Abstract
All-inorganic cesium lead bromide (CsPbBr3) perovskite quantum dots (QDs) represent premier candidates for ultra-high-definition displays and solid-state lighting owing to their narrow emission linewidths, high photoluminescence quantum yield (PLQY), and spectral purity. However, post-deposition film processing remains a delicate challenge, as uncontrolled thermal exposure frequently induces surface ligand detachment, defect generation, and particle sintering. In this study, we systematically investigate the influence of thermal annealing conditions—varying temperatures from 40 °C to 140 °C and environments (nitrogen versus ambient air)—on the structural integrity, defect chemistry, and photoluminescence characteristics of CsPbBr3 QD thin films. Steady-state and time-resolved photoluminescence measurements reveal that mild thermal annealing at 80 °C in an inert nitrogen atmosphere enhances the PLQY up to 91.8% and extends the average exciton lifetime to 24.6 ns by facilitating optimal ligand reorganization and passivating shallow surface trap states. In contrast, temperatures exceeding 100 °C induce severe desorption of oleic acid and oleylamine ligands, triggering the formation of non-radiative bromine vacancy (V_Br) defects and particle coalescence, which degrades optical performance. Integrating the 80 °C annealed QD films into green perovskite light-emitting diodes (PeLEDs) yields a peak external quantum efficiency of 18.7% with a maximum luminance of 42,300 cd/m² and noticeably enhanced operational durability. These findings delineate clear boundary conditions for the thermal processing of perovskite nanomaterials in high-efficiency optoelectronic devices.
