Screen printing of silver nanoparticles on the source/drain electrodes of organic thin-film transistors

Herein, we systematically investigate the screen printing of Ag nanoparticle (AgNP) inks for the use of source and drain (S/D) electrodes of organic thin-film transistors (OTFTs), controlling printing process condition such as printing speed annealing temperature, as well as the surface modification for the substrate. The optimization of screen-printed AgNPs showed high electrical conductivity, nice pattern-fidelity and good adhesion to the substrate. Although the printed AgNP pattern indicated the thickness of about 11 μm (measured at the center area of the pattern) which is too high compared with that of semiconductor layer (∼100 nm), the edge side of the pattern showed the trapezoid shape with an angle of 18.2° enabling the feasible charge injection and extraction between electrodes and semiconductor layer. Based on the optimized AgNP S/D electrode, the OTFTs with 2,9-di-decyl-dinaphtho-[2,3-b:2,3-f]-thieno-[3,2-b]thiophene (C10-DNTT) semiconductor layer were fabricated on Si/SiO2 and flexible polyethylene terephthalate (PET) substrates with bottom-gate, bottom-contact (BGBC) and top-gate, bottom-contact (TGBC) device structure, respectively. Consequently, BGBC on Si/SiO2 showed the best device performance, with a μFET of 0.186 cm2V−1s−1 and threshold voltage (Vth) of −0.41 V. In addition, TGBC OTFTs on the PET substrate obtained an electrical performance with a μFET of 0.012 cm2V−1s−1.