Yong Zi-Jun, Guo Shao-Qiang, Ma Ju-Ping, Zhang Jun-Ying, Li Zhi-Yong, Chen Ya-Meng, Zhang Bin-Bin, Zhou Yang, Shu Jie, Gu Jia-Li, Zheng Li-Rong, Bakr Osman M, Sun Hong-Tao
College of Chemistry, Chemical Engineering and Materials Science , Soochow University , Jiangsu , 215123 , China.
Department of Physics , Beihang University , Beijing , 100191 , China.
J Am Chem Soc. 2018 Aug 8;140(31):9942-9951. doi: 10.1021/jacs.8b04763. Epub 2018 Jul 26.
All-inorganic perovskite nanocrystals (NCs) have emerged as a new generation of low-cost semiconducting luminescent system for optoelectronic applications. The room-temperature photoluminescence quantum yields (PLQYs) of these NCs in the green and red spectral range approach unity. However, their PLQYs in the violet are much lower, and an insightful understanding of such poor performance remains missing. We report a general strategy for the synthesis of all-inorganic violet-emitting perovskite NCs with near-unity PLQYs through engineering local order of the lattice by nickel ion doping. A broad range of experimental characterizations, including steady-state and time-resolved luminescence spectroscopy, X-ray absorption spectra, and magic angle spinning nuclear magnetic resonance spectra, reveal that the low PLQY in undoped NCs is associated with short-range disorder of the lattice induced by intrinsic defects such as halide vacancies and that Ni doping can substantially eliminate these defects and result in increased short-range order of the lattice. Density functional theory calculations reveal that Ni doping of perovskites causes an increase of defect formation energy and does not introduce deep trap states in the band gap, which is suggested to be the main reason for the improved local structural order and near-unity PLQY. Our ability to obtain violet-emitting perovskite NCs with near-perfect properties opens the door for a range of applications in violet-emitting perovskite-based devices such as light-emitting diodes, single-photon sources, lasers, and beyond.
全无机钙钛矿纳米晶体（NCs）已成为用于光电子应用的新一代低成本半导体发光系统。这些纳米晶体在绿色和红色光谱范围内的室温光致发光量子产率（PLQYs）接近100%。然而，它们在紫色光谱范围内的PLQYs要低得多，且对于这种不佳性能仍缺乏深刻的理解。我们报道了一种通用策略，通过镍离子掺杂来调控晶格的局部有序性，从而合成具有接近100% PLQYs的全无机紫色发光钙钛矿纳米晶体。一系列实验表征，包括稳态和时间分辨发光光谱、X射线吸收光谱以及魔角旋转核磁共振光谱，表明未掺杂纳米晶体中低PLQY与卤化物空位等本征缺陷引起的晶格短程无序有关，而镍掺杂可以大幅消除这些缺陷并导致晶格短程有序性增加。密度泛函理论计算表明，钙钛矿的镍掺杂会导致缺陷形成能增加，且不会在带隙中引入深陷阱态，这被认为是局部结构有序性改善和接近100% PLQY的主要原因。我们获得具有近乎完美性能的紫色发光钙钛矿纳米晶体的能力为基于紫色发光钙钛矿的器件（如发光二极管、单光子源、激光器等）的一系列应用打开了大门。
