Assessing Optical Properties of CH₃NH₃PbBr₃ Single Crystals across the Structural Phase Transitions by Spectroscopic Ellipsometry

Abstract

Lead halide perovskites have drawn considerable attention on account of their potential applications in solar cell and optoelectronic devices. To realize such technological possibilities, the optical characterizations of these materials must be assessed. This paper presents a comprehensive study of the temperaturedependent optical properties of CH 3 NH 3 PbBr 3 single crystals between 4.5 and 400 K within an energy range of 0.73 to 6.42 eV determined through spectroscopic ellipsometry. The profile of the room-temperature refractive index was typical of a semiconductor and decreased markedly with an increase in temperature with thermo-optic coefficients of approximately −4.18 × 10 −4 and −3.29 × 10 −4 K −1 at 600 and 1200 nm, respectively. The cooling− heating cycles of the extinction coefficient reflected the thermal hysteresis of the first-order orthorhombic−tetragonal structural phase transition. Moreover, the Urbach energy, fundamental band gap, exciton peak position, exciton binding energy, and interband transition energies were considerably affected during the structural phase transitions of orthorhombic−tetragonal I at 130 K, tetragonal I−tetragonal II at 150 K, and tetragonal II−cubic at 240 K. These results provide crucial information for the design and fabrication of lead halide perovskite-based devices at various temperatures.

Indium-Tin-Oxide-Induced Tunability of Nonlinear Optical Absorption from CH3NH3PbBr3 Nanostructure-Based Films: Implications for Nonlinear Optical Devices

“…The XRD patterns of MAPbBr 3 films grown on blank substrates and ITO buffer layers with different precursor concentrations are shown in Figure b. Similar peaks were also reported in other studies. , The diffraction peaks at 14.85, 21.15, 25.95, 30.10, 33.75, 45.85, 53.23, and 63.4° (2θ) corresponded with (100), (110), (111), (200), (210), (300), (222), and (400) crystal planes, respectively. The characteristic peaks of the ITO were visible in MAPbBr 3 /ITO, as shown in Figure S2 in the Supporting Information.…”

Fabrication of High-Stability and -Sensitivity Perovskite Nanoparticles with a Core–Shell Structure for Surface-Enhanced Raman Scattering

“…43 The diffraction peaks at 14.85, 21.15, 25.95, 30.10, 33.75, 45.85, 53.23, and 63.4°(2θ) correspond to the (100), ( 110), ( 111), ( 200), ( 210), (300), (222), and (400) crystal planes, respectively. 44,45 Studies have indicated that both the substrate material and the thickness of the spin-coated perovskite layer can affect the crystalline quality of the perovskite. 46 According to Bragg's law, specific interplanar spacing (d) will result in intense diffraction peaks at specific angles (θ).…”

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

“…8 The listed approaches were used to determine the optical constants of the most studied iodide perovskite MAPbI 3 1,2,4,5,7,8 and mixed-cation (MA,FA)PbI 3 , 11 bromide perovskites CsPbBr 3 , 6,12,13 MAPbBr 3 12−14 and FAPbBr 3 , 12,13 and chloride perovskite MAPbCl 3 . 9 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 14 and (MA,FA)-PbI 3 11 and from 77 K for MAPbI 3 . 4 Direct measurement of the refractive index in semiconductors is possible by observation of the interference of light reflected from the front and back surfaces of the crystal (Fabry−Perot interference).…”

“…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 .…”

“…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 …”