Adhesive-free transfer of gold patterns to PDMS-based nanocomposite dielectric for printed high-performance organic thin-film transistors

Low-cost, adhesive-free direct transfer of gold patterns onto PDMS-based nanocomposite dielectric layer was investigated to significantly improve contact resistance at electrode -semiconductor interface in organic thin-film transistors (OTFTs). In particular, the nanocomposite film made from PDMS and solution-processable titanium dioxide nanoparticles was applied as dielectric layer in OTFTs, while transfer of gold patterns with a resolution lower than 3 μm is realized without use of any adhesive but through increased adhesion between gold and nanocomposite film of higher thickness and dielectric constant formed by in situ PDMS cross-linking process. Dielectric constant of the nanocomposite shows a dependence on the ratio of titanium dioxide nanoparticles to PDMS and the dielectric thickness was optimized for the best transfer efficiency. The organic transistors fabricated by this process demonstrate a high mobility of 0.038 cm²/(V s) and on/off ratio of 1 × 10⁴ to 1 × 10⁵. The electrode-semiconductor interface is evaluated by transmission line model to have width-normalized contact resistance of ~100 kO cm while the inert property of dielectric-semiconductor interface gives low hysteresis (δV_th = 1.2 V) and low threshold voltage (Vth =-1.3 V) in the devices. This process can be readily adapted into a low-cost mass manufacturing process for printed organic electronics.