香港科技大学吕海鹏团队报道了杂化层状钙钛矿中卤素键引起的Rashba能带分裂和体光伏效应。相关研究成果于2023年5月17日发表在《德国应用化学》。

非共价相互作用在引导有机-无机杂化晶体的自组装中起着至关重要的作用。在杂化卤化物钙钛矿中，氢键一直是最重要的非共价相互作用。

该文中，研究人员展示了另一种非共价相互作用，即卤键相互作用，它在一系列新的二维（2D）钙钛矿（ICH2CH2NH3）2（CH3NH3）n-1PbnI3n+1（n是层厚度，n=14）中引导对称性破坏组装。结构分析表明，卤键强度随层厚度的变化而变化。对于奇数（n=1，3）层状钙钛矿，更强的卤素相互作用导致中心对称结构，而对于n=2层状钙钛矿，较弱的卤素键导致非中心对称结构。瞬态反射光谱显示，对于n=2结构，辐射复合率（k2~0）受到抑制，自旋寿命延长，表明Rashba能带分裂效应增强。通过可逆的体光伏效应进一步证实了结构的不对称性。

该工作提供了一种新的设计策略，使混合钙钛矿具有与结构不对称相关的新兴特性和功能。

附：英文原文

Title: Rashba Band Splitting and Bulk Photovoltaic Effect Induced by Halogen Bonds in Hybrid Layered Perovskites

Author: Jie Xue, Yuling Huang, Yang Liu, Zhongwei Chen, Herman H. Y. Sung, Ian D. Williams, Zonglong Zhu, Lingling Mao, Xihan Chen, Haipeng Lu

Issue&Volume: 2023-05-17

Abstract: Non-covalent interactions play an essential role in directing the self-assembly of hybrid organic-inorganic crystals. In hybrid halide perovskites, hydrogen bonding has been the paramount non-covalent interaction. Here, we show another non-covalent interaction, namely, the halogen bond interaction, that directs a symmetry-breaking assembly in a new series of two-dimensional (2D) perovskites (ICH2CH2NH3)2(CH3NH3)n-1PbnI3n+1 (n is the layer thickness, n = 14). Structural analysis shows that the halogen bond strength varies with the layer thickness. For the odd number (n = 1, 3) layered perovskites, stronger halogen interaction leads to centrosymmetric structures, whereas for the n = 2 layered perovskites, weaker halogen bonds result in non-centrosymmetric structures. Transient reflection spectroscopy shows a suppressed radiative recombination rate (k2 ~ 0) and prolonged spin lifetime for n = 2 structure, suggesting an enhanced Rashba band splitting effect. The structural asymmetry is further confirmed with a reversible bulk photovoltaic effect. Our work provides a new design strategy to enable hybrid perovskites with emerging properties and functionalities associated with structural asymmetry.

DOI: 10.1002/anie.202304486

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202304486