  Hybrid organic/inorganic-semiconductor systems have important applications in
both molecular electronics and in photo-responsive materials. The
characterization of the interface and of the electronic excited-states of these
hybrid systems remains a challenge for state-of-the-art computational methods,
as the systems of interest are large. In the present investigation, we present
for the first time a many-body Green's function Bethe-Salpeter investigation of
a series of photochromic molecules adsorbed onto TiO2 nanoclusters. Based on
these studies, the performance of TD-DFT is assessed. Using a state-of-the-art
computational protocol, the photochromic properties of different hybrid systems
are assessed. This work shows that qualitatively different conclusions can be
reached with TD-DFT relying on various exchange-correlation functionals for
such organic/inorganic interfaces, and paves the way to more accurate
simulation of many materials.
