DE4416247A1 - Dye-stabilised photovoltaic cell module - Google Patents

Abstract

A monolithic series-connected dye-sensitised photovoltaic module consists of photo-electrodes (4) in the form of dye-sensitised nano-porous semiconductor layers on an electrically conductive transparent substrate (1), an electron transporting electrolyte and counter-electrodes (6). The novelty is that the photo-electrodes (4) are arranged in parallel strips on an electrical coating (2), interrupted between the photo-electrodes, and are coated, opt. with interposition of a porous electrically insulating interlayer (5), with counter-electrodes (6) of porous electroconductive material so the counter-electrodes contact one side of the conductive coating of adjacent photo-electrodes. After dye adsorption through the counter-electrodes (6) and interlayers (5) onto the photo-electrodes (4), electrolyte filling of the pores of the porous layers (4-6) and sealing with a cover layer (8), a series-connection of photovoltaic cells is created on a common substrate. The counter-electrodes (6) may consists of an electroconductive polymer (e.g. polyaniline, polypyrrole or polythiophene) and may be electrically insulated from one another by non-porous insulation (e.g. silicone rubber).

Description

The invention relates to monolithic, series-connected, dye-sensitized photovoltaic modules made from dye-sensitized nanoporous semiconductor electrodes as photo electrodes on electrically conductive, transparent substrate, an electron transfer electrolyte and There are counter electrodes. Single photovoltaic cells of this type already exist (Journal of the American Chemical Society, Volume 115, Year 1993, pages 6382-6390). Thereafter, tin oxide coated glass as an electrically conductive, transparent substrate with a porous Semiconductor layer made of nanocrystalline titanium dioxide provided as a photoelectrode and sensitized to visible light by adsorption of a dye. Of the dye excited by light absorption injects electrons into the Titanium dioxide, which enter the external circuit via the conductive substrate and can do electrical work there. The oxidized dye is through an electron-transferring electrolyte that reduces the pores of the Fills the photoelectrode and the space up to the counter electrode. The The counter electrode usually also consists of glass coated with tin oxide with platinum is activated catalytically from the outer circuit transfer incoming electrons back to the electrolyte.

The production of large-area cells has so far been difficult connected because the distance between the photo and counter electrodes due to Unevenness of the separate substrates quickly becomes too large (<20 µm), so that Ohmic losses and even diffusion limitation of the photocurrent in the Electrolyte layer occur. In addition, the conductivity of the substrate is not sufficient to derive the photocurrents generated by large-area cells. When The solution is the one known from amorphous silicon cells Series connection of strip-shaped individual cells to modules in which the Counter electrode of one cell with the photoelectrode of the next cell electrical is connected (Solar Energy, volume 23, year 1979, pages 145-147). At the current structure of the dye-sensitized photovoltaic cell however, this would require an electrically conductive bridge from the conductive Substrate through the electrolyte to the other substrate. Apart from Material problems in the presence of the corrosive electrolyte is the manufacture linear contacts between the superimposed substrates  Temperatures that do not destroy the dye lead to difficult realize.

The invention has for its object the distance from photo and To keep the counterelectrode small even with large cells and several Connect cells to a photovoltaic module in series.

According to the invention, this object is achieved in that several Photoelectrodes are arranged on the same substrate in parallel strips and, possibly separated by a porous insulator layer, with porous Counter electrodes are coated so that they are the conductive substrate of the contact the next photoelectrode. The dye can then be through the porous counter electrodes on the photo electrodes adsorb. The pores of the coatings are finally covered with electrolyte filled and the module sealed with a top layer. This arrangement is explained in more detail below using an exemplary embodiment.

The porous insulator layer preferably consists of a fine-grained glass or ceramic powder.

Metal powders are particularly suitable for the porous counterelectrode, electrically conductive ceramic powder, carbon powder or carbon felt, as well electrically conductive polymers. The porous surface of the counter electrode can can be activated catalytically by depositing a platinum metal.

Adjacent counter electrodes are preferably replaced by a non-porous insulator, which can be identical to the top layer, from each other isolated.

The porous layers are expediently by screen printing applied. The porous layers can also initially cover the entire surface applied and only subsequently divided into parallel strips.

The invention has the following advantages: Photo and counter electrodes are arranged one above the other on the same substrate so that their distance is independent gig of bumps in the substrate remains minimal. The electrolyte does not form additional layer, but is fixed in the porous layers. The Counter electrode has an enlarged due to its porous nature Surface what their activity for electron exchange with the Electrolytes increased. The series connection of several cells results from a fold overlap of the counter electrodes with the conductive substrate of each subsequent photoelectrode. All electrical connections are formed before the dye is sensitive to heat and moisture and electrolyte are applied. The top layer is only used for sealing and electrical insulation, but has no current-carrying function.

An embodiment of the invention is shown in the drawing and is described in more detail below.

