Directionally Patterned Large-Area Poly(3-hexylthiophene) Field-Effect Transistors via Flow-Blade Printing Method Using Coffee-Ring Effect: Uniform Performance Regardless of Pattern Fabrication Condition and Applications

To apply the solution-processed organic field-effect transistors (OFETs) to practical device manufacturing, there is a need for a processing technology capable of patterning organic semiconductors with high reproducibility and uniform shape in a large area. Herein, the facile, scalable strategy to fabricate poly(3-hexylthiopehene-2,5-diyl) (P3HT) patterns through the flow-blade coating process. Controlling the stick-slip motion by the coffee-ring effect in low-/high-speed conditions induces the repetition of the advancing and receding of the contact line of the solution, which enables us to fabricate deposition of P3HT in low-speed regions and spacing in high-speed regions. Various surface-modified dielectrics with self-assembled monolayers (SAMs) influenced the morphological properties of patterned P3HT and indicated that the optimum condition for OFETs was achieved in alkyl-terminated SAM-treated cases. Additionally, various analysis tools including grazing-incidence wide-angle X-ray diffraction and near-edge X-ray absorption fine structure reveals that the flow-blade coating produces P3HT patterns with enhanced edge-on orientation compared to spin-casting and forms electrically and morphologically consistent films regardless of the pattern width. As a result, the practical large-area integrated OFET arrays on 4 in. wafer substrate exhibited highly uniform electrical characteristics (average field-effect mobility of 0.095 cm2/(V s)) with a deviation value of 0.0109.