Electrical characterization of Cu(In,Ga)Se2 thin-film solar cells and the role of defects for the device performance

Electrical analysis of Cu(In,Ga)Se2-based heterojunction devices shows that recombination in the space-charge region is the dominant recombination mechanism which determines the open-circuit voltage of these devices. We identify a specific defect as the relevant recombination center. The concentration of this defect varies with the Ga-content in the absorber alloy with the highest concentration in pure CuGaSe2. In this material, tunneling-enhanced recombination plays a major role for recombination.