"Photon Splitting: From One to Four Charge Carriers"

Researchers have recorded an ultrafast movie of the photon-to-electricity conversion process in pentacene, a molecular material that shows conversion of one photon into four charges, instead of the usual two. This excitation doubling, called exciton fission, could be extremely useful for high-efficiency photovoltaics. The researchers used time- and angle-resolved photoemission spectroscopy to observe the dynamics of electrons on the femtosecond time scale, which is a billionth of a millionth of a second, and captured images of the fleeting excited electrons for the first time. They identified the mechanism of the free charge carrier-doubling process, which is crucial for the use of organic semiconductors in innovative photovoltaic applications and to further boost the conversion efficiency of today's solar-cells.