Characterization of Cu-poor surface on Cu-rich CuInSe 2 film prepared by evaporating binary selenide compounds and its effect on solar efficiency

Abstract

Binary selenide compounds, In 2Se 3 and Cu 2Se, were employed in a three-stage co-evaporation process to prepare CuInSe 2 films. The composition and thickness of Cu-poor regions on Cu-rich CIS film were varied by the evaporation rate of In 2Se 3 and Se in the third stage. The Cu-poor regions were indistinguishable from CuInSe 2 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 CuInSe 2 film from Cu-rich composition to In-rich composition. Introducing 100-nm-thick CuIn 3Se 5 onto the surface of Cu-rich CuInSe 2 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/CuInSe 2 was attributed to the improved cell efficiency.