Researchers have printed complete integrated circuits with more than 1,000 organic electrochemical transistors. Printing electronic circuits with a line width of approximately 100 micrometers places high demands on print technology. To solve the problem, the team developed screen-printing frames with meshes that can print extremely fine lines and printing ink with the right properties. The material used is the polymer PEDOT:PSS.
At least three challenges have been dealt with: reducing the circuit size, increasing the quality such that the probability that all transistors in the circuit work lie as close to 100% as possible, and solving integration with the silicon-based circuits needed to process signals and communicate with the surroundings.
Printed circuits were used to create an interface with traditional silicon-based electronic components. Several types of printed circuits based on organic electrochemical transistors were built. One of these is a shift-register, which can form an interface and deal with the contact between the silicon-based circuit and other electronic components such as sensors and displays. This results in a silicon chip with fewer contacts, which needs a smaller area and is less expensive.
The development of ink to print the thin lines and improvements of the screen-printing frames contributed not only to the miniaturization process but also to achieving higher quality. More than 1,000 organic electrochemical transistors can be placed on an A4-sized plastic substrate and can be connected in different ways to create different types of printed integrated circuits.
These large-scale integrated circuits (LSI) can be used, for example, to power an electrochromic display — itself manufactured as printed electronics — or another part of the online electronic world that the Internet of Things brings.