As in more traditional organic polymer thin-film solar cells, the polymer material in the experimental system absorbs photons of light. To convert this energy to electricity, each photon-absorbing electron must split apart from its hole companion at the interface of the polymer and the nanowire a region known as the p-n junction.
Once the electron and hole split, the electron travels down the nanowire the electron superhighway and merges seamlessly with the electron-capturing electrode. This rapid shuttling of electrons from the p-n junction to the electrode could serve to make future photovoltaic devices made with polymers more efficient.
In effect, we used nanowires to extend an electrode into the polymer material, said co-author Edward Yu, a professor of electrical engineering at UCSDs Jacobs School of Engineering.
While the electrons travel down the nanowires in one direction, the holes travel along the nanowires in the opposite direction until the nanowire dead ends. At this point, the holes are forced to travel through a thin polymer layer before reaching their electrode.
Todays thin-film polymer photovoltaics do not provide freed electrons with a direct path from the p-n junction to the electrode a situation which increases recombination between holes and electrons and reduces efficiency in converting sunlight to electricity. In many of todays polymer photovoltaics, interfaces between two different polymers serve as the p-n junction. Some experimental photovoltaic designs do include nanowires or carbon nanotubes, but these wires and tubes are not electrically connected to an electrode. Thus, they do not minimize electron-hole recombination by providing electrons with a direct path from the p-n junction to the electrode the way the new UCSD design does.
Before these kinds of electron superhighways can be incorporated into photovoltaic devices, a series of technical hurdles must be addressed including th
|Contact: Daniel Kane|
University of California - San Diego