Photovoltaic cells utilizing mesh electrodes

In one aspect, the invention provides photovoltaic cells that utilize a mesh electrode on at least one exposure side of the photovoltaic cell. Preferably, the mesh electrode is a metallic mesh. In one embodiment, the invention provides dye-sensitized solar cells (DSSC) having a wire mesh exposure side electrode and a photovoltaic material comprising a photosensitized interconnected nanoparticle layer. In one embodiment, the wire mesh electrode functions as the cathode of the DSSC. In another embodiment, the wire mesh electrode functions as the anode of the DSSC. In addition, embodiments are provided where wire mesh electrodes are used for the anode and the cathode of a DSSC.

 

What is claimed is:

1. A photovoltaic cell comprising:

first substrate;

a second substrate;

a significantly light transmitting metallic mesh electrode partially embedded in the second substrate;

a first electrode disposed between the significantly light transmitting metallic mesh electrode and the first substrate;

a dye-sensitized interconnected nanoparticle layer disposed between the first electrode and the significantly light transmitting metallic mesh electrode; and

charge carrier media disposed between the first electrode and the significantly light transmitting metallic mesh electrode.

2. The photovoltaic cell of claim 1, wherein the first electrode comprises a significantly light transmitting material.

3. The photovoltaic cell of claim 1, wherein the first electrode comprises indium tin oxide.

4. The photovoltaic cell of claim 1, wherein the first electrode comprises a metallic mesh electrode.

5. The photovoltaic cell of claim 1, wherein the first electrode comprises a metal foil.

6. The photovoltaic cell of claim 1, wherein the significantly light transmitting metallic mesh electrode has a transmisivity in the range from about 60% to about 95%.

7. The photovoltaic cell of claim 1, wherein the metallic material of the metallic mesh electrode comprises at least one of palladium, platinum, titanium, stainless steel, and alloys thereof.

8. The photovoltaic cell of claim 1, wherein the significantly light transmitting metallic mesh electrode has a resistivity less than about 3 ohm (Ω) per square.

9. The photovoltaic cell of claim 1, wherein the dye-sensitized interconnected nanoparticle layer comprises nanoparticles of materials selected from the group consisting of selenides, sulfides, tellurides, titanium oxides, tungsten oxides, zinc oxides, zirconium oxides, and one or more combinations thereof.

10. The photovoltaic cell of claim 1, wherein the dye-sensitized interconnected nanoparticle layer comprises dye-sensitized interconnected titanium dioxide nanoparticles.

11. The photovoltaic cell of claim 1, wherein the dye-sensitized interconnected nanoparticle layer comprises particles with an average size in the range from about 5 nm to about 300 nm.

12. The photovoltaic cell of claim 1, wherein the dye-sensitized interconnected nanoparticle layer comprises particles with an average size in the range from about 10 nm to about 40 nm.

13. The photovoltaic cell of claim 1, wherein the dye-sensitized interconnected nanoparticle layer comprises a photosensitizing agent.

14. The photovoltaic cell of claim 13, wherein the photosensitizing agent comprises a dye.

15. The photovoltaic cell of claim 13, wherein the photosensitizing agent comprises an organic molecule selected from the group consisting of cyanines, merocyanines, phthalocyanines, pyrroles and xanthines.

16. The photovoltaic cell of claim 13, wherein the photosensitizing agent comprises a metal ion selected from the group consisting of divalent and trivalent metals.

17. The photovoltaic cell of claim 16, wherein the photosensitizing agent comprises at least one of a ruthenium transition metal complex, an osmium transition metal complex, and an iron transition metal complex.

18. The photovoltaic cell of claim 1, wherein the charge carrier media comprises an electrolyte redox system.

19. The photovoltaic cell of claim 1, wherein the charge carrier media comprises a polymeric electrolyte.

20. The photovoltaic cell of claim 1, wherein the charge carrier media comprises a conductive polymer.

21. The photovoltaic cell of claim 1, wherein the charge carrier media transmits at least about 60% of incident visible light.

22. The photovoltaic cell of claim 1, further comprising a catalytic media disposed between the first electrode and the significantly light transmitting metallic mesh electrode.

23. The photovoltaic cell of claim 22, wherein the catalytic media comprises platinum.

24. The photovoltaic cell of claim 22, wherein the catalytic media comprises a conductive polymer.

25. The photovoltaic cell of claim 1, wherein at least one of the first and second substrates have has a flexural modulus in the range from about 1,500 MPa to about 5,000 MPa.

26. The photovoltaic cell of claim 1, wherein the first and second substrates are flexible and significantly light transmitting.

27. The photovoltaic cell of claim 1, wherein at least one of the first and second substrates comprise a polyethylene naphthalate material.

28. The photovoltaic cell of claim 1, wherein the first and second substrates have a glass transition temperature of less than about 350° C.

