Photovoltage decay processes in Cu(In, Ga)Se2 solar cells studied by photo-assisted Kelvin probe force microscopy

The temporally-averaged photovoltages were measured on Cu(In, Ga)Se₂ [CIGS] solar cells under the intermittent light excitation by photo-assisted Kelvin probe force microscopy to evaluated a time constant τ for photovoltage decay and a contribution ratio r of fast carrier recombination process in the entire recombination processes. The results indicate that the sample with higher Ga content exhibited longer τ and larger r, from which we have investigated the influences of both the carrier transport across the potential barrier and the carrier separation around the grain boundary on the entire photo-carrier recombination processes.