High-Speed Production of Crystalline Semiconducting Polymer Line Arrays by Meniscus Oscillation Self-Assembly

Evaporative self-assembly of semiconducting polymers is a low-cost route to fabricating micrometer and nanoscale features for use in organic and flexible electronic devices. However, in most cases, rate is limited by the kinetics of solvent evaporation, and it is challenging to achieve uniformity over length- and time-scales that are compelling for manufacturing scale-up. In this study, we report high-throughput, continuous printing of poly(3-hexylthiophene) (P3HT) by a modified doctor blading technique with oscillatory meniscus motion-meniscus-oscillated self-assembly (MOSA), which forms P3HT features ∼100 times faster than previously reported techniques. The meniscus is pinned to a roller, and the oscillatory meniscus motion of the roller generates repetitive cycles of contact-line formation and subsequent slip. The printed P3HT lines demonstrate reproducible and tailorable structures: nanometer scale thickness, micrometer scale width, submillimeter pattern intervals, and millimeter-to-centimeter scale coverage with highly defined boundaries. The line width as well as interval of P3HT patterns can be independently controlled by varying the polymer concentration levels and the rotation rate of the roller. Furthermore, grazing incidence wide-angle X-ray scattering (GIWAXS) reveals that this dynamic meniscus control technique dramatically enhances the crystallinity of P3HT. The MOSA process can potentially be applied to other geometries, and to a wide range of solution-based precursors, and therefore will develop for practical applications in printed electronics.

Three-dimensional micropatterning of semiconducting polymers via capillary force-assisted evaporative self-assembly

Controlled evaporative self-assembly of semiconducting polymers has mostly been studied on 2-dimensional flat substrates. In this study, we reported capillary-assisted evaporative self-assembly of poly(3-hexylthiophene 2,5-diyl) (P3HT) into 3-D micro-ring patterns through the stick-slip phenomenon within a 3-dimensional cylinder. We deconvoluted the well-known two-step stick-slip phenomenon into three regimes through in situ monitoring of the P3HT self-assembly process using a high-speed camera: pinning and deposition; depinning and slip; and retraction regimes. Furthermore, we investigated the effects of various parameters associated with the self-assembly, including polymer concentration, tilt angle, magnetic field, and evaporation temperature, thus achieving self-assembled microarchitectures with diverse dimensions ranging from dots to lines and networks. The self-assembled microstructures were analyzed qualitatively and quantitatively by evaluating the fast Fourier transform image, surface coverage, fractal dimension and lacunarity of the micropatterns.

One-step assembly of multi-layered structures with orthogonally oriented stripe-like patterns on the surface of a capillary tube

We developed a robust method to construct large-scale multi-layered assemblies with orthogonally oriented stripes on a capillary tube using a confined evaporative self-assembly (CESA) method. A mixture of conductive polymer poly(3-hexylthiophene) (P3HT) and biocompatible polylactic acid (PLA) was chosen as the model polymer and the molecular chain orientation of P3HT in an individual stripe could be assessed by laser confocal polarization Raman spectroscopy. These structures could provide contact cues to guide the growth of smooth muscle cells for potential tissue engineering applications.

Unraveling the real structures of solution-based and surface-bound poly(3-hexylthiophene) (P3HT) oligomers: a combined theoretical and experimental study

While the crystalline structure for regio-regular poly(3-hexylthiophene) (P3HT) in thin films is well established, the conformation of P3HT chains in solution has received less attention.

Integration of poly(3-hexylthiophene) conductive stripe patterns with 3D tubular structures for tissue engineering applications

P3HT was self-assembled into large-scale conductive stripe patterns based on confined evaporative self-assembly. These conductive stripe patterns could induce cell alignment and provide spatial electric signals to modulate cellular behaviors.

Si-nanocrystal/P3HT hybrid films with a 50- and 12-fold enhancement of hole mobility and density: films prepared by successive drop casting

Hybrid silicon nanocrystal (Si-NC)/poly(3-hexylthiophene) (P3HT) films serve as the active layers of quantum dot/polymer hybrid photovoltaics. To achieve effective photovoltaic properties, it is necessary to enhance the charge carrier mobility and carrier density of the P3HT films. A 50- and 12-fold enhancement of the hole mobility and hole density, respectively, was achieved along the out-of-plane direction of a Si-NC/P3HT hybrid film, which corresponds to the carrier-migration direction between the photovoltaic electrodes. According to time-of-flight, electronic absorption, Raman, atomic force microscopy, photoluminescence lifetime, and X-ray diffraction measurements, the significant enhancement of the mobility and density was attributed to both an increase in the P3HT crystallinity and the dissociation efficiency of P3HT excitons on the addition of Si-NCs to the P3HT films. These enhancements were achieved using a film preparation method developed in the present study, which has been named successive drop casting.

Self-assembly of large-scale P3HT patterns by confined evaporation in the capillary tube

Large-scale P3HT stripe patterns based on a controlled evaporation self-assembly method in a capillary tube have been fabricated.

Large-scale highly ordered hierarchical structures of conjugated polymer via self-assembly from mixed solvents

Highly-ordered large scale patterns of poly(3-hexylthiophene) (P3HT) can be produced via confined evaporative self-assembly (CESA) from mixed solvents in one-step.