n- and p-Type Dopants for Halide Perovskites

The halide perovskites, such as cesium tin bromide (CsSnBr₃) and methylammonium lead iodide (MAPI), are high-performing light emitters, with applications in lighting, displays, and photovoltaics. All of these applications would benefit from better control over the perovskites’ electrical conductivity. However, it has proven difficult to achieve high p-type carrier concentrations in these materials, and reliable n-type-doping strategies have not been developed. In this work, possible dopants are first evaluated in the halide perovskites using first-principles calculations based on a hybrid functional with spin-orbit coupling. This approach not only leads to accurate predictions for band structure and band offsets, but also provides a better description of dopant properties. We assess whether dopant impurities (such as Ag, Na, and Cu for acceptors, and Bi, Sc, and Y for donors) can act as shallow dopants on the proper substitutional site, and whether other configurations of these impurities might lead to compensation of potential electrical conductivity. Among the p-type dopants considered, sodium and silver are identified as the most promising acceptors for achieving p-type conductivity, and optimum chemical potential conditions for these dopants are identified [1]. Turning to donor doping, we find that common n-type dopants such as Bi are deep defects [2]. We demonstrate the validity of our first-principles calculations by comparing with optical measurements of Bi-doped CsPbBr₃ crystals. Bi donors are found to give rise to characteristic near-infrared luminescence, in good agreement with theoretical predictions. While Bi is a deep donor in the halide perovskites, yttrium and scandium are identified as promising donor dopants that are capable of yielding n-type conductivity in a variety of halide perovskite systems [2].<br/><br/><br/>[1] J. Phys. Chem. 127, 12735 (2023).<br/>[2] Chem. Mater. 33, 6200 (2021).<br/><br/>This work was supported by the ONR/NRL 6.1 Basic Research Program.