29. The photovoltaic cell of claim 1, wherein the first and second substrates have a glass transition temperature in the range from about 10° C. to about 150° C.

30. The photovoltaic cell of claim 1, wherein the metallic mesh electrode is disposed such that it functions as a cathode.

31. A photovoltaic module comprising a plurality of photovoltaic cells of claim 1 electrically connected in at least one of series and parallel.

32. A flexible fabric comprising the photovoltaic cell of claim 1.

33. The photovoltaic cell of claim 1, wherein at least one of the first and second substrates comprises a woven material.

34. The photovoltaic of claim 33, wherein the woven material comprises at least one of cotton, flax, and nylon.

35. The photovoltaic cell of claim 1, wherein the metallic mesh electrode is an expanded metallic mesh electrode.

BACKGROUND OF THE INVENTION

The desire to reduce our consumption of and dependency on fossil fuel has been largely responsible for the development of many photovoltaic materials and devices. The widespread adoption of photovoltaics as an energy source has principally been restricted by the costs and technical difficulties associated with fabricating photovoltaic cells. The energy and material costs of such cells must be recoverable in the electrical energy produced by the cells over some reasonable time frame for photovoltaic cells to be a commercially feasible energy source.

When manufacturing a typical photovoltaic cell comprising a photovoltaic material disposed between two electrodes (sandwich-type), the transparency of one or both of the electrodes to incident light can be a source of economic and technical concerns. In a sandwich-type cell at least one side of the cell is an exposure side, i.e., a side of the cell through which incident light passes to reach the photovoltaic material. As the maximum output energy of a photovoltaic material depends on the amount of incident light it receives, sandwich-type photovoltaic cells almost invariably use a semiconductor oxide film (such as, e.g., indium tin oxide) as the exposure side electrode. Although such semiconductor oxide films are relatively costly, difficult to manufacture and only semiconductors, prior art photovoltaic cells employ these films because it is generally believed and taught that their transparency, combined with conductivity is required to produce a useful photovoltaic cell.

SUMMARY OF THE INVENTION

The invention provides various embodiments of photovoltaic cells which utilize a mesh electrode on at least one exposure side of the photovoltaic cell. Suitable mesh electrode materials include, but are not limited to, metallic wires, conductive polymeric fibers, metal coated or metallized synthetic polymeric fibers (such as, e.g., nylons) and metal coated or metallized natural fibers (such as, e.g., flax, cotton, wool and silk). Preferably, the mesh electrode comprises a metallic mesh, such as, for example, a metal wire mesh and/or metal coated or metallized fibers. As used herein, the term "wire" refers not only to mesh strands substantially circular or elliptical in cross section, but also to strands of non-circular and non-elliptical cross section, such as, for example, semicircular, square, and rectangular cross section.

Although the wires or fibers of a metallic mesh are opaque (i.e., they block light), the photovoltaic cells of the invention can provide several advantages over prior art cells that utilize semiconductor oxide films as exposure side electrodes. For example, the conductivity of a metallic mesh electrode, being composed of a highly conductive metal (such as, e.g., stainless steel or titanium) exceeds that of the best transparent semiconductor oxide films currently available. In addition, in various embodiments, the formation of a photovoltaic cell using a mesh electrode also reduces or eliminates the cost and technical problems associated with using semiconductor oxide film electrodes in such cells. Further, the use of a flexible mesh electrode facilitates the fabrication of the photovoltaic cells of the invention via a continuous manufacturing process (such as, e.g., roll-to-roll, web) as opposed to the batch processes typically used to make photovoltaic cells on rigid substrates.

Further, although the opaque portions of the mesh electrodes of the invention inherently reduce overall electrode transmisivity, by proper choice of wire (or fiber) diameter and the number of wires (or fibers) per unit area of the mesh, in various embodiments the invention provides mesh electrodes with a transmisivity that exceeds 80%. In various embodiments, the photovoltaic cells of the invention comprise a exposed side mesh electrode having a transmisivity in the range from about 60% to about 95%. It is preferred that the exposed side mesh electrode have a transmisivity greater than about 80%, and more preferred that the transmisivity is greater than about 90%.

According to one aspect, the invention provides a photovoltaic cell that comprises a photosensitized nanomatrix layer and a charge carrier media disposed between two electrodes, where at least one exposure side electrode is made of an opaque material in the form of a mesh. Preferably, the photovoltaic cells also include a catalytic media disposed adjacent to at least one of the electrodes to facilitate charge transfer or current flow to and/or from an electrode and the charge carrier media.

