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Even though lead halide perovskite has been demonstrated as a promising optoelectronic material for next-generation display applications, achieving high-efficiency and stable pure-red (620~635 nm) emission to cover the full visible wavelength is still challenging. Here, we report perovskite light-emitting diodes emitting pure-red light at 628 nm achieving high external quantum efficiencies of 26.04%. The performance is attributed to successful synthesizing strongly confined CsPbI3 quantum dots with good stability. The strong binding 2-naphthalene sulfonic acid ligands are introduced after nucleation to suppress Ostwald ripening, meanwhile, ammonium hexafluorophosphate exchanges long chain ligands and avoids regrowth by strong binding during the purification process. Both ligands enhance the charge transport ability of CsPbI3 quantum dots. The state-of-the-art synthesis of pure red CsPbI3 quantum dots achieves 94% high quantum efficiency, which can maintain over 80% after 50 days, providing a method for synthesizing stable strong confined perovskite quantum dots. Li et al. report the regulation of perovskite quantum dot growth after nucleation by designing ligand exchange utilising proton transfer. The Ostwald ripening and regrowth are prohibited with an external quantum efficiency of 26.04% achieved in the pure-red perovskite light-emitting diodes. [ABSTRACT FROM AUTHOR]

Perovskite light‐emitting diodes (PeLEDs) based on quasi‐2D perovskites have attracted great attention in the past few years. Although significant achievements are made in device performance, fabrication of high‐efficiency PeLEDs with pure‐red (620–635 nm) light emission remains a significant challenge, which inhibits their practical application for full‐color displays. Herein, a series of efficient red PeLEDs at 625 nm are realized by employing volatile alkylammonium chlorides (propylammonium chloride) passivators. The interaction of PbI2 with propylamine (PA)...H+Cl− in the precursor solution effectively passivates the defects, leading to reduced non‐radiative recombination and enhanced device performance. By optimizing the amount of PACl, an external quantum efficiency (EQE) of 16.1% and a maximum brightness of 1701 cd m−2 are achieved, among the best‐performing quasi‐2D I‐based PeLEDs with emissions ranging from 620 to 635 nm. This work provides a new route to improve the stability and efficiency of pure‐red PeLEDs. [ABSTRACT FROM AUTHOR]

Inorganic perovskite quantum dots (QDs) have garnered significant attention due to their outstanding optical properties. However, perovskite quantum dot light‐emitting diodes (Pe‐QLEDs) still face challenges related to their fluorescence efficiency and electron injection. First, the electron transport layer (ETL) leads to severe non‐radiative recombination due to fluorescence quenching in CsPbI3 QDs. Second, there is an electron injection imbalance resulting from low electron injection efficiency, leading to reduced non‐radiative recombination and external quantum efficiency. To address these issues, this study introduces two interface layer materials with different electron affinities, 1,3,5‐Tris(3‐pyridyl‐3‐phenyl)benzene (TmPyPB) and 2,4,6‐Tris(3′‐(pyridine‐3‐yl)biphenyl‐3‐yl)‐1,3,5‐triazine (TmPPPyTz). These materials not only passivated defects on the surface of CsPbI3 QDs films but also effectively prevented the fluorescence quenching of CsPbI3 QDs by the PO‐T2T (ETL). TmPPPyTz, with a relatively lower LUMO energy level, further improved energy level matching, significantly enhancing electron injection efficiency. Ultimately, using interface engineering with the TmPPPyTz interface layer, the devices achieved an outstanding 25.80% champion‐level external quantum efficiency (EQE) for Pe‐QLEDs with only a sub‐bandgap voltage of 1.7 V and half‐life (T50) is 17.99 h at 100 nits. This research provided an effective method to enhance the performance of CsPbI3 Pe‐QLEDs, addressing long‐standing issues inhibiting their efficiency. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylene dioxythiophene)/poly(styrene sulfonic acid), abbreviated as PEDOT:PSS, is widely used in light-emitting diodes, solar cells, sensors, and other functional devices due to its high conductivity, transparency, and solution processability. In this study, the photo-reactive cross-linking agent 2,4-hexadiyne-1,6-diol (HOD) was introduced for a comparative study of photo-crosslinking in PEDOT:PSS AI 4083 (denoted as 4083) and PEDOT:PSS PH1000 (denoted as PH1000). The results showed that the aggregation state of 4083 was different from that of PH1000, ascribed to the composition of 4083 and PH1000 and the mechanism of the photo-crosslinking agent. Based on these findings, quantum dot light-emitting diode (QLED) devices were fabricated using direct photo-crosslinking PH1000. The work function based on PH1000 as a hole-injected layer (HIL) was increased from 5.03 eV to 5.22 eV, and the external quantum efficiency (EQE) was increased from 17.2% to 18.9%. This result provided a feasible solution for the application of PH1000 in high-performance QLED displays. [ABSTRACT FROM AUTHOR]

