Intrinsic microcrystalline silicon for solar cells

For the application in thin film solar cells intrinsic microcrystalline silicon was prepared by very high frequency plasma enhanced chemical vapour deposition in a high purity system. Discharge powers between 5 and 50 W and silane concentrations of 2 - 8 % in hydrogen were used to influence the deposition rates and the structure of the material. At high powers and silane concentration, material with high crystallinity at maximum deposition rates of 4.8 Angstrom/s was obtained. The performance of the different materials was investigated in pin and nip type solar cells. In addition the suitability of magnetron sputtered and texture etched ZnO films as light scattering substrates for this type of solar cell is investigated and compared with a commercial transparent conductive oxide substrate. The ZnO substrate shows excellent light scattering performance yielding solar cell efficiencies of up to 7 % for an active layers thickness of 1 mu m. Maximum efficiencies of 7.5 % are obtained for both the pin and nip structures.