Intrinsic doping limit and defect-assisted luminescence in Cs4PbBr6

Cs4PbBr6 is a member of the extended halide perovskite family that is built from isolated (zero-dimensional) PbBr64− octahedra with Cs+ counter ions. The material exhibits anomalous optoelectronic properties: optical absorption and weak emission in the deep ultraviolet (310–375 nm) with efficient luminescence in the green region (∼540 nm). Several hypotheses have been proposed to explain the giant Stokes shift including: (i) phase impurities; (ii) self-trapped exciton; (iii) defect emission. We explore, using first-principles theory and self-consistent Fermi level analysis, the unusual defect chemistry and physics of Cs4PbBr6. We find a heavily compensated system where the room-temperature carrier concentrations (