Strain-induced tunable optoelectronic properties of inorganic halide perovskites APbCl 3 (A = K, Rb, and Cs) Md. Rasidul Islam 1* , Abdullah Al Mamun Mazumder 2 , Md. Rayid Hasan Mojumder 2 , A. S. M. Zadid Shifat 3 , and M. Khalid Hossain 4 1 Department of Electrical and Electronic Engineering, Bangamata Sheikh Fojilatunnesa Mujib Science & Technology University (BSFMSTU), Jamalpur- 2012, Bangladesh 2 Department of Electrical and Electronic Engineering, Khulna University of Engineering & Technology, Khulna-9203, Bangladesh 3 Optical Science and Engineering University of New Mexico, Albuquerque, United States of America 4 Institute of Electronics, Atomic Energy Research Establishment, Bangladesh Atomic Energy Commission, Dhaka 1349, Bangladesh * E-mail: rasidul@bsfmstu.ac.bd Received November 19, 2022; revised December 22, 2022; accepted January 4, 2023; published online January 31, 2023 Halide perovskites are promising photovoltaic, solar cell, and semiconductor materials. Density-functional theory (DFT) models address compressive and tensile biaxial strain effects on APbCl 3 , where A = (K, Rb, and Cs). This research shows how A-cation impacts bandgap energy and band structure. The direct bandgap for KPbCl 3 , RbPbCl 3 , and CsPbCl 3 is found 1.612, 1.756, and 2.046 eV, respectively; increases from A = K to Cs. When spin–orbital coupling (SOC) is introduced, bandgaps in KPbCl 3 , RbPbCl 3 , and CsPbCl 3 perovskites are reduced to 0.356, 0.512, and 0.773 eV, respectively. More tensile strain widens the bandgap; compressive strain narrows it. Without SOC, the bandgaps of KPbCl 3 , RbPbCl 3 , and CsPbCl 3 were tuned from 0.486 to 2.213 eV, 0.778 to 2.289 eV, and 1.168 to 2.432 eV, respectively. When the compressive strain is increased, the dielectric constant of APbCl 3 decreases (redshift) and increases (blueshift) as the tensile strain is increased. Strain improves APbCl 3 perovskite’ s optical performance. © 2023 The Japan Society of Applied Physics 1. Introduction Recently, organic–inorganic lead halide perovskites (OILHP) have gained significant research attention in photovoltaic engineering because of their fascinating features that include reasonable bandgap, wide availability, and extraordinary ab- sorption capacity of visible light at low manufacturing budget. 1–11) As of 2020, the OILHP solar cells have also shown 25.5% power conversion efficiency (PCE). 12) However, expo- sure to moisture, light, and temperature has a considerable negative impact on the long-term stability of OILHPs. 13,14) Therefore, it is imperative to discover a suitable solution to the OILHPs’ instability problem. It was shown that the replacement of the organic cations NH 2 CHNH 2 + /CH 3 NH 3 + by inorganic cations, like K + /Rb + /Cs + /Li + , may considerably alleviate the thermal and optical instability issues of CH 3 NH 3 PbI 3 and NH 2 CHNH 2 PbI 3 . 15,16) After the challenge of instability was resolved, inorganic lead halide perovskites (ILHP) showed remarkable promise for application in optoelectronic devices. With an appropriate inorganic cation, Zhu et al. 17) found that OILHP and ILHP had equivalent characteristics for tunable efficiency, and band edge carriers. Dimesso et al. 18) have found that by employing the self-organization technique, any Li, Na, K, or Cs-cation-containing ILHP may be produced experimen- tally at ambient temperature. The sole disadvantage of the ILHPs is a quite higher bandgap value above 1.45 eV, notwithstanding its potential for usage in optoelectronic technologies like photonic crystals, solar cells, LEDs, and radiation detectors. 19–24) The Shockley–Queisser theory predicts that when the perovskite material’s bandgap is controlled to the region of 1.2–1.4 eV, the perovskite solar cells might attain a PCE up to 33%. 25) Recently, it has been discovered that compositional dimension and strain engineering modifications are advantageous for electronic bandgap modula- tion and optical absorbance. 26–30) The bigger size of organic cations allows them to hold additional nucleons compared to their inorganic counterparts. As a result, the electronic band structure and absorbance characteristics vary depending on the atomic size. Furthermore, the ILHPs’ physical characteristics may be greatly altered by the biaxial strain without affecting the structure’s symmetry. According to D. Liu et al., 31) tensile and compressive strain effectively regulated the dielectric function and the electronic bandgap of CsGeI 3 inorganic perovskite. As said by A. K. Hossain et al., 32) compressive stress caused the CsSnCl 3 , a cubic inorganic perovskite to change from a semiconductor to a metallic state with remarkable optoelectronic characteristics ideal for solar applications. According to their calculations, the bandgap underestimated for the metal halide CsSnCl 3 is roughly 1.857 eV when compared to the predicted bandgap of 0.943 eV and the measured bandgap of 2.8 eV. Generally, the primary role of the perovskite layer is to behave as a sensitizer, absorbing solar energy or acting as a transport layer for electrons or holes. It is usual practice to spin-coated the perovskite layer over the electron/hole transport layer. Since this research conducted the optoelectronic properties of the APbCl 3 (where A = K, Rb, and Cs) perovskites in the presence of strain and concluded to observing a very large optical peak with suitable bandgap, it could be incorporated as the material for the perovskite layer of a perovskite solar cell. The APbCl 3 may offer reasonable flexibility in optoelectronic property matching for solar cell design and optimization. Therefore, the details work about APbCl 3 perovskite is very essential to apply in optoelectronic devices. The objective of this research is to carry out a thorough and methodical investigation of the strain-driven optical and electrical characteristics of APbCl 3 (where A = K, Rb, and Cs) employing first-principles computations developed on density functional theory (DFT). KPbCl 3 , RbPbCl 3 , and CsPbCl 3 materials were subjected to a biaxial strain that ranged from -6% to +6% in order to extract properties that were acceptable for implement in optoelectronic applications and photovoltaic cells. 2. Computational details In this study, we have employed the first-principles DFT along with Norm Conserving pseudopotential 33) and 011002-1 © 2023 The Japan Society of Applied Physics Japanese Journal of Applied Physics 62, 011002 (2023) REGULAR PAPER https://doi.org/10.35848/1347-4065/acb09e