Unusual capacitance emission transients in CIGS caused by large defect entropy changes

Capacitance transient data from bias-pulse experiments on CdS/CIGS solar cells show an unusual behavior at high temperatures. Above 350 K a minority carrier trap, with a larger activation energy than a majority carrier trap, emits faster than the lower activation-energy minority trap. A simple enthalpy model for trap emission cannot explain this counterintuitive behavior, but the more complete Gibbs free energy model that includes entropy can explain it. We show that entropy plays a major role in carrier emission from traps in CIGS.