Charge injection across self-assembly monolayers in organic field-effect transistors: Odd-even effects

Pablo Stoliar, Rajendra Kshirsagar, Massimiliano Massi, Paolo Annibale, Cristiano Albonetti, Dago M. De Leeuw, Fabio Biscarini*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

119 Citations (Scopus)

Abstract

We investigate the role of self-assembly monolayers in modulating the response of organic field-effect transistors. Alkanethiol monolayers of chain length n are self-assembled on the source and drain electrodes of pentacene field-effect transistors. The charge carrier mobility μ exhibits large fluctuations correlated with odd-even n. For n < 8, μ increases by 1 order of magnitude owing to the decrease of the hole injection barrier and the improved molecular order at the organic-metallic interface. For n ≥ 8, μ decays exponentially with an inverse decay length β = 0.6 Å-1. Our results show that (i) charge injection across the interface occurs by through-bond tunneling of holes mediated by the alkanethiol layer; (ii) in the long-chain regime, the charge injection across the alkanethiol monolayer completely governs the transistor response; (iii) the transistor is a sensitive gauge for probing charge transport across single monolayers. The odd-even effect is ascribed to the anisotropic coupling between the alkanethiol terminal bond and the HOMO level of ordered pentacene molecules.

Original languageEnglish
Pages (from-to)6477-6484
Number of pages8
JournalJournal of the American Chemical Society
Volume129
Issue number20
DOIs
Publication statusPublished - 23 May 2007

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