High-performance solution-processed organic thin-film transistors based on a soluble DNTT derivative

We here report optimization of thin-film fabrication of 2-(4-ethyloctyl)dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (2-EO-DNTT), a soluble DNTT derivative, by spin-coating. The key to fabricate suitable thin films for high-performance TFTs is to control the nucleation and crystallites growth on the substrate during spin-coating; dropwise addition of the solution onto the spinning substrates enabled reproducible fabrication of such thin films, not only on the conventional Si/SiO₂ substrate but also glass substrates with the gate dielectric consisting of AlO_x/phosphonic acid self-assembled monolayers (SAMs). As a result, the present method realized fabrication of solution-processed TFTs with high mobility (>1.0 cm² V⁻¹ s⁻¹), good environmental, operational, and thermal stability, and low-voltage operation (<3.0 V), all of which are mostly comparable to those of the vapor-processed parent DNTT-TFTs. These results clearly indicate that 2-EO-DNTT is the solution-processable alternative of DNTT.