Field-assisted femtosecond pump/probe measurements on conjugated systems

The exciton dissociation in presence of an electric field is investigated in light emitting diodes of ladder-type poly(para-phenylene). The experimental setup allows us to directly observe the dynamics of the dissociation process with femtosecond-time resolution. Charge carriers are generated by two separate mechanisms. For early times, we observe an intra-chain dissociation corresponding to breaking during spectral relaxation. For longer times, we observe a time independent dissociation mechanism due to on-chain dissociation.