We determine the efficiencies for the formation of excitons and charge carriers following ultrafast photoexcitation of a semiconducting polymer (MEH-PPV). The simultaneous, quantitative determination of exciton and charge photoyields is achieved through subpicosecond studies of both the real and the imaginary components of the complex conductivity over a wide frequency range. Predominantly excitons, with near-unity quantum efficiency, are generated on excitation, while only a very small fraction (<10-2) of free charges are initially excited, consistent with rapid (~100 fs) hot exciton dissociation. These initial charges are very short lived, decaying on subpicosecond time scales.

Phys. Rev. Lett.

Hendry, E., Schins, J. M., Candeias, L. P., Siebbeles, L., & Bonn, M. (2004). Efficiency of exciton and charge carrier photogeneration in a semiconducting polymer. Phys.Rev.Lett., 92(Article number: 196601), 1–4. doi:10.1103/physrevlett.92.196601