Ultrafast dissociation of triplets in pentacene induced by an electric field

Singlet fission into a pair of triplet excitons in pentacene is envisaged to be a potential carrier multiplication route in organic photovoltaics. In order to shed light on the dissociation dynamics of the triplet states we performed electric field induced pump-probe experiments on polycrystalline films of pentacene. We find that the nascent triplet pair formed immediately after the fission process is susceptible to dissociation in the presence of the electric field. By measuring the temporal dynamics of the dissociation, we estimate its binding energy to be approximately 320 meV. After about 2 ps the triplets diffuse away from each other and the field assisted dissociation is substantially reduced. Our results suggest that if the nascent triplet pairs could be harvested at the interface in a device, the efficiency of the process would be higher.