On the Luminescence of Cs3Bi2Br9 Single Crystals

Abstract The luminescence properties of Cs 3 Bi 2 Br 9 single crystals are reported. Cs 3 Bi 2 Br 9 is an ordered perovskite, structurally and electronically related to the cesium lead halides. Emission and excitation spectra are measured at 4.2 K. The luminescence originates from the recombination of excitons bound to defects, except for a sharp line at 459.2 nm, which is ascribed to free exciton recombination. The band‐gap transition takes place at about 2.7 eV and is found to be direct and allowed. The intensity of the emission bands and the decay times are measured as a function of temperature. The results are interpreted assuming detrapping and exciton migration.