Effect of first-stage temperature on Cu(In,Ga)Se-2 solar cells using the evaporation of binary selenide compounds

Abstract

Cu(In,Ga)Se-2 films were prepared by a three-stage process using the evaporation of In2Se3, Ga2Se3, Cu2Se, and Se. In the first stage, the (In,Ga)(2)Se-3 layer was deposited at the substrate temperatures of 150degreesC and 325degreesC by the evaporation of In2Se3, Ga2Se3, and Se. The CIGS film had small grains with a bi-layer morphology at 150degreesC, while the film had large grains without the bi-layer morphology at 325degreesC. As the first-stage temperature increased, the CdS/ Cu(In,Ga)Se2 solar efficiency was improved from 9.3% to 11.7% for 0.21 cm 2 active area. The efficiency improvement was attributed to the reduction of the recombination at the CdS/ Cu(In,Ga)Se-2 interface and recombination within Cu(In,Ga)Se-2 film bulk due to the increase of Cu(In,Ga)Se-2 grain size. These findings were supported by the increased hole density, reduced reverse saturation current, and enhanced spectral response with increasing the first-stage temperature. (C) 2002 Elsevier Science B.V. All rights reserved.