Meniscus‐guided organic semiconductor single crystals: From fluid dynamics to morphology control and multifunctional applications

Abstract Organic semiconductor (OSC) single crystals, featuring grain‐boundary‐free structures and long exciton diffusion lengths, are highly attractive for high‐performance devices and diverse functional applications. Meniscus‐guided coating has emerged as a powerful technique to fabricate large‐area OSC films by inducing ordered molecular assembly. Within the confined meniscus, however, complex fluid flows, including evaporation‐driven capillary flow and Marangoni convection, govern mass transport and present a significant challenge for achieving uniform crystallization. Unlike previous reviews focused on deposition mechanisms or device applications, this review provides a fundamental perspective centered on fluid dynamics. Our key contribution is the systematic dissection of this complex mass transport into two orthogonal components: parallel mass transfer along the coating direction and lateral mass transfer perpendicular to it. We further analyze how the delicate balance between these directional flows, nucleation/growth kinetics, and the receding of the triple‐phase contact line governs the final crystal orientation, uniformity, and morphology. We further survey their integration into multifunctional devices, including organic field‐effect transistors, sensors, photodetectors, and neuromorphic systems. Consequently, this work establishes the causal chain from fluid phenomena to crystal quality and, ultimately, to device functionality. This mechanism‐based understanding offers clear guidance for the rational design and predictive fabrication of high‐quality OSC single crystals for advanced multifunctional applications across optoelectronics, flexible electronics, and emerging intelligent devices.