  By means of full-potential all-electron density-functional theory and
many-body perturbation theory, we compute the band alignment at a prototypical
hybrid inorganic/organic interface. The electronic properties of a model system
built of poly(\emph{para}-phenylene) and \emph{rs}-ZnO are studied in two
different geometries, employing several approaches of increasing
sophistication. To this extent, we explore models for predicting the level
alignment, which are based on the knowledge of the electronic structure of the
individual constituents and are commonly used for semiconductor interfaces. For
their evaluation in the context of hybrid materials, we perform an
\textit{ab-initio} study of the entire system, including a quasiparticle
description of the electronic structure within the $G_0W_0$ approximation.
Based on this, we quantify the impact of structure, charge redistribution,
orbital hybridization, and molecular polarization on the band offsets and the
alignment type. We highlight not only known limitations of predicting the level
alignment at a hybrid inorganic/organic interface by simple models, but also
demonstrate how structural details of the interface components impact the
results.
