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A hydrogen-bonded amine-group doping strategy is proposed for effectively suppressing color-shift of blue PeLEDs. The theoretical and experimental results demonstrated that the N−H⋯X interaction between −NH 2 dopants and Pb−X lattices can increase the potential barriers of halide ion migration and hence stabilize the emitting wavelength even at high voltage loads, making the strategy attractive for developing color-stable perovskite optoelectronic devices for lighting and display applications. [Display omitted] Voltage loading-induced change in the electroluminescence (EL) wavelength of mixed halide perovskite light-emitting diodes (PeLEDs), so-called color-shift, has become an inevitable phenomenon, which is seriously unfavorable to their applications in lighting and display. Here, we achieve color-stable blue PeLEDs via a hydrogen-bonded amine-group doping strategy. Selecting guanidine (GA) or formamidinium (FA) as amine-group (−NH 2) doping source for CsPbBr x Cl 3− x quantum dots (QDs), experimental and theoretical results reveal that the strong N−H⋯X (X = Br/Cl) bonding can be produced between −NH 2 dopants and Pb−X lattices, thereby increasing the migration barrier of halide anions. Resultantly, color-stable sky-blue devices were realized with emission peaks fixed at 490.5 (GA) and 492.5 (FA) nm without any obvious shift as the voltage increases, in sharp contrast devices without N−H⋯X producing a 15 nm red-shift from 487 to 502 nm. Not only that, maximum external quantum efficiency is improved to 3.02% and 4.14% from the initial 1.3%. This finding offers a convenient boulevard to achieve color-stable PeLEDs with high efficiency. [ABSTRACT FROM AUTHOR]

According to the thinner emitting layer and stronger electric field in perovskite light‐emitting diodes (PeLEDs) than those in perovskite solar cells, the strong electric‐field‐driven ion‐migration is a key issue for the operational stability of PeLEDs. Here, a methylene‐bis‐acrylamide cross‐linking strategy is proposed to both passivate defects and suppress ion‐migration with an emphasis on the suppressing mechanism via in situ investigations. As typical results, in addition to the enhanced external quantum efficiency (EQE, 16.8%), PeLEDs exhibit preferable operational stability with a half lifetime (T50) of 208 h under continuous operation with an initial luminance of 100 cd m−2. Moreover, the EQE of cross‐linked LEDs can maintain above 15% during 25 times scanning as the devices are measured every 4 days. To the authors' knowledge, this is the highest stability published until now for high‐efficiency PeLEDs with EQE over 15%. The in situ/ex situ mechanism investigation demonstrates that such cross‐linking increases binding energy from 0.54 to 0.92 eV and activation energy from 0.21 to 0.5 eV. Hence, it suppresses ligands breaking away and ion migration, which prevents ions from moving inside and across crystals. The proposed cross‐linking passivation strategy thus provides an effective methodology to fabricate stable perovskites‐based photoelectric devices. [ABSTRACT FROM AUTHOR]

Perovskite quantum-dot-based light-emitting diodes (QLEDs) possess the features of wide gamut and real color expression, which have been considered as candidates for high-quality lightings and displays. However, massive defects are prone to be reproduced during the quantum dot (QD) film assembly, which would sorely affect carrier injection, transportation and recombination, and finally degrade QLED performances. Here, we propose a bilateral passivation strategy through passivating both top and bottom interfaces of QD film with organic molecules, which has drastically enhanced the efficiency and stability of perovskite QLEDs. Various molecules were applied, and comparison experiments were conducted to verify the necessity of passivation on both interfaces. Eventually, the passivated device achieves a maximum external quantum efficiency (EQE) of 18.7% and current efficiency of 75 cd A−1. Moreover, the operational lifetime of QLEDs is enhanced by 20-fold, reaching 15.8 h. These findings highlight the importance of interface passivation for efficient and stable QD-based optoelectronic devices. Perovskite quantum-dots are promising candidates for light-emitting diodes but the defects limit the device performance. Here Xu et al. show a passivation strategy to reduce the defect density at both interfaces, which increases the external quantum efficiency (EQE) and lifetime by more than 2-fold and 20-fold, respectively. [ABSTRACT FROM AUTHOR]

Lead halide perovskite, as an emerging semiconductor, provides a fire‐new opportunity for high‐definition display and solid‐state lighting. Earthshaking improvements are implemented in green, red, and near‐infrared perovskite light‐emitting diodes (PeLEDs). However, blue PeLEDs are still far behind in performance, which restricts the development of PeLEDs in practical applications. Herein, a facile energy cascade channel strategy via one‐step self‐organized and controllable 2D/3D perovskite preparation by introducing guanidine hydrobromide (GABr) is developed that greatly improves the efficiency of blue PeLEDs. The 2D/3D perovskite structure boosts the energy cascade to induce energy transfer from the wide into the narrow bandgap domains and inhibit free charge diffusion, which increases the density of electrons and holes, and enhances the radiative recombination. Profiting from this energy cascade channels, the external quantum efficiency of blue PeLEDs, emitting at 492 nm, is considerably enhanced from 1.5% of initial blue device to 8.2%. In addition, device operating stability under ambient conditions is also improved by 2.6‐fold. The one‐step self‐organized 2D/3D hybrid perovskites induced by GABr pave a new and simple route toward high‐performance blue emission PeLEDs. [ABSTRACT FROM AUTHOR]

Recently, inorganic cesium–lead halide perovskites with high thermal stability have attracted much attention as promising light‐emitting material for research of perovskite‐based light‐emitting diodes (PeLEDs) toward high‐definition displays. However, the CsPbI3‐based red PeLEDs still suffer low external quantum efficiency (EQE) and poor device stability due to the spontaneous phase transition from cubic CsPbI3 (α‐CsPbI3) to nonradiative orthorhombic phase (δ‐CsPbI3) under ambient conditions. Here, a feasible approach is reported on phase engineering by incorporating the long‐chain cation (e.g., 2‐(naphthalene‐1‐yl)ethanamine (NEA)) in CsPbI3 for stable and high‐performance CsPbI3‐based red light‐emitting diodes (LEDs). A high EQE of 8.65% is successfully achieved for the characteristic red emission at ≈682 nm representing the highest value among Cs‐based red PeLEDs up to now. More importantly, the corresponding PeLEDs exhibit outstanding stability with EQE retaining 90% after 3 months of storage. These results verify the potential of using cesium‐based inorganic perovskite as viable alternatives to methylammonium (MA)‐ or formamidinium (FA)‐based perovskite for desirable practical applications. Stable α‐CsPbI3 is synthesized by incorporating cation 2‐(naphthalene‐1‐yl)ethanamine (NEA) for perovskite‐based light‐emitting diodes (PeLED). A high external quantum (EQE) of 8.65% is successfully demonstrated for the characteristic red emission ≈682 nm representing the highest value among Cs‐based red PeLEDs up to now. More importantly, corresponding PeLEDs exhibit outstanding stability with EQE retaining 90% after 3 months storage. [ABSTRACT FROM AUTHOR]