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

Abstract

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.