上海交通大学赵一新团队报道了基于亚稳态和稳态n-己基溴化铵的低维钙钛矿背后的机制。相关研究成果发表在2023年4月1日出版的国际学术期刊《美国化学会杂志》。

在钙钛矿太阳能电池中，钝化含有高浓度缺陷，特别是深能级缺陷的表面或界面的缺陷，是显著提高器件功率转换效率和稳定性的最重要课题之一。长链烷基溴化铵已被广泛且普遍地用于钝化处理。然而，由于这些烷基溴化铵基低维钙钛矿的形成路线和确切结构尚不清楚，其背后的机制仍未得到很好的探索。

该文中，研究人员研究了一种包括薄膜和单晶的n-己基溴化铵（HABr）基低维钙钛矿的物理和化学特性。首先，HA2PbBr4钙钛矿膜和时效的单晶显示出与新鲜制备的单晶不同的X射线衍射花样。研究发现，新鲜的HA2PbBr4单晶由于晶格应变的弛豫而随着时效而结构变化，表现出亚稳相，而HA2PbBr4钙钛矿膜作为时效的单晶是相当稳定的。在与FAPbI₃反应时，HABr可以插入FAPbI₃^-晶格中，形成HAFAPbI₃Br的混合阳离子钙钛矿，其处于分解和形成的动态平衡中。相反，HABr与过量PbI₂的反应形成稳定的HA₂PbI₂Br₂钙钛矿。

基于这些发现，通过使HABr与过量的PbI₂反应，合理地开发了HA₂PbI₂Br₂钝化的FACs基钙钛矿，基于该钙钛矿的光伏材料比HAFAPbI₃Br钙钛矿钝化的光伏材料更稳定、更有效。

该发现为更深入地研究含溴低维钙钛矿及其光电应用铺平了道路。

附：英文原文

Title: Myth behind Metastable and Stable n-Hexylammonium Bromide-Based Low-Dimensional Perovskites

Author: Yingping Fan, Haoran Chen, Xiaomin Liu, Meng Ren, Yugang Liang, Yao Wang, Yanfeng Miao, Yuetian Chen, Yixin Zhao

Issue&Volume: April 1, 2023

Abstract: In perovskite solar cells, passivating the surface or interface that contains a high concentration of defects, specifically deep-level defects, is one of the most important topics to substantially enhance the power conversion efficiency and stability of the devices. Long-chain alkylammonium bromides have been widely and commonly adapted for passivation treatment. However, the mechanism behind is still not well explored as the formation route and the exact structure of these alkylammonium bromide-based low-dimensional perovskites are unclear. Herein, we investigate the physical and chemical properties of an n-hexylammonium bromide (HABr)-based low-dimensional perovskite including both thin films and single crystals. First of all, the HA2PbBr4 perovskite film and aged single crystal demonstrate different X-ray diffraction patterns from those of the fresh as-prepared single crystal. We found that the fresh HA2PbBr4 single crystal exhibits a metastable phase as its structure changes with aging due to the relaxation of crystal lattice strains, whereas the HA2PbBr4 perovskite film is pretty stable as the aged single crystal. Upon reacting with FAPbI3, HABr can be intercalated into the FAPbI3 lattice to form a mixed-cation perovskite of HAFAPbI3Br, which is in a dynamic equilibrium of decomposition and formation. In contrast, the reaction of HABr with excess PbI2 forms a stable HA2PbI2Br2 perovskite. Based on such findings, we rationally develop a HA2PbI2Br2-passivated FACs-based perovskite by reacting HABr with excess PbI2, the photovoltaics based on which are more stable and efficient than those passivated by the HAFAPbI3Br perovskite. Our discovery paves way for a more in-depth study of bromide-containing low-dimensional perovskites and their optoelectronic applications.

DOI: 10.1021/jacs.3c01684

Source: https://pubs.acs.org/doi/10.1021/jacs.3c01684