The "micromorph" solar cell: extending a-Si:H technology towards thin film crystalline silicon

Progress of solar cells based on plasma deposited hydrogenated microcrystalline silicon (/spl mu/c-Si:H), as well as on combined a-Si:H//spl mu/c-Si:H stacked "micromorph" solar cells is reported. /spl mu/c-Si:H p-i-n cells with a thickness of 3.6 /spl mu/m, deposited with the use of a gas-purifier, are shown to have a short-circuit current of over 25 mA/cm/sup 2/, and a stable efficiency of 7.7%. a-Si:H//spl mu/c-Si:H tandem cells with 13% initial, and with 10% degraded state efficiency are also demonstrated. In addition, methods to further increase the efficiency of combined a-Si:H//spl mu/c-Si:H solar cells are discussed. This includes the introduction of a ZnO reflector layer between a-Si:H and /spl mu/c-Si:H component cells, a new concept of which first experimental results are given.