As used herein, the term "photosensitized nanomatrix layer" includes a photosensitized layer comprising nanoparticles, a heterojunction composite material, or combinations thereof. In one embodiment, the photosensitized nanomatrix layer includes one or more types of interconnected nanoparticles and can also include a photosensitizing agent. Examples of suitable nanoparticles include, but are not limited to, nanoparticles of titanium oxides, zirconium oxides, zinc oxides, tungsten oxides, niobium oxides, lanthanum oxides, tin oxides, terbium oxides, tantalum oxides, and combinations thereof. The photosensitizing agent can be, for example, a dye or organic molecule, such as, e.g., a xanthine, cyanine, merocyanine, pthalocyanine or pyrrole. In another embodiment, the photosensitized nanomatrix layer comprises a heterojunction composite material, such as, for example, a composite of fullerene in polythiophene. It is to be understood that, in various embodiments, long-range order is not required of the photosensitized nanomatrix layer. For example, the photosensitized nanomatrix layer need not be crystalline, nor must the particles or phase regions be arranged in a regular, repeating, or periodic array.

In one embodiment, at least one exposure side electrode is a mesh electrode comprised of a metallic material. Preferably, the metallic material comprises platinum, stainless steel, and/or alloys thereof. Other suitable metallic materials include, but are not limited to palladium, titanium, and alloys thereof. It is further preferred that a mesh electrode comprise a flexible mesh material. Flexible mesh materials facilitate the fabrication of the present invention's photovoltaic cells with continuous manufacturing processes, such as, e.g., roll-to-roll or web processes.

In another embodiment, at least one exposure side electrode comprises a mesh electrode with a semiconductor oxide film deposited in the openings of the mesh. Although in such embodiments semiconductor oxides are used, the production specifications for the semiconductor oxide film can be less stringent than those that may be required for a prior art photovoltaic cell. For example, because of the mesh electrode the cell does not need to rely on the semiconductor oxide film alone to convey current from the cell to an external load. Accordingly, for example, lower quality semiconductor oxide films (e.g., those with lower conductivity) could be used than may otherwise be required in a prior art photovoltaic cell.

In another embodiment, the photovoltaic cell of the present invention further comprises a first substrate and a second substrate between which the two electrodes, photosensitized nanomatrix layer and charge carrier media are disposed. In one version, a mesh electrode is partially embedded in the first substrate where, e.g., the first substrate is an exposure side substrate. Preferably, at least a portion of the mesh electrode is coated with a catalytic media, either before partial embedding into the first substrate, after partial embedding, or both before and after partial embedding. In another version, the partially embedded mesh electrode further comprises a semiconductor oxide film deposited on the first substrate and in the openings of the mesh.

In another aspect, the present invention provides a flexible photovoltaic material comprising a first flexible substrate, a flexible mesh electrode, and a first flexible electrode, where a photosensitized nanomatrix layer and a charge carrier media are both disposed between the first flexible electrode and the flexible mesh electrode. Suitable first flexible electrodes include, but are not limited to, mesh electrodes, conductive foils, and conductive films. In one embodiment, the first flexible electrode is disposed adjacent the first flexible substrate. In another embodiment, the first flexible electrode comprises a metal layer deposited on the first flexible substrate.

In another aspect, the invention provides a photovoltaic cell that comprises a photoactive material disposed between two electrodes, where at least one exposure side electrode is made of an opaque material in the form of a mesh. The photoactive material can be a form of silicon (such as, e.g., crystalline, polycrystalline, amorphous), a thin film type photoconducter, or a photosensitized nanomatrix material.

In another aspect, the invention provides a photovoltaic module having two or more photovoltaic cells of the present invention interconnected in series, parallel, or combinations of both. Preferably, the photovoltaic module is formed of photovoltaic cells disposed between a first substrate and a second substrate. The photovoltaic cells each comprise a photosensitized nanomatrix layer and charge carrier media disposed between a first electrode and a mesh electrode. In one embodiment, an electrically insulative material is disposed between the photovoltaic cells and two or more of the photovoltaic cells are electrically connected in series by a wire embedded in the electrically insulative material that is in electrical contact with the mesh electrode of one photovoltaic cell and the first electrode of another photovoltaic cell. Preferably, the electrically insulative material also has adhesive properties, which, e.g., can facilitate combining two substrates, or substrate portions, to form a photovoltaic module according to the invention.

In another aspect, the invention provides methods for fabricating photovoltaic modules comprising a plurality of the photovoltaic cells of the present invention, the methods facilitate the production of such photovoltaic modules using a continuous manufacturing processes, such as roll-to-roll or web processes. In one embodiment, the method comprises: forming a group of photovoltaic cell portions on a first substrate; disposing between at least two of the cell portions on the first substrate an electrically insulative material; forming a group of photovoltaic cell portion on a second substrate; embedding a wire in the electrically insulative material between at least two photovoltaic cell portions on the first substrate; combining the respective substrates and photovoltaic cell portions to form a plurality of photovoltaic cells, wherein at least two photovoltaic cells are electrically connected in series by the wire.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the invention will be more fully understood from the following descriptions of various embodiments of the invention and the accompanying drawings. In the drawings like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

