A Facile Method for the Growth of Organic Semiconductor Single Crystal Arrays on Polymer Dielectric toward Flexible Field‐Effect Transistors

Abstract

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.

Large-scale patterning of π-conjugated materials by meniscus guided coating methods

“…The ribbon width monotonically decreases with increasing dip-coating speed. The average ribbon thickness was determined to be approximately of 14 and 65 nm for withdrawing speed of the substrate of U = 0.02 and 0.07 mm/s, respectively, which is consistent with the expected trend that the average film thickness is inversely facile, and effective polar surface-confined crystallization (PSCC) method to achieve highly aligned OSSCs on the polymer dielectric, [78]. In this method, patterned PVP surface with alternating polarity difference was used as a growth substrate to guide the aligned growth of OSSCs.…”

Heterogeneous Wettability Surfaces: Principle, Construction, and Applications

“…The patterning of sacrificial coating is realized by printing or photolithography of a photoresist. [ 39,40 ] After plasma treatment, the regions without coating become more wettable. The sacrificial coating can be easily removed by washing with water or organic reagents (Figure 2d).…”

“…The heterogeneous wettability substrate exhibits excellent capability in precise liquid manipulation, and it has attracted enormous research interest for various applications by rational design of the wettability heterogeneity on the surface. For example, high-quality organic semiconductor single crystal arrays are facilely patterned on heterogeneous wettability substrates for flexible field-effect transistors (FETs), [39] and nanoliter-scale sample droplets with concentration as low as femtoliter mole are detected through the coupling effect of enrichment and surface-enhanced Raman scattering (SERS) on Au-areole-deposited wettability-patterned substrates. [35] In this section, we summarize typical applications focused on optic/electronic device fabrication and biosensing/detection using heterogeneous wettability surfaces.…”

“…Jie and coworkers fabricated more wettable/less wettable alternate stripes on a poly(4‐vinylphenol) (PVP) film for growth of organic semiconductor single crystal arrays. [ 39 ] When they blade‐coated the organic semiconductor single crystal precursor with toluene as the solvent on the patterned PVP film, the precursor only adhered to the more wettable stripes, due to its stronger polarity and larger surface adhesion, rather than on the less wettable regions ( Figure a). With the evaporation of the solvent, the organic molecules nucleated and crystallized into a highly ordered crystal array.…”

“…Reproduced with permission. [ 39 ] Copyright 2019, Wiley‐VCH. c) Spin coating of a perovskite organic precursor on a patterned‐wettability substrate to fabricate a single crystal array.…”