Numerical modeling of graded band gap CIGS solar cells

The high efficiency reported by NREL for CIGS (Cu(In,Ga)Se/sub 2/) solar cells demonstrates the potential of band gap grading in producing high efficiency thin film solar cells. In order to reap the full benefits of this design strategy, a clear understanding of the fundamental device physics of these structures is needed. The purpose of this paper is to examine the role grading of the band gap plays in achieving high conversion efficiencies. To aid in this examination, a detailed numerical device simulation program, ADEPT, is used.