Managing Edge States in Reduced‐Dimensional Perovskites for Highly Efficient Deep‐Blue LEDs
Keyu Wei, Minghuan Cui, Cejun Hu, Shuo Wei, Zheng Zhang, Tong Zhou, Jia Zhang, Xinxin Yue, Kailin Yin, Changjiu Sun, Saisai Li, Yanxing Feng, Saif M. H. Qaid, Dongbing Zhao, Xuewen Fu, Wei Zhang, Chaochao Qin, Yufang Liu, Yuanzhi Jiang, Mingjian Yuan
Abstract
Abstract Pure‐halide reduced‐dimensional perovskites, featuring large exciton binding energy and tunable bandgap, show great potential for high‐efficiency deep‐blue perovskite light‐emitting diodes (PeLEDs). However, their efficiency, particularly in the low n ‐value phase domain (“ n ” represents the number of octahedral sheets), lags behind analogous perovskite emitters. Herein, it is demonstrated that the vibration of edge‐dangling octahedra in the low n ‐value phase activates notorious exciton‐phonon (EP) coupling, thereby deteriorating efficiency. To address this issue, an approach is reported to manage edge‐state lattices by introducing tris(4‐fluorophenyl) phosphine (TFP) ligands. Attributed to the large steric hindrance of TFP ligands and their strong binding affinity for edge‐dangling octahedra, the edged‐octahedral tilting reconstruction can effectively suppress lattice vibration and inhibit EP coupling. This strategy yields deep‐blue emitting film with a spectral linewidth of 21 nm and a photoluminescence quantum yield of 85% at low excitation densities. The resulting PeLEDs achieve deep‐blue emission at 469 nm, with a maximum luminance of 2,428 cd m −2 and a maximum external quantum efficiency of 10.4%, marking them among the most efficient deep‐blue PeLEDs reported. The strategy also showcases universality for higher n ‐value reduced‐dimensional perovskites. It is believed that the observation, along with the edge‐state management strategy, lays the groundwork for further advancements in reduced‐dimensional perovskite optoelectronic devices.