Combined low-temperature photoluminescence and thermally stimulated current studies in Cu3In5S9 layered single crystals

Photoluminescence (PL) and thermally stimulated current (TSC) spectra of Cu3In5S9 layered crystals grown by Bridgman method have been studied in the photon energy region of 1.20–1.65 eV and the temperature range of 15–70 K (PL) and in the temperature region of 10–130 K (TSC). A broad PL band centered at 1.484 eV was observed at T = 15 K. Radiative transitions from shallow donor level located at 16 meV to moderately deep acceptor level located at 120 meV were suggested to be responsible for the observed PL band. TSC curve of Cu3In5S9 crystal exhibited one broad peak at about 60 K. The activation energy of trap level was found to be 17 meV. An energy level diagram showing transitions in the band gap of the crystal was plotted taking into account the results of PL and TSC measurements carried out below room temperature. Moreover, the absorption edge of Cu3In5S9 crystals have been studied through transmission and reflection measurements in the photon energy range 1.13–1.85 eV. The band gap energy was determined as 1.61 eV.