Design of p-type transparent conducting oxides Sn2GeO4 by an ab initio evolutionary structure search

In contrast to n-type transparent conducting oxides (TCOs), very few p-type TCOs have been discovered to date. In this work, we predicted two new tin-germanate-based compounds (Sn2GeO4) as potential p-type TCOs with exceptionally low hole effective masses and wide band gap energies. Through detailed electronic structure calculations, we revealed that the Sn2GeO4 compounds possess sufficiently wide band gaps (3.24 eV) for transparency, and very small effective masses (0.46) for hole carriers due to the influence of divalent Ge2+. Our study shows the potential for band engineering of Sn2+ and Ge2+ cations with (n − 1)d10ns2 electronic configurations as p-type TCOs; this could expand the materials family for the future design and development of p-type TCOs.