On the way towards high efficiency thin film silicon solar cells by the micromorph concept
- Univ. de Neuchatel (Switzerland). Inst. de Microtechnique; and others
Recently the authors have demonstrated that compensated or midgap intrinsic hydrogenated microcrystalline silicon ({micro}c-Si:H), as deposited by the Very High Frequency Glow Discharge (VHG-GD) technique, can be used as active layer in p-i-n solar cells. Compared to amorphous silicon (a-Si:H), {micro}c-Si:H was found to have a significantly lower energy bandgap of around 1 eV. The combination of both materials (two absorbers with different gap energies) leads to a real tandem cell structure, which was called the micromorph cell. Micromorph cells can make better use of the sun`s spectrum in contrast to conventional double-stacked a-Si:H/a-Si:H tandems. The present study will show that the compensation technique (involving boron microdoping) used so far for obtaining midgap {micro}c-Si:H can be replaced by the application of a gas purifier. The use of this gas purifier has a beneficial influence on the transport properties of undoped intrinsic {micro}c-Si:H. By this procedure, increased cell efficiencies in both, single microcrystalline silicon p-i-n as well as micromorph cells could be obtained. In the first case 7.7% stable, and in the second case 13.1% initial efficiency could be achieved under AM1.5 conditions. Preliminary light-soaking experiments performed on the tandem cells indicate that microcrystalline silicon could contribute to an enhancement of the stable efficiency performance. Micromorph cell manufacturing is fully compatible to a-Si:H technology; however, its deposition rate is still too low. With further increase of the rate, a similar cost reduction potential like in a-Si:H technology can be extrapolated.
- OSTI ID:
- 527608
- Report Number(s):
- CONF-960401--; ISBN 1-55899-323-1
- Country of Publication:
- United States
- Language:
- English
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