Electronic properties of anatase-TiO2 codoped by cation-pairs from hybrid density functional theory calculations

► n-p compensated codoping gives large gap narrowing without valence band movement. ► Cu and Mo/W-doping has larger gap narrowing than Al and Nb/Ta due to d-d repulsion. ► Cu/Mo-doping is amongst the best of the studied candidates due to the largest gap narrowing. ► Codoping tends to decrease transparent conduction vis-à-vis Nb, Ta, Mo, W-doping.