Field induced electro-optical characterization in poly-3-hexylthiophene MIS capacitor

We investigated the electro-optical properties of the transmitted light in MIS capacitor consisting of P3HT/polyimide double-layered device by optical charge modulation spectroscopy (CMS) technique. A pronounced charge-induced subgap transition, the direct evidence for the polaronic nature of the transition from delocalized polaron, was observed in accumulation in the wave length between 650 nm and 1100 nm, and it almost disappeared in fully depletion of positive gate voltage. The charge induced optical transition measured at 766 nm increases linearly with the amplitude of AC modulation in accumulation, whereas it was suppressed when the positive large gate bias was applied to the film. On the other hand, the CMS curves observed between 460 nm and 650 nm changed a little with gate voltage and it was considered as the electro-absorption effect related to the interfacial traps at P3HT/polyimide interface.