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Beyond the 2D Field‐Effect Charge Transport Paradigm in Molecular Thin‐Film Transistors

Benvenuti, Emilia; Portale, Giuseppe; Brucale, Marco; Quiroga, Santiago D.; Baldoni, Matteo; MacKenzie, Roderick C.I.; Mercuri, Francesco; Canola, Sofia; Negri, Fabrizia; Lago, Nicolò; Buonomo, Marco; Pollesel, Andrea; Cester, Andrea; Zambianchi, Massimo; Melucci, Manuela; Muccini, Michele; Toffanin, Stefano

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Authors

Emilia Benvenuti

Giuseppe Portale

Marco Brucale

Santiago D. Quiroga

Matteo Baldoni

Francesco Mercuri

Sofia Canola

Fabrizia Negri

Nicolò Lago

Marco Buonomo

Andrea Pollesel

Andrea Cester

Massimo Zambianchi

Manuela Melucci

Michele Muccini

Stefano Toffanin



Abstract

Organic field-effect transistors (OFETs) are considered almost purely interfacial devices with charge current mainly confined in the first two semiconducting layers in contact with the dielectric with no active role of the film thickness exceeding six to eight monolayers (MLs). By a combined electronic, morphological, structural, and theoretical investigation, it is demonstrated that the charge mobility and source–drain current in 2,20-(2,20-bithiophene-5,50-diyl)bis(5-butyl-5H-thieno[2,3-c]pyrrole-4,6)-dione (NT4N) organic transistors directly correlate with the out-of-plane domain size and crystallite orientation in the vertical direction, well beyond the dielectric interfacial layers. Polycrystalline films with thickness as high as 75 nm (≈30 MLs) and 3D molecular architecture provide the best electrical and optoelectronic OFET characteristics, highlighting that the molecular orientational order in the bulk of the film is the key-enabling factor for optimum device performance. X-ray scattering analysis and multiscale simulations reveal the functional correlation between the thickness-dependent molecular packing, electron mobility, and vertical charge distribution. These results call for a broader view of the fundamental mechanisms that govern field-effect charge transport in OFETs beyond the interfacial 2D paradigm and demonstrate the unexpected role of the out-of-plane domain size and crystallite orientation in polycrystalline films to achieve optimum electronic and optoelectronic properties in organic transistors.

Journal Article Type Article
Online Publication Date Aug 15, 2022
Publication Date 2023-01
Deposit Date Aug 25, 2022
Publicly Available Date Mar 15, 2023
Journal Advanced Electronic Materials
Electronic ISSN 2199-160X
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 9
Issue 1
Article Number 2200547
DOI https://doi.org/10.1002/aelm.202200547
Public URL https://durham-repository.worktribe.com/output/1193617

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Copyright Statement
© 2022 The Authors. Advanced Electronic Materials published by Wiley-VCH GmbH

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.





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