FILM PROPERTY CONTROL OF HYDROGENATED AMORPHOUS-SILICON GERMANIUM FORSOLAR-CELLS

The optoelectric properties of a-SiGe:H alloys, deposited by the plasm a chemical vapor deposition (plasma-CVD) method, were investigated wit h precise measurement of their germanium content (C(Ge)) and hydrogen content (CH). This investigation revealed that the optical gap of a-Si Ge: H alloys can be approximated by a linear function of C(H) and C(Ge ) and various combinations Of CH and C(Ge) resulted in identical optic al gaps. For each optical gap, the optimum composition for the lowest defect density was derived by comparison with the subgap absorptions m easured by the constant photocurrent method (CPM). Based on these, the highest conversion efficiency of 3.7% under red light illumination (> 650 nm) for a 1 CM2 a-SiGe single-junction solar cell was achieved.