Balancing Surface Hydrophobicity and Polarizability of Fluorinated Dielectrics for Organic Field‐Effect Transistors with Excellent Gate‐Bias Stability and Mobility. Issue 15 (8th June 2016)

• Record Type: Journal Article
• Authors: Jang, Mi; Lee, Minjung; Shin, Hwanho; Ahn, Joongyu; Pei, Mingyuan; Youk, Ji Ho; Yang, Hoichang
• Is Part Of: Advanced materials interfaces. Volume 3:Issue 15(2016)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2016-06-08
• Subjects: fluorocopolymers -- gate‐bias stability -- hydrophobicity -- organic field‐effect transistors -- polarizability; Materials science -- Periodicals; 620.11
• DOI: 10.1002/admi.201600284
• Languages: English
• ISSNs: 2196-7350

Abstract

Abstract : It is demonstrated that treating dielectrics with fluorinated polymers, which have excellent hydrophobicity, chemical inertness, and the lowest polarizability, yields a semiconductor‐compatible surface energy and excellent charge detrapping characteristics. Fluorocopolymers, polystyrene‐ random ‐poly(2, 3, 4, 5, 6‐pentafluorostyrene) (PS‐ r ‐PPFS) copolymers with different 2, 3, 4, 5, 6‐pentafluorostyrene (PFS) loadings, are synthesized to modify a SiO2 gate dielectric using radical polymerization. Surface energy ( γ ) of the copolymer‐treated SiO2 dielectrics decreases from 40.7 to 24.0 mJ m −2 with increasing PFS mol% in the copolymer. Pentacene organic field‐effect transistors (OFETs) show field‐effect mobility ( μ FET ) values ranging from 0.82 (for 0 mol% PFS) to 0.25 cm 2 V −1 s −1 (for 100 mol% PFS). Enhancing the bias stress stability without affecting the μ FET value is achieved via the introduction of a small mol% fluorocarbon segments onto the PS‐ r ‐PPFS backbone. 15 mol% PFS‐loaded fluorocopolymer‐coated SiO2 substrate yields a γ value of 35 mJ m −2, close to that (38 mJ m −2 ) of the lowest‐ γ crystal surface of pentacene, and the corresponding OFETs have μ FET values up to 0.81 cm 2 V −1 s −1 and excellent gate‐bias stress stability in comparison to the rich fluorinated dielectric systems, which has degraded μ FET values ranging from 0.2 to 0.4 cm 2 V −1 s −1 . Abstract : Excellent gate‐bias stress stability of pentacene organic field‐effect transistors (OFETs) can be achieved without any degradation in charge carrier mobility by introducing small mol% of fluorocarbon moieties into the styrene‐based copolymers. This optimizes dielectric surface properties (energy of 35.0 mJ m −2 and roughness of 0.26 nm) to induce highly ordered pentacene crystals, and minimizes trapping of injected charge carriers in OFETs.