A strong electric field has been shown to reverse the light-induced degradation of amorphous silicon solar cells while exposed to intense illumination at moderate temperatures. The rate of reversal increases with temperature, illumination intensity, and with the strength of the reverse bias field. The reversal process exhibits an activation energy on the order of 0.9 eV and can be increased by the trapping of either electrons or holes in the presence of a strong electric field.

The light-induced degradation of amorphous silicon solar cells can be reversed by the application of a strong electric field in the dark, and the rate of reversal increases with field strength, temperature, and light intensity. The activation energy for annealing the degradation in the dark is reduced from about 1.34 eV under open circuit conditions to 1.16 eV by applying a strong reverse bias. When the degraded cells are exposed to intense illumination in addition to a strong reverse bias, the activation energy for the recovery of the performance decreases to about 0.77 eV. Both the light-induced degradation and the reversal of the degradation can be explained by a model based on proton motion within a metastable defect complex.

With the advent of new multijunction thin film solar cells, amorphous silicon photovoltaic technology is undergoing a commercial revival with about 30 megawatts of annual capacity coming on-line in the next year. These new a−Si multijunction modules should exhibit stabilized conversion efficiencies on the order of 8%, and efficiencies over 10% may be obtained in the next several years. The improved performance results from the development of amorphous and microcrystalline silicon alloy films with improved optoelectronic properties and from the development of more efficient device structures. Moreover, the manufacturing costs for these multijunction modules using the new large-scale plants should be on the order of $1 per peak watt. These modules may find widespread use in solar farms, photovoltaic roofing, as well as in traditional remote applications.

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An irreversible light-enhanced degradation has been observed in amorphous silicon solar cells exposed to intense illumination (50 suns) at elevated temperature (≳130 °C). Unlike the light-induced degradation observed at lower temperatures, the light-enhanced degradation observed at elevated temperatures is not reversed by annealing and it not suppressed by a strong reverse bias. An analysis of the time decay of the short-wavelength spectral response at various temperatures indicates that the degradation mechanism is associated with the diffusion of hydrogen at elevated temperatures both in the dark and under intense illumination.