Guo Yongchang, Zou Bingsuo, Yang Fan, Zheng Xuan, Peng Hui, Wang Jianping
Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology, Beijing, 100081, P. R. China and Beijing National Laboratory for Molecular Sciences, Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.
Guangxi Key Lab of Processing for Nonferrous Metals and Featured Materials and Key Lab of New Processing Technology for Nonferrous Metals and Materials, Ministry of Education, School of Resources, Environments and Materials, Guangxi University, Nanning 530004, China.
Phys Chem Chem Phys. 2021 May 5;23(17):10153-10163. doi: 10.1039/d1cp01136g.
In organic-inorganic hybrid ionic lead halide perovskites with a naturally arranged layered structure, the dielectric polarization effect caused by the dielectric mismatch between the organic and inorganic layers takes effect in their optical responses. But this effect has received little attention. Here we used infrared transient spectroscopy to study FAPbBr3 perovskite polycrystalline films before and after PMMA film passivation and found that there is a dielectric polarization effect at the interface between the organic cation layer and the inorganic lattice layer inside the perovskite lattice, and also at the interface between the PMMA film and perovskite film. Due to the dielectric polarization effect and the spatial confinement of the surface electronic (or polaron) state, the luminescence intensity of the passivated perovskite film is significantly enhanced, and the exciton lifetime is greatly increased. Dielectric polarization enhances their efficient transient absorption (TA) and leads to the intramolecular vibration frequency red-shifts, which exhibited the combined relaxation kinetics of the large polaron with dielectric polarization in the perovskite film. Dielectric polarization between the internal lattice and the nanocrystal surface of the perovskite film shows different relaxation processes. The polarization-dependent TA spectrum reveals that the dielectric polarization field causes light-induced anisotropy by changing the chemical bond configurations. These direct TA experimental observations help us to understand the influence of the dielectric polarization effect on the electronic state in various organic-inorganic nanocomposite perovskites.
在具有天然排列层状结构的有机-无机杂化离子型卤化铅钙钛矿中，有机层和无机层之间的介电失配所引起的介电极化效应在其光学响应中起作用。但这种效应很少受到关注。在此，我们使用红外瞬态光谱研究了聚甲基丙烯酸甲酯（PMMA）薄膜钝化前后的FAPbBr3钙钛矿多晶薄膜，发现钙钛矿晶格内部的有机阳离子层与无机晶格层之间的界面处以及PMMA薄膜与钙钛矿薄膜之间的界面处存在介电极化效应。由于介电极化效应和表面电子（或极化子）态的空间限制，钝化后的钙钛矿薄膜的发光强度显著增强，激子寿命大幅增加。介电极化增强了它们的有效瞬态吸收（TA）并导致分子内振动频率红移，这在钙钛矿薄膜中表现出大极化子与介电极化的组合弛豫动力学。钙钛矿薄膜内部晶格与纳米晶体表面之间的介电极化显示出不同的弛豫过程。偏振相关的TA光谱表明，介电极化场通过改变化学键构型引起光致各向异性。这些直接的TA实验观察结果有助于我们理解介电极化效应对各种有机-无机纳米复合钙钛矿中电子态的影响。
