Photoluminescence study of Pr3+ doped CaGa2S4 in wide excitation intensity and temperature range

The photoluminescence (PL) of CaGa2S4:Pr3+ chalcogenide semiconductor compound is studied. The PL spectrum consists of a set of intense sharp lines at 494, 631, 654, and 741 nm, formed by intra-4f transitions of Pr3+ ions. The energy level diagram of CaGa2S4:Pr3+ is proposed. A broad structural band in the PL excitation spectra in the range of 270–360 nm is assumed with superposition of host related and 4f2 → 4f15d1 direct excitation transition bands whereas a sharp line at 456 nm—with 3H4 → 3P2 direct excitation. The PL decays at intensive emission lines at room temperature were found to obey nonexponential law with time constant in the range of 1.1–2.1 μs for fast decay component and of 4.5–6.3 ms for slow one. Thermal quenching by only 50% and 75% of the PL intensity of CaGa2S4:Pr3+ with 7 and 3 at. % Pr3+ ions concentration, respectively, was obtained in the range of 10–300 K. Extreme stability of PL spectra and efficiency of CaGa2S4:Pr3+ compound up to 105 W/cm2 of excitation power density was achieved.