Highly luminescent and stable CH3NH3PbBr3 quantum dots with 91.7% photoluminescence quantum yield: Role of guanidinium bromide dopants

Although perovskite quantum dots (PQDs) have received considerable attention, defects in PQDs can significantly degrade the properties and device performance. In this study, we report on an effective strategy for synthesizing highly luminescent CH3NH3PbBr3 quantum dots (QDs) by a simple doping. To remove such defects, guanidinium bromide (GuBr) was doped into the CH3NH3PbBr3 QDs synthesized by the ligand-assisted reprecipitation technique. From XRD and TEM studies, the doping of GuBr into the QD lattices was verified. In addition, the surfaces of PQDs with and without GuBr dopants were analyzed by XPS to trace the metallic Pb acting as a major recombination center. The GuBr doping resulted in the size uniformity of QDs and effectively eliminated defects and metallic Pb, which enhanced the photoluminescence quantum yield (PLQY) through the inhibition of the non-radiative recombination pathway. Furthermore, the recombination dynamics in the QDs were examined by using time-resolved photoluminescence and fluorescence lifetime imaging to verify the role of GuBr dopants. By optimizing the amount of GuBr doping, the CH3NH3PbBr3 QDs with strong green emission achieved a maximum PLQY of 91.7%. •Guanidinium bromide (GuBr) is doped in the MAPbBr3 quantum dot (QD) lattice.•GuBr passivates the defects in MAPbBr3 QDs.•GuBr-doped MAPbBr3 QDs achieve a uniform size and distribution.•GuBr-doped MAPbBr3 QDs exhibit a PLQY of 91.7%.