Recently, impressive external quantum efficiencies (EQEs) exceeding 20% are obtained for green, red, and near-infrared perovskitebased LEDs (PeLEDs) through the efforts of perovskite material optimization and device architecture design. [8-10] These achievements firmly prompt the potential applications of PeLEDs in display and illumination fields. However, compared with the efficient PeLEDs, there is only moderate performance reported for blue PeLEDs, [11-18] which undoubtedly restrict PeLED applications in full-color displays and white-light illumination. Thus, the breakthroughs of the device performance are urgently required for blue PeLEDs. Substantial efforts have been made in the past several years to obtain blue perovskite emitters, such as perovskite nanocrystals (NCs), [19-25] 2D perovskite nanoplatelets, [26-32] and quasi-2D perovskites. [33-39] In particular, the quasi-2D perovskites are rising as efficient luminescent materials for highly performed blue PeLEDs due to the cascade energy landscape for efficient exciton transfer and the subsequent radiative recombination. Typically, the quasi-2D perovskites have a formula of B 2 (APbBr 3) n−1 PbBr 4 , While there has been extensive investigation into modulating quasi-2D perovskite compositions in light-emitting diodes (LEDs) for promoting their electroluminescence, very few reports have studied approaches involving enhancement of the energy transfer between quasi-2D perovskite layers of the film, which plays very important role for achieving high-performance perovskite LEDs (PeLEDs). In this work, a bifunctional ligand of 4-(2-aminoethyl)benzoic acid (ABA) cation is strategically introduced into the perovskite to diminish the weak van der Waals gap between individual perovskite layers for promoting coupled quasi-2D perovskite layers. In particular, the strengthened interaction between coupled quasi-2D perovskite layers favors an efficient energy transfer in the perovskite films. The introduced ABA can also simultaneously passivate the perovskite defects by reducing metallic Pb for less nonradiative recombination loss. Benefiting from the advanced properties of ABA incorporated perovskites, highly efficient blue PeLEDs with external quantum efficiency of 10.11% and a very long operational stability of 81.3 min, among the best performing blue quasi-2D PeLEDs, are achieved. Consequently, this work contributes an effective approach for high-performance and stable blue PeLEDs toward practical applications. Metal halide perovskites have emerged as competitive candidates for the next-generation light-emitting diodes (LEDs) due to their excellent optical properties, such as tunable light emission color, high color purity, and high photoluminescence The ORCID identification number(s) for the author(s) of this article can be found under

The long‐term operational stability of perovskite light‐emitting diodes (PeLEDs), especially red PeLEDs with only several hours typically, has always faced great challenges. Stable β‐CsPbI3 nanocrystals (NCs) are demonstrated for highly efficient and stable red‐emitting PeLEDs through incorporation of poly(maleic anhydride‐alt‐1‐octadecene) (PMA) in synthesizing the NCs. The PMA can chemically interact with PbI2 in the precursors via the coupling effect between O groups in PMA and Pb2+ to favor crystallization of stable β‐CsPbI3 NCs. Meanwhile, the cross‐linked PMA significantly reduces the PbCs anti‐site defect on the surface of the β‐CsPbI3 NCs. Benefiting from the improved crystal phase quality, the photoluminescence quantum yield for β‐CsPbI3 NCs films remarkably increases from 34% to 89%. The corresponding red‐emitting PeLEDs achieves a high external quantum efficiency of 17.8% and superior operational stability with the lifetime, the time to half the initial electroluminescence intensity (T50) reaching 317 h at a constant current density of 30 mA cm−2.

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Quantum-confined CsPbBr3 nanoplatelets (NPLs) with very narrow emission line width are promising candidates for color-saturated blue emitters, but their electroluminescence performance is limited by inferior carrier transport, mostly induced by the surface bulky organic ligands. Many efforts routinely rely on replacing long ligands with short counterparts, resulting in a significant increase in the NPL’s thickness and thus making it difficult to obtain the desired emission color. Herein, we realize short-ligand (butylamine and myristic acid)-capped CsPbBr3 NPLs with almost unaltered emission characteristics by introducing ammonium bromide (NH4Br) to effectively control the crystal growth kinetics and passivate the surface defects. Further, with short conjugation ligand–phenethylammonium bromide (PEABr) postsynthetic treatment, we can dramatically enhance their electrical performance and luminous efficiency (film photoluminescence quantum yields over 80%). With these benefits, a remarkable electroluminescence efficiency of 2% (at 463 nm) has been achieved, which is a record for blue perovskite NPL-based light-emitting diodes.