Inter-band and mid-gap luminescence in CH3NH3PbBr3 single crystal

Photoluminescence is informative to other optoelectronic processes that are less directly accessible in metal halide perovskites . In this study, we conducted optical studies on CH 3 NH 3 PbBr 3 single crystals with robust cubic lattices and atomically flat surfaces. Inter-band luminescence peaking aside from the absorption cutoff was observed, and its shifts toward shorter wavelength upon cooling. Cooling the crystal below 150 K leads to the occurrence of mid-gap luminescence partly at the expense of the inter-band luminescence, which indicates bulk photoluminescence quenching by trap-mediated electronic trapping and subsequent mid-gap radiation following electronic de-trapping. Time-resolved photoluminescence probed at the mid-gap luminescence maxima shows two-stage mono-exponential traces, directly corroborating the trapping and de-trapping processes. In the presence of mid-gap luminescence at low temperatures, time-resolved inter-band luminescence demonstrates triplet decaying pathways, in sharp contrast to the doublet decaying pathways at higher temperatures in the absence of mid-gap luminescence. Time- and temperature-resolved inter-band photoluminescence gave rise to a characteristic photocarrier lifetimes evolution against temperature in a close analogy to the material's dielectric constant .