An electrochemical route for the preparation of chalcopyrite semiconductors

Chalcopyrite semiconductors (CuInSe₂, Cu(In_xGa_(1-x)Se₂) are among the best materials for making the absorber part of efficient thin film solar cells. They are currently prepared by vacuum techniques: evaporation or coevaporation of the elements, sputtering of the metals followed by a selenization step, MBE,… Electrodeposition may provide a cheap way for making large areas of the absorber film. Three classes of questions will be successively considered to present the present status of the work in the field, (i), The process involves chemical and electrochemical reactions. A special study of the reaction mechanism is needed to determine the experimental conditions leading to the right composition (i.e., an In/Cu ratio slightly higher than unity), (ii), As electrodeposition is a room temperature process, a heat treatment is needed to give the as deposited film the convenient optoelectronic properties.(iii), Examples of solar cells using electrodeposited and heat treated films show the actual performances obtained using this preparation technique.