Room temperature annealing of fast state from 1 sun illumination in protocrystalline Si:H materials and solar cells

In order to obtain more insight into the nature of the recovery in the light induced changes at room temperature in hydrogenated amorphous silicon (a-Si:H) solar cells the relaxation of the photocurrents in the light induced changes in protocrystalline a-Si:H thin films were investigated. Immediately upon the removal of 1 sun illumination recoveries in the photocurrents are found like those present in the currents in the dark current-voltage characteristics in corresponding p-i-n solar cells. The striking similarity between the results on thin films and the corresponding dark forward bias current-voltage characteristics of solar cells suggest that the recoveries obtained with low generation rates (5×10¹⁵cm^-3s^-1) in the films are a measure of annealing kinetics of the defect states around midgap in the bulk of the films. The rates of recoveries decrease with higher carrier generation rates and the length of the light induced degradation. Results are presented which indicate that the history of creation and annealing of light induced defect states is important in determining subsequent creation and annealing kinetics.