Charge carrier dynamics at organic interfaces for polymer photovoltaics

The increased energy demand and the importance to find renewable energy resources have been addressed by a scientific effort to improve the power conversion efficiency of organic solar cells. In particular, polymer-based solar cells have experienced a great increase in power conversion efficiency, which recently reached a value over 10%. The possibility to further improve the performance of polymer-based solar cells has encouraged the research to have a close look at the key parameters, which play an important role in the mechanism of charge generation. Specifically, the photo-physical processes and the time scales involved in converting excitons to charges are still poorly understood. Also, the microscopic origin and the nature of the driving force allowing interfacial electron-hole pairs to become free charges and the role played by the sample microstructure in a bulk heterojunction have to be clarified. We have used transient absorption spectroscopy, which provides information about the excited states dynamics with