Figure 7: Comparison between EQEs of a-Si1−xGex:H single-junction cells with and without bandgap graded layers at the p/i and the i/n regions. The circle and square symbols denote the cell with and without bandgap grading, respectively. The p/i and i/n grading widths and the total thickness of absorber were 15, 160, and 230 nm, respectively. The EQEs measured under reverse bias of −0.5 V were represented by the dash lines.