Amorphous silicon germanium solar cells deposited on stainless steel at elevated pressure

This work reports our efforts on improving the deposition rate for amorphous silicon germanium (a-SiGe) absorber layer by increasing the PECVD process pressure. We demonstrate that at an elevated pressure of 1~4 Torr, the deposition rate reaches 3.5~4 ¿/sec, which is about 4 times higher than previous low pressure processes (0.3~0.6 Torr). Deposited at such a high rate, the single junction a- SiGe solar cells exhibit an efficiency comparable to that achieved at low pressure (12.5% initial, 10.4% stabilized). Furthermore, tandem junction cells using the high rate deposited a-SiGe as bottom cell show an initial efficiency as high as 13.27% and a stabilized efficiency of 11.50% after light soaking.