Controllable microstructure of polymer-small molecule blend thin films for high-performance organic field-effect transistors

摘要

The carrier mobility is an important figure of merit and is sensitively influenced by the microstructure of semiconducting films such as crystallization and morphology. Here, a method of blending semiconducting small molecule 2,7-dioctyl[1] benzothieno[3,2-b][1] benzothiophene ( C8-BTBT) and insulating polymer binder is reported to well control the microstructures of blend semiconducting films. It is found that the insulating polymer in the blends prevents the dewetting of C8-BTBT from the SiO2 substrate and provides a platform for C8-BTBT molecules to segregate and crystallize at the air-film interface. By controlling the spinning speed, polymer type and ratio of the blend solution, it is possible to regulate the domain size and the surface roughness of C8-BTBT films, which in turn determines the performances of OTFTs. The bottom gate transistors based on C8-BTBT/polystyrene(PS) blend demonstrate excellent stability and a mobility up to 6.80 cm(2)/Vs due to the large domain size, smooth grain boundary and the phase-separated interface, which shows the potential applications in high-performance flexible and printed electronics.