Selective reaction at grain boundaries addressing organic field effect transistor trap states

Abstract

Trap states generated at grain boundaries often dominate the charge transport behavior of polycrystalline organic field effect transistors (OFETs). While these grain boundaries can be reduced through careful processing, unfortunately they cannot be completely suppressed. In this work, we introduce an approach that renders the grain boundaries inactive. Diels–Alder chemistry, which selectively reacts at the grain boundaries within organic semiconductor thin films, is utilized to attach a dipole-containing molecule in a localized manner. This induced dipole alters the surface potential, shifting the mean energy within the grain boundary and resulting in significantly enhanced device performance. Conductance increases exceed two orders of magnitude with the increase proportional to the amount of grain boundary reacted. In OFETs, this generated a doubling in charge carrier mobility and a reduction in the threshold voltage. The ability to tune the performance and uniformity of fabricated films, regardless of their initial grain size or conductance, represents a significant advance in post-fabrication optimization.