Star-shaped molecules based on a triphenylamine core derivatized with various combinations of thienylenevinylene conjugated branches and electron-withdrawing indanedione or dicyanovinyl groups have been synthesized. UV-vis absorption and fluorescence emission data show that the introduction of the electron-acceptor groups induces an intramolecular charge transfer that results in a shift of the absorption onset toward longer wavelengths and a quenching of photoluminescence. Cyclic voltammetry shows that all compounds present a reversible first oxidation process whose potential increases with the number of electron-withdrawing groups in the structure. Prototype bulk and bilayer heterojunction solar cells have been realized using fullerene C60 derivatives as acceptor material. The results obtained with both kinds of devices show that the introduction of electron-acceptor groups in the donor structure induces an extension of the photoresponse in the visible spectral region, an increase of the maximum external quantum efficiency, and an increase of the open-circuit voltage under white light illumination. These synergistic effects allow reaching power conversion efficiencies of approximately 1.20% under simulated AM 1.5 solar irradiation at 100 mW cm(-2).

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Simple single-layered diodes based on a glass-forming triphenylamine-thienylenevinylene with internal charge transfer show a photovoltaic effect in solar light and red electroluminescence when forward biased (see figure and cover). The use of an additional layer of C60 as electron acceptor improves the photovoltaic performance without affecting the electroluminescence.

Two novel “hybrid” systems consisting of a triphenylamine core carrying π-conjugated terthienyl branches have been synthesized and characterized by differential scanning calorimetry, X-ray diffraction, cyclic voltammetry, UV−vis absorption, and fluorescence spectroscopy. The semiconductor potentialities of these compounds, which lead to glassy or amourphous films, have been evaluated by their implementation in very simple prototype devices that display electroluminescence at low voltage as well as a photovoltaic effect. Moreover, field-effect transistors based on one of these novel molecules display a high hole mobility (1.1 × 10-2 cm V-1 s-1). These results suggest that molecules leading to amorphous materials could represent a valid alternative as compared to systems that require control of the molecular orientation/organization.