A Study on Reducing Contact Resistance in Solution-Processed Organic Field-Effect Transistors

Sangmoo Choi; Canek Fuentes-Hernandez; Cheng-Yin Wang; Talha M Khan; Felipe A Larrain; Yadong Zhang; Stephen Barlow; Seth R Marder; Bernard Kippelen

doi:10.1021/acsami.6b07029

A Study on Reducing Contact Resistance in Solution-Processed Organic Field-Effect Transistors

ACS Appl Mater Interfaces. 2016 Sep 21;8(37):24744-52. doi: 10.1021/acsami.6b07029. Epub 2016 Sep 12.

Authors

Sangmoo Choi¹, Canek Fuentes-Hernandez¹, Cheng-Yin Wang¹, Talha M Khan¹, Felipe A Larrain¹, Yadong Zhang², Stephen Barlow², Seth R Marder², Bernard Kippelen¹

Affiliations

¹ Center for Organic Photonics and Electronics (COPE), School of Electrical and Computer Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0250, United States.
² Center for Organic Photonics and Electronics (COPE), School of Chemistry and Biochemistry, Georgia Institute of Technology , Atlanta, Georgia 30332-0400, United States.

PMID: 27579570
DOI: 10.1021/acsami.6b07029

Abstract

We report on the reduction of contact resistance in solution-processed TIPS-pentacene (6,13-bis(triisopropylsilylethynyl)pentacene) and PTAA (poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]) top-gate bottom-contact organic field-effect transistors (OFETs) by using different contact-modification strategies. The study compares the contact resistance values in devices that comprise Au source/drain electrodes either treated with 2,3,4,5,6-pentafluorothiophenol (PFBT), or modified with an evaporated thin layer of the metal-organic molecular dopant molybdenum tris-[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd)3), or modified with a thin layer of the oxide MoO3. An improved performance is observed in devices modified with Mo(tfd)3 or MoO3 as compared to devices in which Au electrodes are modified with PFBT. We discuss the origin of the decrease in contact resistance in terms of increase of the work function of the modified Au electrodes, Fermi-level pinning effects, and decrease of bulk resistance by electrically doping the organic semiconductor films in the vicinity of the source/drain electrodes.

Keywords: Fermi-level pinning; TIPS-pentacene/PTAA; contact doping; contact resistance; molybdenum trioxide; molybdenum tris-[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene]; organic field-effect transistors; top-gate geometry.