Efficient and accurate calculation of band gaps of halide perovskites with the Tran-Blaha modified Becke-Johnson potential

We report on a reoptimization of the Tran-Blaha modified Becke-Johnson (TB-mBJ) potential dedicated to the prediction of the band gaps of three-dimensional (3D) and layered hybrid organic-inorganic perovskites (HOPs) within pseudopotential-based density functional theory methods. These materials hold promise for future photovoltaic and optoelectronic applications. We begin by determining a set of parameters for 3D HOPs optimized over a large range of materials. Then we consider the case of layered HOPs. We design an empirical relationship that facilitates the prediction of band gaps of layered HOPs with arbitrary interlayer molecular spacers with a computational cost considerably lower than that of more advanced methods like hybrid functionals or GW. Our study also shows that substituting interlayer molecular chains of layered HOPs with Cs atoms is an appealing and cost-effective route to band gap calculations. Finally, we discuss the pitfalls and limitations of TB-mBJ for HOPs, notably its tendency to overestimate the effective masses due to the narrowing of the band dispersions. We expect our results to extend the use of TB-mBJ for other low-dimensional materials.