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)@en

Silicon nitride (SiNx) is a material with many applications and can be deposited with various deposition techniques. Series of SiNx films were deposited with HWCVD, RF PECVD, MW PECVD and LF PECVD. The atomic densities are quantified using RBS and ERD. The influence of the atomic densities on the Si¿N and Si¿Si bond structure is studied. The density of N¿N bonds is found to be negligible. New Si¿N FTIR proportionality factors are determined which increase with increasing N/Si ratio from 1.2 · 1019 cm¿ 1 for Si rich films (N/Si = 0.2) to 2.4 · 1019 cm¿ 1 for N rich films (N/Si = 1.5). The peak position of the Si¿H stretching mode in the FTIR spectrum is discussed using the chemical induction model. It is shown that especially for Si-rich films the hydrogen content affects the Si¿H peak position. The influence of the composition on the refractive index of the films is discussed on the basis of the Lorentz¿Lorenz equation and the Kramers¿Kronig relation. The decreasing refractive index with increasing N/Si ratio is primarily caused by an increase of the band gap. Keywords: Hot Wire CVD; Silicon nitride@en

A concept of a modulated one-dimensional photonic-crystal (PC) structure is introduced as a back reflector for thin-film solar cells. The structure comprises two PC parts, each consisting of layers of different thicknesses. Using layers of amorphous silicon and amorphous silicon nitride a reflectance close to 100% is achieved over a broad wavelength region (700¿1300 nm). Based on this concept, a back reflector was designed for thin-film microcrystalline silicon solar cells, using n-doped amorphous silicon and ZnO:Al. Simulations show that the short-circuit current of the cell with a modulated PC back reflector closely resembles that of a cell with an ideal reflector. ©2009 American Institute of Physics@en