Photoluminescence and Scintillation Mechanism of Cs4PbBr6

Small bandgap scintillators have gained significant attention in recent years. Especially Cs4PbBr6 is an interesting material, mitigating the small Stokes shift-related problem of perovskites like CsPbBr3. In this work, optical and scintillation properties of Cs4PbBr6 single crystals are investigated as a function of temperature, with a detailed focus at 10 K. The Cs4PbBr6 single crystals were grown using the vertical Bridgman method. Due to incongruent melting, CsPbBr3 inclusions are formed, generating a 540 nm emission band. Prepairing Cs4PbBr6 via solid-state synthesis yields CsPbBr3-inclusion-free material, showing no green 540 nm emission band. In Cs4PbBr6 samples with and without CsPbBr3 inclusions, a new emission band at 610 nm ascribed to an unknown defect was found. Based on the presented experiments, an emission mechanism is proposed for Cs4PbBr6. This shows that both defects and CsPbBr3 inclusions play a role in the emission behavior of Cs4PbBr6 but only the CsPbBr3 inclusions are responsible for the 540 nm emission.