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Quantum-dot light-emitting diodes (QLED) have become a research trend in the field of new displays due to their low cost, wide color gamut, narrow bandwidth, and characteristics that enable production through the solution-gel method. However, the electrical performance of QLED is consistently constrained by energy losses and imbalanced charge carrier injection. This motivates our focus on exciton recombination and energy losses within the quantum-dot layer to enhance the electrical efficiency of QLED. In this work, we introduce a method using a CdZnS quantum dot (B-QD) interlayer to modulate energy transfer and charge carrier transport in QLED devices employing CdSe quantum dot (G-QD) as the emissive layer. By strategically incorporating a B-QD layer between the G-QD and HTL/ETL, we facilitate energy transfer due to the overlap between the excitation wavelength of B-QD and the absorption wavelength of G-QDs. This leads to enhanced energy injection in QLED devices, resulting in a high current efficiency of 39.54 Cd/A and a peak brightness of 522,272 cd/m2 for efficient QLED. The corresponding external quantum efficiency (EQE) is greatly improved from 5.62 % to 9.4 %. Our work provides a straightforward and effective approach to modulate exciton recombination and energy injection and further can be applicable to other photo-electronics devices. [Display omitted] • To design receptors and donors for energy transfer systems, prepare quantum dots with appropriate sizes. • With ZnO isolation layer used for testing energy transfer, it is demonstrated that energy transfer promotes QLED efficiency. • The QLED has achieved a peak brightness of 522,272cd/m² and a current efficiency of 39.54cd/A. [ABSTRACT FROM AUTHOR]

Metal halide perovskite quantum dots (QDs) have significant potential for application in light-emitting diodes (LED) owing to their superior optical properties. However, the dynamic instability of traditional oleic acid/amine ligands has a considerable impact on the optical and chemical properties of the surface. Additionally, one of its insulating qualities restricts the practical application of electroluminescent devices. In this case, the dual-function ligand DDA-MeS can passivate surface defects while also stabilizing chelation on QDs surface. As a result, the electrical performance of green QDs-LED devices is greatly enhanced, the external quantum efficiency is raised to 10.18%, the maximum brightness is also boosted to 8025 cd/m2, and the turn-on voltage is decreased to 2.5 V. This work also provides a novel strategy for the development of green LED devices with dual-function ligands that can be highly effective and bright. • CsPbBr 3 QDs synthesized by thermal injection of bifunctional ligands with S=O and quaternary ammonium groups DDA-MeS modification. • The modified QDs exhibit reduced defect density, and enhanced PLQY and carrier mobility. • High-efficiency perovskite LED based on dual-function ligand modification with EQE of 10.18% and luminance of 8025 cd/m2 is fabricated. [ABSTRACT FROM AUTHOR]

Cesium lead halide (CsPbX 3 , X = Cl, Br, I) perovskite quantum dots (PQDs) have attracted extensive attention due to their high crystal structure stability. However, a large number of defects generally exist on the surface of PQDs, which results in non-radiative recombination and affects the electrical performance of their devices. Here, we report a simple and feasible hybrid ligand passivation strategy to modify PQDs surface defects. Guanidine bromide (GABr) and didecyldimethyl ammonium bromide (DDAB 10) were dissolved in toluene to modify the surface trap state of PQDs. The post-treatment strategy effectively inhibits vacancy defects and improves electrical performance. The strong affinity (N–H...Br) between guanidine ion and halogen not only reduces the defect density of PQDs, but also improves their carrier mobility. The results also show that the guanidine ion is closely bonded to the surface of PQDs, the fluorescence lifetime is longer, and the defect density is smaller. Finally, a green perovskite light-emitting diode (PeLED) device with an EQE of 10.02% and current efficiency of 36.4 cd/A was obtained. [Display omitted] • CsPbBr 3 PQDs modified by DDAB 10 and GABr post-treatment were synthesized by the hot injection (HI) methods. • The modified PQDs exhibit enhanced PL, carrier lifetime, reduced defect density, and smooth PQDs films are obtained. • High-efficiency PeLED based on hybrid ligand modification with EQE of 10.06% and current efficiency of 36.4% is fabricated. [ABSTRACT FROM AUTHOR]

CuInS 2 -based quantum-dots (QDs) have been highlighted as promising photoelectric materials for their low toxicity and color adjustable emissions as well as stability. Here, multi-shell CuInS 2 /ZnS/ZnS QDs with high PLQY of 76% were synthesized by employing a high temperature and long-time growth strategy while highly bright and efficient quantum-dot-light-emitting diodes (QLEDs) were fabricated by using these multi-shell QDs as an emission layer and polyethylenimine (PEI) as an insulating layer, respectively. By introducing PEI between the QDs and ZnO EML layers of the QLEDs, the balance of the carriers within the QDs layer injected from HTL and ETL was greatly improved. As a result, comparing to the QLEDs without PEI, the greatly improved efficiency (1.9 times as high as that of the QLEDs without PEI) has been achieved in the optimized QLEDs with PEI. These QLEDs exhibits an outstanding performance with the maximum EQE of 1.56% and the maximum brightness of 5825 cd/m2. • The QDs were synthesized by a two-step of ZnS shelling strategy. • Highly efficient QLEDs were fabricated by adopting a modified device structure. • The PEI moderately impeded the electron injection, improved charge injection balance within QD active layers. [ABSTRACT FROM AUTHOR]

