How multiple decay paths affect the photoluminescence intensity in CuInS2

The influence of the excitation power on the photoluminescence (PL) intensity of spray-deposited CuInS2 has been studied. Above a certain threshold power, the PL intensity decreases when the excitation power increases, which is a new phenomenon for these materials. The recombination model that we developed earlier to explain the transient absorption behavior of CuInS2 is modified to simulate the power-dependent PL measurements. The model includes state-to-state recombination pathways. It is found that saturation of deep defect states at 1.1 eV inhibits the recombination from the conduction band to defect states at 0.15 and 0.2 eV, when state-to-state coupling is enabled.