Amorphous silicon-based multilayers for photovoltaic applications

Multilayer (ML) structures were fabricated by alternating deposition of hydrogenated amorphous silicon (a-Si:H) and amorphous silicon nitride (a-SiNx:H) using plasma enhanced chemical vapour deposition. The ML structures were grown with and without hydrogen dilution of the source gas mixture. A blue shift of the absorption spectra was observed upon reduction of the a-Si:H thickness below 5 nm. Hydrogen dilution was found to improve the abruptness of the interfaces between subsequent a-Si:H and a-SiNx:H layers to below 1 nm. In order to investigate the potential of a-Si:H based ML structures as absorbers in solar cells and to study transport perpendicular to the interfaces, we have incorporated ML absorbers in a single junction p-i-n solar cell. We have determined the J-V characteristics and the external quantum efficiency of solar cells with a 60 period ML absorber, composed of 5 nm thick a-Si:H and 1 nm thick a-SiNx:H layers. The solar cell with ML absorber operated at efficiency of 1.8% (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)