pISSN 0374-4914 eISSN 2289-0041

## Research Paper

New Phys.: Sae Mulli 2020; 70: 816-821

Published online October 30, 2020 https://doi.org/10.3938/NPSM.70.816

## Far-infrared spectroscopic study on MAPbI$_3$ and MAPbBr$_3$

Jaeseung LIM, Sangheon PARK, Yu-Seong SEO, Myounghoon LEE, Jungseek HWANG*

Department of Physics, Sungkyunkwan University, Suwon 16419, Korea

Correspondence to:jungseek@skku.edu

Received: June 1, 2020; Revised: August 18, 2020; Accepted: August 18, 2020

### Abstract

MAPbX$_3$, is an organic-inorganic perovskite material system which can be applied in various areas such as magneto-optical data storage, solar cells, lasers, LEDs, etc. MAPbI$_3$ and MAPbBr$_3$ are known to undergo a cubic-to-tetragonal transition at temperatures of about 327 K and 220 K and a tetragonal-to-orthorhombic transition at about 150 K and 145 K, respectively. The transmittance spectra of pallet samples are measured in the far-infrared (FIR) region at various temperatures from room temperature to 80 K by using a Fourier transform infrared (FTIR) spectroscopy-type Bruker Vertex 80v spectrometer. The absorption coefficients are obtained and fitted by using the Drude-Lorentz model to obtain other optical constants including the electric permittivity, optical conductivity, and extinction coefficient. Then, the optical conductivity is fitted to obtain the position and damping coefficient of the longitudinal optical (LO) and the transverse optical (TO) phonons for the sample materials, which are used to calculate the electron-phonon coupling constants, polaron mass, and polaron radii.

Keywords: Organic-inorganic perovskite materials, MAPbI$_3$, MAPbBr$_3$, Fourier transform infrared spectroscopy, Far-infrared spectroscopy