Electronic structure of PPP@ZnO from all-electron quasiarticle calculations

We investigate the electronic properties of poly(\emph{para}-phenylene) (PPP) adsorbed on the non-polar (001) surface of rocksalt (\emph{rs}) ZnO using all-electron density functional theory (DFT) as well as quasiparticle (QP) calculations within the \emph{GW} approach. A particular focus is put on the electronic band discontinuities at the interface, where we investigate the impact of quantum confinement, molecular polarization, and charge rearrangement. For our prototypical system, PPP@ZnO, we find a type-I heterostructure. Comparison of the band offsets derived from a QP-treatment of the hybrid system with predictions based on mesoscopic methods, like the Shockley-Anderson model or alignment via the electrostatic potential, reveals the inadequacy of these simple approaches for the prediction of the electronic structure of such inorganic/organic heterosystems. Finally, we explore the optical excitations of the interface compared to the features of the pristine components and discuss the methodological implications for the \emph{ab-initio} treatment of interface electronics.