Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Coating contains embedded solid material
Patent
1992-06-30
1994-01-04
Weisstuch, Aaron
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Coating contains embedded solid material
136265, 136264, 205138, 205144, 205227, 205239, 205316, 205915, 205923, 437 5, C25D 550, C25D 908, C25D 1502, H01L 3118
Patent
active
052757145
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method of producing an absorber layer for solar cells, particularly a CuInSe.sub.2 absorber layer, with the aid of electrodeposition, wherein a ternary semiconductor layer composed of elements of Groups IB, IIIA, and VIA of the Periodic Table of Elements is deposited on an electrically conductive substrate.
TECHNOLOGY REVIEW
A CuInSe.sub.2 thin-film solar cell is typically composed of a substrate which gives the cell the necessary stability. The substrate is coated with the above-mentioned absorber layer, which in the literature is also called an absorber-generator. Customarily, a large-area metal current pickup contact is disposed between the substrate and the absorber layer. The collector, with the aid of which the pn-junction is produced, is disposed on the top face of the absorber layer. In the example of a CuInSe.sub.2 absorber layer the collector is composed of a coating of CdS. Customarily, a more or less fine grid contact is applied to the top face of the collector so as to reduce series resistance. The above relates to the general structure of a thin-film solar cell as it is constructed with the aid of the absorber layer produced according to the method of the invention.
Several complicated, usually physical, processes are available for the manufacture of such absorber layers and, among these processes, the production process employing electrodeposition technology promises to be particularly economical and environmentally friendly. Therefore, the present invention concerns itself with this technology.
At present, a solar cell whose absorber layer is composed of CuInSe.sub.2 appears to hold the greatest promise for success. However, the production of such an absorber layer by electroplating has failed in the past, although it was possible to precipitate layers composed of CuInSe.sub.2 from acidic Cu-chloride, In-chloride, and Se-oxide containing baths. Such ternary baths, however, are unstable and can therefore not be considered for economical manufacture.
Regarding the prior art, reference is made to
SUMMARY OF THE INVENTION
The invention provides a method of producing an absorber layer of a ternary alloy for solar cells with the aid of electrodeposition, wherein a binary alloy is deposited on a substrate from a solution of ions of the elements of Groups IB and IIIA of the Periodic Table of Elements and simultaneously an ultrafine powder of an element of Group VIA of the Periodic Table of Elements that is suspended in the electrolytic bath is incorporated into the alloy in a finely dispersed manner by means of dispersion electrolysis. A subsequent, for example, thermochemical reaction leads to a chemical compound of the I-III-VI.sub.2 type.
With this manner of proceeding, difficulties are avoided as they occurred in the prior art particularly during the electrodepoition of CuInSe.sub.2 caused, in particular, by the instability of the ternary baths. Instead, advantage is taken of the fact that binary CuIn layers can easily be deposited electrolytically into which Se is embedded according to the invention in a finely dispersed form by dispersion electrolysis.
BRIEF DESCRIPTION OF THE FIGURE
The FIGURE is a schematic representation of a copper-indium-selenium dispersion layer (B) that has been deposited by dispersion electrolysis on an electrically conductive substrate (A).
DETAILED DESCRIPTION OF THE INVENTION
This is accomplished according to the invention in that a binary alloy of elements of Groups IB and IIIA of the Periodic Table of Elements is electrodeposited on the substrate simultaneously with the alloy component of Group VIA of the Periodic Table of Elements that is suspended in the electroplating bath; it is incorporated in the binary alloy in finely dispersed form by means of dispersion electrolysis.
The invention thus takes advantage of the realization that binary CuIn layers can easily be deposited electrolytically. The incorporation of selenium--and in general the respective Group VIA element of the Periodic Table of Eleme
REFERENCES:
F. J. Pern et al., Solar Cells, vol. 24, May/Jun. 1988, pp. 81-90.
I. Shih et al., Solar Cells, vol. 16, Jan./Feb. 1986, pp. 283-287.
F. J. Pern et al., Conference Record, 19th IEEE Photovoltaic Specialists Conf. (May 1987), pp. 1295-1298.
Solar Cells, vol. 16 (1986); "Electrodeposition of CuInSe.sub.2 and CuInS.sub.2 Films", Gary Hodes et al., pp. 245-254.
C. D. Lokhande, "Pulse Plated Electrodeposition of CuInSe.sub.2 Films", J. Electrochem. Soc: Electrochemical Science and Technology, vol. 134, No. 7, Jul. 1987, pp. 1727-1729.
R. N. Bhattacharya et al., "Electrodeposition of CuInX (X=Se, Te) Thin Films", Solar Cells, vol. 16, (1986), pp. 237-243.
Bonnet Dieter
Ehrhardt Josef
Hewig Gert
Battelle (Memorial Institute)
Weisstuch Aaron
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