyzor™ in n-butanol 1058.70 10.97 0.465 5.425 Blocking layer 2- cell 2 0.3% Tyzor™ in n-butanol 1060.02 10.92 0.463 5.379

Example 3 - Blocking Layer

[0067] Blocking layers were applied either from 0.1 to 1% of Tyzor™ poly(n-butyl titanate) in n-butanol by spin or blade coating technique or by heating the FTO coated glass slides in 40 mM solution of aqueous TiCI.sub.4 at 70° C. for 30 minutes (academic control). Photoelectrodes were made with and without blocking layer on FTO coated glass using screen printable colloidal TiO.sub.2 (30 nm particle size). The thickness of the TiO.sub.2 layer was ca. 6 microns. The TiO.sub.2 coating was sintered at 500° C. for 30 minutes, cooled to 80° C. and immersed in a 1:1 acetonitrile/t-butanol dye solution containing 0.3 mM D35 dye (Dyenamo, Sweden) and 0.3 mM deoxycholic acid. The anodes were kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark. The dye-sensitized anode was sandwiched with pyrolytically deposited platinum catalyst on an FTO coated glass slide using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of 200 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine in acetonitrile was injected between anode and cathode using pinhole on the cathode. The pinhole was sealed using Meltonix/glass cover using heat sealing process. A conductive silver paint was applied on the contact areas of anode and cathode and dried to form electrical contact. Three cells were fabricated for each set (denoted as cells 1, 2 and 3).

[0068] The photovoltaic performance of the fabricated cell was measured under AM 1.5 conditions at a light intensity of 97 mW/cm.sup.2. The performance of fabricated photovoltaic cells was characterized using open circuit voltage (V.sub.oc in mV), short circuit current density (J.sub.sc in milliamperes/square centimeter), fill factor and overall photovoltaic conversion efficiency (in %) and shown in Table 3. The fill factor (FF) is defined as the ratio of the maximum power from the photovoltaic cell to the product of V.sub.oc and J.sub.sc.

TABLE-US-00003 Photovoltaic characteristics of 30 nm TiO2 based photovoltaic cells made with and without blocking layer under 1 sun irradiation conditions Blocking layer type Blocking layer deposited from Voc (mV) Jsc (mA/cm.sup.2) Fill factor Efficiency (%) Control blocking layer-cell 1 40 mM TiCl.sub.4 solution 1075.95 7.84 0.573 4.853 Control blocking layer-cell 2 40 mM TiCl.sub.4 solution 1091.35 7.64 0.545 4.569 Control blocking layer-cell 3 40 mM TiCl.sub.4 solution 1072.01 6.78 0.613 4.483 No blocking layer- cell 1 0% Tyzor™ in n-butanol 1039.86 6.33 0.634 4.194 No blocking layer- cell 2 0% Tyzor™ in n-butanol 1048.39 5.79 0.639 3.898 No blocking layer- cell 3 0% Tyzor™ in n-butanol 1052.43 5.86 0.651 4.035 blocking layer- cell 1 0.3% Tyzor™ in n-butanol 1036.47 7.05 0.634 4.660 blocking layer- cell 2 0.3% Tyzor™ in n-butanol 1033.73 7.31 0.637 4.837 blocking layer- cell 3 0.3% Tyzor™ in n-butanol 1058.16 6.61 0.626 4.401

Example 4 - Blocking Layer

[0069] Blocking layers were applied from 0.1 to 1% of Tyzor™ poly(n-butyl titanate) in n-butanol by spin or blade coating technique (Blocking Layers -1. No blocking layer; 2. Coated from 0.3% Tyzor™; 3. Coated from 0.6 % Tyzor™; 4. Coated from 1% Tyzor™). An aqueous dispersion containing 20% by weight of TiO.sub.2 (Degussa P25 with a particle size of 21±5 nm) and 5% by weight of poly(4-vinyl pyridine) was prepared and applied on the prepared electrodes with and without blocking layer using blade coating technique. The thickness of the TiO.sub.2 layer was ca. 6 microns. The TiO.sub.2 coating was sintered at 500° C. for 30 minutes, cooled to 80° C. and immersed in a 1:1 acetonitrile/t-butanol dye solution containing 0.1 mM D35 dye (Dyenamo, Sweden) and 0.1 mM deoxycholic acid. The anodes were kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark. The dye-sensitized anode was sandwiched with pyrolytically deposited platinum catalyst on an FTO coated glass slide using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of 200 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine in 3-methoxypropionitrile was injected between anode and cathode using pinhole on the cathode. The pinhole was sealed using Meltonix/glass cover using heat sealing process. A conductive silver paint was applied on the contact areas of anode and cathode and dried to form electrical contact.

[0070] The photovoltaic performance of the fabricated cell was measured under indoor light irradiation conditions at 3 light levels. The performance of fabricated photovoltaic cells was characterized using open circuit voltage (V.sub.oc in mV), short circuit current density (J.sub.sc in microamperes/square centimeter), fill factor and overall photovoltaic conversion efficiency (in %) and shown in Table 4. The fill factor (FF) is defined as the ratio of the maximum power from the photovoltaic cell to the product of V.sub.oc and J.sub.sc.

