Analysis of light-induced degradation in amorphous silicon alloy p-i-n solar cells

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Abstract
We present results of computer simulations of the characteristics of amorphous silicon alloy p‐i‐n solar cells in both undegraded and degraded conditions for illumination through the n+ or p+ layers. Changes in device performance upon degradation correlate well with realistic changes in the minority carrier diffusion length of the intrinsic layer. The results of our model are in good agreement with experimental data and lead us to conclude that the observed degradation in the electronic properties of amorphous silicon alloys are only consistent with the observed increases in the localized state density if the photoinduced metastable defects have larger capture cross sections than the localized states in as‐deposited material. The analysis of recombination losses shows that upon degradation, primarily because of the decrease in the minority carrier diffusion length, cells illuminated through the n+ layer exhibit a loss of short‐wavelength response whereas those illuminated through the p+ layer exhibit a loss of long‐wavelength response.