8% efficient CuInS2 solar cells by electrochemically removed Cu-S Phases

Investigations on how to replace the toxic KCN etching for the removal of Cu-S phases during the preparation of CuInS2 (CIS) absorber layers by electrochemical procedures are presented. Starting from a simple anodic treatment in V2+/V3+ electrolyte, a more complex photoelectrochemical technique is developed which consists of different consecutive etching steps for the dissolution of the predominant CuS and for the removal of remaining Cu2S and a small sacrificial layer of CuInS2. This new method also offers the possibility of in situ quality control of the CIS in a photoelectrochemical solar cell (PECS) setup. Further examination of the treated films is carried out using X-ray emission spectroscopy, X-ray photoelectron spectroscopy (XPS) and by further processing of the samples to create solid state solar cells. The specimen yield conversion efficiencies of 3.3% in PECS and 8% in solid state devices