Photocurrent EDMR Measurement and Carrier Behavior of TIPS-Pentacene Under FET Device Operation

The carrier dynamics of the organic semiconductor materials plays very important role in the device applications, because it is strongly related to the device performance. We report the electrically detected magnetic resonance (EDMR) study of a drop-casted film of 6,13–bis((triisopropylsilyl)ethynyl)pentacene (TIPS-Pn) under the field-effect transistor (FET) device operating condition. The EDMR signal could not be observed without light-irradiation even under the FET device operating condition (carrier injected condition). This means that the electrically injected carries (e–h pair) do not have spin polarization and notable spin-selective pathway after the charge injection. Under the light irradiation, the EDMR signals were detected in the FET device both with and without the V_GS (gate-source voltage applied to the FET device) and the intensity depended on the V_GS. When 0 > V_GS > V_TH, which is near the threshold voltage of the carrier injection, the signal intensity increased with increasing |V_GS| but in the region V_GS < V_TH (|V_GS| >|V_TH|), the EDMR intensity decreased. This phenomenon has been reproduced by solving the rate equations assuming the re-combination between the photo generated electron (pe) and the injected hole (h), which is strong related to the device structures.