Efficient Solvent-Assisted Post-Treatment for Molecular Rearrangement of Sprayed Polymer Field-Effect Transistors

Polymer-based field-effect transistors are fabricated using the gas-assisted spray technique, and their performance is considerably improved when a solvent-assisted post-treatment method, solvent sprayed overlayer (SSO), is used. The SSO method is a unique treatment that can facilitate chain packing to increase crystallinity within the sprayed polymer layers, which inherently have a kinetically trapped amorphous chain morphology with lack of crystallinity due to rapid solvent evaporation. The device performance was drastically improved after SSO relative to conventional post-treatment, thermal annealing (TA). This occurred because SSO can rearrange the polymer chains into a dominantly edge-on crystal orientation, which is preferential for charge transport, whereas TA increases the crystallinity without rearrangement of the crystal orientation resulting in a complex of edge-on and face-on. The development of edge-on crystal domains after SSO within the active layers was responsible for the significant improvement in performance. The SSO is a simple and effective post-treatment method that validates the use of spray process and holds promise for use in other high-throughput processes for OFETs fabrication.