Verification of phototransistor model for Cu(In,Ga)Se2 solar cells

Previous studies of Cu(In,Ga)Se2 thin film solar cells showed that the long-term stability critically depends on the bias across the junction. As a result of a dark anneal the current–voltage (IV)-characteristics in the dark showed a blocking behavior with increasing anneal time. In the final stage the device exhibits an open circuit voltage (Voc) which is independent from the illumination intensity, a crossover of the dark and illuminated IV-characteristics and Voc saturation for decreasing temperatures. These characteristics also occur in the initial state prior to the endurance test, however, at low temperature (