Template-Induced Unidirectional Crystallization of Organic Semiconductors on Polar Noncentrosymmetric Crystals

Crystallization control of organic conjugated functional materials is essential for the development of high-performance, next-generation organic optoelectronic devices and circuits. Here, we studied the crystallization of conjugated molecules on noncentrosymmetric polar 2,7-diphenyl-9H-fluoren-9-one (DPFO) single crystals. The unidirectional template-induced crystallization effect of organic semiconductors on polar crystals is shown. Single crystals of triclinic rubrene grew along the direction of the template’s cumulative dipole moment. The coincidence of crystal cell parameters between the crystallized material and the template was demonstrated to be necessary for the effect. According to quantum chemical calculations, electrostatic interactions act as a guiding force for the docking effect due to the channels of low electrostatic potential energy above the DPFO surface. The molecular orientation of rubrene crystals points to the terminal phenylene group of DPFO and rubrene interacting via C–H···π interactions, hinting at the epitaxial nature of the unidirectional crystallization effect. Additionally, we demonstrated the implementation of the obtained heterostructures into functional organic field-effect transistors performing at the level of free-standing triclinic rubrene single crystals. Therefore, template-induced unidirectional crystallization on polar crystals is a prospective approach for shaping the future of organic optoelectronics.