Improved π-Conjugation Structure of Vacuum-Processable Organic Semiconductor Mediated from Molecular Crystal Templates

Highly π-conjugated self-assembly of organic semiconductors near gate dielectrics is important for achieving high performance in organic thin film transistors (OTFTs). This paper reports that a preexisting <i>N</i>,<i>N</i>-ditridecyl-3,4,9,10-perylenetetracarboxylic diimide (PTCDI-C₁₃) monolayer (ML) on a polymer-passivated silicon oxide dielectric stimulates the 2D crystal growth of the same ad-molecules during subsequent film deposition, resulting in a dramatic enhancement of the π-conjugated structure with suppressed grain boundaries. The crystal template-mediated PTCDI-C₁₃ films could develop layered crystallites with highly intermolecular ordering of edge-on semiconductor molecules perpendicular to the substrate. The crystal reorganization of PTCDI-C₁₃ deposited on the ML-thick crystal template drove the 2D crystal growth of a semiconductor on a heterointerface instead of 3D crystal growth. The charge carrier mobility along the template-mediated crystal grains within a 40 nm-thick film was up to 2.70 cm² V^-1 s^-1, 4 times higher than the 0.68 cm² V^-1 s^-1 in the ordinary polycrystalline domains developed directly at a heterointerface. Thus, using the predeposited crystal templates may be a good strategy to control the crystal structure and obtain high-quality organic thin films by vacuum deposition or orthogonal solvent film procedures.