Chemical Doping Reveals Band-like Charge Transport at Grain Boundaries in Organic Transistors

Abstract

Organic semiconductors are highly promising as channel materials for energy-efficient, cost-effective, and flexible electronics. However, grain boundaries (GBs) can cause significant device performance variation, posing a major challenge for the development of high-performance organic circuits. In this work, we effectively passivated GB-induced traps in monolayer organic thin-film transistors (OTFTs) via p-type doping with the organic salt TrTPFB. The doping strategy broadens the mobility edge, effectively shielding GB-induced energy barriers and Coulomb scattering, and promotes deeper nonlocalized hybridization states for conduction. Consequently, the charge transport mechanism transitions from multiple trapping and release (MTR) to a more band-like behavior, even when GBs are present within the device channel. The doped OTFTs demonstrate ultralow mobility variation (1.4%) and threshold voltage variation (4.9%), as well as record-low contact resistant of R_C = 0.6 Ω·cm, outperforming most single-crystal technologies. These performance metrics render doped monolayer polycrystalline films highly promising candidates for industrial-scale organic electronics.