Abstract-Phonon Mode Transformation across the Orthohombic-Tetragonal Phase Transition in a Lead-Iodide Perovskite CH3NH3PbI3: A Terahertz Time-Domain Spectroscopy Approach.

La-O-Vorakiat C, Kadro JM, Salim T, Zhao D, Ahmed T, Lam YM, Zhu JX, Marcus RA, Michel-Beyerle ME, Chia EE.

http://www.ncbi.nlm.nih.gov/pubmed/26633131

We study the temperature-dependent phonon modes of the organometallic lead iodide perovskite CH3NH3PbI3: thin film across the terahertz (0.5-3 THz) and temperature (20-300 K) ranges. These modes are related to the vibration of the Pb-I bonds. We found that two phonon modes in the tetragonal phase at room temperature split into four modes in the low-temperature orthorhombic phase. By use of the Lorentz model fitting, we analyze the critical behavior of this phase transition. The carrier mobility values calculated from the low-temperature phonon mode frequencies, via two theoretical approaches, were found to agree reasonably with the experimental value (~2000 cm2V-1s-1) from a previous time-resolved THz spectroscopy work. We have thus established a possible link between THz phonon modes and the transport properties of perovskite-based solar cells.