H Out-Diffusion and Device Performance in n-I-p Solar Cells Utilizing High Temperature Hot Wire a-Si:H I-Layers

Research output: Contribution to conferencePaper

Abstract

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 latticereconstruction, 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% initial active area device,fabricated at 16.5..Alpha../s, using the insights obtained in this study. Light soaking data are also reported.
Original languageAmerican English
Number of pages8
StatePublished - 1998
EventNCPV Program Review Meeting - Denver, Colorado
Duration: 8 Sep 199811 Sep 1998

Conference

ConferenceNCPV Program Review Meeting
CityDenver, Colorado
Period8/09/9811/09/98

NREL Publication Number

  • NREL/CP-520-25481

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