Blue emissive perovskites can be prepared by incorporating chlorine into bromine‐based perovskites to tune their bandgap. However, mixed‐halide perovskites exhibit intrinsic phase instability, particularly under electrical potential, owing to halide migration. To achieve high‐performance blue perovskite‐based light‐emitting diodes (PeLEDs) with operational stability, organic ammonium cations are used for passivating the anionic defects of the CsPbBr2Cl film. Diphenylpropylammonium chloride (DPPACl), used as a passivating agent, successfully prevents the spectral instability of blue PeLEDs by passivating the Cl− vacancies. Consequently, the blue PeLED prepared with this passivating agent delivers excellent device performance with a maximum external quantum efficiency of 3.03%. Moreover, upon tuning the DPPACl concentration, the PeLED emits stably in the deep‐blue spectral region (464 nm) with a half‐life time of 420 s. Thus, the use of organic ammonium cation as a passivating agent is an effective strategy for developing high‐performance blue PeLEDs with operational stability.

The morphology, crystal size, and trap density of perovskite films significantly affect the luminescent properties of perovskite light-emitting diodes (PeLEDs). Recently, numerous studies have been conducted on ligands that surround the surface of perovskite crystals and passivate the trap sites to improve the performance of PeLEDs. In this study, a 4-aminobenzonitrile (ABN) ligand improved the performance of methylammonium lead bromide (MAPbBr3)-based PeLEDs by reducing the MAPbBr3 crystal size to the nanoscale and reducing the trap density. Moreover, the properties of PeLEDs with ABN were further improved using a surface-modified hole-transport layer (HTL) with a hydrophilic polymer. Finally, a bright green PeLED was fabricated, which exhibited the maximum luminance of 3350 cd/m2 with an external quantum efficiency of 8.85%. Therefore, it is believed that the use of proper ligands for the perovskite layer and the optimization of the charge-transport layer have great potential for the development of high-performance PeLEDs.

Perovskite light-emitting diodes (PeLEDs) have garnered considerable interest in recent years owing to their unique optoelectronic properties. However, the performance of PeLEDs is limited by their low quantum efficiency and unbalanced charge injection. In this study, to address these issues, a novel co-hole transport layer (HTL) of 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) and poly(9-vinylcarbazole) (PVK) is introduced into PeLEDs. By optimizing the composition ratio of CBP and PVK, the performance of CsPbBr 3 -based PeLEDs is significantly improved via efficient Förster resonant energy transfer and an enhanced charge transfer owing to the well-aligned energy levels of the HTLs with the emission layers. The PeLED with an optimized composition ratio of the PVK 0.5 -CBP 0.5 HTL exhibits the best device performance with a luminance of 31641 cd•m −2 , current efficiency of 39.2 cd•A −1 , and external quantum efficiency of 15.4%. Thus, the proposed strategy engineering dual transfer of energy and charge is expected to be revolutionary in the field of PeLED research.

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