Ligand Field‐Induced Exotic Dopant for Infrared Transparent Electrode: W in Rutile SnO2

Transparent conductive oxides (TCOs) exhibiting high near‐infrared (NIR) transmittance are one of the key materials for highly efficient thin‐film solar cells with widened spectral sensitivity. To realize excellent NIR transparency in a TCO film, developing a dopant providing high mobility (µ) carriers is quite important. Herein, it is demonstrated that W is a high‐μ dopant in rutile SnO2, which is unexpected from the conventional strategy. A combination of electrical transport property measurements and hybrid density functional theory calculations reveals that W behaves as a singly charged donor (W5+) showing minimized ionized impurity scattering. This charge state is realized by the splitting of the W 5d t2g‐states originating not only from the octahedral crystal field but also hybridization with the O 2p orbitals, whose contribution has not been considered in transition metal‐doped TCOs. Hybridization between metal d orbital and O 2p orbitals would provide a new guide for designing a novel dopant of NIR transparent conductors.