Structural, mechanical and optoelectronic properties of perovskites XPbI ₃ (X = Al, Ga, In, Tl) for photovoltaic applications based on density functional theory

Abstract In this work, the structural, elastic and optoelectronic properties of XPbI 3 (X = Al, Ga, In, Tl) crystals are investigated via using density functional theory (DFT) approach. Based on the structural optimization, the calculated lattice constants of AlPbI 3 , GaPbI 3 , InPbI 3 and TlPbI 3 crystals are 6.303, 6.312, 6.323, 6.331 Å. The calculated formation energy and elastic constants shows that the materials are all mechanically and thermodynamically stable. According to the Poisson’s ratio and B/G, XPbI 3 perovskites are ductile and ionic bonding materials. The electronic properties of these materials show that AlPbI 3 , GaPbI 3 , InPbI 3 and TlPbI 3 are all direct band gap semiconductors, whose band gap values are 1.784 eV, 1.853 eV, 1.908 eV, 1.921 eV, respectively. The optical properties of XPbI 3 perovskites, including the dielectric function, reflectivity, absorption coefficient, refractive index, were also calculated, showing that they have high dielectric constant, refractive index, and absorption coefficients, which are favorable for their application in photovoltaic cells, and other optoelectronic devices. Our work provides a theoretical basis for studying the physical properties and application potential of XPbI 3 (X = Al, Ga, In, Tl) crystals.