H out-diffusion and device performance in n-i-p solar cells using high temperature hot wire a-Si:H i-layers
- United Solar Systems Corporation, Troy, Michigan 48084 (United States)
Hydrogen out-diffusion from the n/i interface region plays a major role in controlling the fill factor (FF) and resultant efficiency of n-i-p a-Si:H devices, with the i-layer deposited at high substrate temperatures by the hot wire technique. Modeling calculations have shown that a thin, highly defective layer at this interface, perhaps caused by significant H out-diffusion and incomplete lattice reconstruction, results in sharply lower device FFs due to the large voltage dropped across this defective layer. We have therefore employed buffer layers designed to retard this out-diffusion. We find that an increased H content, either in the n-layer or a thin intrinsic low temperature buffer layer, does not significantly retard this out-diffusion, as observed by SIMS H profiles on devices. However, if this low temperature buffer layer is thick enough, the out-diffusion is minimized, yielding nearly flat H profiles and a much improved device performance. We discuss this behavior in the context of the H chemical potentials and H diffusion coefficients in the high temperature, buffer, n-, and stainless steel substrate layers. Finally, we report a 9.8{percent} initial active area device, fabricated at 16.5 {Angstrom}/s, using the insights obtained in this study. Light soaking data are also reported. {copyright} {ital 1999 American Institute of Physics.}
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC36-83CH10093
- OSTI ID:
- 700938
- Report Number(s):
- CONF-980935-; ISSN 0094-243X; TRN: 9915M0046
- Journal Information:
- AIP Conference Proceedings, Vol. 462, Issue 1; Conference: 15. National Center for Photovoltaics program review conference, Denver, CO (United States), 9-11 Sep 1998; Other Information: PBD: Mar 1999
- Country of Publication:
- United States
- Language:
- English
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