Charge carrier dynamics in organic semiconductors by position dependent optical probing

We investigate charge carrier transport in poly-(3-hexylthiophene) films where sizable lateral photovoltaic effects are observed. Spatiotemporal measurements of the lateral photovoltage (LPV) using a local optical probe are carried out on device structures consisting of the semiconducting polymer film with a Schottky-type backcontact and a front pair of Ohmic contacts. We employ a spreading impedance approach in the context of a discrete circuit element model to obtain a quantitative understanding of the spatial dependence and the frequency response of the lateral photovoltage. An excellent agreement between theoretical model and experiment is found, leading to an understanding of the origin of LPV in organic systems.