Article pubs.acs.org/JPCC
Charge-Transfer Dynamics in Poly(3hexylthiophene):Perylenediimide‑C60 Blend Films Studied by Ultrafast Transient Absorption Kimmo M. Kaunisto,* Paola Vivo, Rajeev K. Dubey,† Vladimir I. Chukharev, Alexander Efimov, Nikolai V. Tkachenko, and Helge J. Lemmetyinen Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere, Finland ABSTRACT: Electron-transfer characteristics of 1,7-dipyrrolidinyl-substituted perylenediimide-fullerene (PyPDI-C60) dyad were studied in solid films by an ultrafast transient absorption technique. The research was further expanded to study a poly(3hexylthiophene) (P3HT):PyPDI-C60 blend to reveal the charge-transfer processes that take place in bulk heterojunction films, which are potentially suitable for photovoltaic applications. This knowledge is of paramount importance when designing organic photovoltaics since the performance of thin film devices is affected by mechanisms taking place at the molecular level upon photoexcitation. It was demonstrated that the chargeseparated state, formed after an electron transfer from the PyPDI to the fullerene moiety of the dyad, has a lifetime of tens of picoseconds. A charge-separated state in which the hole is localized in the P3HT and the electron is in the fullerene moiety with a lifetime of
