Charge trapping and luminescence of the mixed size CsPbBr₃ particles grown in one batch

Cesium lead bromide (CsPbBr₃, CPB) powder formed by micro-, nanocrystals (MC, NC) and quantum dots (QD) was synthesized as free-standing and polystyrene covered. Luminescence was multicomponent, in general, ranging from below 1.9 eV up to about 2.6 eV. The ultrafast decay kinetics exhibited strong decay time component with the value of 260 ps. Electron paramagnetic resonance (EPR) revealed surface defects like O₂⁻ and some spin transitions most likely originating from some complex defect, supposedly F-V_k(H) dimer center under the constant ultraviolet (UV) light irradiation at the temperature T = 10 K. The thermal release of the electrons from the O₂⁻ center was correlated with the 117 K thermally stimulated luminescence (TSL) peak. Coating with polystyrene resulted in the about doubly increased decay time of luminescence. The O₂⁻ and F-V_k(H) EPR resonances were not observed as well. The TSL peak which might be ascribed to the O₂⁻ was not clearly detected anymore. The glow curve was composed of one very broad peak typical for the amorphous materials. At the same time, the polystyrene prevented the MCs creation. The existence of charge/energy transfer between the CPB and polystyrene due to the chemical bonding was assumed and confirmed also by calculations.