ELECTROCHEMICAL ETCHING PROCESS FOR THE SELECTIVE REMOVAL OF CONTAMINANT PHASES ON THE SURFACE OF A SULPHIDE-CONTAINING CHALCOPYRITE SEMICONDUCTOR

摘要

The removal of contaminant phases by etching processes is an important methodological step in the production of thin-layer solar cells which are made from chalcopyrite semiconductors. The etching method known from DE 100 22 652 C2 uses an electrochemical principal in the cathodic potential region with a support electrolyte of reduced effect and manages without toxic substances in contrast to the wet-chemical etching method with highly-toxic potassium cyanide. A sufficiently high degree of efficiency cannot however be achieved in solar cells with the correspondingly etched semiconductor layers. According to the etching method of the invention, a redox electrolyte with oxidising properties for the surface to be purified is applied and a complex potential profile in the anodic potential region introduced. The surface of the sulphide-containing chalcopyrite semiconductor can be optimally purified of contaminant phases, by an optimisation of the potential profile on changing the parameters for the anodic potential region, maxima and minima, and positive/negative introduction speeds for the potential and the interval lengths and numbers thereof, such that a degree of efficiency in the production of solar cells is achieved which up to now was only achieved with semiconductor layers etched by means of a toxic process. Various in- and ex-situ control possibilites for the achieved purification state are possible.