Optimized Charge Transport in Molecular Semiconductors by Control of Fluid Dynamics and Crystallization in Meniscus-Guided Coating

The effects of the casting speed and solute concentration on the crystallization of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) during meniscus-guided coating (MGC) are investigated, and three morphological subregimes with increasing casting speed are identified: I) an isotropic domain-like structure; II) unidirectionally aligned crystalline bands; and III) a corrugated dendritic morphology. Interestingly, increasing the solute concentration does not affect these morphologies but merely the associated transition velocities. Numerical simulation of both the fluid dynamics in the coating bead and the crystallization itself not only explains these morphological trends but also the decrease in the width of the crystalline bands of morphology II with the casting speed. They demonstrate that the latter provides an optimal processing window for organic field-effect transistors, with minimized charge trapping, maximized on/off ratio, and reliability factor.

Automated summary

The study investigates the effects of casting speed and solute concentration on the crystallization of C8-BTBT during MGC, identifying three morphological subregimes. Increasing solute concentration does not change the morphologies but affects transition velocities. Numerical simulations explain the optimal processing window for organic field-effect transistors.