Understanding the Meniscus-Guided Coating Parameters in Organic Field-Effect-Transistor Fabrications

Meniscus-guided coating (MGC) is mainly applicable on the soluble organic semiconductors with strong pi-pi overlap for achieving single-crystalline organic thin films and high-performance organic field-effect-transistors (OFETs). In this work, four elementary factors including shearing speed (v), solute concentration (c), deposition temperature (T), and solvent boiling point (T-b) are unified to analyze crystal growth behavior in the meniscus-guided coating. By carefully varying and studying these four key factors, it is confirmed that v is the thickness regulation factor, while c is proportional to crystal growth rate. The MGC crystal growth rate is also correlated to latent heat (L) of solvents and deposition temperature in an Arrhenius form. The latent heat of solvents is proportional to T-b. The OFET channels grown by the optimized MGC parameters show uniform crystal morphology (Roughness R-q < 0.25 nm) with decent carrier mobilities (average mu = 5.88 cm(2) V-1 s(-1) and highest mu = 7.68 cm(2) V-1 s(-1)). The studies provide a generalized formula to estimate the effects of these fabrication parameters, which can serve as crystal growth guidelines for the MGC approach. It is also an important cornerstone towards scaling up the OFETs for the sophisticated organic circuits or mass production.