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The self‐organization of organic polymer semiconductors into ordered supramolecular assemblies commensurate with efficient charge transport is achieved by tuning a range of process parameters (e.g., film deposition method (spin vs drop cast), solvent boiling point (low vs high boiling point), polymer‐dielectric interface treatment, and post‐deposition processing (solvent vapor or thermal annealing)). However, these strategies present limitations for large‐scale high‐throughput processing due to associated pre‐ and/or post semiconductor deposition steps. Here, photoinduced anisotropic supramolecular assembly of P3HT chains in solution is demonstrated. UV irradiation provides for enhanced intramolecular ordering of solubilized polymer chains, and thereby effects formation of anisotropic supramolecular polymer assemblies via favorable π–π stacking (intermolecular interaction). Molecular ordering is thus dramatically enhanced with concomitant, enhanced charge transport characteristics of corresponding films. Additional pre‐ and/or post treatments are avoided.

Abstract1D poly(3,4‐ethylenedioxythiophene) (PEDOT) nanomaterials, including ellipsoidal nanoparticles, nanorods, and nanotubes, are fabricated via chemical oxidation polymerization in reverse (water‐in‐oil) microemulsions. The reverse cylindrical micelles are prepared with sodium bis(2‐ethylhexyl) sulfosuccinate (AOT) and aqueous FeCl3 solution in hexane. The morphology of the final products is determined by carefully tuning the degree of oxidation potential at the micelle surface. Notably, the fabrication of gram‐scale amounts of products is possible under optimized synthetic conditions, suggesting that this methodology is appropriate for the large‐scale production of the corresponding nanomaterials. The as‐prepared PEDOT nanomaterials are applied to the precise detection of alcohol vapors. The chemical sensors based on the PEDOT nanomaterials present excellent reversibility and reproducibility in response.

An inverse relationship between mechanical ductility and mobility/molecular ordering in conjugated polymer systems was determined definitively through systematic interrogation of poly(3-hexylthiophene) (P3HT) films with varied degrees of molecular ordering and associated charge transport performance. The dilemma, whereby molecular ordering required for efficient charge transport conclusively undermines the applicability of these materials for stretchable, flexible device applications, was resolved using a polymer blend approach. Specifically, the molecular interactions between dissimilar polymer materials advantageously induced semiconducting polymer ordering into efficient π−π stacked fibrillar networks. Changes in the molecular environment surrounding the conjugated polymer during the elastomer curing process further facilitated development of high mobility networked semiconductor pathways. A processed P3HT: poly(dimethylsiloxane) (PDMS) composite afforded a semiconducting film that exhibits superior ductility and notable mobility versus the single-component polymer semiconductor counterpart.

We demonstrate that supramolecular assembly and subsequent enhancement of charge transport characteristics of conjugated polymers can be facilitated simply by adding small amounts of a more volatile poor solvent, which can hydrogen bond with the majority solvent. Addition of up to 2 vol % acetone to a precursor solution of poly(3-hexylthiophene) (P3HT) in chloroform leads to approximately a 4-fold increase in P3HT field-effect mobility. The improvement is associated with hydrogen bonding interactions between acetone and chloroform which decrease the evaporation rate of the mixed solvent. P3HT is less soluble in the binary solvent than in the more readily vaporized chloroform component, and this characteristic enables the supramolecular assembly of P3HT chains at the nanoscale. Two-dimensional molecular ordering of the polymer film was controlled by varying the quantity of poor solvent added to the precursor solution, and the correlation between field-effect mobility and molecular ordering was investigated. Hansen solubility parameters were used to systematically understand how the solvent mixture enhances the alignment and assembly of polymer chains and influences subsequent thin film properties. The value of the relative energy difference (RED) of the solvent with respect to P3HT increased from less than 1 to more than 1 during film formation, which indicates that the solvent characteristics are initially those of a good solvent but transform into those of a poor dissolution medium. A mechanistic illustration of the molecular ordering process during film formation is postulated.

Very few studies have reported oriented crystallization of conjugated polymers directly in solution. Here, solution crystallization of conjugated polymers in a microfluidic system is found to produce tightly π-stacked fibers with commensurate improved charge transport characteristics. For poly(3-hexylthiophene) (P3HT) films, processing under flow caused exciton bandwidth to decrease from 140 to 25 meV, π-π stacking distance to decrease from 3.93 to 3.72 Å and hole mobility to increase from an average of 0.013 to 0.16 cm(2) V(-1) s(-1), vs films spin-coated from pristine, untreated solutions. Variation of the flow rate affected thin-film structure and properties, with an intermediate flow rate of 0.25 m s(-1) yielding the optimal π-π stacking distance and mobility. The flow process included sequential cooling followed by low-dose ultraviolet irradiation that promoted growth of conjugated polymer fibers. Image analysis coupled with mechanistic interpretation supports the supposition that "tie chains" provide for charge transport pathways between nanoaggregated structures. The "microfluidic flow enhanced semiconducting polymer crystal engineering" was also successfully applied to a representative electron transport polymer and a nonhalogenated solvent. The process can be applied as a general strategy and is expected to facilitate the fabrication of high-performance electrically active polymer devices.

Controlling the morphology of polymer semiconductors remains a fundamental challenge that hinders their widespread applications in electronic and optoelectronic devices and commercial feasibility. Although conjugated polymer nanowires (NWs) are envisioned to afford high charge-carrier mobility, the alignment of preformed conjugated polymer NWs has not been reported. Here, we demonstrate an extremely simple and effective strategy to generate well-aligned arrays of one-dimensional (1D) polymer semiconductors that exhibit remarkable enhancement in charge transport using a solution shear-coating technique. We show that solution shear coating of poly(alkylthiophene) NWs induces extension or coplanarization of the polymer backbone and highly aligned network films, which results in enhanced intra- and intermolecular ordering and reduced grain boundaries. Consequently, highly aligned poly(3-hexylthiophene) NWs exhibited over 33-fold enhancement in the average carrier mobility, with the highest mobility of 0.32 cm(2) V(-1) s(-1) compared to pristine films. The presented platform is a promising strategy and general approach for achieving well-aligned 1D nanostructures of polymer semiconductors and could enable the next generation of high-performance flexible electronic devices for a wide range of applications.

Poly(3-hexylthiophene) (P3HT) in trichlorobenzene solution self-assembles and exhibits liquid crystal ordering when confined to rectangular capillaries. The relative proportion of polymer assemblies increases with time, as determined by UV−vis spectroscopic analysis. Polarized optical microscopy (POM) reveals development of birefringence and monodomainlike long-range ordering. Micro-Raman spectroscopy was used to calculate the orientational order parameters, ⟨P 2 ⟩ and ⟨P 4 ⟩, of the liquid-crystalline P3HT solutions. The order parameter ⟨P 2 ⟩ increased with time up to 0.35, indicating increased anisotropy. The calculated depolarization ratio (ρ v ) from depolarized dynamic light scattering measurements points to the time-dependent formation of highly ordered P3HT nanostructures, whereas cryogenic transmission electron microscopy was employed for the direct visualization of the rodlike assemblies. POM shows that the observed anisotropy can be preserved in P3HT films drawn from aged solutions. These results suggest that P3HT self-assembly leads to a liquid-crystalline solution of conjugated polymer aggregates, which may lead to a viable approach for optimization of processes for organic electronic device applications. Such ordered and oriented conjugated polymer assemblies have many desirable attributes for high-performance device applications, where the ability to control nanothrough macroscale molecular ordering is required.