Physics of amorphous silicon alloy p-i-n solar cells

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Abstract
We present a comprehensive computer simulation of amorphous silicon alloy p‐i‐n solar cells which has enabled us to establish the physical mechanisms governing device operation. This has been carried out by analyzing the free‐carrier, space‐charge, recombination rate, and electric field profiles as well as the corresponding current‐voltage characteristics for a variety of device parameters and illumination conditions. We interpret these results in terms of the asymmetrical density of localized states in these alloys and its effect on the basic recombination paths. We also demonstrate that for uniformly absorbed light, cell performance is primarily controlled by the hole transport properties, and not by the sum of the carrier drift lengths, or their mobility‐lifetime products. This concept of a ‘‘limiting carrier’’ also applies to the case of nonuniform illumination. Photovoltaic performance is calculated both as a function of device thickness as well as material quality. Finally, we compare the results from our simulation with those obtained from other models for these devices.