Self-defect-passivation by Br-enrichment in FA-doped Cs_1-xFA_xPbBr₃ quantum dots: towards high-performance quantum dot...

Halide vacancy defect is one of the major origins of non-radiative recombination in the lead halide perovskite light emitting devices (LEDs). Hence the defect passivation is highly demanded for the high-performance perovskite LEDs. Here, we demonstrated that FA doping led to the enrichment of Br in Cs_1-xFA_xPbBr₃ QDs. Due to the defect passivation by the enriched Br, the trap density in Cs_1-xFA_xPbBr₃ significantly decreased after FA doping, and which improved the optical properties of Cs_1-xFA_xPbBr₃ QDs and their QD-LEDs. PLQY of Cs_1-xFA_xPbBr₃ QDs increased from 76.8% (x = 0) to 85.1% (x = 0.04), and L_max and CE_max of Cs_1-xFA_xPbBr₃ QD-LEDs were improved from L_max = 2880 cd m^-2 and CE_max = 1.98 cd A^-1 (x = 0) to L_max = 5200 cd m^-2 and CE_max = 3.87 cd A^-1 (x = 0.04). Cs_1-xFA_xPbBr₃ QD-LED device structure was optimized by using PVK as a HTL and ZnO modified with b-PEI as an ETL. The energy band diagram of Cs_1-xFA_xPbBr₃ QD-LEDs deduced by UPS analyses.