Preparation of undoped and doped microcrystalline silicon (/spl mu/c-Si:H) by VHF-GD for p-i-n solar cells

The electronic transport properties of /spl mu/c-Si:H materials were investigated. The /spl mu/c-Si:H was deposited by the very high frequency-glow discharge (VHF-GD) technique at an RF-excitation of 70 MHz. Very thin

doped layers (100-400 /spl Aring/) were studied. Conductivities higher than 10/sup -3/ (/spl Omega/ cm)/sup -1/ could be achieved for films thicker than 150 /spl Aring/. The as-deposited /spl mu/c-Si:H is a slightly -type material and compensation was obtained by /spl mu/-doping with boron. Light-induced degradation of the compensated film showed better stability than for a-Si:H. Entirely /spl mu/c-Si:H p-i-n solar cells were prepared by incorporating the compensated layer in the structure. The /spl mu/c-Si:H cells show indeed an increase in the spectral response beyond 750 nm compared to amorphous silicon solar cells. These results indicate that the slightly doped /spl mu/c-Si:H is a new promising photovoltaically active material, which merits closer investigation.<>