Self-defect-passivation by Br-enrichment in FA-doped Cs1-xFAxPbBr3 quantum dots: towards high-performance quantum dot light-emitting diodes

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-x)FA(x)PbBr(3) QDs. Due to the defect passivation by the enriched Br, the trap density in Cs(1-x)FA(x)PbBr(3) significantly decreased after FA doping, and which improved the optical properties of Cs(1-x)FA(x)PbBr(3) QDs and their QD-LEDs. PLQY of Cs(1-x)FA(x)PbBr(3) QDs increased from 76.8% (x = 0) to 85.1% (x = 0.04), and L-max and CEmax of Cs(1-x)FA(x)PbBr(3) QD-LEDs were improved from L-max = 2880 cd m(-2) and CEmax = 1.98 cd A(-1) (x = 0) to L-max = 5200 cd m(-2) and CEmax = 3.87 cd A(-1) (x = 0.04). Cs(1-x)FA(x)PbBr(3) 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-x)FA(x)PbBr(3) QD-LEDs deduced by UPS analyses.