Efficient Electron Transfer and Sensitizer Regeneration in Stable π-Extended Tetrathiafulvalene-Sensitized Solar Cells

• Published in: Journal of the American Chemical Society Vol. 132; no. 14; pp. 5164 - 5169
• Main Authors: Wenger, Sophie, Bouit, Pierre-Antoine, Chen, Qianli, Teuscher, Joël, Censo, Davide Di, Humphry-Baker, Robin, Moser, Jaques-E, Delgado, Juan Luis, Martín, Nazario, Zakeeruddin, Shaik M, Grätzel, Michael
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14-04-2010
• Subjects: Chemical Sciences; Electrochemistry; Electrons; Heterocyclic Compounds - chemistry; Kinetics; Membranes, Artificial; Molecular Structure; Organic chemistry; Oxidation-Reduction; Porosity; Solar Energy; Surface Properties; Titanium - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja909291h

The development of metal-free organic sensitizers is a key issue in dye-sensitized solar cell research. We report successful photovoltaic conversion with a new class of stable tetrathiafulvalene derivatives, showing surprising electrochemical and kinetic properties. With time-resolved spectroscopy we could observe highly efficient regeneration of the photo-oxidized tetrathiafulvalene sensitizers, which were attached to a mesoporous TiO2 film, by a redox mediator in the pores (iodide/tri-iodide), even though the measured driving force for regeneration was only ∼150 mV. This important proof-of-concept shows that sensitizers with a small driving force, i.e. the oxidation potential of the sensitizer is separated from the redox potenial of the mediator by as little as 150 mV, can operate functionally in dye-sensitized solar cells and eventually aid to reduce photovoltage losses due to poor energetic alignment of the materials.