Thursday, 15 September, 2011
Reduced Charge Transfer Exciton Recombination in Organic Semiconductor Heterojunctions by Molecular Doping
F. Deschler, E. Da Como, T. Limmer, R. Tautz, T. Godde, M. Bayer, E. von Hauff, S. Yilmaz, S. Allard, U. Scherf, and J. Feldmann -
Phys. Rev. Lett., Vol. 107 (12), 127402 (2011)
We investigate the effect of molecular doping on the recombination of electrons and holes localized at conjugated-polymer–fullerene interfaces. We demonstrate that a low concentration of p-type dopant molecules (<4% weight) reduces the interfacial recombination via charge transfer excitons and results in a favored formation of eparated carriers. This is observed by the ultrafast quenching of photoluminescence from charge transfer excitons and the increase in photoinduced polaron density by ∼70%. The results are consistent with a reduced formation of emissive charge transfer excitons, induced by state filling of tail states.