All Electrohydrodynamic Printed Flexible Organic Thin Film Transistors

The demand of cost-effective fabrication of printed flexible transistors has dramatically increased in recent years due to the need for flexible interface devices for various application including e-skins, wearables, and medical patches. In this study, electrohydrodynamic (EHD) printing processes are developed to fabricate all the components of polymer-based organic thin film transistors (OTFTs), including source/drain and gate electrodes, semiconductor channel, and gate dielectrics, which streamline the fabrication procedure for flexible OTFTs. The flexible transistors with top-gate-bottom-contact configuration are fabricated by integrating organic semiconductor (i.e., poly(3-hexylthiophene-2,5-diyl) blended with small molecule 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene), conductive polymer (i.e., poly (3,4-ethylenedioxythiophene) polystyrene sulfonate), and ion-gel dielectric. These functional inks are carefully designed with orthogonal solvents to enable their compatible printing into multilayered flexible OTFTs. The EHD printing process of each functional component is experimentally characterized and optimized. The fully EHD-printed OTFTs show good electrical performance with mobility of 2.86 x 10(-1) cm(2) V-1 s(-1) and on/off ratio of 10(4), and great mechanical flexibility with small mobility change at bending radius of 6 mm and stable transistor response under hundreds of bending cycles. The demonstrated all printing-based fabrication process provides a cost-effective route toward flexible electronics with OTFTs.