Direct visualization and modeling of carrier distribution in organic light emitting transistor

• Carrier distribution in organic light emitting transistor channel was determined.
• Second-harmonic generation images were clearly observed in the emission region.
• A transmission line model well accounted for the observed carrier behavior.

By using microscopic electric field induced second harmonic generation (EFISHG) measurement, we studied the carrier distribution in the channel of organic light emitting transistors with an active layer of poly(9,9-di-n-octylfluorene-alt-benzothiadiazole). EFISHG signals were clearly observed in the point where the electroluminescence is generated. Results suggested that the highest enhancement of the electric field is on zero-potential position in the channel, which represents the meeting point of electrons and holes and is an origin of the electroluminescence. The transmission line model analysis of the carrier distribution of the channel supported this conclusion.