TABLE-US-00004 Photovoltaic characteristics photovoltaic cells made using D35 with and without blocking layer under indoor light conditions of various light intensities Light Intensity (lux) Blocking Layer Voc (V) Jsc (.Math.A/cm.sup.2) FF Power density (.Math.W/cm.sup.2) Percent improvement in performance 375 lux 1 0.81 21 0.58 9.87 - - 2 0.87 22 0.69 13.21 33.84 - 3 0.88 19 0.66 11.04 11.85 - 4 0.88 20 0.69 12.14 23 Light Intensity (lux) Blocking Layer Voc (V) Jsc (.Math.A/cm.sup.2) FF Power density (.Math.W/cm.sup.2) Percent improvement in performance 740 lux 1 0.85 39 0.51 16.91 - - 2 0.91 44 0.61 24.42 44.41 - 3 0.91 38 0.57 19.71 16.56 - 4 0.91 40 0.6 21.84 29.15 1100 lux 1 0.87 56 0.48 23.39 - - 2 0.93 66 0.54 33.15 41.73 - 3 0.93 57 0.51 27.04 15.6 - 4 0.93 58 0.54 29.13 24.54

Example 5 - Blocking Layer

[0071] Blocking layers were applied from 0.1 to 1% of Tyzor™ [poly(n-butyl titanate)] in n-butanol by spin or blade coating technique (Blocking Layers -1. No blocking layer; 2. Coated from 0.3% Tyzor™; 3. Coated from 0.6 % Tyzor™; 4. Coated from 1% Tyzor™). Photoelectrodes were made with and without blocking layer on FTO coated glass using aqueous P25 TiO.sub.2 with 5% polyvinylpyridine binder (21 nm particle size). The thickness of the TiO.sub.2layer was ca. 6 microns. The TiO.sub.2 coating was sintered at 500° C. for 30 minutes, cooled to 80° C. and immersed in a 1:1 acetonitrile/t-butanol dye solution containing 0.3 mM BOD4 dye (WBI-synthesized, see structure at end of Examples) and 0.3 mM deoxycholic acid. The anodes were kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark. The dye-sensitized anode was sandwiched with pyrolytically deposited platinum catalyst on an FTO coated glass slide using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of 200 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of Lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine in 3-methoxypropionitrile was injected between anode and cathode using pinhole on the cathode. The pinhole was sealed using Meltonix/glass cover using heat sealing process. A conductive silver paint was applied on the contact areas of anode and cathode and dried to form electrical contact.

[0072] The photovoltaic performance of the fabricated cell was measured under indoor light irradiation conditions at 3 light levels. The performance of fabricated photovoltaic cells was characterized using open circuit voltage (V.sub.oc in mV), short circuit current density (J.sub.sc in microamperes/square centimeter), fill factor and overall photovoltaic conversion efficiency (in %) and shown in Table 5. The fill factor (FF) is defined as the ratio of the maximum power from the photovoltaic cell to the product of V.sub.oc and J.sub.sc.

TABLE-US-00005 Photovoltaic characteristics photovoltaic cells made using BOD4 with and without blocking layer under indoor light conditions Light Intensity (lux) Blocking Layer Voc (V) Jsc (.Math.A/cm.sup.2) FF Powder density (.Math.W/cm.sup.2) Percent improvement in performance 375 lux 1 0.88 20 0.54 9.50 - - 2 0.92 25 0.64 14.72 54.95 - 3 0.9 20 0.69 12.42 30.74 - 4 0.91 19 0.66 11.41 20.11 740 lux 1 0.92 41 0.46 17.35 - - 2 0.95 48 0.52 23.71 36.66 - 3 0.93 40 0.58 21.58 24.38 - 4 0.95 37 0.56 19.68 13.43 1100 lux 1 0.94 59 0.41 22.74 - - 2 0.97 70 0.45 30.56 34.39 - 3 0.96 59 0.5 28.32 24.54 - 4 0.97 55 0.5 26.68 17.33

Example 6 - Effect of Solvent on the Indoor Light Performance of Copper Redox Based DSPC with D35 Dye

[0073] FTO coated glasses were cut into 2 cm×2 cm size and cleaned by washing with successive 1% aqueous Triton™ X-100 solution, DI-water, and iso-propanol. After drying at room temperature, the cleaned FTO glasses were treated with corona discharge (.sup.~13000 V) for approximately 20 seconds on the conducting side. A 20% aqueous P25 dispersion was blade coated (8 microns thick) on the FTO side. The coating area was trimmed to 1.0 cm.sup.2. The TiO.sub.2 coated anode was sintered at 450° C. for 30 minutes, cooled to about 80° C. and dropped into a dye solution containing 0.1 mM D35 dye (Dyenamo, Sweden) and 0.1 mM chenodeoxycholic acid in 1:1 acetonitrile/t-butanol. The anodes were kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark. The dye-sensitized anode was sandwiched with either electrochemically deposited PEDOT catalyst or pyrolytic platinum catalyst on an FTO coated glass slide using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of 200 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of Lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine in a select solvent was injected between anode and cathode using pinhole on the cathode. The pinhole was sealed using Meltonix/glass cover using heat sealing process. A conductive silver paint was applied on the contact areas of anode and cathode and dried to form electrical contact. The performance of the fabricated cell was measured under indoor light exposure conditions and is shown in Table 6.

