Coupling of organic cation and inorganic lattice in methylammonium lead halide perovskites: Insights into a pressure-induced isostructural phase transition
Coupling of organic cation and inorganic lattice in methylammonium lead halide perovskites: Insights into a pressure-induced isostructural phase transition
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DOI：
10.1103/physrevmaterials.4.105403
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发表时间：
2020-10
影响因子：
3.4
通讯作者：
Sorb Yesudhas;Randy Burns;B. Lavina;S. Tkachev;Jiuyu Sun;C. Ullrich;S. Guha
中科院分区：
文献类型：
--
作者：
Sorb Yesudhas;Randy Burns;B. Lavina;S. Tkachev;Jiuyu Sun;C. Ullrich;S. Guha
有机-无机杂化金属卤化物钙钛矿（OIHP）材料为其光电性能的工程设计提供了一个可调的平台。虽然对OIHP家族单晶和薄膜进行了一些高压研究，但对$\mathrm{C}{\mathrm{H}}_{3}\mathrm{N}{\mathrm{H}}_{3}$ （MA）阳离子与八面体晶格框架的动态耦合的确切性质以及在压力下结构相变的机制并没有很好地了解。通过结合光致发光（PL）、基于同步加速器的x射线衍射和拉曼散射研究，作为甲基溴化铅（$\mathrm{M}\mathrm{A}\mathrm{Pb}{\mathrm{Br}}_{3}$）压力的函数，我们揭示了由于MA阳离子和$\mathrm{Pb}{\mathrm{Br}}_{6}$晶格通过氢键耦合而导致的等结构相变。PL峰位置在$\ensuremath{\sim}$ 1 GPa和$\ensuremath{\sim}$ 3 GPa处的急剧不连续与高压XRD和拉曼散射研究中观察到的结构变化有关。在密度泛函理论中计算了电子带边缘作为压力的函数。在2 GPa时，激子峰的PL峰位置、强度和宽度发生了显著变化，这与高压拉曼散射研究中观察到的变化一致。在2gpa时，MA阳离子的晶格模式和C—H/N—H弯曲模式和拉伸模式的频率表现出异常变化和其他细微差别。有机部分的旋转和取向无序性在2gpa时开始抑制，在3.0 GPa时完成有序，导致有序-无序型立方II （$Im\overline{3}$）向正交（$Pnma$）相变。随着在2gpa下的同工结构转变的揭示，本文强调了分子振动对$\mathrm{M}\mathrm{A}\mathrm{Pb}{\mathrm{Br}}_{3}$在压力下的电子性质的影响。
Organic-inorganic hybrid metal-halide perovskite (OIHP) materials provide a tunable platform for engineering their optoelectronic properties. Although several high-pressure studies have been conducted from the OIHP family of single crystals and films, the exact nature of the dynamic coupling of the $\mathrm{C}{\mathrm{H}}_{3}\mathrm{N}{\mathrm{H}}_{3}$ (MA) cation with the octahedral lattice framework and the mechanisms responsible for the structural phase transformation under pressure are not well captured. By combined photoluminescence (PL), synchrotron-based x-ray diffraction, and Raman-scattering studies as a function of pressure from methylammonium lead bromide ($\mathrm{M}\mathrm{A}\mathrm{Pb}{\mathrm{Br}}_{3}$), we shed light on an isostructural phase transition due to the coupling of the MA cation and the $\mathrm{Pb}{\mathrm{Br}}_{6}$ lattice through hydrogen bonding. The sharp discontinuities at $\ensuremath{\sim}$ 1 GPa and $\ensuremath{\sim}$ 3 GPa in the PL peak positions correlate with the structural changes observed in high-pressure XRD and Raman-scattering studies. The electronic band edge as a function of pressure is calculated within density-functional theory. The PL peak position, intensity and width of the excitonic peak show significant changes at 2 GPa, which corroborate the changes observed in high-pressure Raman-scattering studies. The frequencies of the lattice modes and the C--H/N--H bending and stretching modes of the MA cation show anomalous changes and other nuances at 2 GPa. The suppression of rotational and orientational disorder of the organic moiety is initiated at 2 GPa and the ordering is completed by 3.0 GPa, leading to an order-disorder type cubic II ($Im\overline{3}$) to orthorhombic ($Pnma$) phase transition. Along with the revelation of an isostructural transformation at 2 GPa, this paper highlights the impact of molecular vibrations on the electronic properties of $\mathrm{M}\mathrm{A}\mathrm{Pb}{\mathrm{Br}}_{3}$ under pressure.