Time-resolved photoluminescence (PL) measurements have been carried out for CuGaS2 single crystals with a slightly Cu-rich composition grown by an iodine transport method. PL lines at 2.460 eV, 2.457 eV, 2.417 eV, 2.404 eV, 2.397 eV and 2.295 eV exhibited biexponential decay. The relationship between the decay time of the fast component (τ f ) and the localization energy (E loc) can be given by τ f ∝E loc 1.25. On the other hand, the decay times of the slow components (τ s ) have been classified into two groups having different trends τ s ∝E loc 2.7 and E loc 0.5. The difference between the two groups is discussed in terms of native defects and the iodine impurity included in the luminescence centers.

Decay properties of sharp zero-phonon photoluminescence (PL) lines at 2.460 eV, 2.457 eV, 2.417 eV, 2.404 eV, 2.397 eV and 2.295 eV have been studied for CuGaS2 single crystals grown by an iodine transport method. These PL lines exhibited biexponential decay. The relationship between the decay time of the fast component (τ f ) and the exciton localization energy (E loc ) can be given by τ f ∝E loc 1.25. On the other hand, the decay times of the slow components (τ s ) have been classified into two groups having different trends τ s ∝E loc 2.7 and E loc 0.5.