TABLE-US-00006 Photovoltaic characteristics of copper photovoltaic cells under 720 lux indoor light exposure Dye Cathode catalyst Electrolyte solvent Voc (mV) Jsc (.Math.A/cm.sup.2.sub.) Fill factor Power Density in .Math.W/cm.sup.2 D35 PEDOT acetonitrile 800 77 0.7 43.0 D35 Pyrolytic Pt acetonitrile 810 67 0.711 38.5 D35 Pyrolytic Pt Sulfolane 940 65 0.63 38.5 D35 Pyrolytic Pt GBL 800 73 0.694 40.5

Example 7 - Effect of Redox Couple on the Indoor Light Performance of Copper Redox Based DSPC

[0074] FTO coated glasses were cut into 2 cm×2 cm size and cleaned by washing with successive 1% aqueous Triton™ X-100 solution, DI-water, and isopropanol. After drying at room temperature, the cleaned FTO glasses were treated with corona discharge (.sup.~13000 V) for approximately 20 seconds on the conducting side. A 20% aqueous P25 dispersion was blade coated (8 microns thick) on the FTO side. The coating area was trimmed to 1.0 cm.sup.2. The TiO.sub.2 coated anode was sintered at 450° C. for 30 minutes, cooled to about 80° C. and dropped into a dye solution containing 0.1 mM D35 dye (Dyenamo, Sweden) and 0.1 mM chenodeoxycholic acid in 1:1 acetonitrile/t-butanol. The anodes were kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark. The dye-sensitized anode was sandwiched with either electrochemically deposited PEDOT catalyst or pyrolytic platinum catalyst on an FTO coated glass slide using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of 200 mM bis(2,9-dimethyl-1,10-phenanthroline) copper (I) bis(trifluorosulfon)imide, 50 mM bis(2,9-dimethyl-1,10-phenanthroline) copper (II) bis(trifluorosulfon)imide, 100 mM of Lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine in a select solvent was injected between anode and cathode using pinhole on the cathode. The pinhole was sealed using Meltonix/glass cover using heat sealing process. A conductive silver paint was applied on the contact areas of anode and cathode and dried to form electrical contact. The performance of the fabricated cell was measured under indoor light exposure conditions and is shown in Table 7.

TABLE-US-00007 Photovoltaic characteristics of copper photovoltaic cells under 720 lux indoor light exposure Dye Cathode catalyst Electrolyte solvent Voc (mV) Jsc (.Math.A/cm.sup.2) Fill factor Power Density in .Math.W/cm.sup.2 D35 PEDOT acetonitrile 800 77 0.7 43.0 D35 Pyrolytic Pt acetonitrile 810 67 0.711 38.5 D35 PEDOT acetonitrile 900 44 0.7 27.7 D35 Pyrolytic Pt acetonitrile 884 46 0.72 29.40

Example 8 - Effect of Solvent on the Indoor Light Performance of Copper Redox Based DSPC with BOD4 Dye

[0075] FTO coated glasses were cut into 2 cm×2 cm size and cleaned by washing with successive 1% aqueous Triton™ X-100 solution, DI-water, and iso-propanol. After drying at room temperature, the cleaned FTO glasses were treated with corona discharge (.sup.~13000 V) for approximately 20 seconds on the conducting side. A 20% aqueous P25 dispersion was blade coated (8 microns thick) on the FTO side. The coating area was trimmed to 1.0 cm.sup.2. The TiO.sub.2 coated anode was sintered at 450° C. for 30 minutes, cooled to about 80° C. and dropped into a dye solution containing 0.3 mM BOD4 dye and 0.3 mM chenodeoxycholic acid in 1:1 acetonitrile/t-butanol. The anodes were kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark. The dye-sensitized anode was sandwiched with either electrochemically deposited PEDOT catalyst or pyrolytic platinum catalyst on an FTO coated glass slide using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of 200 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine in a select solvent was injected between anode and cathode using pinhole on the cathode. The pinhole was sealed using Meltonix/glass cover using heat sealing process. A conductive silver paint was applied on the contact areas of anode and cathode and dried to form electrical contact. The performance of the fabricated cell was measured under indoor light exposure conditions and is shown in Table 8.

TABLE-US-00008 Photovoltaic characteristics of copper photovoltaic cells under 720 lux indoor light exposure Dye Cathode catalyst Electrolyte solvent Voc (mV) Jsc (.Math.A/cm.sup.2) Fill factor Power Density in .Math.W/cm.sup.2 BOD4 PEDOT acetonitrile 763 61 0.678 31.55 BOD4 Pyrolytic Pt acetonitrile 765 74 0.648 36.68 BOD4 Pyrolytic Pt Sulfolane 900 58 0.695 36.28 BOD4 PEDOT GBL 760 70 0.725 38.57 BOD4 Pyrolytic Pt GBL 780 85 0.71 47.03

Example 9 - Effect of Solvent/Solvent Mixtures on the Indoor Light Performance of Copper Redox Based DSPC with 80% D13 and 20% XY1b Dye Mixture

