Zhao Shenghe, Yu Hui, Jia Yongheng, Zhou Yang, Zhang Zheng, Zhao Ni
Department of Electronic Engineering, The Chinese University of Hong Kong, New Territories, Hong Kong, 999077, China.
Small Methods. 2024 Feb;8(2):e2300572. doi: 10.1002/smtd.202300572. Epub 2023 Jul 19.
Postdeposition halide exchange has been a popular strategy for tuning the emission wavelength of metal halide perovskites and is particularly attractive in achieving deep-blue perovskite light-emitting diodes (PeLEDs), where the quality of the emissive layer is largely limited by the low solubility of chlorides in perovskite precursor solution. In this work, the halide exchange strategy is examined for deep-blue PeLEDs, with a focus on understanding the role of the organic cations of the halide salt (i.e., the chloride source for ion exchange) in modifying the properties of the perovskite films and consequently the PeLED performances. By comparatively investigating the treatment effects of two model systems, namely phenethylammonium chloride and 2,2-diphenylethylammonium chloride (DPEACl), it is found that although the two chlorides produce highly similar photoluminescence properties of the perovskite films, they create different landscapes for current flow in the PeLEDs. In particular, the bulky branch-structured DPEA cations exhibit minimal disturbance to the perovskite grains while providing highly effective inter-grain void filling and thus leakage current blocking, leading to 3D perovskite-based PeLEDs with a record high peak external quantum efficiency of 6.4% at 462 nm. The study highlights the importance of organic cation selection in the halide exchange processes for PeLEDs.
沉积后卤化物交换一直是调节金属卤化物钙钛矿发光波长的常用策略，在实现深蓝色钙钛矿发光二极管（PeLED）方面特别具有吸引力，其中发光层的质量在很大程度上受氯化物在钙钛矿前驱体溶液中低溶解度的限制。在这项工作中，研究了用于深蓝色PeLED的卤化物交换策略，重点是了解卤化物盐的有机阳离子（即离子交换的氯源）在改变钙钛矿薄膜性质以及PeLED性能方面的作用。通过比较研究两种模型体系，即苯乙氯化铵和2,2-二苯乙氯化铵（DPEACl）的处理效果，发现尽管这两种氯化物产生的钙钛矿薄膜光致发光性质高度相似，但它们在PeLED中产生了不同的电流分布情况。特别是，体积较大的支链结构DPEA阳离子对钙钛矿晶粒的干扰最小，同时提供了高效的晶粒间空隙填充，从而实现了漏电流阻断，使得基于3D钙钛矿的PeLED在462nm处具有创纪录的6.4%的高峰值外量子效率。该研究突出了有机阳离子选择在PeLED卤化物交换过程中的重要性。
