Parrey Ismahan Duz, Bilican Fuat, Kursun Celal, Kart Hasan Huseyin, Parrey Khursheed Ahmad
Science Faculty, Department of Physics, Pamukkale University, Denizli 20160, Türkiye.
Department of Physics, Faculty of Sciences, Kahramanmaras Sutcu Imam University, Kahramanmaras 46040, Turkey.
ACS Omega. 2023 Jul 12;8(29):26577-26589. doi: 10.1021/acsomega.3c03469. eCollection 2023 Jul 25.
Due to their intrinsic stability and reduced toxicity, lead-free halide double perovskite semiconductors have become potential alternatives to lead-based perovskites. In the present study, we used density functional theory simulations to investigate the mechanical stability and band gap evolution of double perovskites CsAgBiX (X = Cl and Br) under an applied pressure. To investigate the pressure-dependent properties, the hydrostatic pressure induced was in the range of 0-100 GPa. The mechanical behaviors indicated that the materials under study are both ductile and mechanically stable and that the induced pressure enhances the ductility. As a result of the induced pressure, the covalent bonds transformed into metallic bonds with a reduction in bond lengths. Electronic properties, energy bands, and electronic density of states were obtained with the hybrid HSE06 functional, including spin-orbit coupling (HSE06 + SOC) calculations. The electronic structure study revealed that CsAgBiX samples behave as X-Γ indirect gap semiconductors, and the gap reduces with the applied pressure. The pressure-driven samples ultimately transform from the semiconductor to a metallic phase at the given pressure range. Also, the calculations demonstrated that the applied pressure and spin-orbit coupling of the states pushed VBM and CBM toward the Fermi level which caused the evolution of the band gap. The relationship between the structure and band gap demonstrates the potential for designing lead-free inorganic perovskites for optoelectronic applications, including solar cells as well as X-ray detectors.
由于其固有的稳定性和较低的毒性，无铅卤化物双钙钛矿半导体已成为铅基钙钛矿的潜在替代品。在本研究中，我们使用密度泛函理论模拟来研究双钙钛矿CsAgBiX（X = Cl和Br）在施加压力下的机械稳定性和带隙演化。为了研究压力依赖特性，所施加的静水压力范围为0 - 100 GPa。机械行为表明，所研究的材料既具有延展性又具有机械稳定性，并且所施加的压力增强了延展性。由于施加的压力，共价键转变为金属键，键长减小。使用包含自旋轨道耦合（HSE06 + SOC）计算的杂化HSE06泛函获得了电子性质、能带和电子态密度。电子结构研究表明，CsAgBiX样品表现为X - Γ间接带隙半导体，并且带隙随着施加的压力而减小。在给定压力范围内，压力驱动的样品最终从半导体转变为金属相。此外，计算表明，施加的压力和态的自旋轨道耦合将价带顶（VBM）和导带底（CBM）推向费米能级，这导致了带隙的演化。结构与带隙之间的关系证明了设计用于光电子应用的无铅无机钙钛矿的潜力，包括太阳能电池以及X射线探测器。