FIGS. 1A and 1B are schematic cross-sectional views of various embodiments of a photovoltaic cell comprising a mesh electrode according to the invention;

FIGS. 2A and 2B are schematic cross-sectional views of various embodiments of a photovoltaic cell comprising a mesh electrode and a semiconductor oxide film according to the invention;

FIGS. 3A to 3D are schematic cross-sectional views of a portion of a photovoltaic cell according to various embodiments of the invention comprising a partially embedded mesh electrode;

FIG. 4A is a schematic cross-sectional view of one embodiment of photovoltaic cells and a photovoltaic module according to the invention having one exposure side;

FIG. 4B is a schematic cross-sectional view of one embodiment of photovoltaic cells and a photovoltaic module according to the invention having two exposure sides;

FIGS. 5A and 5B are photomicrographs of embodiments of a mesh electrode;

FIG. 6 depicts various embodiments of a continuous manufacturing process that may be used to form a photovoltaic cell or photovoltaic module of the present invention;

FIG. 7 is a schematic cross-sectional view of one embodiment of photovoltaic cells in accordance with one aspect of the present invention comprising a photoactive material;

FIG. 8 depicts an exemplary chemical structure of an illustrative embodiment of a polylinker for nanoparticles of an oxide of metal M, in accordance with the invention;

FIG. 9 depicts another exemplary chemical structure of an illustrative embodiment of a polylinker, in accordance with the invention, for nanoparticles of an oxide of metal M;

FIG. 10A shows an exemplary chemical structure for an interconnected nanoparticle film with a polylinker, in accordance with the invention;

FIG. 10B shows the interconnected nanoparticle film of FIG. 3A attached to a substrate oxide layer, in accordance with the invention;

FIG. 11 depicts the chemical structure of poly(n-butyl titanate);

FIG. 12A shows the chemical structure of a titanium dioxide nanoparticle film interconnected with poly(n-butyl titanate), in accordance with the invention;

FIG. 12B shows the interconnected titanium dioxide nanoparticle film of FIG. 12A attached to a substrate oxide layer, in accordance with the invention;

FIG. 12C shows the interconnected titanium dioxide nanoparticle film of FIG. 12A attached to a mesh electrode, in accordance with the invention;

FIG. 13 depicts an illustrative embodiment of a continuous manufacturing process that may be used to form the flexible photovoltaic cells, in whole or part;

FIG. 14 depicts a current-voltage curve for an exemplary solar cell;

FIG. 15 shows a current-voltage curve for an exemplary solar cell, in accordance with the invention;

FIG. 16 shows current-voltage curves for two additional exemplary solar cells;

FIG. 17 depicts an illustrative embodiment of the coating of a semiconductor primer layer coating, according to the invention;

FIGS. 18A-18C depict chemical structures for exemplary co-sensitizers, in accordance with the invention;

FIGS. 19A-19B depict additional exemplary chemical structures of co-sensitizers, in accordance with the invention;

FIG. 20 shows a graph of the absorbance of the 455 nm cut-off filter (GC455) used to characterize photovoltaic cells;

FIG. 21. shows a graph of the absorbance of diphenylaminobenzoic acid;

FIG. 22 depicts an illustrative embodiment of an electrolyte gelled using metal ions; and

FIG. 23 depicts a gel electrolyte formed by the complexing of an organic polymer by lithium ions.

DETAILED DESCRIPTION OF THE INVENTION

A. Photovoltaic Cells Utilizing a Mesh Electrode

The invention provides various embodiments of photovoltaic cells that utilize a mesh electrode on at least one exposure side of the photovoltaic cell. Preferably, the mesh electrode comprises a metallic mesh, such as, for example, a metal wire mesh and/or metal coated or metallized fibers.

In one embodiment, the invention provides dye-sensitized solar cells (DSSC) having a wire mesh exposure side electrode, where the photosensitized nanomatrix layer of the cell comprises a photosensitized interconnected nanoparticle material. In one embodiment, the wire mesh electrode can function as the transparent cathode of a DSSC. Preferably, the mesh is at least partially coated with a catalytic media. For example, the mesh can be plantinized by electrochemical deposition, such as, for example, by using chloroplatinic acid in an electrochemical cell; by vacuum deposition; or by pyrolysis of a coating containing a platinum compound, e.g. chloroplatinic acid. In another embodiment, the wire mesh electrode can function as the anode of the DSSC where, for example, the photosensitized interconnected nanoparticle material is coated on the wire mesh. In addition, wire mesh electrodes can be used as both the anode and the cathode of a DSSC where, for example, light transmission through both sides of the cell is deemed advantageous.

