Hu Yilei, Jiang Xingxing, Wu Tianhui, Xue Yanyan, Wu Chao, Huang Zhipeng, Lin Zheshuai, Xu Jun, Humphrey Mark G, Zhang Chi
China-Australia Joint Research Center for Functional Molecular Materials, School of Chemical Science and Engineering, Tongji University Shanghai 200092 China
Technical Institute of Physics and Chemistry, Chinese Academy of Sciences Beijing 100190 China.
Chem Sci. 2022 Jul 27;13(35):10260-10266. doi: 10.1039/d2sc02137d. eCollection 2022 Sep 14.
A wide bandgap is an essential requirement for a nonlinear optical (NLO) material. However, it is very challenging to simultaneously engineer a wide bandgap and a strong second-harmonic generation (SHG) response, particularly in NLO materials containing second-order Jahn-Teller (SOJT) distorted units. Herein, we employ a bandgap engineering strategy that involves the dual fluorination of two different types of SOJT distorted units to realize remarkably wide bandgaps in the first examples of 5d-transition metal (TM) fluoroiodates. Crystalline AWOF(IOF) (A = Rb (RWOFI) and Cs (CWOFI)) exhibit the largest bandgaps yet observed in d-TM iodates (4.42 (RWOFI) and 4.29 eV (CWOFI)), strong phase-matching SHG responses of 3.8 (RWOFI) and 3.5 (CWOFI) × KHPO, and wide optical transparency windows. Computational studies have shown that the excellent optical responses result from synergism involving the two fluorinated SOJT distorted units ([WOF] and [IOF]). This work provides not only an efficient strategy for bandgap modulation of NLO materials, but also affords insight into the relationship between the electronic structure of the various fluorinated SOJT distorted units and the optical properties of crystalline materials.
宽带隙是非线性光学（NLO）材料的一项基本要求。然而，同时设计出宽带隙和强二次谐波产生（SHG）响应极具挑战性，尤其是在含有二阶 Jahn-Teller（SOJT）畸变单元的 NLO 材料中。在此，我们采用一种带隙工程策略，该策略涉及对两种不同类型的 SOJT 畸变单元进行双重氟化，以在首例 5d 过渡金属（TM）氟碘酸盐中实现显著的宽带隙。晶体 AWOF(IOF)（A = Rb（RWOFI）和 Cs（CWOFI））展现出在 d-TM 碘酸盐中迄今观测到的最大带隙（4.42（RWOFI）和 4.29 eV（CWOFI））、3.8（RWOFI）和 3.5（CWOFI）×KHPO 的强相位匹配 SHG 响应以及宽光学透明窗口。计算研究表明，优异的光学响应源于涉及两个氟化 SOJT 畸变单元（[WOF]和[IOF]）的协同作用。这项工作不仅为 NLO 材料的带隙调制提供了一种有效策略，还深入揭示了各种氟化 SOJT 畸变单元的电子结构与晶体材料光学性质之间的关系。
