Wu Xiaoxi, Tan Liang Z, Shen Xiaozhe, Hu Te, Miyata Kiyoshi, Trinh M Tuan, Li Renkai, Coffee Ryan, Liu Shi, Egger David A, Makasyuk Igor, Zheng Qiang, Fry Alan, Robinson Joseph S, Smith Matthew D, Guzelturk Burak, Karunadasa Hemamala I, Wang Xijie, Zhu Xiaoyang, Kronik Leeor, Rappe Andrew M, Lindenberg Aaron M
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA.
The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA.
Sci Adv. 2017 Jul 26;3(7):e1602388. doi: 10.1126/sciadv.1602388. eCollection 2017 Jul.
Femtosecond resolution electron scattering techniques are applied to resolve the first atomic-scale steps following absorption of a photon in the prototypical hybrid perovskite methylammonium lead iodide. Following above-gap photoexcitation, we directly resolve the transfer of energy from hot carriers to the lattice by recording changes in the mean square atomic displacements on 10-ps time scales. Measurements of the time-dependent pair distribution function show an unexpected broadening of the iodine-iodine correlation function while preserving the Pb-I distance. This indicates the formation of a rotationally disordered halide octahedral structure developing on picosecond time scales. This work shows the important role of light-induced structural deformations within the inorganic sublattice in elucidating the unique optoelectronic functionality exhibited by hybrid perovskites and provides new understanding of hot carrier-lattice interactions, which fundamentally determine solar cell efficiencies.
飞秒分辨率电子散射技术被应用于解析典型的杂化钙钛矿甲基碘化铅吸收光子后的首个原子尺度步骤。在带隙以上的光激发之后，我们通过记录10皮秒时间尺度上平均平方原子位移的变化，直接解析了热载流子向晶格的能量转移。对时间相关对分布函数的测量显示，碘-碘相关函数出现了意外的展宽，同时保持了铅-碘距离。这表明在皮秒时间尺度上形成了旋转无序的卤化物八面体结构。这项工作展示了无机亚晶格内光致结构变形在阐明杂化钙钛矿独特的光电功能方面的重要作用，并为热载流子-晶格相互作用提供了新的理解，而这种相互作用从根本上决定了太阳能电池的效率。
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