Investigation of electronic and optical properties in bismuth/antimony co-doped methylammonium lead bromide

Abstract

Lead halide perovskites, exemplified by methylammonium lead bromide (MAPbBr3 ), represent a cornerstone in the pursuit of next-generation photovoltaic materials owing to their tunable optoelectronic properties, defect tolerance, and cost-effective synthesis. However, their intrinsic bandgap limitations and carrier recombination pathways necessitate advanced doping strategies to enhance performance. Herein, den- sity functional theory calculations were employed, utilizing the Perdew–Burke–Ernzerhof functional for structural optimization and the Heyd–Scuseria–Ernzerhof hybrid functional for precise electronic structure determination. Computations were conducted in a 2 × 2 × 2 cubic supercell, probing a spectrum of substitutional configurations at Pb2+ sites, including single-dopant systems (MAPb0.875 Sb0.125 Br3 and MAPb0.875 Bi0.125 Br3 ) and co-doped variants up to high concentrations, such as MAPb0.5 Sb0.125 Bi0.375 Br3 and MAPb0.5 Sb0.375 Bi0.125 Br3 . Band structures, interpolated via maximally localized Wannier functions using the selected columns of the density matrix with k-point sampling method, reveal a pristine direct bandgap of 2.32 eV at the Γ point, which narrows non-rigidly upon doping due to the introduction of deep donor states from heterovalent Sb3+ and Bi3+ impurities. These states manifest as midgap impurity bands, shifting the conduction band minimum downward while preserving valence band integrity. Optical properties, derived from time-dependent density functional pertur- bation theory via the Lanczos recursion algorithm, exhibit a pronounced redshift in the absorption onset and an enhanced intensity in the imaginary dielectric function (ε2 ) across the visible spectrum, attributed to broadened interband transitions and synergistic dopant-induced polarizability. Formation energy calculations confirm the thermodynamic accessibility of these co-doped configurations