Synergistic Ternary Doping Strategy Boosts the Performance of Monolayer-Scale Molecular Crystals.

Abstract

Achieving high conductivity in organic single crystals without disrupting their performance-enabling long-range molecular order is a central challenge in organic electronics. To approach this goal, we here introduce a universal synergistic ternary doping strategy comprising a primary dopant (FeCl₃), a secondary acceptor (F4TCNQ), and a salt additive (LiTFSI), which enables a cooperative, nondisruptive surface‑doping mechanism that retains the pristine crystalline lattice and resolves this conflict. This strategy is highlighted by enabling an over nine‑order‑of‑magnitude increase in conductivity of DPA single crystals, which arises from the combined effects of efficient charge transfer, electrostatic homogenization, and stabilized anion exchange. Concurrently, it reduces the contact resistance by more than 90% to only 93.32 Ω·cm in the corresponding OFETs. When applied to the ultimate physical limit of monolayer-scale molecular crystals (BTBTT6-syn and C6-DPA), the strategy achieves a high conductivity as high as 10.19 S·cm^- ¹ and a near-vanishing contact resistance of 17.03 Ω·cm in the doped OFETs. This work provides a powerful and general pathway to unlock the full carrier potential of crystalline organic semiconductors for next-generation devices.