High-Energy Optical Transitions and Optical Constants of CH₃NH₃PbI₃ Measured by Spectroscopic Ellipsometry and Spectrophotometry

Abstract

Optoelectronics based on metal halide perovskites (MHPs) have shown substantial promise, following more than a decade of research. For prime routes of commercialization such as tandem solar cells, optical modeling is essential for engineering device architectures, which requires accurate optical data for the materials utilized. Additionally, a comprehensive understanding of the fundamental material properties is vital for simulating the operation of devices for design purposes. In this article, we use variable angle spectroscopic ellipsometry (SE) to determine the optical constants of CH 3 NH 3 PbI 3 (MAPbI 3 ) thin films over a photon energy range of 0.73 to 6.45 eV. We successfully model the ellipsometric data using six Tauc-Lorentz oscillators for three different incident angles. Following this, we use critical-point analysis of the complex 1 arXiv:1909.03907v1 [physics.app-ph] 9 Sep 2019 dielectric constant to identify the well-known transitions at 1.58, 2.49, 3.36 eV, but also additional transitions at 4.63 and 5.88 eV, which are observed in both SE and spectrophotometry measurements. This work provides important information relating to optical transitions and band structure of MAPbI 3 , which can assist in the development of potential applications of the material.

Nonresonant Exciton–Plasmon Interaction in Metal–Chalcogenide (CuxS)/Perovskite (CsPbBr3) Based Colloidal Heterostructure

“…Excellent agreement between theory and experiment is obtained for both the shape and the width of the curve. The possible transitions were extracted from the second-derivative spectra of ε 2 using the method of critical point (CP) analysis. , The origin of the transitions was determined from the band structure of CsPbBr 3 (Figure c and Table ). E a in both cases corresponds to the excitonic band-edge transitions ( R → R ); the rest originates from the transitions to the conduction band from different states in the valence band.…”

Ion-mediated hopping electrode polarization model for impedance spectra of CH3NH3PbI3

“…Experimental analyses have also been reported by means of ultraviolet-visible optical absorption and transmittance spectroscopies, 59,60 spectroscopic ellipsometry, and spectrophotometry. [60][61][62] In the tetragonal phase (∼160-330 K), Onoda-Yamamuro et al 63 and Mohanty et al 64 measured the static dielectric constant at 1 MHz by IS vs temperature with ε 60 À 120 and thermal gradients @ε/@T À0:3 K À1 . At room temperature, Ding et al 30 showed ε spectrum above 50 too.…”

Low-Temperature Refractive Index Dispersion in MAPbI3 Halide Perovskite Single Crystal

“…The main method for determining the optical constants of halide perovskites is ellipsometry of thin polycrystalline films. − Although this method provides both the imaginary and the real part of the dielectric constant of the material, it is extremely sensitive to the state of the sample surface: its roughness, the presence of contamination, or an oxide layer. Thin perovskite films may have a surface of fairly high optical quality, but results of optical measurements will greatly depend on the film manufacturing method, the size, and orientation of its constituent grains.…”

“…In a number of works, ellipsometry has been applied to perovskite single crystals. − Alternative methods for determining the optical constants of perovskites are simultaneous reflection and transmission measurements , and Brewster angle measurements from polished or natural facets of single crystals . The listed approaches were used to determine the optical constants of the most studied iodide perovskite MAPbI 3 ,,,,, and mixed-cation (MA,FA)­PbI 3 , bromide perovskites CsPbBr 3 , ,, MAPbBr 3 − and FAPbBr 3 , , and chloride perovskite MAPbCl 3 . Most of the above-mentioned studies were performed at room temperature or in its close vicinity, with the exception of cryogenic studies from 4 K for MAPbBr 3 and (MA,FA)­PbI 3 and from 77 K for MAPbI 3 …”