Terahertz study of ambipolar transport in the semiconducting polymer poly-diketopyrrolopyrrole-terthiophene (PDPP3T)

Abstract

Terahertz electromodulation spectroscopy is used to investigate charge transport in the semiconducting polymer poly-diketopyrrolopyrrole-terthiophene (PDPP3T). Both electrons and holes show band transport with a preferential conduction along the polymer chain. In devices with oriented thin-films, mobilities of 2.0 and 12.8 cm2/V s are measured for electrons and holes, respectively. Temperature-resolved and long-time measurements suggest that only a fraction of the injected charge carriers participate in band transport. Carrier trapping into localized states is identified as the major factor that limits the overall mobilities. According to the Ioffe–Regel criterion, the material's inherent mobilities are expected to significantly exceed the observed values.