Growth of SnX (X = Br, I) Single Crystals with Self-Trapped Exciton Emission.

Broadband emission with a large Stokes shift is important to obtain an excellent color rendering index of the solid-state lighting device. Among low-dimensional material and perovskite-like phosphors with broadband self-trapped emission, Sn-based phosphors have attracted much attention due to their high photoluminescence quantum yield (PLQY). However, the disadvantage is that the synthesis of Sn-based phosphors needs to be performed in a glovebox. Upon photoexcitation, the broadband emission of self-trapped excitons results from exciton-phonon coupling induced by the transient distortion of the lattice. Low-dimensional material structures often promote self-trapped emission because of more vibrational degrees of freedom and easier polarization under photoexcitation. Here, zero-dimensional (0D) SnX (X = Br, I) single crystals are synthesized by the solvent evaporation method in the air. SnX emits blue light, broadband yellow light, and deep red light, among which SnBr has the best luminescence performance. The photoluminescence quantum yield (PLQY) of SnBr reaches 85% and the Stokes shift reaches 265 nm. The PL intensity of SnX is linearly related to excitation power, which preliminarily indicates that the origin of SnX luminescence is attributed to self-trapped emission (STE). The white light-emitting diodes (WLEDs) were fabricated using yellow-emitting SnBr and blue-emitting BaMgAlO:Eu, which has a low correlated color temperature (3160 K) and a relatively common color rendering index (79).