Photovoltaic elements having long-term stability that can be precipitated out of solutions, and in-situ method for producing said elements

Abstract

The present invention relates to a photovoltaic element comprising one front electrode and one further electrode comprising respectively one glass substrate and one electrically conductive electrode layer which is disposed on the glass substrate, at least two porous carrier layers which are disposed between the two electrodes, the two electrodes being connected to the adjacent porous carrier layers without a spatial interval, a plurality of glass solder webs disposed between the two electrodes for fixing the at least two porous carrier layers, and at least one photovoltaically active material which is introduced into the at least two porous carrier layers and has a concentration gradient.

Claims

1. A photovoltaic element comprising: a front electrode and a further electrode wherein each of the front electrode and the further electrode comprises a glass substrate, an electrically conductive electrode layer which is disposed on the glass substrate and one electron- or hole-selective layer, at least two porous carrier layers which are disposed between the front electrode and the further electrode, wherein the front electrode and the further electrode are each directly connected to one of the at least two porous carrier layers without a spatial interval, a plurality of glass solder webs disposed between the front electrode and the further electrode for fixing the at least two porous carrier layers, and at least one photovoltaically active material which is introduced into the at least two porous carrier layers and has a concentration gradient wherein the at least one photovoltaically active material is a semiconducting perovskite having a general form K-M-A3, wherein K is a cation, M is a metal, and A is an anion.

2. The photovoltaic element according to claim 1, wherein the electrically conductive electrode layer of the front electrode and/or the electrically conductive electrode layer of the further electrode is transparent.

3. The photovoltaic element according to claim 1, wherein the at least two porous carrier layers have a different pore size, wherein a porous carrier layer next to the front electrode having the smallest pore size and a pore size of a porous carrier layers increasing at increasing distance from the front electrode.

4. The photovoltaic element according to claim 1, wherein the at least two porous carrier layers are electrically conductive or electrically insulating.

5. The photovoltaic element according to claim 1, wherein an extension of the at least two porous carrier layers between adjacent glass solder webs is 3 to 10 mm and/or the thickness of all of the at least two porous carrier layers in total is 0.5 to 20 m.

6. The photovoltaic element according to claim 1, wherein the at least two porous carrier layers consist of a material selected from the group consisting of TiO.sub.2, TiN, SiN, TiC, SiC, Al.sub.2O.sub.3, ZrO.sub.2, SiO.sub.2, Fe.sub.2O.sub.3, nickel oxides, chromium oxides, cobalt oxides, glass pigments, carbon black, graphite, and combinations thereof.

7. The photovoltaic element according to claim 1, wherein the electrically conductive electrode layer consists of a material selected from the group consisting of SnO.sub.2:F, ZnO:Al, indium tin oxide, and combinations thereof.

8. The photovoltaic element according to claim 1, wherein the electron- or hole-selective layer comprises a material selected from the group consisting of titanium dioxide, nickel oxide, tungsten oxide, iron oxide, chromium oxide, cobalt oxide, manganese oxide, molybdenum oxide, niobium oxide, copper oxide, antimony oxide, tin oxide, zinc oxide, bismuth oxide, lead oxide, cerium oxide, carbon black, platinum, silver and palladium.

9. The photovoltaic element according to claim 1, wherein channel structures for pouring in solutions are introduced inside the front electrode and the further electrode and also between the glass solder webs and the at least two porous carrier layers.

10. The photovoltaic element according to claim 1, wherein in the semiconducting perovskites of the general form K-M-A3 the K is selected from the group consisting of Cs.sup.+, CH.sub.3NH.sub.3.sup.+, Li.sup.+, imidazolium cations, ammonium cations, pyridinium cations, bipyridyls, Ca.sup.2+ and Mg.sup.2+, M is selected from the group consisting of Pb, Sn, Bi, Fe, Mn, Cu, Co, W, Ti and Zn and A is selected from the group consisting of I.sup., Cl.sup., F.sup., Br.sup., SCN.sup., BF.sub.4.sup., OTf.sup.,MnO.sub.4.sup., S.sup.2, and SO.sub.4.sup.2.

11. A photovoltaic module comprising an internal electrical series connection of at least two photovoltaic elements, each including: a front electrode and a further electrode wherein each of the front electrode and the further electrode comprises a glass substrate, an electrically conductive electrode layer which is disposed on the glass substrate and one electron- or hole-selective layer, at least two porous carrier layers which are disposed between the front electrode and the further electrode, wherein the front electrode and the further electrode are each directly connected to one of the at least two porous carrier layers without a spatial interval, a plurality of glass solder webs disposed between the front electrode and the further electrode for fixing the at least two porous carrier layers, and at least one photovoltaically active material which is introduced into the at least two porous carrier layers and has a concentration gradient wherein the at least one photovoltaically active material is a semiconducting perovskite having a general form K-M-A3, wherein K is a cation, M is a metal, and A is an anion.

