Pressure-Dependent Polymorphism and Band-Gap Tuning of Methylammonium Lead Iodide Perovskite
Shaojie Jiang, Yanan Fang, Ruipeng Li, Hai Xiao, Jason Crowley, Chenyu Wang, Timothy J. White, William A. Goddard III, Zhongwu Wang, Tom Baikie, Jiye Fang
Abstract
We report the pressure-induced crystallographic transitions and optical behavior of MAPbI_3 (MA=methylammonium) using in situ synchrotron X-ray diffraction and laser-excited photoluminescence spectroscopy, supported by density functional theory (DFT) calculations using the hybrid functional B3PW91 with spin-orbit coupling. The tetragonal polymorph determined at ambient pressure transforms to a ReO_3-type cubic phase at 0.3 GPa. Upon continuous compression to 2.7 GPa this cubic polymorph converts into a putative orthorhombic structure. Beyond 4.7 GPa it separates into crystalline and amorphous fractions. During decompression, this phase-mixed material undergoes distinct restoration pathways depending on the peak pressure. In situ pressure photoluminescence investigation suggests a reduction in band gap with increasing pressure up to ≈0.3 GPa and then an increase in band gap up to a pressure of 2.7 GPa, in excellent agreement with our DFT calculation prediction.
Group Members
Jiang, S., Fang, Y., Li, R., Xiao, H., Crowley, J., Wang, C., White, T. J., III, W. A. G., Wang, Z., Baikie, T., & Fang, J. (2016). Pressure-Dependent Polymorphism and Band-Gap Tuning of Methylammonium Lead Iodide Perovskite. *Angewandte Chemie International Edition in English*, *55*(22), 6540-6544. https://doi.org/10.1002/anie.201601788