Dual-solvent-induced persistent nanoscale wet film for controllable two-dimensional molecular crystallization toward polarization-sensitive photodetectors

Two-dimensional organic semiconductor single crystals (2D OSSCs) have great potential for use in high-performance optoelectronic devices. However, challenges associated with controlling complex fluid dynamics and molecular mass transfer during solution-based processes hinder large-scale high-quality production. To address this issue, we developed a nanoconfinement-driven approach for controlling molecular crystallization, improving isotropic molecular mass transfer in fluids, and regulating the morphology of the 2D molecular film. Using a dual-solvent strategy, we created a stable nanoscale extended evaporation meniscus that modulates molecular nucleation and growth dynamics, thereby facilitating the direct shift from one-dimensional to two-dimensional crystals. Dual solvents are essential for generating and maintaining nanoscale wet films during meniscal recession, which is crucial for 2D crystal engineering. Mechanistic studies revealed that adhesion in a dual-solvent system is vital for meniscus formation while disjoining pressure maintains its stability. We also systematically evaluated several [1]benzothieno[3,2-b][1]benzothiophenes (BTBTs) bearing various alkyl chains, which revealed how molecular interactions affect morphology during printing. Organic-field-effect transistors fabricated using 2D OSSCs have significantly higher carrier mobilities than those with striped structures. Moreover, the highly ordered 2D C8-BTBT single-crystal thin film exhibited high sensitivity to polarized ultraviolet light, boasting a dichroic ratio of 2.80 and demonstrating exceptional imaging capabilities for polarized ultraviolet light.