Bar‐Coated Organic Thin‐Film Transistors with Reliable Electron Mobility Approaching 10 cm² V⁻¹ s⁻¹

Abstract

Abstract The realization of high‐performance n‐type organic thin‐film transistors (OTFTs) via solution processing remains challenging, while these devices are considered highly desirable as basic elements for organic circuits. Apart from the designing of semiconducting materials, the controlling of thin‐film microstructures using specific processing techniques is also effective to enhance OTFT performance. In this work, bar coating—a meniscus‐guided and high throughput production compatible technique—is utilized to orient a diketopyrrolopyrrole‐based conjugated polymer (P4FTVT‐C32) for uniaxially aligned thin film with large crystalline grains, assisted by polyethylenimine ethoxylated interlayer. The anisotropic molecular arrangement of the bar‐coated thin films is confirmed by X‐ray diffraction, atomic force microscopy, and polarized UV−vis absorption analyses. OTFTs based on the oriented thin films exhibit remarkable charge transport anisotropy. High saturation and linear mobility up to 9.38 and 8.35 cm 2 V −1 s −1 along with high on/off ratio of 10 5 –10 6 is achieved when the electric field is parallel to the coating direction. These are the highest reliable electron mobilities obtained from solution‐processed OTFTs, considering their high reliability factor >80%. These results demonstrate that the electron mobility of conjugated polymers can be significantly improved by proper solution processing at optimized interfaces.