Unconventional approaches to combine optical transparency with electrical conductivity

Combination of electrical conductivity and optical transparency in the same material -- known to be a prerogative of only a few oxides of post-transition metals, such as In, Sn, Zn and Cd -- manifests itself in a distinctive band structure of the transparent conductor host. While the oxides of other elements with $s^2$ electronic configuration, for example, Mg, Ca, Sc and Al, also exhibit the desired optical and electronic features, they have not been considered as candidates for achieving good electrical conductivity because of the challenges of efficient carrier generation in these wide-bandgap materials. Here we demonstrate that alternative approaches to the problem not only allow attaining the transport and optical properties which compete with those in currently utilized transparent conducting oxides (TCO), but also significantly broaden the range of materials with a potential of being developed into novel functional transparent conductors.