Controlled 2D growth of organic semiconductor crystals by suppressing "coffee-ring" effect

Owing to enhanced charge transport efficiency arising from the ultrathin nature, two-dimensional (2D) organic semiconductor single crystals (OSSCs) are emerging as a fascinating platform for high-performance organic field-effect transistors (OFETs). However, "coffee-ring" effect induced by an evaporation-induced convective flow near the contact line hinders the large-area growth of 2D OSSCs through a solution process. Here, we develop a new strategy of suppressing the "coffee-ring" effect by using an organic semiconductor: polymer blend solution. With the high-viscosity polymer in the organic solution, the evaporation-induced flow is remarkably weakened, ensuring the uniform molecule spreading for the 2D growth of the OSSCs. As an example, wafer-scale growth of crystalline film consisting of few-layered 2,7-didecylbenzothienobenzothiophene (C₁₀-BTBT) crystals was successfully accomplished via blade coating. OFETs based on the crystalline film exhibited a maximum hole mobility up to 12.6 cm²·V^-1·s^-1, along with an average hole mobility as high as 8.2 cm²·V^-1·s^-1. Our work provides a promising strategy for the large-area growth of 2D OSSCs toward high-performance organic electronics.