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Achieving efficient blue electroluminescence (EL) remains the fundamental challenge that impedes perovskite light‐emitting diodes (PeLEDs) towards commercial applications. The bottleneck accounting for the inefficient blue PeLEDs is broadly attributed to the poor‐emissive blue perovskite emitters based on either mixed halide engineering or reduced‐dimensional strategy. Herein, we report the high‐performing sky‐blue PeLEDs (490 nm) with the maximum EQE exceeding 15 % by incorporating a molecular modifier, namely 4,4′‐Difluorophenone, for significantly suppressing the non‐radiative recombination and tuning of the low‐dimensional phase distribution of quasi‐2D blue perovskites, which represents a remarkable paradigm for developing the new generation of blue lighting sources. [ABSTRACT FROM AUTHOR]

Compared with green and red perovskite light‐emitting diodes (PeLEDs), the development of blue PeLEDs has been lagging due to high defect density and inferior carrier transport. Herein, a novel defect‐passivation strategy is proposed to fabricate efficient sky‐blue PeLEDs by using isocyanate molecules. This strategy not only significantly reduces the nonradiative recombination loss caused by defects but also improves the injection and transport capacities of carriers by reducing the confinement effect. Benefiting from the passivation engineering and the reduction of confinement effect, the prepared sky‐blue PeLEDs present a significantly improved external quantum efficiency of 12.5% at 489 nm, which is 1.5 times higher than that of the control device. Meanwhile, the universality of isocyanate‐based passivators to improve the performance of PeLEDs is also demonstrated. The finding of this study provides a new reference for the selection of novel passivation agents to construct highly efficient blue PeLEDs. [ABSTRACT FROM AUTHOR]

Metal halide perovskite materials have shown excellent optoelectronic properties suitable for light‐emitting diodes. With the development of technology in recent years, the performance of perovskite light‐emitting diodes (PeLEDs) has been improved rapidly, which can be almost comparable with that of the organic light‐emitting diodes (OLEDs) and quantum‐dot light‐emitting diodes counterparts. However, the toxicity of lead in perovskites may be unacceptable to consumers, which severely hinders the commercial applications of PeLEDs. Therefore, massive efforts on more environment‐friendly PeLEDs should be invested, prompting them potential candidates for next‐generation display devices. In this review, the synthesis methods and preparation processes of perovskite emitting layers that are successfully utilized in environment‐friendly PeLEDs are first summarized. Then, a comprehensive analysis of development on the applications of both less‐lead and lead‐free PeLEDs is reported. Finally, the possible strategies to further improve the performance of environment‐friendly PeLEDs are given. [ABSTRACT FROM AUTHOR]

Compared with highly efficient green, red, and near-infrared perovskite light-emitting diodes (PeLEDs), the performance of blue PeLEDs is still unsatisfactory due to the serious spectral instability issue at high working voltages. In this work, a multidentate amine-based ligand with four amino groups is utilized to achieve spectral stable blue quasi-2D PeLEDs. As a result, the optimized quasi-2D perovskite films exhibit stable photoluminescence spectra under continuous UV illumination and heating. Finally, the blue quasi-2D PeLEDs emitting at 478 nm with the peak external quantum efficiency up to 4.8% are achieved. Meanwhile, there is no obvious peak shift of the electroluminescence spectral under high external working voltages, exhibiting excellent spectral stability. The findings in this work confirm the validity of this strategy, providing a strategy to achieve steady blue PeLEDs. [ABSTRACT FROM AUTHOR]

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