N-i-p Micromorph Solar Cells on Aluminium Substrates

The first successful deposition of 'micromorph' silicon tandem solar cells of the n-i-p-n-i-p configuration is reported. In order to implement the 'micromorph' solar cell concept, four key elements had to be prepared: First, the deposition of mid-gap, intrinsic microcrystalline silicon (μc-Si:H) by the 'gas purifier method', second, the amorphous silicon (a-Si:H) n-i-p single junction solar cell, third, the microcrystalline silicon n-i-p single junction solar cell and fourth, the ability of depositing on aluminium sheet substrates. All the solar cells presented have been deposited on flat aluminium sheets, using a single layer antireflection coating to couple the light into the cell. It is shown, that this antireflection concepttogether with a flat substrateholds for amorphous single junction solar cells, but it reaches its limit with the extended range of spectral response of the 'micromorph' cell. The best initial efficiencies for each category of n-i-p cells on flat substrates were: 8.7% for the amorphous silicon single junction cell, 4.9% for the microcrystalline silicon single junction cell and 9.25% for the 'micromorph' tandem cell.