Design of p -type transparent conductors from inverted band structure: The case of inorganic metal halide perovskites

Abstract

Transparent conductors (TCs), which bring two seemingly contraindicated properties, conductivity and transparency, together into one material, enable many critical technologies. Significant successes have been achieved for $n$-type TCs, such as Sn-doped $\mathrm{I}{\mathrm{n}}_{2}{\mathrm{O}}_{3}$, but developing their $p$-type counterparts has still encountered a big challenge, mainly due to the intrinsic band structure of conventional semiconductors. Here, we propose that a class of wide-gap inorganic metal halide perovskites have great potential as ideal $p$-type TCs, because of their inverted band structure compared to $n$-type TCs, i.e., they have $s$-like wave-function character at the top of the valence band, and $p$-like wave-function character at the lower valence bands and the bottom of the conduction band, which results in significantly improved $p$-type dopability, high hole mobility, and good optical transparency. This insight of designing $p$-type TCs from an inverted band structure opens an avenue for the future design of critical optoelectronic materials.