Polymer dielectrics with intrinsic mechanical flexibility are considered as a key component for flexible organic field-effect transistors (OFETs). However, it remains a challenge to fabricate highly aligned organic semiconductor single crystal (OSSC) arrays on the polymer dielectrics. Herein, for the first time, a facile and universal strategy, polar surface-confined crystallization (PSCC), is proposed to grow highly aligned OSSC arrays on poly(4-vinylphenol) (PVP) dielectric layer. The surface polarity of PVP is altered periodically with oxygenplasma treatment, enabling the preferential nucleation of organic crystals on the strong-polarity regions. Moreover, a geometrical confinement effect of the patterned regions can also prevent multiple nucleation and misaligned molecular packing, enabling the highly aligned growth of OSSC arrays with uniform morphology and unitary crystallographic orientation. Using 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene (C8-BTBT) as an example, highly aligned C8-BTBT single crystal arrays with uniform molecular packing and crystal orientation are successfully fabricated on the PVP layer, which can guarantee their uniform electrical properties. OFETs made from the C8-BTBT single crystal arrays on flexible substrates exhibit a mobility as high as 2.25 cm 2 V −1 s −1 , which has surpassed the C8-BTBT polycrystalline film-based flexible devices. This work paves the way toward the fabrication of highly aligned OSSCs on polymer dielectrics for high-performance, flexible organic devices.

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