Description

DETAILED DESCRIPTION

(1) The present invention is explained in more detail with reference to the subsequent Figures and also examples without restricting the invention to the specially illustrated parameters.

(2) FIG. 1 shows the cross-section through a photovoltaic element according to the invention. It comprises a front electrode consisting of a glass substrate (1), an electrically conductive layer (2) and a thin electron- or hole-selective layer (7) and also a further electrode consisting of a glass substrate (5), an electrically conductive layer (4) and a thin electron- or hole-selective layer (11). Between the two electrodes, three porous carrier layers (8, 9, 10) are disposed, the two electrodes being connected to the adjacent porous carrier layers without a spatial interval. Glass solder webs (3) are disposed between the two electrodes such that they fix the three porous carrier layers. The porosity of the carrier layers thereby reduces from the top to the bottom. Hence the inner surface of the carrier layers and hence the capillary effect increases from the top to the bottom. The channels (6, 12) serve for introducing solutions into the porous carrier layers.

(3) According to the method according to the invention, photovoltaically active materials dissolved in a solvent are introduced through filling holes, distributed by the channels (6, 12) and also the uppermost carrier layer (10) in a planar manner and absorbed in the carrier layers (8, 9) lying thereunder due to capillary forces. The central carrier layer (9) hereby serves as liquid reservoir. Subsequently, the solvent is evaporated and discharged again through the uppermost carrier layer (10) and the channels (6, 12). The drying and the accompanying reduction in quantity of the solvent therefore take place from the top to the bottom. In other words, this leads to a concentration of the photovoltaically active materials and ultimately to a precipitation with a high filler content in the lowermost carrier layer (8). This carrier layer (8) hence absorbs the photovoltaically active materials which form an electrical contact to the front electrode (1, 2, 7). The electrical contacting to the second electrode (4, 5, 11) is implemented analogously, solutions made of polymeric materials which are preferably equipped to be conductive and/or materials which are equipped to be conductive with for example carbon blacks or carbon nanotubes being used for precipitation in the carrier layers (9) and (10).

(4) The relative dimensions are represented greatly distorted in FIG. 1. The ratio of height to width is in reality H/W=10.sup.510.sup.4.

EXAMPLE

(5) Sheets of float glass coated with fluorine-doped tin oxide are provided with channel structures. Subsequently, a compact approx. 20 nm thick TiO.sub.2 layer (blocking layer) is applied by spray pyrolysis. Now, in succession, the carrier layers (nanoporous TiO.sub.2 as lowermost 0.4 m thick layer, highly porous TiO.sub.2 as central 3 m thick layer, microporous Al.sub.2O.sub.3 as uppermost likewise 2 m thick layer) and the glass solder are printed onto the front electrode by screen printing and sintered at 450 C. (the different porosities and pore sizes are hereby produced in the carrier layers) and also subsequently are melted in a temperature step (650 C.) with the rear electrode by means of the printed glass solder webs. Thus a complete glass body which surrounds the printed carrier layers is produced. Merely two filling openings for introducing the active materials are now still open.

(6) PbI.sub.2 in a DMF solution (500 mg/ml) is now pressed into the layers through a filling opening and the channel structures. By means of the different pore sizes of the three carrier layers (pore size is reduced in the direction of the front electrode), the PbI.sub.2 is transported into the lowermost layer on the front electrode by capillary effect. Now the DMF is dried by means of nitrogen at temperature and the active material remains in the layer. In the next step, CH.sub.3NH.sub.3I in an isopropanol solution (10 mg/ml) is introduced into the cell structure. The material is likewise moved by means of capillary forces through the layers (in one reaction, the perovskite is now produced in the form CH.sub.3NH.sub.3PbI.sub.3). Subsequently acetonitrile for rinsing the upper layers is pressed through the cell structure and once again dried by means of nitrogen. As last step, a solution of Spiro-OmeTAD (Merck) in chlorobenzene (100 mg/ml), mixed with electrically conductive carbon black particles (Degussa Printex), is introduced into the structure and dried once again by means of nitrogen at temperature. Finally, the filling holes are sealed and the cell structure is contacted via the TCO lying outside the glass solder webs.