Polymer photovoltaics is currently the only technology which can solve major problems with manufacturing cost and speed facing all other photovoltaic technologies. In spite of many advantages, however, the efficiency of polymer solar cells is still rather low compared to silicon-based solar cells.
In a recent paper published in Physical Review Letters, we investigate one of the crucial mechanisms which limit the efficiency of polymer solar cells. We use a unique optical technique, known as ultrafast time-resolved THz spectroscopy, which directly monitors the electric conductivity of the electrical charges generated by light in the solar cell with unprecedented time resolution. Our measurements reveal that within the polymer solar cell, only one third of the electric charges generated by the incoming light are available for current generation in the solar cell device, while the remaining two thirds of the charges are trapped. A modification of this ratio will directly influence the overall efficiency of the solar cell. This gives solar cell developers an invaluable experimental tool in the quest to increase the efficiency of next generation solar cells by new polymer chemistry and device design.
The investigation was spearheaded by Dr. David Cooke, who is now heading the Ultrafast THz Laboratory at McGill University, Montreal, Canada, in close collaboration with world-leading polymer solar cell expert, Prof. Frederik Krebs, Department of Energy Conversion and Storage at the Technical university of Denmark.
Read the official DTU press release (in Danish).