Pursuing High-Performance Organic Field-Effect Transistors through Organic Salt Doping

Doping is an effective strategy for controlling the charge density and device performance of thin-film electronics. Herein, a new doping system is reported for organic electronics using the organic salt p-dopant N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate (DTB) to significantly improve the device performance of indacenodithiophene-co-benzothia-diazole (IDT-BT) organic field-effect transistors (OFETs). With optimized doping ratios, the hole mobility increases almost fourfold from 0.32 to 1.15 cm² V^–1 s^–1 and the threshold voltage reduces from −38 to 0 V. Moreover, systematical electrical characterizations demonstrate that the contact resistance and activation energy dramatically reduce in the doped devices. Such reductions are ascribed to the shift of the Fermi energy level closer to the transport level and the lowered density of trap states in doped semiconductors, as revealed by ultraviolet photoelectron spectroscopy and low-frequency noise measurements, respectively. This study also demonstrates that the trap density increases when the doping ratio is high, explaining the device performance degradation at high doping ratios. This is the first time that DTB organic salt is used as an efficient dopant to improve the performance of OFETs, demonstrating a promising route for employing organic salt dopants to achieve high-performance OFETs.