High-performance microcrystalline and amorphous silicon solar cells are the key elements for a successful combination to form the “micromorph” tandem cell [1,2]. A microcrystalline silicon (μc-Si:H) solar cell in the n-i-p configuration was fabricated by the VHF PE-CVD deposition process. The cell has a conversion efficiency exceeding 9% (VOC=520 mV, FF=73%, JSC=24.2 mA/cm2). This result was achieved by a successful combination of the following elements: first a fine-tuning of the silane concentration (SC) in hydrogen feedstock gas used for deposition of the intrinsic <i> absorber layer, second, the incorporation of an optimised back-reflecting substrate into the cell; and, third, the ideal combination of each of these key-components.
Compared to earlier results with n-i-p-type μc-Si:H solar cells, a substantial increase in VOC was now obtained, while maintaining reasonable JSC-values. Earlier investigations on the role of the i-layer material had revealed a trade-off between cells with high JSC but low VOC or cells of low JSC and high VOC. In the present contribution the authors now show the successful combination of a cell with an acceptable VOC and good JSC generation in the long-wavelength region (above 700 nm). This is mainly because of suitable light-diffusing back-reflectors which perform well with respect to both, optical and electrical aspects.