High, Anisotropic, and Substrate-Independent Mobility in Polymer Field-Effect Transistors Based on Preassembled Semiconducting Nanofibrils

Nanostructured Molecular Packing of Polymer Films Formed on Water Surfaces

In this study, we examined the nanostructured molecular packing and orientations of poly[[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)] (P(NDI2OD-T2)) films formed on water for the application of nanotechnology-based organic electronic devices. First, the nanoscale molecule-substrate interaction between the polymer and water was modulated by controlling the alkyl side chain length in NDI-based copolymers. Increasing alkyl side chain lengths induced a nanomorphological transition from face-on to edge-on orientation, confirmed by molecular dynamics simulations revealing nanostructural behavior. Second, the nanoscale intermolecular interactions of P(NDI2OD-T2) were controlled by varying the volume ratio of the high-boiling-point additive solvent in the binary solvent blends. As the additive solvent ratio increased, the nanostructured molecular orientation of the P(NDI2OD-T2) films on water changed remarkably from edge-on to bimodal with more face-on crystallites, thereby affecting charge transport. Our finding provides essential insights for precise nanoscale morphological control on water substrates, enabling the formation of high-performance polymer films for organic electronic devices.

Unconventional Nanofabrication for Supramolecular Electronics

The scientific effort toward achieving a full control over the correlation between structure and function in organic and polymer electronics has prompted the use of supramolecular interactions to drive the formation of highly ordered functional assemblies, which have been integrated into real devices. In the resulting field of supramolecular electronics, self-assembly of organic semiconducting materials constitutes a powerful tool to generate low-dimensional and crystalline functional architectures. These include 1D nanostructures (nanoribbons, nanotubes, and nanowires) and 2D molecular crystals with tuneable and unique optical, electronic, and mechanical properties. Optimizing the (opto)electronic properties of organic semiconducting materials is imperative to harness such supramolecular structures as active components for supramolecular electronics. However, their integration in real devices currently represents a significant challenge to the advancement of (opto)electronics. Here, an overview of the unconventional nanofabrication techniques and device configurations to enable supramolecular electronics to become a real technology is provided. A particular focus is put on how single and multiple supramolecular fibers and gels as well as supramolecularly engineered 2D materials can be integrated into novel vertical or horizontal junctions to realize flexible and high-density multifunctional transistors, photodetectors, and memristors, exhibiting a set of new properties and excelling in their performances.

Langmuir-Blodgett Thin Films of Diketopyrrolopyrrole-Based Amphiphiles

We report on two π-conjugated donor-acceptor-donor (D-A-D) molecules of amphiphilic nature, aiming to promote intermolecular ordering and carrier mobility in organic electronic devices. Diketopyrrolopyrrole was selected as the acceptor moiety that was disubstituted with nonpolar and polar functional groups, thereby providing the amphiphilic structures. This structural design resulted in materials with a strong intermolecular order in the solid state, which was confirmed by differential scanning calorimetry and polarized optical microscopy. Langmuir-Blodgett (LB) films of ordered mono- and multilayers were transferred onto glass and silicon substrates, with layer quality, coverage, and intermolecular order controlled by layer compression pressure on the LB trough. Organic field-effect transistors and organic photovoltaics devices with active layers consisting of the amphiphilic conjugated D-A-D-type molecules were constructed to demonstrate that the LB technique is an effective layer-by-layer deposition approach to fabricate self-assembled, ordered thin films.

Homogenous Dispersion of MoS2 Nanosheets in Polyindole Matrix at Air-Water Interface Assisted by Langmuir Technique

Two-dimensional (2D) inorganic layered materials when embedded in organic polymer matrix exhibit exotic properties that are grabbing contemporary attention for various applications. Here, nanosheet morphology of molybdenum disufide (MoS₂) synthesized via one-pot facile hydrothermal reaction are exfoliated in benign aqueous medium in the presence of indole to obtain a stable dispersion. These exfoliated nanosheets then act as host to template the controlled polymerization of indole. The preassembled MoS₂-polyindole (MoS₂-PIn) nanostructures are reorganized at the air-water interface using the Langmuir method to facilitate maximum interfacial interaction between nanosheet and polymer. This report emphasizes large area, homogeneous dispersion of uniform-sized MoS₂ nanosheets (40-60 nm diameter) in the PIn matrix and the formation of stable and uniform film via the Langmuir-Schaefer (LS) method. These self-assembled, MoS₂ decorated PIn LS films are characterized using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The fabricated LS films in sandwiched structure Al/MoS₂-PIn/ITO as the Schottky diode portrayed remarkable enhancements in charge transport properties. Our study illustrates the potential of the MoS₂-PIn LS film in electronic applications and opens a new dimension for uniform dispersion of 2D materials in other polymers via the Langmuir method for device fabrication and enhancement of electrical properties.