Improving the air-stability of n-type organic thin-film transistors by polyacrylonitrile additive

Semiconducting and insulating polymer blend transistors have been studied to improve their air stability and create stretchable devices for skin electronics. Electron-transporting (or n-type) semiconducting polymers have significant problems regarding their device stability and performances. In this study, we tried to solve the stability issue of the n-type organic thin-film transistors (OTFTs). In order to extend the device lifetime, polyacrylonitrile (PAN) was introduced as an additive to the typical n-type naphthalenediimide (NDI)-based polymer, namely, P(NDI2T-OD) or N2200. PAN was well mixed with P(NDI2T-OD) to produce homogeneous solutions in chloroform/chlorobenzene mixtures when the PAN proportion was less than 5 wt%. The stability of the OTFTs stored in air was evaluated based on the electron mobility μe, threshold voltage Vth, and Ion/Ioff ratio. Adding a small amount of PAN can significantly improve the stability and μe values of the OTFTs probably due to the gas barrier and water trapping characteristics of the PAN.