Design strategy for p-type transparent conducting oxides

Transparent conducting oxides (TCOs), combining the mutually exclusive functionalities of high electrical conductivity and high optical transparency, lie at the center of a wide range of technological applications. The current design strategy for n-type TCOs, making wide bandgap oxides conducting through degenerately doping, obtains successful achievements. However, the performances of p-type TCOs lag far behind the n-type counterparts, primarily owing to the localized nature of the O 2 p-derived valence band (VB). Modulation of the VB to reduce the localization is a key issue to explore p-type TCOs. This Perspective provides a brief overview of recent progress in the field of design strategy for p-type TCOs. First, the introduction to principle physics of TCOs is presented. Second, the design strategy for n-type TCOs is introduced. Then, the design strategy based on the concept of chemical modulation of the valence band for p-type TCOs is described. Finally, through the introduction of electron correlation in strongly correlated oxides for exploring p-type TCOs, the performance of p-type TCOs can be remarkably improved. The design strategy of electron correlation for p-type TCOs could be regarded as a promising material design approach toward the comparable performance of n-type TCOs.