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Perovskite quantum dots (PeQDs) are promising nanoscale emitters in a generation of high-performance, large-area, and low-cost light-emitting diodes (LEDs) due to their superior emissive properties and excellent solution processability. Despite the tremendous advancement in luminescence efficiency in PeQDs, the design principle of the hole-transporting layer for PeQDs-based LEDs is still limited. Here, we investigate the discrepancy in electroluminescence properties of PeQDs-based LEDs with two widely used hole-transporting layers, namely, poly-[bis-(4-phenyl)-(2,4,6-trimethylphenyl)-amine] (PTAA) and poly-(9,9-dioctylfluorene-co-N-(4-(3-methylpropyl)) diphenylamine) (TFB). The results show that the TFB-based PeQD-LEDs exhibit much inferior performance than the PTAA-based device (7% vs 18% for external quantum efficiency) although the PeQDs show better optical properties when depositing on TFB hole-transporting layers. Theoretical calculation and comprehensive spectroscopic analysis indicate a weaker interaction between PeQDs and TFB polymers, which is attributed to the larger steric hindrance of TFB than that of PTAA. As a result, electrical characterizations identify a poor hole injection efficiency from the TFB to the PeQDs emissive layer when compared with the PTAA hole-transporting layers, thus leading to poor device performance. This work reveals the interaction between the hole-transporting layer and PeQDs on the performance of electroluminescence beyond the energy level and mobility of hole-transporting materials, which promotes an understanding of the hole injection mechanism in PeQDs-based LEDs. [ABSTRACT FROM AUTHOR]

High‐performance pure red perovskite light‐emitting diodes (PeLEDs) with an emission wavelength shorter than 650 nm are ideal for wide‐color‐gamut displays, yet remain an unprecedented challenge to progress. Mixed‐halide CsPb(Br/I)3 emitter‐based PeLEDs suffer spectral stability induced by halide phase segregation and CsPbI3 quantum dots (QDs) suffer from a compromise between emission wavelength and electroluminescence efficiency. Here, we demonstrate efficient pure red PeLEDs with an emission centered at 638 nm based on PbClx‐modified CsPbI3 QDs. A nucleophilic reaction that releases chloride ions and manipulates the ligand equilibrium of the colloidal system is developed to synthesize the pure red emission QDs. The comprehensive structural and spectroscopic characterizations evidence the formation of PbClx outside the CsPbI3 QDs, which regulates exciton recombination and prevents the exciton from dissociation induced by surface defects. In consequence, PeLEDs based on PbClx‐modified CsPbI3 QDs with superior optoelectronic properties demonstrate stable electroluminescence spectra at high driving voltages, a record external quantum efficiency of 26.1 %, optimal efficiency roll‐off of 16.0 % at 1000 cd m−2, and a half lifetime of 7.5 hours at 100 cd m−2, representing the state‐of‐the‐art pure red PeLEDs. This work provides new insight into constructing the carrier‐confined structure on perovskite QDs for high‐performance PeLEDs. [ABSTRACT FROM AUTHOR]

Halide perovskite light emitting diodes (LEDs) have gained great progress in recent years. However, mixed-halide perovskites for blue LEDs usually suffer from electroluminescence (EL) spectra shift at a high applied voltage or current density, limiting their efficiency. In this work, we report a strategy of using single-layer perovskite quantum dots (QDs) film to tackle the electroluminescence spectra shift in pure-blue perovskite LEDs and improve the LED efficiency by co-doping copper and potassium in the mixed-halide perovskite QDs. As a result, we obtained pure-blue halide perovskite QD-LEDs with stable EL spectra centred at 469 nm even at a current density of 1,617 mA·cm−2. The optimal device presents a maximum external quantum efficiency (EQE) of 2.0%. The average maximum EQE and luminance of the LEDs are 1.49% and 393 cd·m−2, increasing 62% and 66% compared with the control LEDs. Our study provides an effective strategy for achieving spectra-stable and highly efficient pure-blue perovskite LEDs. [ABSTRACT FROM AUTHOR]

Highly photo-thermal resistant pure-red-emitting CsPbI 3 quantum dots (QDs) with a 640 nm emission and ∼100% photoluminescence quantum yield (PL QY) are demonstrated via an in-situ reacted multiple-anchoring ligands strategy. The excellent heat resistance ensures that the CsPbI 3 QDs can withstand the hot-melt extrusion manufacturing process, enabling the first demo-of-concept perovskite-integrated diffusion plates for efficient light conversion. [Display omitted] • This paper first reports the CsPbI 3 QDs-integrated diffusion plates for display backlights. • The CsPbI 3 QDs withstand heat up to 180 °C, ensuring the hot-melt extrusion manufacturing process. • An in-situ reacted multiple-anchoring ligands to synthesize the highly photo-thermal resistant QDs is developed. The poor photo-thermal resistant property of halide perovskites impedes their integration into the diffusion plate for display backlights. Pure-red perovskite emitters, the dominant component for display, are vulnerable to phase transformation and their optical properties are extremely sensitive to thermal and photo-irradiation. Tremendous efforts in the past years yielded no successes in utilizing pure-red perovskite emitters for display backlights. Here, we report the first pure-red-emitting CsPbI 3 quantum dots (QDs) integrated diffusion plates. An in-situ reacted multiple-anchoring ligands to synthesize the highly photo-thermal resistant QDs is developed. The resulting CsPbI 3 QDs film possesses pure-red emission of 640 nm with a photoluminescence quantum efficiency (PL QY) of above 90%, high photo-resistant property under 450 nm light irradiation, nearly reversible PL QY and a stable cubic phase when suffering high temperatures up to 180 °C. These characteristics ensure the CsPbI 3 QDs integrate into the polystyrene matrix through hot-melt extrusion while retaining high optical properties. The CsPbI 3 and CsPbBr 3 -based diffusion plates cover a color area of 130% of the National Television System Committee and 97% of the Rec. 2020. Our results bring perovskites emitters a step closer to display applications. [ABSTRACT FROM AUTHOR]