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.