Vibrational Properties of the Organic鈥揑norganic Halide Perovskite CH3NH3PbI3 from Theory and Experiment: Factor Group Analysis, First-Principles Calculations, and Low-Temperature Infrared Spectra

详细信息    查看全文

• 作者：Miguel A. P茅rez-Osorio ; Rebecca L. Milot ; Marina R. Filip ; Jay B. Patel ; Laura M. Herz ; Michael B. Johnston ; Feliciano Giustino
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：November 19, 2015
• 年：2015
• 卷：119
• 期：46
• 页码：25703-25718
• 全文大小：800K
• ISSN：1932-7455

文摘

In this work, we investigate the vibrational properties of the hybrid organic/inorganic halide perovskite MAPbI₃ (MA = CH₃NH₃) in the range 6鈥?500 cm^鈥? by combining first-principles density-functional perturbation theory calculations and low-temperature infrared (IR) absorption measurements on evaporated perovskite films. By using a group factor analysis, we establish the symmetry of the normal modes of vibration and predict their IR and Raman activity. We validate our analysis via explicit calculation of the IR intensities. Our calculated spectrum is in good agreement with our measurements. By comparing theory and experiment, we are able to assign most of the features in the IR spectrum. Our analysis shows that the IR spectrum of MAPbI₃ can be partitioned into three distinct regions: the internal vibrations of the MA cations (800鈥?100 cm^鈥?), the cation librations (140鈥?80 cm^鈥?), and the internal vibrations of the PbI₃ network (<100 cm^鈥?). The low-frequency region of the IR spectrum is dominated by Pb鈥揑 stretching modes of the PbI₃ network with B_u symmetry and librational modes of the MA cations. In addition, we find that the largest contributions to the static dielectric constant arise from Pb鈥揑 stretching and Pb鈥揑鈥揚b rocking modes, and that one low-frequency B_2u Pb鈥揑 stretching mode exhibits a large LO鈥揟O splitting of 50 cm^鈥?.