Thin-film dye-sensitized solar cells (DSCs) based on mesoporous semiconductor electrodes are low-cost alternatives to conventional silicon devices1,2. High-efficiency DSCs typically operate as photoanodes (n-DSCs), where photocurrents result from dye-sensitized electron injection into n-type semiconductors. Dye-sensitized photocathodes (p-DSCs) operate in an inverse mode, where dye-excitation is followed by rapid electron transfer from a p-type semiconductor to the dye (dye-sensitized hole injection). Such p-DSCs and n-DSCs can be combined to construct tandem solar cells3 (pn-DSCs) with a theoretical efficiency limitation well beyond that of single-junction DSCs (ref. 4). Nevertheless, the efficiencies of such tandem pn-DSCs have so far been hampered by the poor performance of the available p-DSCs (refs 3, 5–15). Here we show for the first time that p-DSCs can convert absorbed photons to electrons with yields of up to 96%, resulting in a sevenfold increase in energy conversion efficiency compared with previously reported photocathodes7. The donor–acceptor dyes, studied as photocathodic sensitizers, comprise a variable-length oligothiophene bridge, which provides control over the spatial separation of the photogenerated charge carriers. As a result, charge recombination is decelerated by several orders of magnitude and tandem pn-DSCs can be constructed that exceed the efficiency of their individual components.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $16.58 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
The authors would like to thank the Victorian Government (Department of Primary Industries, ETIS SERD), the ARC Centre of Excellence for Electromaterials Science (ACES), the German Academic Exchange Service (DAAD-Go8 joint research cooperation scheme) and the International Science Linkage Project CG 100059 (DIISR, Australia) for financial support. Furthermore, they would like to acknowledge the ARC for providing equipment support through LIEF, as well as supporting U.B. with an Australian Research Fellowship. Special thanks also to Monash University for supporting U.B. with a Monash Research Fellowship, as well as JGC Catalysts and Chemicals Ltd, Kitakyushu-Shi (Japan) for providing samples of TiO2 screen-printing paste. We would like to thank the German Federal Ministry of Education and Research (BMBF) for financially supporting our research on organic solar-cell materials in the frame of a joint project (OPEG) and the Alexander von Humboldt Foundation for a grant for A.M. This work was also supported by the German Science Foundation (DFG) in the frame of a Collaborative Research Center (SFB 569). Finally we would also like to thank L. Kane-Maguire for assistance in the manuscript preparation process.