Improving Electrical Stability and Ideality in Organic Field‐Effect Transistors by the Addition of Fullerenes: Understanding the Working Mechanism

Electrical instability and nonideality due to undesirable electron injection are often‐encountered problems for high‐mobility organic field‐effect transistors (OFETs) with low‐bandgap polymer semiconductors. Due to electron trapping and the resulting accumulation of negative charges on the silicon dioxide dielectric, transfer curves deviate from ideality characteristics and double‐slopes are observed as the devices are operated for extended periods of time. One way to circumvent those is to use an electron‐acceptor additive, such as fullerene and its derivatives. This work interprets the mechanisms of how fullerene derivatives suppress electron transport and electrical instability while maintaining high hole mobility in p‐type OFETs. This study shows that hole transport of the active layer is uninterrupted upon the addition of the electron acceptors. Most importantly, the added fullerene derivatives out‐compete SiO₂ to acquire electrons that are injected into the polymers. Electrical instability and double‐slope induced from electron trapping at SiO₂ surface are thereby suppressed.