Professor Michael Grätzel
Tittel: Nanostructured Photosystems for the Generation of Electricity and Fuels from Sunlight».
Torsdag 16. mai 2013, Kl. 11:15
Auditorium 1, Kjemisk institutt, Universitetet i Oslo.
Michael Grätzel holder også en ekstraforelesning Onsdag 15. mai kl. 13.15
Årets Hasselforeleser er Professor Michael Grätzel.
Han arbeider ved Basic Science Faculty, Ecole Polytechnique Fédérale de Lausanne, Sveits.
Basic Science Faculty, Ecole Polytechnique Fédérale de Lausanne, Switzerland
Learning from the concepts used by green plants photosynthesis, we have developed nanostructured systems affording efficient solar light harvesting and conversion to electricity and fuels. Solar cells using dyes or pigment nanoparticles as light harvesters supported by mesoscopic oxide films have emerged as credible contenders to conventional p-n junction photovoltaic devices.
Separating light absorption from charge carrier transport dye sensitized mesoscopic solar cells (DSCs) were the first to use a three-dimensional nanocrystalline junction for solar electricity production. 1-4 The standard AM 1.5 solar to electric power conversion efficiency (PCE) has reached 12.9% for laboratory cells and 9.9 % for PV modules 5. In ambient light the DSC outperforms all other PV cells. Solid-state devices using perovskite light harevsters currently attain 12% PCE.6,7
Excellent long-term stability has fostered first commercial applications, the industrial production of DSC’s exceeding presently the MW/year scale. The direct generation of fuels, such as hydrogen from water and sunlight has furthermore been achieved by the judicious design of photosystems composed of nanostructured Fe2O3 or Cu2O films 8.
Figure 1. Left: Schematic presentation of a solar cell based on the sensitization of nanocrystalline TiO2 particles (grey colour by dye molecules (red color). Right: Mesoscopic iron oxide (hematite) film accomplishing water cleavage by visible light.
Professor at the Ecole Polytechnique Fédérale de Lausanne Michael Graetzel directs there the Laboratory of Photonics and Interfaces. He pioneered the use of mesoscopic materials in energy conversion devices including photovoltaic cells, photo-electrochemical devices for the generation of fuels by sunlight as well as lithium insertion batteries.
He discovered a new type of solar cell based on dye sensitized nanocrystalline oxide films. His recent awards include the Swisselectric Research Award. the Albert Einstein World Award of Science, the Paul Karrer Gold Medal, the 2010 Millenium Technology Grand Prize and the 2009 Balzan Prize. He received a doctoral degree in Natural Science from the Technical University Berlin and nine honorary doctor's degrees from European and Asian Universities.
Author of over 1000 publications, which received over 100'000 citations (H-factor 151) and several books, he is a fellow of the European Academy of Science and of the Royal Society of Chemistry (UK) as well as a Max Planck Fellow, and a Honorary member of the Société Vaudoise de Sciences Naturelles.
Onsdag 15. mai kl. 13.15 i Auditorium 2, Kjemisk institutt, Universitetet i Oslo.
Michael Grätzel, Ecole Polytechnique de Lausanne Switzerland
The performance of solar energy conversion devices employing mesoscopic photoelectrodes depends critically on the mesostructure. This is evident for the dye sensitized solar cell (DSC) where charge percolation through the TiO2 nanoparticle network to the transparent conductive (TCO) electrodes takes milliseconds.
Slow charge extraction increases chances of electron-hole recombination at the mesoporous oxide - electrolyte interface, and limits DSCs to be used with only a few electrolytes or hole conductors that offer low recombination rates. These limitations can be overcome by judicious molecular engineering of the sensitizer and with advanced nanostructuring techniques. Here we describe our latest advances in optimizing the photon harvesting and the charge transport in these solar conversion systems by applying novel mesoscopic film structures.
We shall describe the dynamics of the salient electron transfer and transport processes involved in the solar light harvesting and conversion including femotsecond charge carrier generation by interfacial electron transfer from the excited sensitizer in the conduction band of the oxide nanoparticles. Strikingly high efficiency and excellent stability has been reached rendering these systems competitive with conventional p-n junction solar cells.
Figure 1. Mesoporous TiO2 beads for high performance dye sensitized solar cells.
Literature: F. Sauvage, D. Chen, P. Comte, F. Huang, L.-P. Heiniger, Y.-B. Cheng, R.A. Caruso, M. Graetzel "Dye-Sensitized Solar Cells Employing a Single Film of Mesoporous TiO2 Beads Achieve Power Conversion Efficiencies Over 10%" ACS-Nano 4, No. 8, 4420-4425 (2010)