[0076] FTO coated glasses were cut into 2 cm×2 cm size and cleaned by washing with successive 1% aqueous Triton™ X-100 solution, DI-water, and iso-propanol. After drying at room temperature, the cleaned FTO glasses were treated with corona discharge (.sup.~13000 V) for approximately 20 seconds on the conducting side. A 20% aqueous P25 dispersion was blade coated (8 microns thick) on the FTO side. The coating area was trimmed to 1.0 cm.sup.2. The TiO.sub.2 coated anode was sintered at 450° C. for 30 minutes, cooled to about 80° C. and dropped into a dye solution containing 0.24 mM D13 dye, 0.06 mM of XY1b dye (Dyenamo, Stockholm, SE) (see structure at end of Examples) and 0.3 mM chenodeoxycholic acid in 1:1 acetonitrile/t-butanol. The anodes were kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark. The dye-sensitized anode was sandwiched with either electrochemically deposited PEDOT catalyst or pyrolytic platinum catalyst on an FTO coated glass slide using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of 250 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of Lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine in a select solvent was injected between anode and cathode using pinhole on the cathode. The pinhole was sealed using Meltonix /glass cover using heat sealing process. A conductive silver paint was applied on the contact areas of anode and cathode and dried to form electrical contact. The performance of the fabricated cell was measured under indoor light exposure conditions and photovoltaic characteristics are summarized in Tables 9A and 9B.

TABLE-US-00009 Photovoltaic characteristics of Indoor Photovoltaic cells with various solvent based electrolytes at 374 lux indoor light exposure Electrolyte Solvent Voc (mV) Jsc (.Math.A/cm.sup.2) Fill factor Power Density (.Math.W/cm.sup.2) GBL 888 43 0.65 24.6 Sulfolane 981 40 0.568 22.29 3-methoxy propionitrile 914 47 0.65 27.92 Propylene carbonate 915 42 0.67 25.13 1:1 Sulfolane:GBL 911 43 0.65 25.46 1:1 Sulfolane:PC 933 45 0.65 27.29 1:1 GBL:MPN 916 44 0.7 28.21 1:1 sulfolane:PC 940 38 0.640 22.86 1:1 sulfolane:MPN 957 40 0.65 24.88

TABLE-US-00010 Photovoltaic characteristics of Indoor Photovoltaic cells with various solvent based electrolytes of 1120 lux indoor light exposure Electrolyte Solvent Voc (mV) Jsc (.Math.A/cm.sup.2) Fill factors Power Density (.Math.W/cm.sup.2) GBL 924 123 0.579 65.80 Sulfolane 1016 107 0.371 40.33 3-methoxy propionitrile 952 139 0.52 68.81 Propylene carbonate 959 123 0.488 57.56 1:1 Sulfolane:GBL 949 123 0.499 58.24 1:1 GBL:MPN 957 125 0.628 75.12 1:1 sulfolane:PC 981 97 0.46 43.77 1:1 sulfolane:MPN 1001 116 0.434 50.39

Example 10. Effect of Solvent Ratio in GBL/Sulfolane Based Copper Redox Electrolyte on The Indoor Light Performance of DSPC with 80% D13 and 20% XY1b Dye Mixture

[0077] FTO coated glasses were cut into 2 cm×2 cm size and cleaned by washing with successive 1% aqueous Triton™ X-100 solution, DI-water, and iso-propanol. After drying at room temperature, the cleaned FTO glasses were treated with corona discharge (.sup.~13000 V) for approximately 20 seconds on the conducting side. A 20% aqueous P25 dispersion was blade coated (8 microns thick) on the FTO side. The coating area was trimmed to 1.0 cm.sup.2. The TiO.sub.2 coated anode was sintered at 450° C. for 30 minutes, cooled to about 80° C. and dropped into a dye solution containing 0.24 mM D13 dye, 0.06 mM of XY1b dye (Dyenamo, Sweden) and 0.3 mM chenodeoxycholic acid in 1:1 acetonitrile/t-butanol. The anodes were kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark. The dye-sensitized anode was sandwiched with either electrochemically deposited PEDOT catalyst or pyrolytic platinum catalyst on an FTO coated glass slide using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of 250 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of Lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine in a select solvent was injected between anode and cathode using pinhole on the cathode. The pinhole was sealed using Meltonix /glass cover using heat sealing process. A conductive silver paint was applied on the contact areas of anode and cathode and dried to form electrical contact. The performance of the fabricated cell was measured under indoor light exposure conditions and photovoltaic characteristics are summarized in Table 10.

