Nonthermally activated exciton transport in crystalline organic semiconductor thin films

The temperature dependent exciton transport in the prototypical organic semiconductor di-indeno-perylene (DIP) is investigated by photoluminescence quenching. Analysis by an advanced diffusion model including interference and morphological aspects reveals an exciton diffusion length of about 60 nm at room temperature, which relates to the long-range order induced by the DIP molecular shape. Above 80 K, singlet exciton transport is thermally activated with an energy of 10 to 20 meV. Below 80 K, exciton motion becomes temperature independent and is supported by the crystalline structure of the transport layer in combination with the reduced phonon interaction.