Significant Performance Improvement in n-Channel Organic Field-Effect Transistors with C 60 :C 70 Co-Crystals Induced by Poly(2-ethyl-2-oxazoline) Nanodots

• Published in: Advanced materials (Weinheim) 2021-08, Vol.33 (31), p.e2100421
• Main Authors: Nam, Sungho, Khim, Dongyoon, Martinez, Gerardo T, Varambhia, Aakash, Nellist, Peter D, Kim, Youngkyoo, Anthopoulos, Thomas D, Bradley, Donal D C
• Format: Article
• Language: English
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202100421

Solution-processed organic field-effect transistors (OFETs) have attracted great interest due to their potential as logic devices for bendable and flexible electronics. In relation to n-channel structures, soluble fullerene semiconductors have been widely studied. However, they have not yet met the essential requirements for commercialization, primarily because of low charge carrier mobility, immature large-scale fabrication processes, and insufficient long-term operational stability. Interfacial engineering of the carrier-injecting source/drain (S/D) electrodes has been proposed as an effective approach to improve charge injection, leading also to overall improved device characteristics. Here, it is demonstrated that a non-conjugated neutral dipolar polymer, poly(2-ethyl-2-oxazoline) (PEOz), formed as a nanodot structure on the S/D electrodes, enhances electron mobility in n-channel OFETs using a range of soluble fullerenes. Overall performance is especially notable for (C -I )[5,6]fullerene (C ) and (C -D )[5,6]fullerene (C ) blend films, with an increase from 0.1 to 2.1 cm V s . The high relative mobility and eighteen-fold improvement are attributed not only to the anticipated reduction in S/D electrode work function but also to the beneficial effects of PEOz on the formation of a face-centered-cubic C :C co-crystal structure within the blend films.