TABLE-US-00011 I-V characteristics of 9/1 E3,7z/XY1b photovoltaic cells with various electrolytes under 2 indoor light conditions Electrolyte 750 lux light irradiation 1120 lux irradiation Solvent Voc (mV) Jsc (.Math.A/cm.sup.2) ff PD (.Math. W/cm.sup.2) Voc (mV) Jsc (.Math. A/cm.sup.2) ff PD (.Math. W/cm.sup.2) GBL cell 1 920.97 80 0.607 44.72 932.48 120 0.560 62.63 GBL cell 2 911.12 79 0.726 52.25 926.34 125 0.666 77.09 GBL cell 3 925.54 82 0.638 48.41 928.26 126 0.582 68.79 GBL -average 919.21 80.33 0.66 48.46 929.03 123.67 0.6 69.5 3/1 GBL/sulfolane cell 1 925.54 82 0.638 48.41 938.22 126 0.582 68.79 3/1 GBL/sulfolane cell 2 929.80 96 0.556 49.64 943.97 140 0.509 67.27 3/1 GBL/sulfolane cell 3 927.62 80 0.612 45.43 935.46 116 0.569 61.71 3/1 GBL/sulfolane -average 927.65 86 0.6 47.83 939.22 127.33 0.55 65.92 1/1 GBL/sulfolane cell 1 942.5 81 0.588 44.91 956.75 123 0.529 62.26 1/1 GBL/sulfolane cell 2 933.56 75 0.484 33.88 945.37 106 0.444 44.48 1/1 GBL/sulfolane cell 3 936.99 72 0.527 35.55 948.59 100 0.480 45.53 1/1 GBL/sulfolane -average 937.68 76 0.53 38.11 950.24 109.67 0.48 50.76 ⅓ GBL/sulfolane cell 1 937.96 70 0.529 34.73 951.91 100 0.483 45.98 ⅓ GBL/sulfolane cell 2 946.31 71 0.545 36.61 963.11 104 0.489 47.6 ⅓ GBL/sulfolane -average 942.14 70.5 0.54 35.67 957.51 102 0.49 46.79 Sulfolane cell 1 1010.31 69 0.413 28.78 1028.37 89 0.367 33.58 Sulfolane cell 2 996.65 67 0.375 25.02 1012.51 87 0.339 29.88 Sulfolane cell 3 1001.62 76 0.415 31.57 1018.13 99 0.362 36.48 Sulfolane -average 1002.86 70.67 0.40 28.46 1019.67 91.67 0.36 33.31

Example 11. Effect of Solvent Mixtures on the Indoor Light Performance of Copper Redox Based DSPC with Various Dye and Dye Cocktails

[0078] FTO coated glasses were cut into 2 cm×2 cm size and cleaned by washing with successive 1% aqueous Triton™ X-100 solution, DI-water, and isopropanol. After drying at room temperature, the cleaned FTO glasses were treated with corona discharge (.sup.~13000 V) for approximately 20 seconds on the conducting side. A 20% aqueous P25 dispersion was blade coated (8 microns thick) on the FTO side. The coating area was trimmed to 1.0 cm.sup.2. The TiO.sub.2 coated anode was sintered at 450° C. for 30 minutes, cooled to about 80° C. and dropped into a dye solution containing 0.3 mM D35/0.3 mM chenodeoxycholic acid or 0.24 mM D35 dye, 0.06 mM of XY1b dye (Dyenamo, Sweden) and 0.3 mM chenodeoxycholic acid or 0.24 mM D13 dye, 0.06 mM of XY1b dye (Dyenamo, Sweden) and 0.3 mM chenodeoxycholic acid in 1:1 acetonitrile/t-butanol. The anodes were kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark. The dye-sensitized anode was sandwiched with either electrochemically deposited PEDOT catalyst or pyrolytic platinum catalyst on an FTO coated glass slide using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of 250 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of Lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine in a select solvent mixture was injected between anode and cathode using pinhole on the cathode. The pinhole was sealed using Meltonix /glass cover using heat sealing process. A conductive silver paint was applied on the contact areas of anode and cathode and dried to form electrical contact. The performance of the fabricated cell was measured under indoor light exposure conditions and photovoltaic characteristics are summarized in Tables 11A and 11B. In each instance the electrolyte solvent is a 1:1 v/v mixture.

TABLE-US-00012 Photovoltaic characteristics of Indoor Photovoltaic cells with varied electrolytes and cathode catalysts at 365 lux light exposure Dye/catalyst Electrolyte solvent Cell Area (cm.sup.2) Voc (mV) Jsc (.Math.A/cm.sup.2) Max Power (.Math.W) Power density (.Math.W/cm.sup.2) D35 -cell with Pt GBL:MPN 1.103 782 32 18 15 D35 -cell with PEDOT GBL: MPN 1.035 755 27 15 14.49 D35 -cell with Pt Sulfolane:MPN 1.050 880 35 18 17.14 D35 -cell with PEDOT Sulfolane:MPN 0.998 899 33 20 20.04 D35:XY1b (80:20) with Pt GBL:MPN 0.945 797 46 23 24.33 D35:XY1b (80:20) with PEDOT GBL:MPN 1.140 806 48 31 27.19 D35:XY1b (80:20) with Pt Sulfolane:MPN 0.903 892 43 18 19.93 D35:XY1b (80:20) with PEDOT Sulfolane:MPN 0.998 905 50 31 31.06 D13:XY1b (80:20) with Pt GBL:MPN 1.050 893 46 26 24.76 D13:XY1b (80:20) with PEDOT GBL:MPN 1.103 889 42 31 28.18 D13:XY1b (80:20) with Pt Sulfolane:MPN 0.990 952 46 26 26.26 D13:XY1b (80:20) with PEDOT Sulfolane:MPN 1.045 970 48 34 32.69