FIGS. 1A and 1B depict photovoltaic cells 100, 101 in accordance with various embodiments of the invention, which include a photosensitized nanomatrix layer 102, 103 and a charge carrier media 106, 107 disposed between a first electrode 108, 109 and a mesh electrode 112, 113 on an exposure side 114, 115 of the photovoltaic cell 100, 101. As depicted in FIG. 1A the mesh electrode 112 serves as a cathode of the photovoltaic cell 100, whereas as depicted in FIG. 1B the mesh electrode 113 serves as an anode of the photovoltaic cell 101. Preferably, the photovoltaic cell further includes a catalytic media 118, 119. In one embodiment, the catalytic media 118 is disposed in electrical contact with the charge carrier media 106 and the mesh electrode 112. In another embodiment, the catalytic media 119 is disposed in electrical contact with the charge carrier media 107 and the first electrode 109. In addition, a wire or lead line (not shown) may be connected to the first electrode and/or mesh electrode to electrically connect the photovoltaic cell to an external load.

Preferably, the photovoltaic cell also includes two substrates between which the electrodes, the photosensitized nanomatrix layer and the charge carrier media are disposed. Referring again FIGS. 1A and 1B, in various embodiments, the photovoltaic cell includes a first significantly light transmitting substrate 120, 121 and a second substrate 124, 125. Preferably, the substrates are also flexible to facilitate, for example, formation of the photovoltaic cell by a continuous manufacturing process.

In various embodiments, a protective coating may be substituted for one or more substrates or used in addition to one or more substrates. Protective coatings can be selected, for example, based on their ability to keep contaminants (e.g., dirt, water or oxygen) out of a cell, to keep chemicals or compositions in a cell, and to protect or ruggedize the cell. Suitable protective coatings include, but are not limited to, fluorocarbon polymers.

As used herein, the term "significantly light transmitting substrate" refers to a substrate that transmits at least about 60% of the visible light incident on the substrate in a wavelength range of operation. Suitable substrates include flexible, semi-rigid and rigid substrates. Preferably, the thickness of a substrate is in the range from about 6 micrometers (μm or microns) to about 200 μm. Examples of suitable flexible substrates include, but are not limited to, substrates with a flexural modulus of less than about 5,000 mega pascals (MPa) for the thickness of substrate material used in the photovoltaic cell. As discussed in further detail below, methods of nanoparticle interconnection are provided herein that enable construction of a flexible photovoltaic cell according to the invention at temperatures and heating times compatible with flexible, significantly light transmitting substrate. Preferably, the flexible, significantly light transmitting substrates comprise a polymeric material. Suitable substrate materials include, but are not limited to, polyethylene terephthalates (PETs), polymides, polyethylene naphthalates (PENs), polymeric hydrocarbons, cellulosics, or combinations thereof.

Substrates for use in the photovoltaic cells of the present invention may be colored or colorless. Preferably, a substrate is non-scattering and transparent. A substrate may have one or more substantially planar surfaces or may be substantially non-planar. For example, a non-planar substrate may have a curved or stepped surface (e.g., to form a Fresnel lens) or be otherwise patterned.

The mesh electrode of the photovoltaic cell comprises a conductive mesh material. Suitable mesh materials include, but are not limited to, metals (such as, for example, palladium, platinum, titanium, stainless steels, and alloys thereof) and conductive polymers such as, e.g., poly(3,4-ethylene dioxythiophene), polythiopene derivatives and polyaniline. Preferably, the mesh material comprises metal wire. The conductive mesh material can also comprise an electrically insulative material that has been rendered conductive by, for example, a metal coating or metallization. The electrically insulative material can comprise a fiber such as, for example, a textile fiber or optical fiber. Examples of suitable fibers include synthetic polymeric fibers (such as, e.g., nylons) and natural fibers (such as, e.g., flax, cotton, wool and silk). Preferably, the mesh electrode is flexible to facilitate, for example, formation of the photovoltaic cell by a continuous manufacturing process.

The mesh electrodes of the invention may take a wide variety of forms with respect to, for example, wire (or fiber) diameters and mesh densities (i.e., the number of wires (or fibers) per unit area of the mesh). The mesh can be, for example, regular or irregular, with any number of opening shapes. It is to be understood that the form factors of the mesh are not critical to the present invention. Suitable mesh form factors (such as, e.g., wire diameter and mesh density) can be chosen, for example, based on the conductivity of the wire (or fibers) of the mesh, the transmisivity desired, flexibility, and/or mechanical strength.

In one embodiment, the mesh electrode comprises a metal wire mesh with an average wire diameter in the range from about 1 μm to about 400 μm, and an average open area between wires in the range from about 60% to about 95%. In one version, the metal wire mesh has an average wire diameter in the range from about 10 μm to about 200 μm, and an average open area between wires in the range from about 75% to about 90%. In one version, the mesh electrode comprises a stainless steel woven wire mesh with an average wire diameter in the range from about 25 μm to about 35 μm, and an average open area between wires in the range from about 80% to about 85%. Preferably, the stainless steel comprises 332 stainless steel or some other stainless steel suitably resistant to any corrosive properties of e.g., the charge carrier material or nanomatrix layer. For example, in some embodiments 316 stainless steel is sufficiently corrosion resistant.

