Characterization of Cu-poor surface on Cu-rich CuInSe2 film prepared by evaporating binary selenide compounds and its effect on solar efficiency

Binary selenide compounds, In2Se3 and Cu2Se, were employed in a three-stage co-evaporation process to prepare CuInSe2 films. The composition and thickness of Cu-poor regions on Cu-rich CIS film were varied by the evaporation rate of In2Se3 and Se in the third stage. The Cu-poor regions were indistinguishable from CuInSe2 film in microstructure and were precisely characterized by Auger electron microscopy, microenergy dispersive X-ray spectroscopy. and Rutherford backscattering spectroscopy. A 9.25% efficiency in an active area of 0.16 cm(2) was achieved by inverting the surface of CuInSe2 film from Cu-rich composition to In-rich composition. Introducing 100-nm-thick CuIn3Se5 onto the surface of Cu-rich CuInSe2 film increased the cell efficiency to 9.59%, due to the increased fill factor and open circuit voltage. A lowering of the interface recombination current at the CdS/CuInSe2 was attributed to the improved cell efficiency. (C) 2002 Elsevier Science B.V All rights reserved.