Screen Printing of Silver and Carbon Nanotube Composite Inks for Flexible and Reliable Organic Integrated Devices

Systematic studies on the screen printing of Ag paste and multiwalled carbon nanotube (CNT) composite inks were performed to explore the feasibility of the screen printing technique in the electrode patterning of organic integrated circuits. By the in-depth consideration of the physical properties of the Ag/CNT composite ink as well as the printing conditions, the optimized Ag/CNT patterns screen-printed on substrates exhibited good pattern fidelity and stable electrical conductance against external tensile stretching. Significantly, the screen-printed Ag/CNT patterns had trapezoidal-shaped edges at an angle of 9.5°; these edges were essential for charge injection and extraction between the Ag/CNT electrodes and the semiconductor active layer when the organic semiconductors were deposited on the trapezoidal-shaped edges. Using the trapezoidal-shaped edge Ag/CNT electrodes, p- and n-type organic thin-film transistors (OTFTs) with a bottom-gate-bottom-contact geometry were fabricated, which exhibited reliable device performances during repetitive electrical sweeps. Finally, the good pattern ability and robust electrical performance of screen-printed Ag/CNT electrodes are advantageous for the integration of OTFTs while preparing logic circuits, including complementary inverters, NAND, and NOR gates. The composite inks synthesized in this study exhibited ideal physical properties suitable for the screen printing process and demonstrated the feasibility of using the Ag/CNT composite ink for practical application in organic electronic products.