First-Principles Investigation of the Structural, Elastic, Electronic, and Optical Properties of α- and β-SrZrS3: Implications for Photovoltaic Applications.

Henry Igwebuike Eya,Nelson Y Dzade,Esidor Ntsoenzok

doi:10.3390/ma13040978

Abstract

Transition metal perovskite chalcogenides are attractive solar absorber materials for renewable energy applications. Herein, we present the first–principles screened hybrid density functional theory analyses of the structural, elastic, electronic and optical properties of the two structure modifications of strontium zirconium sulfide (needle–like α–SrZrS3 and distorted β–SrZrS3 phases). Through the analysis of the predicted electronic structures, we show that both α– and β–SrZrS3 materials are direct band gaps absorbers, with calculated band gaps of 1.38, and 1.95 eV, respectively, in close agreement with estimates from diffuse–reflectance measurements. A strong light absorption in the visible region is predicted for the α– and β–SrZrS3, as reflected in their high optical absorbance (in the order of 105 cm−1), with the β–SrZrS3 phase showing stronger absorption than the α–SrZrS3 phase. We also report the first theoretical prediction of effective masses of photo-generated charge carriers in α– and β–SrZrS3 materials. Predicted small effective masses of holes and electrons at the valence, and conduction bands, respectively, point to high mobility (high conductivity) and low recombination rate of photo-generated charge carriers in α– and β–SrZrS3 materials, which are necessary for efficient photovoltaic conversion.

Highlights

Perovskite materials have attracted significant attention from researchers due to their potential in various applications
Inorganic–organic halide perovskite materials represent a great breakthrough in the development of solar cell materials with the power conversion efficiency rising from 3.6 to about 24%, since the first application in 2009 by Kojima et al [1]
We consider that the assigned reflection peaks in the density functional theory (DFT) X–ray diffraction (XRD) spectrum may become useful in clarifying future experiments, for instance to distinguish between the α–SrZrS3 and β–SrZrS3 phases

Summary

Introduction

Perovskite materials have attracted significant attention from researchers due to their potential in various applications. Compared to lead halide perovskites, chalcogenide perovskites materials are more environmentally friendly (component elements are earth–abundant and non–toxic) and possess superior electronic and optical properties, suggesting their potential ideal for low–cost tandem solar cell application. Sun et al [3] in their theoretical studies, predicted that the band gaps of CaTiS3 (1.0 eV), BaZrS3 (1.75 eV), CaZrSe3 (1.3 eV), and CaHfSe3 (1.2 eV) having the distorted perovskite structure are suitable for making single–junction solar cells. They are generally n–type semiconductors, with thin–films of BaZrS3 recently to have carrier densities in the range of. Based on the calculated optical absorbance, reflectivity, and refractive index, we demonstrate that α– and β–SrZrS3 are suitable solar absorber materials for solar cell and other optoelectronic applications

Computational Details

Structural Properties

Mechanical Properties

Electronic Properties

Optical Properties

Summary and Conclusions