Synergistic passivation of alkali halides enables highly efficient perovskite QLEDs

Abstract

Perovskite quantum dots (QDs) have been identified as propitious candidates for next-generation high-definition displays owing to their excellent photoelectric properties, such as size-tuneable optical bandgaps, narrow emission and extraordinary charge-transport properties. However, during the purification process of QD synthesis, QDs are always accompanied by problems of ligand falling off and mismatches of Pb atoms, which will decrease the photoluminescence quantum yield (PLQY) of QDs and affect the device performance adversely. Here, a simple method by doping alkali halide CaCl₂ as a co-precursor is proposed to improve the optoelectronic properties of CsPbI₃ QDs. Excess halide anions could provide a halide-rich environment and efficiently passivate surface defect states of CsPbI₃ QDs. Meanwhile, introducing alkali metal ions could reduce nonradiative decay rates by suppressing the defects originating from Pb atoms with insufficient coordination in CsPbI₃ QDs. These results will stimulate research on LEDs for next-generation high-definition display technologies.