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The Substrate is a pH-Controlled Second Gate of Electrolyte-Gated Organic Field-Effect Transistor

Lookup NU author(s): Professor Mark GeogheganORCiD



This is the authors' accepted manuscript of an article that has been published in its final definitive form by American Chemical Society, 2016.

For re-use rights please refer to the publisher's terms and conditions.


© 2016 American Chemical Society.Electrolyte-gated organic field-effect transistors (EGOFETs), based on ultrathin pentacene films on quartz, were operated with electrolyte solutions whose pH was systematically changed. Transistor parameters exhibit nonmonotonic variation versus pH, which cannot be accounted for by capacitive coupling through the Debye-Helmholtz layer. The data were fitted with an analytical model of the accumulated charge in the EGOFET, where Langmuir adsorption was introduced to describe the pH-dependent charge buildup at the quartz surface. The model provides an excellent fit to the threshold voltage and transfer characteristics as a function of the pH, which demonstrates that quartz acts as a second gate controlled by pH and is mostly effective from neutral to alkaline pH. The effective capacitance of the device is always greater than the capacitance of the electrolyte, thus highlighting the role of the substrate as an important active element for amplification of the transistor response.

Publication metadata

Author(s): Di Lauro M, Casalini S, Berto M, Campana A, Cramer T, Murgia M, Geoghegan M, Bortolotti CA, Biscarini F

Publication type: Article

Publication status: Published

Journal: ACS Applied Materials and Interfaces

Year: 2016

Volume: 8

Issue: 46

Pages: 31783-31790

Print publication date: 23/11/2016

Online publication date: 11/11/2016

Acceptance date: 22/09/2016

Date deposited: 21/01/2021

ISSN (print): 1944-8244

ISSN (electronic): 1944-8252

Publisher: American Chemical Society


DOI: 10.1021/acsami.6b06952


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