Molecular host–guest complexes: Shielding of guests on semiconductor surfaces

A recent and promising development in the field of renewable energy is the use of molecular containers (cyclodextrins, cucurbiturils, Cram-type hosts, and calixarenes) to bind encapsulated chromophores or redox-active compounds to the surface of TiO2 nanoparticles and other nanostructured wide bandgap metal oxide semiconductors. The host provides an alternative method of adsorption of molecules on semiconductors and shields the guest from the heterogenous interface. The novel hybrid systems exhibited photophysical and electrochemical properties that differ from the properties of layers obtained by directly attaching the chromophore to the semiconductor through binding groups, including slower and homogeneous interfacial electron recombination dynamics. In addition to DSSCs, the guest@host/semiconductor systems find applications as sensors, electrochromic windows, and LEDs.