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Stereochemically Active Lone Pairs and Nonlinear Optical Properties of Two-Dimensional Multilayered Tin and Germanium Iodide Perovskites

Li, Xinyu and Guan, Yan and Li, Xiaotong and Fu, Yongping (2022) Stereochemically Active Lone Pairs and Nonlinear Optical Properties of Two-Dimensional Multilayered Tin and Germanium Iodide Perovskites. Journal of the American Chemical Society, 144 (39). pp. 18030-18042. ISSN 0002-7863. doi:10.1021/jacs.2c07535.

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Two-dimensional (2D) metal halide perovskites are promising tunable semiconductors. Previous studies have focused on Pb-based structures, whereas the multilayered Sn- and Ge-based analogues are largely unexplored, even though they potentially exhibit more diverse structural chemistry and properties associated with the more polarizable ns2 lone-pair electrons. Herein, we report the synthesis and structures of 2D tin iodide perovskites (BA)₂(A)Sn₂I₇, where BA = n-butylammonium and A = methylammonium, formamidinium, dimethylammonium, guanidinium, or acetamidinium, and those of 2D germanium iodide perovskites (BA)₂(A)Ge₂I₇, where A = methylammonium or formamidinium. By comparing these structures along with their Pb counterparts, we establish correlations between the effect of group IV-cation’s lone-pair stereochemical activity on the perovskite crystal structures and the resulting semiconducting properties such as bandgaps and carrier–phonon interactions and nonlinear optical properties. We find that the strength of carrier–phonon interaction increases with increasing lone-pair activity, leading to a more prominent photoluminescence tail on the low-energy side. Moreover, (BA)₂(A)Ge₂I₇ exhibit strong second harmonic generation with second-order nonlinear coefficients of ∼10 pm V⁻¹ that are at least 10 times those of Sn counterparts and 100 times those of Pb counterparts. We also report the third-order two-photon absorption coefficients of (BA)₂(A)Sn₂I₇ to be ∼10 cm MW⁻¹, which are one order of magnitude larger than those of the Pb counterparts and traditional inorganic semiconductors. These results not only highlight the role of lone-pair activity in linking the compositions and physical properties of 2D halide perovskites but also demonstrate 2D tin and germanium iodide perovskites as promising lead-free alternatives for nonlinear optoelectronic devices.

Item Type:Article
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URLURL TypeDescription
Li, Xiaotong0000-0001-7107-7273
Fu, Yongping0000-0003-3362-2474
Additional Information:This work is supported by the National Natural Science Foundation of China (grant no. 22271006). Y.F. thanks Peking University and Beijing National Laboratory for Molecular Sciences for startup funding. The measurements of single-crystal XRD and nonlinear optical spectroscopy were performed at the Analytical Instrumentation Center of Peking University/the Center for Physicochemical Analysis and Measurements in ICCAS. The help from Dr. Yi Qiu for single-crystal XRD measurements was acknowledged.
Funding AgencyGrant Number
National Natural Science Foundation of China22271006
Peking UniversityUNSPECIFIED
Beijing National Laboratory for Molecular SciencesUNSPECIFIED
Issue or Number:39
Record Number:CaltechAUTHORS:20221003-756400000.13
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117207
Deposited By: Melissa Ray
Deposited On:06 Oct 2022 19:56
Last Modified:06 Oct 2022 19:56

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