The Direct Solution-Process Crystallization of π-Conjugated Small Molecules In-Situ Integrated Planar Electrodes

Organic electronic devices have seen a new enthusiasm in flexible electronics. Indeed, they know new applications and improved performances even fabricated at low temperatures by low-cost solution-process and printing technologies. Nonetheless, some critical aspects remain to be improved, such as organic semiconductor (OSC) patterning and the control and alignment of organic crystal growth in the desired location and direction. Herein, a new controlled OSC solution-growth processing, which directly occurs within planar electrodes patterning, is reported. A capillary-driven flow occurs in air-opened microchannels and then confines the OSC solution before growing these crystals in the desired region and direction. 1) The modeling, 2) fabrication, 3) experimental functionality of such capillary-driven flow techniques, and 4) growth of OSC single-colored crystals in situ integrated planar device electrodes are reported. Polarized optical images show large crystal growth (i.e., >100 μm) of typical π-conjugated small molecules (diF-TES-ADT and C8-BTBT). By such a technology, benefits from both 1) the meniscus-guided coating mechanisms and 2) advantages of maskless and noncontact digital printing technologies are taken. Finally, these results visualize the directional control of OSC single-crystal growth in a printing-compatible (dispensing, inkjet) route in a reliable and reproducible way.