Tuning of metal work functions with self-assembled monolayers

B de Boer*, A Hadipour, R Foekema, T van Woudenbergh, MM Mandoc, VD Mihailetchi, PWM Blom

*Corresponding author for this work

    Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

    2 Citations (Scopus)

    Abstract

    Tuning the work functions of metals was demonstrated by chemically modifying the metal surface through the formation of chemisorbed self-assembled monolayers (SAMs) derived from 1H,1H,2H,2H-perfluorinated alkanethiols and hexadecanethiol. The ordering inherent in the SAMs creates an effective, molecular dipole at the metal/SAM interface, which increased the work function of Ag (Phi(Ag) similar to 4.4 eV) to 5.5 eV (DeltaPhi similar to 1.1 eV) for 1H,1H,2H,2H-perfluorinated alkanethiols. Hexadecanethiol on the other hand shifted Phi(Ag) toward 3.8 eV (DeltaPhi similar to 0.6 eV) and raised the energy barrier for hole injection. These SAMs on Au were less efficient. 1H,1H,2H,2H-perfluorodecanethiol raised Phi(Ag) (4.9 eV) by 0.5 eV to 5.4 eV, whereas hexadecanethiol decreased DeltaPhi by only 0.1 eV. These chemically modified electrodes were applied in the fabrication of pLEDs and the hole conduction of MEH-PPV was investigated. An ohmic contact for hole injection between a silver electrode functionalized with the perfluorinated SAMs, and MEH-PPV with a HOMO of 5.2 eV was established. Conversely, a silver electrode modified with a SAM of hexadecanethiol lowered Phi(Ag) to 3.8 eV, creating an efficient energy barrier for hole injection. This method demonstrates a simple and attractive approach to modify and improve metal/organic contacts in organic electronic devices like LEDs and photovoltaic cells.

    Original languageEnglish
    Title of host publicationORGANIC OPTOELECTRONICS AND PHOTONICS
    EditorsPL Heremans, M Muccini, H Hofstraat
    Place of PublicationBELLINGHAM
    PublisherSPIE - INT SOC OPTICAL ENGINEERING
    Pages18-25
    Number of pages8
    ISBN (Print)0-8194-5387-0
    DOIs
    Publication statusPublished - 2004
    EventConference on Organic Optoelectronics and Photonics - , France
    Duration: 28-Apr-200430-Apr-2004

    Publication series

    NamePROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE)
    PublisherSPIE-INT SOC OPTICAL ENGINEERING
    Volume5464
    ISSN (Print)0277-786X

    Other

    OtherConference on Organic Optoelectronics and Photonics
    CountryFrance
    Period28/04/200430/04/2004

    Keywords

    • self-assembly
    • SAM
    • work function tuning
    • interfaces
    • dipole
    • perfluorinated alkanethiols
    • LEDs
    • photovoltaic cells
    • ATOMIC-FORCE MICROSCOPY
    • ELECTRONIC DEVICES
    • WETTING PROPERTIES
    • MOLECULAR PACKING
    • CHARGE INJECTION
    • GOLD
    • SURFACES
    • ALKANETHIOLS
    • DEPENDENCE
    • DISULFIDES

    Cite this