In another embodiment, the mesh electrode comprises a metal coated fiber mesh with an average fiber diameter in the range from about 10 μm to about 400 μm, and an average open area between fibers in the range from about 60% to about 95%. In one version, the fiber mesh has an average fiber diameter in the range from about 10 μm to about 200 μm, and an average open area between fibers in the range from about 75% to about 90%. In one version, the mesh electrode comprises nylon fibers coated with titanium having a thickness in the range from about 1 μm to about 50 μm; the resultant mesh has an average fiber diameter in the range from about 10 μm to about 250 μm, and an average open area between fibers in the range from about 60% to about 95%.

In various embodiments, the mesh electrode further includes a transparent semiconductor oxide film deposited in the openings of the mesh. Because of the mesh electrode, the cell does not need to rely on the transparent semiconductor oxide film alone to convey current from the cell to an external load. This can allow, for example, the use of lower quality semiconductor oxide films (e.g., those with lower conductivity) and/or thinner films than may otherwise be required in a prior art photovoltaic cell.

In one embodiment, the semiconductor oxide film does not substantially coat the wires (or fibers) of the mesh electrode. In another embodiment, the mesh electrode is coated with a transparent semiconductor oxide film. The transparent semiconductor oxide film can provide a transparent, uniform, semiconductor surface between the wires of the mesh electrode. Preferably, the transparent semiconductor oxide film and the mesh electrode are in electrical contact, as a result, the mesh electrode facilitates conducting electrons out of the cell to an external load. For example, for a mesh electrode serving as an anode in a DSSC, the transparent semiconductor oxide film can provide a semiconductor surface for the interconnected nanoparticle material and aid in removing photogenerated electrons from the interconnected nanoparticle material. Further, for example, for a mesh electrode serving as a cathode in a DSSC, the transparent semiconductor oxide film can provide a semiconductor surface for a catalytic media and/or charge carrier media and aid in electron transfer to these media from the mesh electrode.

Referring to FIGS. 2A and 2B, in various embodiments, the photovoltaic cells 200, 201 include a photosensitized nanomatrix layer 202, 203 and a charge carrier media 206, 207 disposed between a first electrode 208, 209, a mesh electrode 212, 213 on an exposure side 214, 215 of the photovoltaic cell 200, 201, and a transparent semiconductor oxide film 216, 217 disposed at least in the openings of the mesh electrode. Preferably, the photovoltaic cell further includes a catalytic media 218, 219. In one embodiment, the catalytic media 218 is disposed in electrical contact with the charge carrier media 206 and the mesh electrode 212; and the catalytic media preferably is also disposed in electrical contact with at least a portion of the transparent semiconductor oxide film 216. In another embodiment, the catalytic media 219 is disposed in electrical contact with the charge carrier media 207 and the first electrode 209; and preferably the catalytic media is also disposed in electrical contact with at least a portion of the transparent semiconductor oxide film 217. In addition, a wire or lead line (not shown) may be connected to the first electrode and/or mesh electrode to electrically connect the photovoltaic cell to an external load. Preferably, the photovoltaic cell further includes a first significantly light transmitting substrate 220, 221 and a second substrate 224, 225. Preferably, the substrates are flexible to facilitate, for example, formation of the photovoltaic cell by a continuous manufacturing process. In various embodiments, a protective coating may be substituted for one or more substrates or used in addition to one or more substrates.

Suitable transparent semiconductor oxide film materials include, but are not limited to, indium tin oxide ("ITO"), a fluorine-doped tin oxide, tin oxide, or the like. In one embodiment, the transparent semiconductor oxide film is deposited as a layer between about 100 nm and about 500 nm thick. In another embodiment the transparent semiconductor oxide film is between about 150 nm and about 300 nm thick.

In various embodiments, the mesh electrode is partially embedded into a substrate of the photovoltaic cell. In one embodiment, partially embedding the mesh electrode into a substrate of the cell facilitates fabrication by a continuous manufacturing process and fabrication of a more rugged cell. In one embodiment, a mesh electrode is partially embedded in the first substrate where, e.g., the first substrate is an exposure side substrate. Preferably, at least a portion of the mesh electrode is coated with a catalytic media, either before partial embedding into the first substrate, after partial embedding, or both before and after partial embedding.

