Microcrystalline silicon n-i-p solar cells deposited entirely by the hot-wire chemical vapor deposition technique

We describe a series of microcrystalline (mu c) silicon n-i-p solar cell devices fabricated entirely by the hot-wire chemical vapor deposition technique. These devices are deposited on flat stainless-steel at a substrate temperature below 250 degrees C, and are evaluated using solar-cell performance and quantum-efficiency (QE) measurements. We explore the effect of crystallite size, as examined by X-ray diffraction, by varying the hydrogen-to-silane ratio from 5 to 40, while keeping the mu c-n and the mu c-p layers the same. We find a significant blue shift of the QE peak and an enhancement of red response compared with a standard a-Si:H solar cell. The blue shift increases with increasing hydrogen-to-silane ratio. We attribute this shift to the i-layer becoming more n-type with increasing hydrogen dilution. We also use a hydrogen gas purifier and find a large improvement in device performance.