Fan Yingping, Chen Haoran, Liu Xiaomin, Ren Meng, Liang Yugang, Wang Yao, Miao Yanfeng, Chen Yuetian, Zhao Yixin
School of Environmental Science and Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Jiao Tong University, Shanghai 200240, China.
Shanghai Non-carbon Energy Conversion and Utilization Institute, Shanghai 200240, China.
J Am Chem Soc. 2023 Apr 12;145(14):8209-8217. doi: 10.1021/jacs.3c01684. Epub 2023 Apr 1.
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 -hexylammonium bromide (HABr)-based low-dimensional perovskite including both thin films and single crystals. First of all, the HAPbBr 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 HAPbBr single crystal exhibits a metastable phase as its structure changes with aging due to the relaxation of crystal lattice strains, whereas the HAPbBr perovskite film is pretty stable as the aged single crystal. Upon reacting with FAPbI, HABr can be intercalated into the FAPbI lattice to form a mixed-cation perovskite of HAFAPbIBr, which is in a dynamic equilibrium of decomposition and formation. In contrast, the reaction of HABr with excess PbI forms a stable HAPbIBr perovskite. Based on such findings, we rationally develop a HAPbIBr-passivated FACs-based perovskite by reacting HABr with excess PbI, the photovoltaics based on which are more stable and efficient than those passivated by the HAFAPbIBr perovskite. Our discovery paves way for a more in-depth study of bromide-containing low-dimensional perovskites and their optoelectronic applications.
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，是大幅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，由于这些基于烷基溴化铵的低维钙钛矿的形成途径和确切结构尚不清楚，其背后的机制仍未得到充分探索。在此，我们研究了基于正己基溴化铵（HABr）的低维钙钛矿的物理和化学性质，包括薄膜和单晶。首先，HAPbBr钙钛矿薄膜和老化的单晶表现出与新鲜制备的单晶不同的X射线衍射图案。我们发现，新鲜的HAPbBr单晶呈现亚稳相，因为其结构会随着老化而因晶格应变的弛豫而发生变化，而HAPbBr钙钛矿薄膜与老化的单晶一样相当稳定。与FAPbI反应时，HABr可插入FAPbI晶格中形成HAFAPbIBr混合阳离子钙钛矿，它处于分解和形成的动态平衡中。相比之下，HABr与过量PbI的反应形成稳定的HAPbIBr钙钛矿。基于这些发现，我们通过使HABr与过量PbI反应，合理地开发了一种基于HAPbIBr钝化的FACs钙钛矿，基于此的光伏器件比由HAFAPbIBr钙钛矿钝化的器件更稳定、更高效。我们的发现为更深入研究含溴低维钙钛矿及其光电应用铺平了道路。
