Effects of Se Flux on the Microstructure of Cu(In,Ga)Se_2 Thin Film Deposited by a Three-Stage Co-evaporation Process

摘要

Cu(In,Ga)Se_2 (CIGS) films were deposited by three-stage co-evaporation of elemental sources and effects of Se flux on CIGS film were investigated. With an appropriate Se flux (15 A/s), faceted and tightly connected CIGS grains were developed at the film surface, and the highest conversion efficiency, 17.57 percent, was achieved in CdS/CIGS solar cells. When the Se flux was high, large grains with less (112) preferred orientation and pores along the grain boundaries were observed. As a result, the cell conversion efficiency was deteriorated. Precise control of Se flux, especially at the third stage, was critical to obtain high-performance CIGS solar cells.