Method of making the compound CuInSe.sub.2

Details Method of making the compound CuInSe.sub.2 Method of making the compound CuInSe.sub.2

1995-02-03

1996-03-26

Niebling, John

Electrolysis: processes, compositions used therein, and methods

Electrolytic coating

Coating contains embedded solid material

205176, 205191, 205228, 205238, C25D 1500

Patent

active

055017860

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a method of making the compound CuInSe.sub.2 (CIS) by depositing a precursor of this compound at least partly electrolytically on a substrate and forming the compound CuInSe.sub.2 by thermal reaction.
2. Description of the Prior Art
DE-C2-4103291 discloses a method of making thin films of CuInSe.sub.2 by galvanic deposition of a layer of Cu/In containing Se dispersed in the form of particles in a stoichiometric ratio, followed by a heat treatment to form the compound CuInSe.sub.2, which acts as a photosensitive semiconductor layer which, once covered with a layer of CdS for example, constitutes a photovoltaic diode.
The electrolytic deposition, in particular of the In, has to meet an economic requirement. It is essential that the price/photovoltaic performance ratio be competitive with other means of production of electric energy. It is for this reason that the methods of deposition of all the compounds in the vapor phase which have already been proposed are much too expensive to produce solar cells at competitive prices. In fact, the deposition of In in the vapor phase brings about a condensation of In on the walls of the chamber. The quantity of In thus lost is substantial. Furthermore, In is an expensive metal.
Not only does electrolytic deposition give rise to difficulties in simultaneously depositing the three elements Cu In Se, but in addition, given the extreme reactivity of Se, it turns out that one of the rare substrates more or less able to resist Se at the moment of the formation of the compound CIS is Mo. Every specialist in electrochemistry knows that molybdenum constitutes a substrate on which it is difficult to deposit metals or alloys with an excellent adhesion by galvanic means. Thus copper can only be deposited with relative difficulty on molybdenum by this means and the alloy In-Cu has a very poor adhesion. Furthermore, molybdenum adheres very poorly on glass which generally forms the most common support for photovoltaic cells.
It will thus be realized that if the problem of jointly depositing Cu In Se has been solved, there remain other problems to solve in order to permit the production of photovoltaic cells with a CuInSe.sub.2 film (hereinafter referred to as CIS) obtained at least partially by galvanic deposition.


SUMMARY OF THE INVENTION

The object of the present invention is precisely to offer a solution to the problem of deposition at least partially by galvanic means of a composite which acts as a precursor to CIS on a substrate of molybdenum.
To this end, this invention has as its object a method of making a CuInSe2 compound by depositing a precursor of this compound at least partly electrolytically on a substrate and forming the CuInSe.sub.2 compound by thermal reaction according to claim 1.
One of the advantages of the solution proposed is the increase in the adhesion of the CuInSe.sub.2 layer on the conductive substrate, thus decreasing at the same time the porosity of the interface. In fact, this reduction in the porosity is at least in part the reason for the improved adhesion of the CIS layer.
The more or less separate deposition of Cu and In, by commencing with one or other of these elements, by galvanic means or by PVD, or by PVD followed by galvanic deposition, with the incorporation of Se in the form of particles in at least one of the Cu or In layers, allows the obtention of a precursor well adapted to the transformation into CIS while maintaining a good adhesion to the substrate. It is known that a large increase in volume of the In/Cu layer occurs upon selenization in the formation of the compound CuInSe.sub.2. It has been observed that the incorporation of a certain proportion of Se in the form of particles in at least one of the layers, which is mainly or wholly In or mainly or wholly Cu, allows a large reduction in this increase in volume and thereby in the risk of delamination of the CIS layer.
In addition to the problem of adhesion, the fact that the Cu and In elements ar

REFERENCES:
patent: 4581108 (1986-04-01), Kapur
patent: 5275714 (1994-01-01), Bonnet
Guillen et al: "Cathodic electrodeposition of CuInSe2 thin films", Thin Solid Films, vol. 195, No. 1/2, Jan. 1991 p. 138--p. 139, p. 141--figure 3.
Singh et al: "Electrodeposited semiconducting CuInSe2 films: I. Preparation, structural and electrical characterisation", Journal of Physics D. Applied Physics, vol. 19, No. 7, Jul. 1986, pp. 1299-1309.
Kumar et al: "Preparation and properties of a Cu-In alloy precursor for CuInSe2 films", Solar Energy Materials vol. 26, No. 1/2, Mar. 1992, pp. 149-158.
Hodes et al: "Electrodeposition of CuInSe2 and CuInS2 films", Solar Cells, vol. 16, No. 1/4, Jan. 1986, pp. 245-254.
Herrero et al: "Electrodeposition of Cu-In alloys for preparing CuInS2 thin films", Solar Energy Materials vol. 20, No. 1/2, Jan. 1990, pp. 53-65.

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