Key role of the meniscus shape in crystallization of organic semiconductors during meniscus-guided coating†
Solution processable organic semiconductors (OSCs) hold advantages for the fabrication of flexible and large-area electronic devices. Meniscus-guided coating (MGC) is one promising technique to tune the crystallization and thin film morphology of OSCs. In this work, we demonstrate the crucial role of the meniscus shape in the fluid flow and crystallization of OSCs during MGC. We demonstrate that angle-dependent dip-coating (ADDC) allows precise control of the meniscus shape. The use of a small meniscus angle during ADDC of 2,7-dioctylbenzothieno[3,2-b]benzothiophene (C8-BTBT) enhances the crystallization and mass deposition of the OSC due to an increased upward fluid flow. The resulting aligned crystalline film with high surface coverage favors the charge carrier transport in C8-BTBT based field-effect transistors. This work provides comprehensive insight into the fundamental mechanism of OSC crystallization during MGC, which is important for the large-area deposition of OSCs for practical electronic applications.