A three‐ to four‐fold increase in power conversion efficiency is reported for poly(3‐alkylthiophene)/fullerene solar cells by simply heating the device to 55 °C for 30 min. This behavior may be due to enhanced diode properties, plus a higher degree of order within the material. The Figure shows the soluble fulleropyrrolidine used as electron acceptor.

A power conversion efficiency of 0.37%, under white light of 80 mW cm-2 intensity, was obtained when a fullerene-azothiophene dyad was used as the active layer of a photovoltaic cell.

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The synthesis and photophysical characterization of a series of fullerene-based, donor-acceptor dyads is presented, along with a description of their behavior as single molecular components in photovoltaic cells. The spectroscopic and photophysical properties of the dyads, investigated by steady-state fluorescence spectroscopy, pico- and nanosecond transient optical spectroscopy and time-resolved electron paramagnetic resonance (EPR) spectroscopy, revealed that the dyads undergo multiple-step energy transfer from the donor singlet excited state to the fullerene triplet excited state, which in turn decays to the donor triplet state. The inefficient formation of a charge-separated state, both in solution and in the solid state, translates into a poor photovoltaic performance of dyads 2 b-4 b if compared to that of dyad 1 b, in which photoinduced electron transfer is operative in the solid state. In addition, the results of the photophysical investigation suggested that the performance of the solar cells was also limited by the low-lying donor triplet excited state that acts as a photoexcitation energy sink.

A cyclopropanation reaction has been used to prepare two methanofullerenes bearing a 2,2'-bipyridine () or pyridine () ligand separated from the fullerene through an oxyethylene macrocyclic spacer. Derivatives and were, in turn, employed to synthesize two fullerene-based ruthenium(ii) and rhenium(i) donor-acceptor dyads whose molecular structure was confirmed by (1)H NMR, (13)C NMR and exact mass determination. The UV-Vis spectrum of the dyads is the superimposition of those of appropriate model systems, indicating that ground-state electronic interactions between the constituent chromophores, in solution, are negligible, in line also with the electrochemical results. The complex voltammetric pattern was characterized by the superimposition of signals attributed to one moiety or another without significant shifts with respect to their models. Furthermore, both species undergo partial chemical degradation in the time scale of cyclic voltammetry upon their multiple reduction. Photophysical properties of and , namely, excited state interactions between the ruthenium(ii) or rhenium(i) complexes and [60]fullerene have been investigated by steady-state and time-resolved UV-Vis-NIR luminescence spectroscopy that was complemented by nanosecond laser flash photolysis in CH(2)Cl(2) solutions. All experimental findings were set into relation with the corresponding reference compounds. More precisely, excitation of the metal complexes in and gives rise to a notable steady-state and time-resolved luminescence quenching of both metal to ligand charge transfer states (i.e., [Ru(bpy)(3)](2+) and [(bpy)Re(CO)(3)(py)](+)). Conclusive evidence about the nature of the photoproducts came from nanosecond laser flash photolysis. In these experiments, only the long-lived and oxygen-sensitive [60]fullerene triplets were detected. Two pathways are envisioned for this [60]fullerene triplet formation. Firstly, intramolecular transduction of the triplet excited state energy evolving from the photoexcited metal complexes. Secondly, intersystem crossing of directly excited [60]fullerene.