Fu Jianhui, Bian Tieyuan, Yin Jun, Feng Minjun, Xu Qiang, Wang Yue, Sum Tze Chien
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore.
Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon, Hong Kong, 999077, PR China.
Nat Commun. 2024 May 29;15(1):4562. doi: 10.1038/s41467-024-48707-1.
Two-dimensional layered organic-inorganic halide perovskites have successfully spread to diverse optoelectronic applications. Nevertheless, there remain gaps in our understanding of the interactions between organic and inorganic sublattices that form the foundation of their remarkable properties. Here, we examine these interactions using pump-probe spectroscopy and ab initio molecular dynamics simulations. Unlike off-resonant pumping, resonant excitation of the organic sublattice alters both the electronic and lattice degrees of freedom within the inorganic sublattice, indicating the existence of electronic coupling. Theoretical simulations verify that the reduced bandgap is likely due to the enhanced distortion index of the inorganic octahedra. Further evidence of the mechanical coupling between these two sublattices is revealed through the slow heat transfer process, where the resultant lattice tensile strain launches coherent longitudinal acoustic phonons. Our findings explicate the intimate electronic and mechanical couplings between the organic and inorganic sublattices, crucial for tailoring the optoelectronic properties of two-dimensional halide perovskites.
二维层状有机-无机卤化物钙钛矿已成功应用于各种光电子领域。然而，我们对构成其卓越性能基础的有机和无机子晶格之间相互作用的理解仍存在差距。在此，我们使用泵浦-探测光谱和从头算分子动力学模拟来研究这些相互作用。与非共振泵浦不同，有机子晶格的共振激发会改变无机子晶格内的电子和晶格自由度，这表明存在电子耦合。理论模拟证实，带隙减小可能是由于无机八面体的畸变指数增加所致。通过缓慢的热传递过程揭示了这两个子晶格之间机械耦合的进一步证据，在此过程中产生的晶格拉伸应变会激发相干纵向声子。我们的研究结果阐明了有机和无机子晶格之间紧密的电子和机械耦合，这对于调整二维卤化物钙钛矿的光电子性能至关重要。