TABLE-US-00013 Photovoltaic characteristics of Indoor Photovoltaic cells with varied electrolytes and cathode catalysts at 1100 lux indoor light exposure Dye/catalyst Electrolyte solvent (v/v) Cell Area (cm.sup.2) Voc (mV) Jsc (.Math.A/cm.sup.2) Max Power (.Math.W) Power Density (.Math.W/cm.sup.2) D35 -cell with Pt GBL:MPN 1.103 843 88 55 50.00 D35 -cell with PEDOT GBL:MPN 1.035 829 81 50 48.31 D35 -cell with Pt Sulfolane:MPN 1.100 958 116 49 44.55 D35 -cell with PEDOT Sulfolane:MPN 0.998 967 97 62 53.68 D35:XY1b (80:20) with Pt GBL:MPN 1.155 861 145 81 70.12 D35:XY1b (80:20) with PEDOT GBL:MPN 1.140 851 144 96 84.21 D35:XY1b (80:20) with Pt Sulfolane:MPN 1.050 936 134 51 48.57 D35:XY1b (80:20) with PEDOT Sulfolane:MPN 0.998 943 143 82 82.16 D13:XY1b (80:20) with Pt GBL:MPN 0.978 924 129 66 67.48 D13:XY1b (80:20) with PEDOT GBL:MPN 1.045 924 121 88 84.21 D13:XY1b (80:20) with Pt Sulfolane:MPN 0.990 998 136 54 54.54 D13:XY1b (80:20) with PEDOT Sulfolane:MPN 1.045 1006 139 85 81.73

Example 12. Effect of Mixed Redox Couple on the Indoor Light Performance of Copper Redox Based DSPC

[0079] FTO coated glasses are cut into 2 cm×2 cm size and cleaned by washing with successive 1% aqueous Triton™ X-100 solution, DI-water, and iso-propanol. After drying at room temperature, the cleaned FTO glasses are treated with Corona (.sup.~13000 V) for approximately 20 seconds on the conducting side. A 20 % aqueous P25 dispersion is blade coated (8 microns thick) on the FTO side. The coating area is trimmed to 1.0 cm.sup.2. The TiO.sub.2 coated anode is sintered at 450° C. for 30 minutes, cooled to about 80° C. and dropped into a dye solution containing 0.24 mM D13 dye, 0.06 mM of XY1b dye (Dyenamo, Sweden) and 0.3 mM chenodeoxycholic acid in 1:1 acetonitrile/t-butanol. The anodes are kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark. The dye-sensitized anode is sandwiched with either electrochemically deposited PEDOT catalyst or pyrolytic platinum catalyst on an FTO coated glass slide using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of [0080] 1. 250 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of Lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine; [0081] 2. 250 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(2,9-dimethyl-1,10-phenanthroline) copper (II) bis(trifluorosulfon)imide, 100 mM of lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine; [0082] 3. 250 mM bis(2,9-dimethyl-1,10-phenanthroline) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of Lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine; or [0083] 4. 250 mM bis(2,9-dimethyl-1,10-phenanthroline) copper (I) bis(trifluorosulfon)imide, 50 mM bis(2,9-dimethyl-1,10-phenanthroline) copper (II) bis(trifluorosulfon)imide, 100 mM of Lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine; in 1:1 (v/v) y-butyrolactone/3-methoxy propionitrile solvent mixture is injected between anode and cathode using pinhole on the cathode. The pinhole is sealed using Meltonix /glass cover using heat sealing process. A conductive silver paint is applied on the contact areas of anode and cathode and dried to form electrical contact. The performance of the fabricated cell is measured under indoor light exposure conditions (740 lux) and photovoltaic characteristics are summarized in Tables 12A and 12B.

TABLE-US-00014 Photovoltaic characteristics of Pt based photovoltaic cells with various redox copper complex combinations at 740 lux indoor light Sample ID Cu(I) complex Cu(II) Complex Voc (mV) Jsc (.Math.A/cm.sup.2) Max Power (.Math.W) % Efficiency 6:1 dmbp:dmbp with Pt CE Cell 1 Cu(dmbp).sub.2TFSI Cu(dmbp).sub.2TFSI.sub.2 937.434 78 52 26.032 6:1 dmbp:dmbp with Pt CE Cell 2 Cu(dmbp).sub.2TFSI Cu(dmbp).sub.2TFSI.sub.2 943.21 76 47 22.404 6:1 dmp:dmp with Pt CE Cell 1 Cu(dmp).sub.2TFSI Cu(dmp).sub.2TFSI.sub.2 861.81 56 36 16.320 6:1 dmp:dmp with Pt CE Cell 2 Cu(dmp).sub.2TFSI Cu(dmp).sub.2TFSI.sub.2 872.60 58 32 17.026 6:1 dmbp:dmp with Pt CE Cell 1 Cu(dmbp).sub.2TFSI Cu(dmp).sub.2TFSI.sub.2 926.75 74 38 20.861 6:1 dmbp:dmp with Pt CE Cell 2 Cu(dmbp).sub.2TFSI Cu(dmp).sub.2TFSI.sub.2 931.69 73 36 21.246 6:1 dmp:dmbp with Pt CE Cell 1 Cu(dmp).sub.2TFSI Cu(dmbp).sub.2TFSI.sub.2 894.66 64 36 17.946 6:1 dmp:dmbp with Pt CE Cell 2 Cu(dmp).sub.2TFSI Cu(dmbp).sub.2TFSI.sub.2 905.89 64 38 18.295

