Perovskite Light‐Emitting Diodes with EQE Exceeding 28% through a Synergetic Dual‐Additive Strategy for Defect Passivation and Nanostructure Regulation

• Published in: Advanced materials (Weinheim) Vol. 33; no. 43; pp. e2103268 - n/a
• Main Authors: Liu, Zhe, Qiu, Weidong, Peng, Xiaomei, Sun, Guanwei, Liu, Xinyan, Liu, Denghui, Li, Zhenchao, He, Fangru, Shen, Chenyang, Gu, Qing, Ma, Fulong, Yip, Hin‐Lap, Hou, Lintao, Qi, Zhengjian, Su, Shi‐Jian
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.10.2021
• Subjects: Additives; Augers; Core-shell structure; defect passivation; dual additives; green perovskite light‐emitting diodes; Light emitting diodes; Materials science; MPEG encoders; Nanocrystals; Optical properties; Perovskites; Polyethylene glycol monomethyl ether acrylate; Quantum efficiency; quasi‐core/shell nanocrystals; Service life assessment; Stability
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202103268

Quasi‐2D perovskites have long been considered to have favorable “energy funnel/cascade” structures and excellent optical properties compared with their 3D counterparts. However, most quasi‐2D perovskite light‐emitting diodes (PeLEDs) exhibit high external quantum efficiency (EQE) but unsatisfactory operating stability due to Auger recombination induced by high current density. Herein, a synergetic dual‐additive strategy is adopted to prepare perovskite films with low defect density and high environmental stability by using 18‐crown‐6 and poly(ethylene glycol) methyl ether acrylate (MPEG‐MAA) as the additives. The dual additives containing COC bonds can not only effectively reduce the perovskite defects but also destroy the self‐aggregation of organic ligands, inducing the formation of perovskite nanocrystals with quasi‐core/shell structure. After thermal annealing, the MPEG‐MAA with its CC bond can be polymerized to obtain a comb‐like polymer, further protecting the passivated perovskite nanocrystals against water and oxygen. Finally, state‐of‐the‐art green PeLEDs with a normal EQE of 25.2% and a maximum EQE of 28.1% are achieved, and the operating lifetime (T50) of the device in air environment is over ten times increased, providing a novel and effective strategy to make high efficiency and long operating lifetime PeLEDs. A dual‐additive strategy is developed to prepare quasi‐core/shell‐structure perovskite nanocrystals by using 18‐crown‐6 and poly(ethylene glycol) methyl ether acrylate as the additives. State‐of‐the‐art external quantum efficiency of 28.1% and increased operating lifetime are achieved for the light‐emitting diodes, owing to the synergetic effect for reduced defect density and improved environmental stability of the perovskite emissive layer.