  In this work we study and contrast implicit solvation models against explicit
atomistic, quantum mechanical models in the description of the band alignment
of semiconductors in aqueous environment, using simulations based on density
functional theory. We find consistent results for both methods for 9 different
terminations across 6 different materials whenever the first solvation shell is
treated explicitly, quantum mechanically. Interestingly this first layer of
explicit water is more relevant when water is adsorbed but not dissociated,
hinting at the importance of saturating the surface with quantum mechanical
bonds. Furthermore, we provide absolute alignments by determining the position
of the averaged electrostatic reference potential in the bulk region of
explicit and implicit water with respect to vacuum. It is found that the
absolute level alignments in explicit and implicit simulations agree within
$\sim 0.1-0.2$ V if the implicit potential is assumed to lie 0.33 V below the
vacuum reference level. By studying the interface between implicit and explicit
water we are able to trace back the origin of this offset to the absence of a
water surface dipole in the implicit model, as well as a small additional
inherent polarization across the implicit-explicit interface.