TABLE-US-00015 Photovoltaic characteristics of electrochemical PEDOT based photovoltaic cells with various redox copper complex combinations at 740 lux indoor light Sample ID Cu(I) complex Cu(II) Complex Voc (mV) Jsc (.Math.A/cm.sup.2) Max Power (.Math.W) % Efficiency 6:1 dmbp:dmbp with PEDOT CE Cell 1 Cu(dmbp).sub.2TFSI Cu(dmbp).sub.2TFSI.sub.2 941.070 80 51 25.739 6:1 dmbp:dmbp with PEDOT CE Cell 2 Cu(dmbp).sub.2TFSI Cu(dmbp).sub.2TFSI.sub.2 934.981 77 49 24.659 6:1 dmp:dmp with PEDOT CE-Cell 1 Cu(dmp).sub.2TFSI Cu(dmp).sub.2TFSI.sub.2 851.83 58 37 17.533 6:1 dmp:dbp with PEDOT CE-Cell 2 Cu(dmp).sub.2TFSI Cu(dmp).sub.2TFSI.sub.2 853.05 62 36 18.060 6:1 dmbp:dmp with PEDOT CE-Cell 1 Cu(dmbp).sub.2TFSI Cu(dmp).sub.2TFSI.sub.2 929.05 75 50 23.742 6:1 dmbp:dbp with PEDOT CE-Cell 2 Cu(dmbp).sub.2TFSI Cu(dmp).sub.2TFSI.sub.2 927.52 75 42 23.356 6:1 dmp:dmbp with PEDOT CE-Cell 1 Cu(dmp).sub.2TFSI Cu(dmbp).sub.2TFSI.sub.2 882.30 65 38 19.760 6:1 dmp:dmbp with PEDOT CE- Cell 2 Cu(dmp).sub.2TFSI Cu(dmbp).sub.2TFSI.sub.2 879.40 66 36 20.051

Example 13

[0084] Fluorine-doped tin oxide (FTO) coated glasses were cut into 2 cm × 2 cm size and cleaned by washing with successive 1% aqueous Triton™ X-100 solution, deionized (DI) water, and isopropanol. After drying at room temperature, the cleaned FTO glasses were treated with corona discharge (.sup.~13000 V) for approximately 20 seconds on the conducting side. An aqueous dispersion containing 20% by weight of TiO.sub.2 (Degussa P25 with a particle size of 21±5 nm) and 5% by weight of poly(4-vinyl pyridine) was prepared and blade coated (6-8 microns thick) on the FTO coated side of the glass. The coating area was trimmed to 1.0 cm.sup.2. The TiO.sub.2 coated anode was sintered at 450° C. for 30 minutes, cooled to about 80° C. and dropped into a dye cocktail solution containing 0.3 mM D35 dye and 0.3 mM chenodeoxycholic acid in 1:1 acetonitrile/t-butanol. The anodes were kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark.

Cathode Preparation

[0085] Solution 1 was prepared by dissolving 0.04 g EDOT (3,4-dioxyethylenethiophene) in 2 mL of n-butanol. Solution 2 was prepared by dissolving 1 g of 40% ferric tosylate solution in n-butanol (0.4 g of Fe salt in 0.6 g of BuOH), 0.033 g 37% HCI, in 0.5 ml of BuOH. Solution 2 solutions were mixed with various amounts of graphenes such as 0%, 5%, and 10% (weight to EDOT monomer).

[0086] Solutions 1 and 2 (with various amounts of graphenes) were mixed well and spin coated on clean fluorine-tin oxide coated glass substrate (substrate was cleaned by 1%Triton™ X100/ water/IPA/corona treatment, and heated by hair dryer for 5 seconds before coating) A spin speed of 1000 rpm for 1 minute was used. The resulting films were air dried, the coating was rinsed with MeOH, dried and heat treated at 100° C. for 30 minutes.

Cell Fabrication

[0087] Prepared cathodes were sandwiched with dye-sensitized anodes using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of 200 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine in acetonitrile was injected between anode and cathode using pinhole on the cathode. The pinhole was sealed using Meltonix /glass cover using heat sealing process. A conductive silver paint was applied on the contact areas of anode and cathode and dried to form electrical contact. Two cells were fabricated for each cathode catalytic material. An electrochemically polymerized PEDOT containing cathode and a pyrolytically deposited platinum containing cathode were used as external controls.

[0088] The performance of the fabricated cell was measured under AM 1.5 conditions at a light intensity of 97 mW/cm.sup.2. The performance of fabricated photovoltaic cells was characterized using open circuit voltage (V.sub.oc in mV), short circuit current density (J.sub.sc in milliamperes/square centimeter), fill factor and overall photovoltaic conversion efficiency (in %) and shown in Table 13. The fill factor (FF) is defined as the ratio of the maximum power from the photovoltaic cell to the product of V.sub.oc and J.sub.sc.

TABLE-US-00016 Photovoltaic characteristics of copper redox based dye-sensitized photovoltaic cells with various graphene content based chemically polymerized PEDOT cathodes under 1 sun irradiation conditions Catalyst on the Cathode Jsc (mA/cm.sup.2) Voc (mV) Fill factor Photovoltaic Conversion efficiency (%) Chemical PEDOT with 0% graphene 5.84 1081 0.45 2.85 6.59 1086 0.46 3.27 Chemical PEDOT with 5% graphene 7.07 1080 0.43 3.25 7.39 1053 0.45 3.49 Chemical PEDOT with 10% graphene 6.53 1084 0.42 2.94 7.13 1073 0.43 3.28 Electrochemical PEDOT with 0% graphene 6.50 1092 0.44 3.12 6.85 1077 0.45 3.29 Pyrolytic platinum 5.98 1050 0.27 1.72 6.08 1055 0.32 2.05

