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.