Solvent-Vapor-Assisted Self-Assembly of Semiconducting Polymers at the Air-Liquid Interface: Impact on Nanoscale Morphology and Optoelectrical Anisotropy

Abstract

Rapid evaporation of volatile solvents sometimes forcefully limits the time of molecular self-organization toward the growth of highly oriented semicrystalline thin films of organic semiconducting polymers (OSPs). We are reporting a unified approach harnessing the key advantages of the "floating-film transfer method"(FTM) along with the effect of solvent-vapor-assisted controlled evaporation of the solvents to fabricate a high-quality active semiconducting layer for better-performing organic field-effect transistors. To accomplish this, regioregular poly(3-hexylthiophene-2,5-diyl) has been used as a model OSP, and the fabricated films were thoroughly characterized using several tools to understand the structure-property correlation by exploring the fundamental properties. Oriented thin films thus fabricated exhibited highly "edge-on"oriented molecular packing with reduced interlamellar spacing, dh00, and extended π-conjugation length and lower exciton bandwidth. Moreover, quantum-dot-like aggregated nanostructuring within the crystalline domains, as evidenced by high-resolution transmission electron microscopy, forms a network of interconnected conductive pathways. This leads to enhanced field-effect mobility along the polymer backbone, μ

= 0.0498 cm2 V-1 s-1, which is around five times higher than that of the thin films prepared by conventional FTM. Thus, our study demonstrated a facile route to obtain uniaxially oriented and highly crystalline OSP films suitable for solution-processed highperformance organic electronic device applications. © 2022 American Chemical Society.