Preferably, overall the mesh electrode is embedded in a substrate to a depth no greater than about 70% of the average diameter of the wire (or fiber) of the mesh. It is preferred that the mesh is embedded in a substrate to the minimum extent possible to sufficiently anchor the mesh to the substrate and thereby maximize the area of the mesh in electrical contact with, for example, a charge carrier or nanomatrix layer. For example, in one embodiment having a woven wire mesh, underlying wires at wire intersections are completely embedded in the substrate, the overlying wires at intersections are not embedded, and the portions of wire between wire intersections are partially embedded.

In various embodiments including a mesh electrode embedded in a substrate, the wires of the mesh electrode extend above the substrate a distance greater than about 30% of the average diameter of the wire (or fiber) of the mesh. In one embodiment, the mesh electrode is embedded in a substrate such that the wires of the mesh electrode preferably extend above the substrate a distance in the range between about 25% and about 50% of the average diameter of the wire (or fiber) of the mesh.

In various other embodiments including a mesh electrode embedded in a substrate, the wires (or fibers) of the mesh electrode are preferably embedded in a substrate to a depth no greater than about 70% of the average diameter of the wire (or fiber) of the mesh. In one embodiment, the wires (or fiber) are embedded in a substrate to a depth in the range between about 50% and about 75% of the average diameter of the wire (or fiber) of the mesh.

Referring to FIGS. 3A and 3B, in various embodiments, the photovoltaic cells 300, 301 include a photosensitized nanomatrix layer 302, 303 and a charge carrier media 306, 307 disposed between a first electrode 308, 309, a mesh electrode 312, 313 on an exposure side 314, 315 of the photovoltaic cell 300, 301 which is partially embedded in a first significantly light transmitting substrate 320, 321. Preferably, the photovoltaic cell further includes a second substrate 324, 325. Preferably, the substrates are flexible to facilitate, for example, formation of the photovoltaic cell by a continuous manufacturing process. In various embodiments, a protective coating may be substituted for one or more substrates or used in addition to one or more substrates.

It is also preferred that the photovoltaic cell further includes a catalytic media 318, 319. In one embodiment, the catalytic media 318 is disposed in electrical contact with the charge carrier media 306 and the mesh electrode 312. In another embodiment, the catalytic media 319 is disposed in electrical contact with the charge carrier media 307 and the first electrode 309. In addition, a wire or lead line (not shown) may be connected to the first electrode and/or mesh electrode to electrically connect the photovoltaic cell to an external load.

In various embodiments, the photovoltaic cells of the present invention having a partially embedded mesh electrode further comprise a semiconductor oxide film deposited in the openings of the mesh. Referring to FIGS. 3C and 3D, in various embodiments, the photovoltaic cells 350, 351 include a photosensitized nanomatrix layer 352, 353 and a charge carrier media 356, 357 disposed between a first electrode 358, 359, a mesh electrode 362, 363 on an exposure side 364, 365 of the photovoltaic cell 350, 351, which is partially embedded in a first significantly light transmitting substrate 370, 371, and a transparent semiconductor oxide film 366, 367 disposed at least in the openings of the mesh electrode. Preferably, the photovoltaic cell further includes a second substrate 374, 375. Preferably, the substrates are flexible to facilitate, for example, formation of the photovoltaic cell by a continuous manufacturing process. In various embodiments, a protective coating may be substituted for one or more substrates or used in addition to one or more substrates.

It is also preferred that the photovoltaic cell further includes a catalytic media 368, 369. In one embodiment, the catalytic media 368 is disposed in electrical contact with the charge carrier media 356 and the mesh electrode 362; and preferably also in electrical contact with at least a portion of the transparent semiconductor oxide film 366. In another embodiment, the catalytic media 369 is disposed in electrical contact with the charge carrier media 357 and the first electrode 359; and preferably also in electrical contact with at least a portion of the transparent semiconductor oxide film 367. In addition, a wire or lead line (not shown) may be connected to the first electrode and/or mesh electrode to electrically connect the photovoltaic cell to an external load.

The first electrodes of the invention (such as, for example, those illustrated in FIGS. 1A-1B, 2A-2B, 3A-3B, and 4-6) may take a wide variety of forms including, but not limited to, a mesh, a metal foil, a deposited metal layer, a conductive polymer film, a semiconductor oxide film, or one or more combinations thereof. Where the first electrode side of the photovoltaic cell is also an exposure side, it is preferred that the first electrode comprises a mesh electrode as described herein, including catalytic media coated mesh electrodes and mesh electrodes with a transparent semiconductor oxide film in the mesh openings. In other embodiments, it is preferred that the first electrode comprises a metal foil. Examples of suitable metal foil materials for the first electrode include, but are not limited to, palladium, platinum, titanium, stainless steels, and alloys thereof. In various embodiments the first electrode comprise a metal foil with an average thickness in the range from between about 10 μm and about 100 μm. Preferably, the metal foil has an average thickness in the range from between about 25 μm and about 50 μm.

