Dual-Interface Engineering of the Source Electrode to Overcome the Intrinsic Injection-Leakage Trade-Off in Organic Schottky Barrier Transistors

Organic Schottky barrier transistors (OSBTs) offer a simplified vertical device architecture, with the channel length defined by the semiconductor thickness. However, the Schottky barrier at the source/semiconductor interface imposes an inherent trade-off: lowering the barrier improves on-current but increases leakage, while raising it suppresses leakage but limits charge injection. Here, these two functions are decoupled by combining a patterned charge injection layer beneath the source electrode with a self-assembled monolayer (SAM) on its top surface. The injection layer, composed of a doped polymer/acceptor, is selectively formed via oxygen-based reactive ion etching (RIE), using the Ag nanowire (AgNW) source electrode as an etch mask. This locally doped region reduces contact resistance and facilitates hole injection under negative gate bias. Meanwhile, a 1-hexadecanethiol (HDT) SAM on the AgNW top surface increases the Schottky barrier height to suppress off-current. This dual-interface engineering yields an on-current of 3.43 × 10⁻⁵ A and an on/off ratio of 3.38 × 10⁷, while ensuring long-term stability. The approach effectively resolves the intrinsic injection-leakage trade-off in OSBTs and provides a general strategy for achieving both high performance and reliability in organic vertical transistors.