Van der Waals Assembled Solution‐processed Organic Monolayer Single‐Crystal Transistor for Electrocardiograph Sensing

Solution-processed organic semiconductors (OSCs) promote the development of the next generation of large-area, low-cost flexible electronics. To date, the properties of the flexible substrates such as chemical compatibility, roughness, and surface energy are still big challenges for the solution process, especially for high-performance ultrathin monolayer OSCs. Herein, van der Waals assembled organic field-effect transistors (OFETs) with layer-by-layer lamination processes are reported. The active layer is an ultrathin single molecular layer 2,9-Didecyldinaphtho[2,3-b:2 ',3 '-f]thieno[3,2-b]thiophene (C-10-DNTT) which maintains decent electrical fidelity with mobility of 10.4 cm(2) V-1 s(-1) after transfer. With the active layer transfer technique, the bias stability of OFETs can be significantly improved by tuning diverse hydrophobic self-assembly monolayers (SAMs) onto the dielectric which is a challenging task before the solution processing organic monolayer. A small subthreshold swing (SS) of 63 mV decade(-1) is achieved by low surface energy phosphonic acid SAMs on high-kappa AlOx dielectric. We further demonstrate a high-gain organic inverter amplifier that can be powered up by a coin cell on the 1.5 mu m conformal parylene substrate and apply it for high-resolution electrocardiograph (ECG) sensing. The ECG sensors can provide a signal-to-noise ratio as high as 34 dB. It is believed that our device demonstrates the prospect of continuous monitoring for human health management.