Modified Becke-Johnson exchange potential: improved modeling of lead halides for solar cell applications

• Main Author: Radi A. Jishi
• Format: Article
• Language: English
• Published: AIMS Press 2016-01-01
• Series: AIMS Materials Science
• Subjects: DFT; lead halides; mBJ; perovskites; photovoltaics; solar cells; spin-orbit
• Online Access: http://www.aimspress.com/Materials/article/606/fulltext.html

We report first-principles calculations, within density functional theory, on the lead halide compounds PbCl₂, PbBr₂, and CH₃NH₃PbBr_3−xClx, taking into account spin-orbit coupling. We show that, when the modified Becke-Johnson exchange potential is used with a suitable choice of defining parameters, excellent agreement between calculations and experiment is obtained. The computational model is then used to study the effect of replacing the methylammonium cation in CH₃NH₃PbI₃ and CH₃NH₃PbBr₃ with either N₂H₅⁺or N₂H₃⁺, which have slightly smaller ionic radii than methylammonium. We predict that a considerable downshift in the values of the band gaps occurs with this replacement. The resulting compounds would extend optical absorption down to the near-infrared region, creating excellent light harvesters for solar cells.