Thin Film Growth of a Charge Transfer Cocrystal (DCS/TFPA) for Ambipolar Thin Film Transistors

The highly luminescent dicyanodistyrylbenzene-based charge-transfer (CT) cocrystal based on isometric donor and acceptor molecules with a mixing ratio of 2:1 is characterized in the thin film regime. Physical vapor deposited films prepared at different substrate temperatures are analyzed in terms of their thin film structure and transistor performance. The thin film morphologies and crystallographic properties including microstrain and mosaic spread strongly dependent on the substrate temperature. Enhanced crystal growth with rising temperatures leads to a better transistor performance reaching its maximum at 90 °C with a hole and electron mobility of 1.6 × 10^-3 and 2.3 × 10^-5 cm² V^-1 s^-1, respectively. At higher temperatures performance decreases limited by percolation pathways between the enlarged crystals.