The figure shows a - not to scale - cross section of the photovoltaic module. The transparent, conductive coating 2 (e.g. fluorine-doped tin oxide, tin-doped indium oxide) on the insulating substrate 1 (e.g. glass, plastic) is removed in parallel lines 3 at the desired distance (e.g. mechanically) Etching or using a laser beam) to define the area of each individual cell.

A dispersion of nanocrystalline semiconductor powder (z. B. Titanium dioxide) is applied (about 10 microns thick, z. B. by screen printing through a suitable mask) as photoelectrodes 4 so that they protrude slightly beyond one edge of the conductive coatings 2 , the leave other edge uncovered. The photoelectrodes 4 can also first be applied over the entire surface and then (for example mechanically, by etching or with a laser beam) divided into parallel strips.

The photoelectrodes 4 may be covered with a dispersion of fine-grained glass or ceramic powder (e.g. aluminum oxide, silicon dioxide) as a porous insulator layer 5 (about 1 μm thick, e.g. by screen printing) in order to avoid short circuits if the material the counterelectrodes 6 forms an ohmic contact with the photoelectrodes 4 .

A metal powder (e.g. a platinum metal, titanium, tungsten, molybdenum, chrome), electrically conductive ceramic powder (e.g. fluorine-doped tin oxide, tin-doped indium oxide), carbon powder or carbon felt, or an electrically conductive polymer (e.g. Polyaniline, polypyrrole, polythiophene), possibly provided with a catalytic coating of a platinum metal, is applied as counterelectrode 6 (a few μm thick) in such a way that it covers the photoelectrodes 4 and the uncoated edge of the conductive coating 2 under the next photoelectrode 4 . As a result, the individual cells arranged in parallel are electrically connected in series to form a module.

The gaps 7 between the counter electrodes 6 can be created both by means of screen printing through an appropriate mask and by subsequent removal (for example mechanically, by etching or with a laser beam). The gaps 7 should be filled with a non-porous insulator (e.g. silicone rubber, glass solder, an organic polymer), which can be identical to the cover layer 8 , in order to avoid cross currents through the electrolyte between the counter electrodes 6 .

Layers 4-6 can be fired at any time to remove unwanted aids (e.g. solvents) and to improve the electrical and mechanical properties by sintering.

The coated substrate 1 is immersed in a dye solution in order to sensitize the photoelectrodes 3 . After drying, the pores of layers 4-6 are filled with electrolyte. The module is sealed by a cover layer 8 (e.g. glass, plastic, anodized aluminum, paint or another insulator) and at the edges. The module is electrically contacted at the first counter electrode 9 and the last photoelectrode 10 of the series circuit.

Claims (6)

1. Monolithic, series-connected, dye-sensitized photovoltaic modules consisting of dye-sensitized, nanoporous semiconductor layers as photoelectrodes ( 4 ) on an electrically conductive, transparent substrate ( 1 ), an electron-transferring electrolyte and counterelectrodes ( 6 ), characterized in that several photoelectrodes ( 4 ) in parallel strips are arranged on the interrupted electrical covering ( 2 ) and, possibly separated by a porous, electrically insulating intermediate layer ( 5 ), are made of porous, electrically conductive material, the counter electrodes ( 6 ) are coated in such a way that they contact the conductive coating ( 2 ) of the adjacent photoelectrode ( 4 ) on one side and thus after adsorption of the dye by the porous counterelectrodes ( 6 ) and intermediate layers ( 5 ) on the photoelectrodes ( 4 ) and filling the pores of the porous layers ( 4- 6 ) with electrolyte and versie gelung with a cover layer ( 8 ), a series connection of photovoltaic cells on a common substrate. 2. Module according to claim 1, characterized in that the porous intermediate layers ( 5 ) consist of a fine-grained glass or ceramic powder (z. B. aluminum oxide, silicon dioxide). 3. Module according to claim 1, characterized in that the counter electrodes ( 6 ) from a metal powder (z. B. a platinum metal, titanium, tungsten, molybdenum, chromium), an electrically conductive ceramic powder (z. B. fluorine-doped tin oxide, tin doped indium oxide), carbon powder or carbon felt, or an electrically conductive polymer (e.g. polyaniline, polypyrrole, polythiophene) and are provided, if necessary, with a catalytic coating of a platinum metal. 4. Module according to claim 1, characterized in that the counter electrodes ( 6 ) by a non-porous insulator (z. B. silicone rubber, glass solder, an organic polymer), which can be identical to the cover layer ( 8 ), are electrically isolated from each other. 5. Modules according to claim 1, characterized in that the porous layers ( 4-6 ) are applied by screen printing. 6. Modules according to claim 1, characterized in that the porous layers ( 4-6 ) are first applied over the entire surface (z. B. by spraying), and only subsequently mechanically, by etching or using a laser beam are divided into parallel strips.