Low activation energy field-effect transistors fabricated by bar-assisted meniscus shearing

Abstract

Here, we study the temperature-dependent transport properties of OFETs with the prototypical OSC 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) co-processed with polystyrene (PS) as the active layer. The active layer is deposited directly on SiO2 using the bar-assisted meniscus shearing (BAMS) method. The co-processing with PS favors a consequential decrease in interfacial trap densities as previously reported. Furthermore, we demonstrate how this processing method leads to devices exhibiting activation energies well below the current state of the art for TIPS-pentacene on SiO2 or other dielectrics. Altogether, our study reports on TIPS-pentacene thin films exhibiting an activation energy (Ea) as low as 15 meV when the active material is blended with PS and processed via BAMS. Such an unprecedentedly low value originates not only from a decrease in the interfacial trap densities but also from trapping energies much shallower than previously reported elsewhere for the same material. This allows us to clarify the previously reported notion that significant passivation of interfacial traps occurs following the separation of PS from TIPS-pentacene into an individual layer at the interface with the insulator and to confirm that the enhanced transport originates from a synergistic effect wherein both trapping density and depth are reduced. ; E.O. and I.S. acknowledge the financial support of the Natural Sciences and Engineering Research Council of Canada (NSERC) (funding Reference Nos. RGPIN-201805092 and RGPIN-2017-06748), the Fonds de recherche du Québec-Nature et technologies (FRQNT). E.O. also acknowledges the financial support of the Canadian Foundation for Innovation (CFI) through the John R. Evans Leaders Fund (JELF). M.M.T. acknowledges funding by the Spanish Ministry with the Project No. GENESIS PID2019-111682RB-I00 and through the "Severo Ochoa" Programme for Centers of Excellence in R&D (No. FUNFUTURE CEX2019-000917-S) and the Generalitat de Catalunya (No. 2017-SGR-918). A.T. acknowledges his FPU fellowship and is enrolled in the UAB Materials Science Ph.D. program. M.B.R. cordially thanks NSERC for support through the Canada Graduate Scholarships–Master's program and the Centre québécois sur les matériaux fonctionnels (CQMF) for his summer scholarship. ; With funding from the Spanish government through the 'Severo Ochoa Centre of Excellence' accreditation (CEX2019-000917-S). ; Peer reviewed