Evidence for proton motion in the recovery of light-induced degradation in amorphous silicon solar cells

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.