Solar Cells Research Gets a Boost
Solar Cells Research Gets a Boost with new methods for conversion of long wavelength light to shorter wavelengths
2006-10-13 11:04:29
source: CCNews
http://www.ccnmag.com/news.php?id=4530
An innovative process that converts low-energy longwave photons (light particles) into higher-energy shortwave photons has been developed by a team of researchers at the Max Planck Institute for Polymer Research in Mainz and at the Sony Materials Science Laboratory in Stuttgart. With the skillful combination of two light-active substances, the scientists have, for the first time, manipulated normal light, such as sunlight, to combine the energy in photons with particular wavelengths (Physical Review Letters, October 4, 2006). This has previously only been achieved with a similar process using high-energy density laser light. The successful outcome of this process could lay the foundation for a new generation of more efficient solar cells.
The efficiency of solar cells today is limited, among other reasons, by the fact that the longwave, low-energy part of the sunlight cannot be used. A process that increases the low level of energy in the light particles (photons) in the longwave range, shortening their wave length, would make it possible for the solar cells to use those parts of light energy that, up to now, have been lost, resulting in a drastic increase in their efficiency. The equivalent has only been achieved previously with high-energy density laser light which, under certain conditions, combines two low-energy photons into one high-energy photon – a kind of photonic fusion.
This is a significant step forward for the scientists at the Max Planck Institute for Polymer Research and at the Sony Materials Science Laboratory. In developing this process, they have succeeded, for the first time, in pairing up photons from normal light, thus altering the wavelength. They used two substances in solution, platinum octaethyl porphyrin and diphenylan-thracene, which converted the longwave green light from a normal light source into shortwave blue light. Similar to the process in laser light, this also pairs up photons, but in a different way.
When a molecule is manipulated by laser light to take up two photons, which is only probable if it is literally bombarded with a laser beam of photons, the molecules in this case only receive one photon. Two photon partners are brought together between the molecules via a different mechanism called triplet-triplet annihilation. By selecting different, corresponding “matchmaker” molecules, it is possible to combine the energy from photons from the entire sunlight spectrum.