Panchromatic response is essential to increase the light-harvesting efficiency in solar cells and long-range energy transfer has recently been used to increase light harvesting inside dye-sensitized mesoscopic solar cells (DSCs).

Michael Grätzel and co-workers, Ecole Polytechnique Fédérale de Lausanne, Switzerland, have increased the efficiency of the solar-to-electric power conversion by placing two commercially available dyes within the porous network of the nanocrystalline TiO₂ film of a DSC. They show that devices with multiple relay dyes perform significantly better than devices where only one of the energy relay dyes is used, with the power conversion efficiency increased by 35 %.

Additional photoresponse from 400–590 nm matching the optical window of the zinc phthalocyanine sensitizer was observed due to Förster resonance energy transfer (FRET) from the two energy relay dyes to the sensitizing dye.

• Incorporating Multiple Energy Relay Dyes in Liquid Dye-Sensitized Solar Cells
  J.-H. Yum, B. E. Hardin, E. T. Hoke, E. Baranoff, S. M. Zakeeruddin et al.,
  ChemPhysChem 2011.
  DOI: 10.1002/cphc.201000854

► Previous news on research by M. Grätzel:

• All the Colors of the Sun
  Ru-based dye and Ti nanoparticles combine to give solar cells of high efficiency and a variety of colors