Highlights: A new proton-promoted in situ ligand exchange strategy based on CsPbI3 quantum dots. The ligand exchange strategy maintains the quantum confinement effect of quantum dots and significantly improves the stability and photophysical properties of CsPbI3 quantum dots. The performance of light-emitting diodes based on CsPbI3 quantum dots is significantly improved, the external quantum efficiency is increased from 18.63% to 24.45%, and the half-operational lifetime is increased by 70 times. CsPbI3 perovskite quantum dots (QDs) are ideal materials for the next generation of red light-emitting diodes. However, the low phase stability of CsPbI3 QDs and long-chain insulating capping ligands hinder the improvement of device performance. Traditional in-situ ligand replacement and ligand exchange after synthesis were often difficult to control. Here, we proposed a new ligand exchange strategy using a proton-prompted in-situ exchange of short 5-aminopentanoic acid ligands with long-chain oleic acid and oleylamine ligands to obtain stable small-size CsPbI3 QDs. This exchange strategy maintained the size and morphology of CsPbI3 QDs and improved the optical properties and the conductivity of CsPbI3 QDs films. As a result, high-efficiency red QD-based light-emitting diodes with an emission wavelength of 645 nm demonstrated a record maximum external quantum efficiency of 24.45% and an operational half-life of 10.79 h. [ABSTRACT FROM AUTHOR]

Perovskite nanocrystals for light‐emitting diodes are often synthesized by uncontrollable metathesis reactions, suffering from low product yield, nonuniform growth, and poor stability. Herein, by controlling the nucleation kinetics with high dissociation constant (Ka or Kb) acids or bases, homogenous one‐route nucleation of perovskite nanocrystals is achieved as the cluster intermediates are eliminated. The stable, shape uniform, and narrow size distribution green nanocrystals are synthesized. The perovskite nanocrystal film exhibites excellent stability in 80% humidity air with only a 10% photoluminescence intensity drop after 16 h. Efficient and stable electroluminescence is demonstrated with an FWHM of 16 nm at 517 nm. The green devices shows a peak EQE of 24.13% with a lifetime T50 of 54 min at 10 000 cd m−2. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) have attracted wide attention from academia and industry because of their advantages such as high emitting efficiency, narrow half-peak width, and continuously adjustable emitting wavelength. QDs light emitting diodes (QLEDs) are expected to become the next generation commercial display technology. This paper reviews the progress of QLED from physical mechanism, materials, to device engineering. The strategies to improve QLED performance from the perspectives of quantum dot materials and device structures are summarized. [ABSTRACT FROM AUTHOR]

Although organic metal halide perovskite light‐emitting diodes (PeLEDs) have been developed rapidly in recent years, their commercialization and further applications are still hindered by ion migration‐induced inferior operational stability. Although the formation of a quasi‐2D structure is a well‐known solution that can efficiently suppress ion migration, the operation lifetime improvement is still limited. In this study, long‐chain phenylbutanammonium is used to replace the commonly used phenethylammonium as the L‐site cations. With large steric hindrance, ion migration inside the PeLEDs is effectively suppressed. Consequently, the PeLED with near‐infrared emission at 763 nm exhibited an operational lifetime (T90) of up to 5.3 h, which is 53‐fold higher than that of the control device. This study demonstrates the feasibility of significant stability improvement using a simple cation engineering strategy for PeLEDs. [ABSTRACT FROM AUTHOR]

This document is a technical paper titled "Efficient Perovskite quantum dots Light Emitting Diodes." It discusses the use of CsPbI3 perovskite quantum dots (QDs) in light-emitting diodes (LEDs) and the challenges faced in their practical applications. The paper presents a new strategy of proton-prompted short-chain ligand exchange in the synthesis of CsPbI3 QDs and the design of interface layers with high electron affinity. These approaches result in improved device performance, with a champion-level external quantum efficiency (EQE) of 25.80% achieved. This study represents the highest reported performance for pure red perovskite quantum dot LEDs to date. [Extracted from the article]

