High fluorescence efficiency of intrinsic ligand-free zero-dimensional Cs4PbBr6particles and microcrystals

Abstract

Ligand-free Cs4PbBr6particles of sub-micron dimensions were fabricated by a simple tip-sonication method showing 85.1% photoluminescence quantum yield (PLQY). Cs4PbBr6microcrystals can be grown under saturated vapor pressure with the particles as nucleation units. Surface traps are the main defects in the Cs4PbBr6particles with smaller size, whereas bulk defects dominate in the larger microcrystals. The intensity of the low energy PL peak increases with excitation intensity at low temperature, which can be assigned to band filling and charge transfer effects. The exciton binding energy of Cs4PbBr6particles is 180 meV which is almost twice that of the Cs4PbBr6microcrystals. Such tight binding..