Voltage-Induced Charge Redistribution in Cu(In, Ga)Se2 Devices Studied With High-Speed Capacitance-Voltage Profiling

Devices made from Cu(In,Ga)Se₂ (CIGS) solar cell material have been evaluated with high-speed capacitance-voltage profiling after stepwise voltage changes. The changes primarily affect near-interface charge at deep acceptors within the CIGS absorber layer and generate temperature-dependent capacitance changes observed in deep-level transient spectroscopy measurements. SCAPS device modeling indicates that the deep acceptor concentration is up to the two orders of magnitude higher than the shallow doping level. High deep acceptor concentrations are found in all materials studied here. The large deep defect levels are high enough to limit minority carrier lifetime and cell efficiency.