The low efficiency and fast degradation of devices from ink-jet printing process hinders the application of quantum dot light emitting diodes on next generation displays. Passivating the trap states caused by both anion and cation under-coordinated sites on the quantum dot surface with proper ligands for ink-jet printing processing reminds a problem. Here we show, by adapting the idea of dual ionic passivation of quantum dots, ink-jet printed quantum dot light emitting diodes with an external quantum efficiency over 16% and half lifetime of more than 1,721,000 hours were reported for the first time. The liquid phase exchange of ligands fulfills the requirements of ink-jet printing processing for possible mass production. And the performance from ink-jet printed quantum dot light emitting diodes truly opens the gate of quantum dot light emitting diode application for industry. Designing efficient and scalable quantum dot LEDs meeting industrial requirements remains a challenge. Here, the authors, by leveraging the liquid phase exchange of d-MX2 ligands, present printed quantum dot LEDs with external quantum efficiency over 16% and half lifetime of more than 1,721,000 hours. [ABSTRACT FROM AUTHOR]

We demonstrate blue/violet emitting devices based on cadmium-free zinc selenide/zinc sulfide core/shell quantum dots. Using poly(N-vinylcarbazole) with a low lying highest occupied molecular orbital energy for the hole transporting layer, enhanced hole injection was observed, resulting in efficient blue/violet emitting devices. The device charge balance was further enhanced by tuning the thicknesses of the hole transporting layer and quantum dot emitting layer. [ABSTRACT FROM AUTHOR]

23.1: Invited Paper: High efficiency and Stability of Ink-jet Printed Quantum Dot Light Emitting Diodes via Dual Ionic Surface Passivation. Here, ink-jet printed quantum dots LEDs with an external quantum efficiency over 16% and half lifetime of more than 1,721,000 hours, were reported for the first time. And the performance from ink-jet printed QLEDs truly opens the gate of quantum dots LED application for industry. [Extracted from the article]

[Display omitted] • WS 2 was used as the hole interface layer to improve the hole transport ability through energy level matching. • The crystal quality of perovskite film was improved by using WS 2 as the hole interface layer. • Obtained high-performance Quasi-2D blue perovskite light-emitting devices with EQE of 3.24%. Due to the deep energy levels, the external quantum efficiency (EQE) of the blue perovskite light-emitting diode (PeLED) is far lower than its green, red, and near-infrared counterparts, which has exceeded 20%. The mismatched energy levels between perovskites and the hole transporting layer (HTL) still hinder the hole injection and consequent improvement of blue PeLED device performance. Here, a two-dimensional material, WS 2 (Tungsten disulfide), was introduced to match the energy levels between perovskites and HTL and enhanced the hole injection. The WS 2 HTL-based perovskite FAPbBr 3-x Cl x blue LED achieved a luminance of 990 cd/m2 with an EQE of 3.24%, which surpasses the performance of previously reported for the formamidinium (FA) based system, indicating the potential of WS 2 for PeLEDs. [ABSTRACT FROM AUTHOR]

ZnO thin films (s-ZnO) were prepared by an in-situ solution process instead of traditional nanocrystalline ZnO (n-ZnO). By optimizing the technological conditions, ZnO thin films with better energy level matching and better transmission performance were prepared (annealed at 180°), and s-ZnO was applied to perovskite LED for the first time to achieve high-performance luminescence. This work reduces the complexity of ZnO process in PeLED device preparation and provides a good strategy for the commercialization of perovskite LED. [Display omitted] • In-situ solution-processed ZnO ETLs were fabricated from zinc acetate dihydrate in 2-methoxyethanol by spin-coating technology. • The performance of S-ZnO PeLEDs is similar to that of n-ZnO based devices with peak efficiency of around 22%. • Compared with traditional ZnO nanocrystals, S-ZnO is easier to prepare. As an alternative method of the electron transport layer (ETL) of Zinc Oxide nanoparticles, an in-situ solution process was developed to prepare ZnO thin films for manufacturing perovskite light-emitting diodes (PeLEDs). After optimizing the processing conditions, the band energy and electron mobility are adjusted appropriately, which shows advantages to balance the carrier injection in PeLEDs. The near-infrared PeLEDs with ZnO film prepared by in-situ method demonstrated external quantum efficiency of 22%, which is compatible with their counterpart using ZnO nanoparticles. Our report provides a feasible strategy for the low-cost fabrication of PeLEDs with high performance. [ABSTRACT FROM AUTHOR]