Semiconductors Used in Photovoltaic and Photocatalytic Devices: Assessing Fundamental Properties from DFT

The photovoltaic and photocatalytic systems generally use at least one semiconductor in their architecture which role is to absorb the light or to transport the charge carriers. Despite the large variety of working principles encountered in these systems, they share some fundamental steps such as light absorption, exciton dissociation, and charge carrier diffusion. These phenomena are governed by fundamental properties of the semiconductor like the bandgap, the dielectric constant, the charge carrier effective masses, and the exciton binding energy. The ability of density functional theory to compute all of these properties is evaluated. From the particularly good results obtained with the HSE06 functional, it can be concluded that DFT is a reliable tool for the evaluation and prediction of these key properties which open nice perpectives for in silico design of improved semiconductors for solar energy application. In the light of these calculations, some experimental observations on the difference of efficiencies between semiconductors like TiO2 anatase and rutile or ZnO are interpreted.