Fast Deposition of Aligning Edge‐On Polymers for High‐Mobility Ambipolar Transistors

Large‐area few‐layer polymer films are prepared using bar‐coating methods at a speed of 120 mm s⁻¹. The morphology and crystalline analysis indicates that the polymer grains are uniformly oriented and the polymer backbones are in the same direction. The resulting mobility is up to 5.5/4.5 cm² V⁻¹ s⁻¹, which is nine times higher than spin‐coating case.

Abstract

Fast deposition of aligning ambipolar polymers for high‐performance organic field‐effect transistors (OFETs) and inverter circuits are highly desired for both scientific studies and industry applications. Here, large‐area and ordered polymer films are prepared by a bar‐coating method at a rate of 120 mm s⁻¹ in air. Atomic force microscopy and grazing‐incidence wide‐angle X‐ray scattering analysis indicate uniform edge‐on poly(fluoroisoindigo‐difluorobithiophene‐fluoroisoindigo‐bithiophene) (PFIBI‐BT) in 11.7 ± 1 nm film (≈5 layers). The elongated, uniformly oriented grains can reduce the adverse effects of the grain boundaries and facilitate charge transport in polymers. Furthermore, OFETs based on parallel film show high hole/electron mobilities up to 5.5/4.5 cm² V⁻¹ s⁻¹, which are approximately nine times of the devices prepared by spin‐coating. The gain of the inverter is as high as 174, which is one of the highest values in polymer inventers currently. These results demonstrate that the excellent bipolar performance of few‐layer PFIBI‐BT can be ensured while achieving the compatibility of the experimental process with industrial preparation.

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