Electron and hole transport in microcrystalline silicon solar cells studied by time-of-flight photocurrent spectroscopy |
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Institution: | 1. Materials Science Department, FCT-UNL, Campus da Caparica, Portugal;2. INESC Microsistemas e Nanotecnologias, Lisbon, Portugal;3. Department of Chemical and Biological Engineering, IST-UTL, Lisbon, Portugal |
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Abstract: | A photocurrent time-of-flight study of carrier transport in microcrystalline silicon pin diodes prepared over a range of crystallinities is presented. Electron and hole drift mobilities at a crystalline volume fraction >0.35 are typically 3.8 and 1.3 cm2/(V s) respectively at 300 K and a thickness to electric field ratio of 1.8 × 10−7 cm2/V. A factor of five enhancement in hole mobility over amorphous silicon persists at a crystalline volume fraction as low as 0.1. Current decays are dispersive and mobilities are thermally activated, although detailed field-dependence is still under investigation. Evidence for a sharp fall in the density of states at 0.13 eV above the valence band edge is presented. Similarities in behaviour with certain amorphous and polymorphous silicon samples are identified. |
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