Flexible and printed organic transistors: From materials to integrated circuits

This article reports on the recent progress in the research and development of flexible and printed organic thin-film transistor (OTFT) devices, including organic materials, fabrication processes, electronic devices, and integrated circuits, and highlights their application to healthcare sensors. The fabrication process flow for printed OTFT devices is described with various printing methods such as inkjet printing, dispensing, reverse-offset printing, and spin-coating. Silver nanoparticle inks are commonly used to form interconnect and electrode layers with inkjet printing and reverse-offset printing. Highly crystalline small-molecule organic semiconductors are patterned on the printed source and drain electrodes. Various integrated circuits such as inverters, D flip-flops (D-FFs), and operational amplifiers (OPAs) are fabricated based on the printed OTFT devices, and their electrical performance is discussed in detail. The potential applications of printed integrated circuits to biosensors are successfully demonstrated on plastic film substrates, enabling various flexible and printed sensor systems for potential use in the Internet of things (IoT) society.