Advances in Efficient Polymerization of Solid-State Trithiophenes for Organic Thermoelectric Thin-Film

The polymerization of solid-state small organic molecules generally involving no less three units has been demonstrated to be an important prospect in the field of organic electrons. Presently, owing to the chemical coupling reactions, the polymerization for solid-state small molecules usually involves the complex operations and results in powder polymers and a poor-quality thin-film by spin coating due to their insoluble property in common solvents. The conventional vapor-phase polymerization (VPP) is a powerful technology and has been widely accepted for a high-quality polymer film. However, the VPP is generally used for a limited small organic molecules, but does not apply to a solid-state organic molecules due to the difficulty of vaporization. Herein, we proposed an upgrade vapor phase polymerization strategy, spin-spray coating polymerization method, to overcome the limitation of traditional VPP by spraying of solid-state trithiophenes as precursors in a common low-boiling point organic solvent for a homogeneous conjugated polymer thin-film. The as-fabricated conjugated polymer films show the uniform morphology with the fast and easy polymerization and acceptable thermoelectric performance compared to the traditional chemical and electrochemical oxidation in solution. This spin-spray coating polymerization technique has also been extended to the derivatives of trithiophenes with different alkyl side chains in thiophene, demonstrating the effective strategy for the development of an uniform polymer thin-film with relatively complex structure.