Interchain effects in the ultrafast photophysics of a semiconducting polymer: THz time-domain spectroscopy of thin films and isolated chains in solution
Schins, Juleon M.
Nienhuys, H. K.
Siebbeles, L. D. A.
University of Exeter (at the time of publication Euan Hendry was affiliated to Leiden University and FOM Institute for Atomic and Molecular Physics); Leiden University; FOM Institute for Atomic and Molecular Physics, Amsterdam; Delft University of Technology; Lund University
Physical Review B
American Physical Society
We compare the generation and decay dynamics of charges and excitons in a model polymer semiconductor (MEH-PPV) in solution and drop-cast thin films, by recording the sub-ps transient complex conductivity using THz time-domain spectroscopy. The results show that the quantum efficiency of charge generation is two orders of magnitude smaller in solution (~10–5) than in the solid film (~10–3). The proximity of neighboring chains in the films apparently facilitates (hot) exciton dissociation, presumably by allowing the electron and hole to separate on different polymer strands. For both samples, photoexcitation leads to the predominant formation of bound charge pairs (excitons) that can be detected through their polarizability. Surprisingly, the polarizability per absorbed photon is a factor of 3 larger in solution than in the film, suggesting that interchain interactions in the film do not result in a substantial delocalization of the exciton wave function.
Euan Hendry, Mattijs Koeberg, Juleon M. Schins, H. K. Nienhuys, V. Sundström, L. D. A. Siebbeles, and Mischa Bonn, Physical Review B, Vol. 71, article 125201 (2005). "Copyright © 2005 by the American Physical Society."
71 (12), article 125201