Doping effect of chalcogens on electronic and optical properties of perovskite LiNbO3 compound: Ab initio calculations

Abstract

In this study, the effects of Sulfur (S), Selenium (Se), and Tellurium (Te) on the electronic and optical properties of LiNbO 3 were studied by using density functional theory (DFT) within Wien2k code based on the generalized gradient approximation (GGA-PBE). Analyses of the studied components revealed that the incorporation of chalcogens in LiNbO 3 effectively reduces the electronic band-gap and that varying the amount and the type of dopant can control the level of band-gap reduction. The band-gap is equal to 2.312 eV, 1.996 eV, and 0.924 eV for 11.11% S, Se, and Te doped LiNbO 3, respectively. For the pure LiNbO 3 , the band-gap is 3.544 eV. Moreover, the absorption is improved in the visible light (380–790 nm) and exceeds 10 5 cm −1 for Te doped-LiNbO 3 . The dielectric constant at zero frequency (ε 1 (0)) is equal to 5.254 for LiNbO 3 and 8.531 for Te doped-LiNbO 3 : 11.11%. Optical conductivity and reflectivity are predicted and the results showed that increasing chalcogens concentration considerably improves the electrical conductivity. Comparisons between the three types of doping were also performed and the results indicated that Te would be the best substitute for oxygen in LiNbO 3; hence ensuring a promising and environmentally friendly new class of solar cells.