Example 14. Electropolymerized PEDOT With Graphenes

[0089] Fluorine-doped tin oxide (FTO) coated glasses were cut into 2 cm × 2 cm size and cleaned by washing with successive 1% aqueous Triton™ X-100 solution, deionized (DI) water, and isopropanol. After drying at room temperature, the cleaned FTO glasses were treated with corona discharge (.sup.~13000 V) for approximately 20 seconds on the conducting side. An aqueous dispersion containing 20% by weight of TiO.sub.2 (Degussa P25 with a particle size of 21±5 nm) and 5% by weight of poly(4-vinyl pyridine) was prepared and blade coated (6-8 microns thick) on the FTO coated side of the glass. The coating area was trimmed to 1.0 cm.sup.2. The TiO.sub.2 coated anode was sintered at 450° C. for 30 minutes, cooled to about 80° C. and dropped into a dye cocktail solution containing 0.3 mM D35 dye and 0.3 mM chenodeoxycholic acid in 1:1 acetonitrile/t-butanol. The anodes were kept in dye solution overnight, rinsed with acetonitrile and air dried in the dark.

Cathode Preparation

[0090] 872 mg Tetra-n-butylammonium hexafluorophosphate (TBHFP) was dissolved in 2.25 mL of acetonitrile (ACN) followed by adding 240 .Math.L of 3,4-ethylenedioxythiophene (EDOT). The resulting solution was added to 225 mL of aqueous sodium dodecylsulfate solution and the resulting suspension was ultrasonicated for 1 hour to get clear emulsion.

[0091] The resulting emulsion was used for electrodeposition of PEDOT under galvanostatic (constant current) mode. The current was set to 200 .Math.A, time was set to 150 s. The working electrode was 2 cm × 2 cm FTO-coated glass slide; the counter electrode was 2 cm × 2.5 cm FTO-coated glass slide. Both electrodes were partially submerged in the EDOT solution with FTO coated sides facing each other, the distance between the electrodes being 2 cm. The PEDOT coated slides were rinsed with isopropanol, allowed to dry under ambient conditions, and stored under ACN.

[0092] The EDOT emulsion was also prepared with various amounts of graphenes (to that of EDOT concentration) and used for electrodeposition of PEDOT/graphene composite catalysts. PEDOT was also electrodeposited on predeposited graphene containing electrodes.

Cell Fabrication

[0093] Prepared cathodes were sandwiched with dye-sensitized anodes using 60 .Math.m thick hot melt sealing film (Meltonix 1170-60PF from Solaronix, Switzerland) window by hot pressing at 125° C. for 45 seconds. A copper redox electrolyte solution consisting of 250 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (I) bis(trifluorosulfon)imide, 50 mM bis(6,6'-dimethyl-2,2'-bipyridine) copper (II) bis(trifluorosulfon)imide, 100 mM of lithium bis(trifluorosulfon)imide and 0.5 M 4-(tertiarybutyl)pyridine in sulfolane was injected between anode and cathode using pinhole on the cathode. The pinhole was sealed using Meltonix /glass cover using heat sealing process. Conductive silver paint was applied on the contact areas of anode and cathode and dried to form electrical contact. Two cells were fabricated for each cathode catalytic material. An electrochemically polymerized PEDOT containing cathode and a pyrolytically deposited platinum containing cathode were used as external controls.

[0094] The performance of the fabricated cell was measured under indoor light irradiation conditions at 740 lux. The performance of fabricated photovoltaic cells was characterized using open circuit voltage (V.sub.oc in mV), short circuit current density (J.sub.sc in milliamperes/square centimeter), fill factor and overall photovoltaic conversion efficiency (in %) and shown in Tables 14A and 14B. The fill factor (FF) is defined as the ratio of the maximum power from the photovoltaic cell to the product of V.sub.oc and J.sub.sc.

TABLE-US-00017 Photovoltaic characteristics of copper redox based dye-sensitized photovoltaic cells with various graphene content based electro-polymerized PEDOT cathodes using mixed EDOT/graphene emulsions Graphene/EDOT ratio in galvanostatic bath Deposition Time (s) Voc (mV) Jsc (.Math.A/cm.sup.2) FF Power density (.Math.W/cm.sup.2) No graphene (control) 120 741 31 0.721 17 0.5/10 premixed using ultrasonic bath 120 770 33 0.712 18 0.5/10 premixed using ultrasonic probe 120 764 36 0.706 19 01/10 premixed using ultrasonic bath 120 780 38 0.716 21 02/10 premixed using ultrasonic bath 120 766 38 0.713 21 02/10 premixed using ultrasonic probe 120 786 36 0.705 20

TABLE-US-00018 Photovoltaic characteristics of copper redox based dye-sensitized photovoltaic cells with PEDOT electro-polymerized on graphene coated cathodes Graphene deposition process ElectroDeposition Time (s) Voc (mV) Jsc (.Math.A/cm.sup.2) FF Power density (.Math.W/cm.sup.2) No graphene (control) 60 841 46 0.705 27 120 846 45 0.705 27 graphene coated from n-BuOH 60 857 47 0.687 28 120 862 48 0.713 29 graphene coated from 1 mM SDS in n-BuOH 60 837 42 0.680 24 120 863 44 0.701 27 graphene coated from 10 mM SDS in n-BuOH 60 838 44 0.699 26 120 843 42 0.706 25

Commercial dye structures (Dyenamo, Stockholm, SE)

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Non-commercial dye structures

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