Role of Multivalent Interactions in Dynamic-Template-Directed Assembly of Conjugated Polymers

Rapid Meniscus-Assisted Solution Printing of Large-Area Stripe Arrays of Highly Oriented Conjugated Polymers for Field-Effect Transistors

The ability to pattern semiconducting conjugated polymers (CPs) and concurrently enable their highly oriented chains represents an important endeavor to render their high charge mobility for electronic devices. However, simple yet generalizable routes to CPs with such desirable characteristics are limited. Herein, we report a robust meniscus-assisted solution printing (MASP) strategy to craft arrays of donor-acceptor CP stripes and scrutinize the correlation between different stripes and their charge transport attributes. Specifically, the MASP constrains the CP solution to evaporate between two nearly parallel plates with a stationary upper plate and a mobile lower plate containing periodic photoresist (PR) microchannels. Orchestrating the MASP speed comparable to the CP crystal growth rate yields CP stripe arrays with highly aligned CP crystals, resulting in the highest carrier mobility. Notably, our MASP technique can conveniently pattern other CPs of interest. It stands out as a simple strategy to impart large-scale production of functional materials for a wide range of applications in optics, electronics, sensors, etc.

Meniscus-Guided Deposition of Organic Semiconductor Thin Films: Materials, Mechanism, and Application in Organic Field-Effect Transistors

Solution-processable organic semiconductors are one of the promising materials for the next generation of organic electronic products, which call for high-performance materials and mature processing technologies. Among many solution processing methods, meniscus-guided coating (MGC) techniques have the advantages of large-area, low-cost, adjustable film aggregation, and good compatibility with the roll-to-roll process, showing good research results in the preparation of high-performance organic field-effect transistors. In this review, the types of MGC techniques are first listed and the relevant mechanisms (wetting mechanism, fluid mechanism, and deposition mechanism) are introduced. The MGC processes are focused and the effect of the key coating parameters on the thin film morphology and performance with examples is illustrated. Then, the performance of transistors based on small molecule semiconductors and polymer semiconductor thin films prepared by various MGC techniques is summarized. In the third section, various recent thin film morphology control strategies combined with the MGCs are introduced. Finally, the advanced progress of large-area transistor arrays and the challenges for roll-to-roll processes are presented using MGCs. Nowadays, the application of MGCs is still in the exploration stage, its mechanism is still unclear, and the precise control of film deposition still needs experience accumulation.

Orientation-Dependent Host-Dopant Interactions for Manipulating Charge Transport in Conjugated Polymers

Molecular orientation plays a critical role in controlling carrier transport in organic semiconductors (OSCs). However, this aspect has not been explored for surface doping of OSC thin films. The challenge lies in lack of methods to precisely modulate relative molecular orientation between the dopant and the OSC host. Here, the impact of molecular orientation on dopant-host electronic interactions by large modulation of conjugated polymer orientation via solution coating is reported. Combining synchrotron-radiation X-ray measurements with spectroscopic and electrical characterizations, a quantitative correlation between doping-enhanced charge carrier mobility and the Herman's orientation parameter is presented. This direct correlation can be attributed to enhanced charge-transfer interactions at host/dopant interface with increasing face-on orientation of the polymer. These results demonstrate that the surface doping effect can be fundamentally manipulated by controlling the molecular orientation of the OSC layer, enabling optimization of carrier transport.