Hole drift-mobility measurements in microcrystalline silicon

We have measured transient photocurrents on several p-i-n solar cells based on microcrystalline silicon. For two of these samples, we were able to obtain conclusive hole drift-mobility measurements. Despite the predominant crystallinity of these samples, temperature-dependent measurements were consistent with an exponential-bandtail trapping model for transport, which is usually associated with noncrystalline materials. We estimated valence bandtail widths of about 31 meV and hole band mobilities of 1-2 cm(2)/V s. The measurements support mobility-edge transport for holes in these microcrystalline materials, and broaden the range of materials for which mobility-edge transport corresponds to an apparently universal band mobility of order 1 cm(2)/V s. (c) 2005 American Institute of Physics.