An effective Quantum Dot Light Emitting Diodes (QLED) was developed by creatively inserting an easily controlled 2D graphene oxide (GO) film between the luminescent layer and the electron transport layer (ETL) as the electron barrier layer (EBL). As compared with the traditional PMMA and other polymer barrier layers, the GO with particular the lamellar two-dimensional structure was more conducive to the control of film thickness by spin-coating. The introduction of GO increased the conduction band edge and inhibited exciton quenching. Simultaneously, since the electron mobility of the ETL was much higher than the hole mobility of the hole transport layer (HTL), GO with high insulation could be used to inhibit the electron injection effectively and achieve the charge transport balance. The green QLEDs with high performances including a current efficiency of 22.51 cd A−1, a power efficiency of 8. 71 lm W−1 and an EQE of up to 5.98% were successively fabricated. This particular architecture of QLED with GO electron barrier layer and creative method of energy band regulation provided an efficient and feasible strategy for the next generation of QLED displays with high performance and solid-state lighting technologies. Figure (a) Schematic of the QLED film configuration and (b) Associated energy level diagram of the QLED. (c) luminescence-EQE at different concentrations of GO solution. (d) voltage-current density at different concentrations of GO solution. Current density as a function of voltage for the electron-only and hole-only devices. Image 1 • Green QLED with excellent performance was achieved by inserting GO film between the luminescent layer and the ETL as EBL. • This particular architecture of QLED exhibited excellent electrical and optical properties. • This particular architecture of QLED provided an efficient and feasible strategy for the next generation of QLED displays. [ABSTRACT FROM AUTHOR]

[Display omitted] • The multi-functional MFCl interface is prepared between the HTL and perovskite. • MFCl reduces the energy band of the HTL, making it more conducive to hole injection. • The controlled nucleation and crystallization of perovskite is achieved. • Good domains and few defects are helpful to the better device performance. • PeLEDs with EQE of 5.22% and a stable EL spectrum are fabricated. Domain distribution, defect density as well as carrier transport all exert some great impact on the performance of quasi-two-dimensional (quasi-2D) perovskites light emitting diodes (PeLEDs). Herein, the novelty multifunctional metformin hydrochloride (MFCl) buried passivated layer was introduced to optimize the crystal dynamics, surface morphology, and electro-luminescent properties of the quasi-2D perovskites. On the one hand, MF ion to some extent optimized the domain distribution just by both decreasing the n = 2 phase and increasing the three-dimensional (3D) phase, which facilitated the charge funnelling. On the other hand, by combining MFCl with PSS or PSS-Na, the energy level of the hole transport layer was effectively adjusted, resulting in an obvious reduction of the injection barrier. As a result, the MFCl-optimized blue quasi-2D PeLEDs with the maximum external quantum efficiency of 5.22 % was achieved, which is 3.6 times higher than that of the device without the MFCl treatment. This work provided favourable strategy for the performance enhancement of blue quasi-2D PeLEDs, in which a multifunction interface was introduced to synchronously improve the phase distribution as well as the defect passivation of quasi-2D perovskite, meanwhile all of those further promoted the charge transportation. [ABSTRACT FROM AUTHOR]

Abstract In this work, we report highly flexible QLEDs based on a quantum dots-polymer composite emitting layer. Conventional quantum dot films exhibit cracks after rough bending. Herein, polymethyl methacrylate (PMMA) was doped into quantum dot solution, acting as binder for neighboring quantum dots. In addition, PMMA can be serving as an electron blocking layer due to its insulating property, and then balancing the charge recombination and improving device performance. The flexible QLEDs have excellent mechanical properties with an ultimate bend radius of 1.5 mm, and they show no significant performance degradation after 500 times bending with radius of 4 mm. The flexible QLEDs exhibit high performance with maximum luminance of 14880 cd/m2 and maximum current efficiency of 21.3 cd/A. Highlights • Flexible quantum dot light-emitting devices (FQLEDs) are fabricated with solution process. • Polymethylmethacrylate (PMMA) was doped into the quantum dot emissive layer. • PMMA can serve as binder for neighboring quantum dots and electron blocking layer. • Charge balance of the FQLEDs is enhanced and the device performance is improved. • FQLEDs exhibits excellent mechanical properties upon serious bending. [ABSTRACT FROM AUTHOR]