Fullerene Additives Convert Ambipolar Transport to p-Type Transport while Improving the Operational Stability of Organic Thin Film Transistors

• Published in: Advanced functional materials 2016-07, Vol.26 (25), p.4472-4480
• Main Authors: Ford, Michael J., Wang, Ming, Phan, Hung, Nguyen, Thuc-Quyen, Bazan, Guillermo C.
• Format: Article
• Language: English
• Subjects: bias stress; Derivatives; Field effect transistors; Fullerenes; high mobility; Mathematical analysis; organic field-effect transistors; semiconductor blends; Semiconductor devices; Semiconductors; Stability; stable; Thin films; Transport
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201601294

Many high charge carrier mobility (μ) active layers within organic field‐effect transistor (OFET) configurations exhibit non‐linear current–voltage characteristics that may drift with time under applied bias and, when applying conventional equations for ideal FETs, may give inconsistent μ values. This study demonstrates that the introduction of electron deficient fullerene acceptors into thin films comprised of the high‐mobility semiconducting polymer PCDTPT suppresses an undesirable “double‐slope” in the current–voltage characteristics, improves operational stability, and changes ambipolar transport to unipolar transport. Examination of other high μ polymers shows general applicability. This study also shows that one can further reduce instability by tuning the relative electron affinity of the polymer and fullerene by creating blends containing different fullerene derivatives and semiconductor polymers. One can obtain hole μ values up to 5.6 cm2 V–1 s–1 that are remarkably stable over multiple bias‐sweeping cycles. The results provide a simple, solution‐processable route to dictate transport properties and improve semiconductor durability in systems that display similar non‐idealities. By using fullerene derivatives as additives in ambipolar polymer semiconductor field‐effect transistors, the suppression of an undesirable double‐slope in the Id1/2 versus Vg plots, improved ION/IOFF, and stable VT and hole μ through bias stress are observed. These findings also provide a convenient route to fabricate p‐type organic field‐effect transistors from ambipolar semiconductors.