Photoluminescence\nand Scintillation Mechanism of Cs<sub>4</sub>PbBr<sub>6</sub>

Small bandgap scintillators have gained significant attention\nin\nrecent years. Especially Cs<sub>4</sub>PbBr<sub>6</sub> is an interesting\nmaterial, mitigating the small Stokes shift-related problem of perovskites\nlike CsPbBr<sub>3</sub>. In this work, optical and scintillation properties\nof Cs<sub>4</sub>PbBr<sub>6</sub> single crystals are investigated\nas a function of temperature, with a detailed focus at 10 K. The Cs<sub>4</sub>PbBr<sub>6</sub> single crystals were grown using the vertical\nBridgman method. Due to incongruent melting, CsPbBr<sub>3</sub> inclusions\nare formed, generating a 540 nm emission band. Prepairing Cs<sub>4</sub>PbBr<sub>6</sub> via solid-state synthesis yields CsPbBr<sub>3</sub>-inclusion-free material, showing no green 540 nm emission band.\nIn Cs<sub>4</sub>PbBr<sub>6</sub> samples with and without CsPbBr<sub>3</sub> inclusions, a new emission band at 610 nm ascribed to an\nunknown defect was found. Based on the presented experiments, an emission\nmechanism is proposed for Cs<sub>4</sub>PbBr<sub>6</sub>. This shows\nthat both defects and CsPbBr<sub>3</sub> inclusions play a role in\nthe emission behavior of Cs<sub>4</sub>PbBr<sub>6</sub> but only the\nCsPbBr<sub>3</sub> inclusions are responsible for the 540 nm emission.