In one embodiment, where the photosensitized nanomatrix layer comprises a dye-sensitized interconnected titanium dioxide nanoparticle material, the first electrode comprises a titanium metal foil about 25 μm thick. In one version, the photosensitized nanomatrix layer is formed directly on the titanium metal foil or on a suitable primer layer (further discussed below).

In another embodiment, the first electrode comprises a metal layer deposited on a substrate. Suitable metals include, but are not limited to, palladium, platinum, titanium, stainless steels, and alloys thereof. In various embodiments the deposited metal layer an average thickness in the range from between about 0.1 μm and about 3 μm. Preferably, a deposited metal layer has an average thickness in the range from between about 0.5 μm and about 1 μm.

In another embodiment, the first electrode comprises a conductive polymer such as, for example, poly(3,4,-ethylene dioxythiopene), polyaniline, and polythiopene derivatives.

In yet another embodiment, the first electrode comprises a significantly light transmitting material, which include transparent semiconductor oxide film such as, for example, ITO, a fluorine-doped tin oxide, tin oxide, or the like. In one version, the first electrode is deposited on a substrate as a layer between about 100 nm and about 500 nm thick. In another version, the first electrode is between about 150 nm and about 300 nm thick.

In another aspect, the present invention provides a flexible photovoltaic material comprising a first flexible substrate, a flexible mesh electrode, and a first flexible electrode, where a photosensitized nanomatrix layer and a charge carrier media are both disposed between the first flexible electrode and the flexible mesh electrode. Preferably, the photovoltaic material includes a catalytic media in electrical contact with the charge carrier media. In addition, in various embodiments the flexible photovoltaic material further comprises a second substrate such that the flexible mesh electrode, first flexible electrode, photosensitized nanomatrix layer and charge carrier media are disposed between the first flexible substrate and the second substrate. In addition, a wire or lead line (not shown) may be connected to the first flexible electrode and/or flexible mesh electrode to electrically connect the photovoltaic material to an external load.

The flexible photovoltaic material may take a wide variety of forms including, but not limited to, those illustrated in FIGS. 1A-1B, 2A-2B, 3A-3B, and 4-6. For example, in various embodiments, the first flexible substrate of the photovoltaic material may be a first significantly light transmitting substrate. Preferably, the flexible, significantly light transmitting substrate comprises a polymeric material. Suitable substrate materials include, but are not limited to, polyethylene terephthalates (PETs), polymides, polyethylene naphthalates (PENs), polymeric hydrocarbons, cellulosics, or combinations thereof.

In other embodiments, the first flexible substrate is not an exposure side substrate. In one version of these embodiments, the first flexible substrate is opaque. In another version, the flexible photovoltaic material further comprises a transparent protective coating on the exposure side of the material. It is to be understood that where the first flexible substrate is not an exposure side substrate a wide range of materials are suitable for use as flexible substrates. Preferable substrate materials include polyethylene terephthalates (PETs), polyimides, polyethylene naphthalates (PENs), and poly carbonates. Other suitable substrate materials include, but are not limited to, cellosics (filled and unfilled); polyamides and copolymers thereof, polyethers, and polyether ketones.

Examples of suitable protective coatings include, but are not limited to fluorocarbon polymers and dysiloxanes. For example, where the flexible photovoltaic material comprises a DSSC having a wire mesh exposure side electrode as the flexible mesh electrode, and where the photosensitized nanomatrix layer of the cell comprises a photosensitized interconnected nanoparticle material, preferred protective coatings include, but are not limited to Tefzel (Dupont).

Suitable first flexible electrodes include, but are not limited to, mesh electrodes, conductive foils, conductive films, and other first electrodes described herein. In one embodiment, the first flexible electrode is disposed adjacent the first flexible substrate. In another embodiment, the first flexible electrode comprises a metal layer deposited on the first flexible substrate. Where the first flexible electrode side of the flexible photovoltaic material is also an exposure side, it is preferred that the first flexible electrode comprises a mesh electrode as described herein that is flexible.

The photosensitized nanomatrix layer of the photovoltaic cells of the present invention can include a photosensitized nanoparticle material, heterojunction composite material, or combinations thereof. As discussed above, it is to be understood that while long-range order can be present in the photosensitized nanomatrix layer, long-range order is not required. For example, the photosensitized nanomatrix layer need not be crystalline, nor must the particles or phase regions be arranged in a regular, repeating, or periodic array. In one embodiment, the photosensitized nanomatrix layer is between about 1 micron (μm) and about 5 μm thick. In another embodiment, the photosensitized nanomatrix layer is between about 5 μm and about 20 μm thick. Preferably, the photosensitized nanomatrix layer is between about 8 μm and about 15 μm thick and comprises photosensitized interconnected nanoparticles.

In one embodiment, the photosensitized nanomatrix layer includes a heterojunction composite material. Suitable heterojunction composite materials incl