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.
Highlights
Colloidal lead halide perovskites have recently emerged as promising materials for light-emitting diodes (LEDs), because of their unique advantages of a tunable emission wavelength, high color purity, and low temperature and cost-effective solution process c apability[1,2,3,4,5,6,7,8,9]
FA doped Cs1–xFAxPbBr3 quantum dots (QDs) have been used for high-efficiency inverted-type QD-light emitting devices (LEDs)
Due to the capability of hydrogen bonding as well as ionic interaction with B r, FA doped in C s1–xFAxPbBr3 QDs significantly increased the content of Br both at the surface and the inner part of C s1–xFAxPbBr3
Summary
Colloidal lead halide perovskites have recently emerged as promising materials for light-emitting diodes (LEDs), because of their unique advantages of a tunable emission wavelength, high color purity, and low temperature and cost-effective solution process c apability[1,2,3,4,5,6,7,8,9]. The performance of QD-LEDs with Cs1−xFAxPbBr3 at the optimized composition (x = 0.04) exhibited the maximum luminance ( Lmax) of 5200 cd m−2 at 5.3 V and the maximum current efficiency ( CEmax) of 3.87 cd A−1 at 5.0 V These are much better than those values for undoped (x = 0) and over-doped (x = 0.055) ones: Lmax = 2880 cd m−2 at 6.2 V and C Emax = 1.98 cd A−1 at 5.9 V for CsPbBr3, and Lmax = 2250 cd m-2 at 5.6 V and CEmax = 2.73 cd A−1 at 5.0 V Cs0.945FA0.055PbBr3, respectively. This FA doping strategy enables us to suppress the non-radiative recombination in luminance layer to improve the performance of QD-LEDs and to realize the high efficiency in optoelectronic devices
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