Growth Regulation of Organic Semiconductor Film on Graphene during Solution Evaporation: From Growth Dynamics to Vibration-Assisted Film Quality Optimization.

Efficient fabrication of high-quality organic semiconductor thin films on flexible substrates is crucial for the development and commercialization of high-performance flexible organic electronics. Here, an atomistic insight study is conducted to elucidate the growth dynamics of C8-DNTT organic semiconductors on graphene during solution evaporation. Owing to the strong interactions between graphene and organic semiconductor molecules, an interfacial layer initially forms on graphene. When the interaction energy among C8-DNTT molecules considerably exceeds that between C8-DNTT and graphene, homogeneous films with an upright molecular orientation can be achieved. However, excessive organic semiconductor molecules lead to the formation of a densely packed structure with high free energy regions. The solvent molecules are forced to escape at defect sites with the lower free energy, which form large voids and grain boundaries. Furthermore, a vibration-assisted strategy is proposed to address the above issue during film preparation. Vibration can enhance the solution temperature and improve spatial arrangement of organic semiconductor molecules. Through vibrational frequency modulation, the tight solution structure is shaken to promote solvent evaporation, and the interaction energy between C8-DNTT and graphene is weakened, leading to a 33.43% increase in the molecular tilt angle. Nevertheless, excessively high frequencies will substantially enhance solution temperature and induce structural changes in flexible molecular chains, which leads to solvent residue and deterioration of film morphology.