Conjugated Polymer Alignment: Synergisms Derived from Microfluidic Shear Design and UV Irradiation

Abstract

Solution shearing has attracted great interest for the fabrication of robust and reliable, high performance organic electronic devices, owing to applicability of the method to large area and continuous fabrication, as well as its propensity to enhance semiconductor charge transport characteristics. To date, effects of the design of the blade shear features (especially the microfluidic shear design) and the prospect of synergistically combining the shear approach with an alternate process strategy have not been investigated. Here, a generic thin film fabrication concept that enhanced conjugated polymer intermolecular alignment and aggregation, improved orientation (both nanoscale and long-range), and narrowed the π-π stacking distance is demonstrated for the first time. The impact of the design of shearing blade microfluidic channels and synergistic effects of fluid shearing design with concomitant irradiation strategies were demonstrated, enabling fabrication of polymer-based devices with requisite morphologies for a range of applications.

Aggregation control in natural brush-printed conjugated polymer films and implications for enhancing charge transport

“…The corresponding μ values were measured in saturation and calculated using standard MOSFET models (1). Spin-coated P3HT films exhibit a chargecarrier mobility (μ sc ) of 0.04 cm 2 V −1 s −1 , comparable with that reported in other studies (19,22,33). For the brush-printed films, a 4.5× increase in carrier mobility is achieved in both the parallel and perpendicular directions compared with spin-coated samples, resulting in μ jj /μ ⊥ = 0.18/0.15 cm 2 V −1 s −1 .…”

“…These experimental results reveal that the natural brush squamae structure is effective in achieving substantial levels of polymer chain alignment and intermolecular aggregation. Similar to physically etched micro-/nanostructured features for shear-printing (3,5,22), the oriented natural squamae induced enhanced polymer chain alignment and controllable liquid transfer, resulting in unique microstructure control and mobility enhancement. The principle effects are proposed to be (i) polymer chain extension owing to the extensional flow during the liquid transfer process and (ii) shear effects during film formation process.…”

“…However, such aggregation processes typically involve solutions, which may be difficult to control and have restricted process windows that are incompatible with manufacture. Shear-printing with physically etched micro-/nanostructured blades is a promising approach to enhance conjugated polymer alignment and crystallinity, hence charge transport (3,5,22). However, the fabrication of these artificial shear features relies on complicated, expensive photolithography and etching.…”

Rapid Formation and Macroscopic Self‐Assembly of Liquid‐Crystalline, High‐Mobility, Semiconducting Thienothiophene

“…Aligned crystalline domain formation in P3HT nanofibers has been demonstrated by UV‐light irradiation‐assisted molecular self‐assembly, which leads to facile charge‐carrier transport and approximately an order of magnitude enhancement in the FET mobility. This enhanced device performance was explained by considering a major contribution to the charge transport from the aligned crystalline domains (in nanofibers) assisted by nonaligned tie‐chains . Interestingly, by using the FTM, we can control the film orientation and direct the alignment of the macromolecules in the channel direction, leading to facile charge‐carrier transport.…”

Manipulation and statistical analysis of the fluid flow of polymer semiconductor solutions during meniscus-guided coating

“…23,24 There are only a few examples of the application of such techniques on polymer OSCs in devices for the specific purpose of realizing strain-induced polymer nucleation during deposition. 25,26 For example, coating blades patterned with short (≈5 μm) hexagonal pillars can manipulate the fluid dynamics of solution shearing during the deposition of all-polymer solar cells and enhance their performance. 13 By increasing extensional flow and the overall strain imparted on the solution-a blend of a semicrystalline donor polymer and amorphous acceptor polymer-strain-induced nucleation of the donor is enhanced, as demonstrated by the increase in the relative degree of crystallinity (rDoC) that increases solar cell performance.…”