Solar cells which exceed 12 percent efficiency.

© 2011 EPFL

© 2011 EPFL

Porphyrin-Sensitized Solar Cells with Cobalt (II/III)–Based Redox Electrolyte Exceed 12 Percent Efficiency.

The iodide/triiodide redox shuttle has limited the efficiencies accessible in dye-sensitized solar cells. Here, the group of Prof. Michaël Grätzel (LPI - Laboratory of Photonics and Interfaces), in collaboration with researchers of the National Chung Hsing University, report mesoscopic solar cells that incorporate a Co(II/III)tris(bipyridyl)–based redox electrolyte in conjunction with a custom synthesized donor-π-bridge-acceptor zinc porphyrin dye as sensitizer (designated YD2-o-C8). The specific molecular design of YD2-o-C8 greatly retards the rate of interfacial back electron transfer from the conduction band of the nanocrystalline titanium dioxide film to the oxidized cobalt mediator, which enables attainment of strikingly high photovoltages approaching 1 volt. Because the YD2-o-C8 porphyrin harvests sunlight across the visible spectrum, large photocurrents are generated. Cosensitization of YD2-o-C8 with another organic dye further enhances the performance of the device, leading to a measured power conversion efficiency of 12.3% under simulated air mass 1.5 global sunlight.

Aswani Yella et al., Science, Vol. 334 no. 6056 pp. 629-634 DOI: 10.1126/science.1209688 (2011)

Nature | Research Highlights Chemistry: Solar-cell progress, Nature 479, 152 (10 November 2011) doi:10.1038/479152d

Nature Chemistry | Research Highlights: Dye-sensitized solar cells - Improving efficiency, Nature Chemistry 4, 4–5 (2012) doi:10.1038/nchem.1237