High rate deposition of a-Si and a-SiGe solar cells near depletion condition

Amorphous silicon (a-Si) and amorphous silicon germanium (a-SiGe) absorber layers are deposited at high rates of 7∼8 Å/sec using RF plasma enhanced chemical vapor deposition. The single junction a-Si top and a-SiGe bottom cells deposited at such a high rate exhibit initial efficiencies of 10.06% and 9.96%, respectively, while the process is not yet fully optimized. A tandem junction cell made using the high rate deposited a-Si and a-SiGe shows an initial efficiency as high as 11.04%. A combination of proper RF power density, gas pressure, and H2 dilution enables the intrinsic layers being deposited near a depletion condition and is responsible for the promising performances.