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

Abstract

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 Cs1−xFAxPbBr3 QDs. Due to the defect passivation by the enriched Br, the trap density in Cs1−xFAxPbBr3 significantly decreased after FA doping, and which improved the optical properties of Cs1−xFAxPbBr3 QDs and their QD-LEDs. PLQY of Cs1–xFAxPbBr3 QDs increased from 76.8% (x = 0) to 85.1% (x = 0.04), and Lmax and CEmax of Cs1–xFAxPbBr3 QD-LEDs were improved from Lmax = 2880 cd m−2 and CEmax = 1.98 cd A−1 (x = 0) to Lmax = 5200 cd m−2 and CEmax = 3.87 cd A−1 (x = 0.04). Cs1–xFAxPbBr3 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 Cs1–xFAxPbBr3 QD-LEDs deduced by UPS analyses.

Efficient and Stable Blue- and Red-Emitting Perovskite Nanocrystals through Defect Engineering: PbX2 Purification

“…Each decay component was associated to the nonradiative recombination promoted by shallow defects (τ 1 ), radiative recombination (τ 2 ), and the presence of deep states (τ 3 ), respectively. 50,63 According to Table S7, τ 3 < τ 2 < τ 1 in MHP growth using PbCl 2 in the absence of Hyd purification. This fact allows us to deduce that the carrier trapping through deep states is favored (high density of Cl − vacancies).…”

“…Further mechanistic insights into the recombination dynamics of the MHPs were obtained by time-resolved PL (TRPL) measurements (Figure S9A), collecting their corresponding average electron lifetimes, τ avg , by fitting the PL decays through a triexponential equation, y = y 0 + A 1 e – x /τ 1 + A 2 e – x /τ 2 + A 3 e – x /τ 3 . Each decay component was associated to the nonradiative recombination promoted by shallow defects (τ 1 ), radiative recombination (τ 2 ), and the presence of deep states (τ 3 ), respectively. , According to Table S7, τ 3 < τ 2 < τ 1 in MHP growth using PbCl 2 in the absence of Hyd purification. This fact allows us to deduce that the carrier trapping through deep states is favored (high density of Cl – vacancies).…”

Surface Ligand Tuning of Coordination Geometry and Pb 6s2 Electronic Pair Stereochemical Activity in MAPbBr3 Perovskite Nanoparticles: A Joint Experimental and Theoretical Insight

“…At the same time, the Br 3d peaks can be deconvoluted into two distinct components from the surface and interior Br − of the MAPbBr 3 crystal (Figure 4b), and this assignment agrees with the increase of the surface/inner Br − peak area ratio from 1.8 in MCs to 3.5 in NPs which means more surface Br − are present in NPs. 16,45 When compared to MCs, the two Br 3d peaks in NPs also show a shift of ∼1.2 eV toward a higher binding energy (Figure 4b), resulting from [PbBr 5 ] 3− -[−OOC−R] − complexes and hydrogen bonding from −NH 3 + . These were also supported by the pioneering work of Luo et al 34 that the MAPbBr 3 NP (∼7.8 nm) peak position of Pb 4f shifted ∼0.9 eV toward high binding energy, while the peak position of Br 3d was observed with similar peak shifts (∼0.8 eV), compared with that in MCs.…”