In Situ Electro-Mechanical Experiments and Mechanics Modeling of Fracture in Indium Tin Oxide-Based Multilayer Electrodes

Authors

  • Cheng Peng,

    1. Department of Mechanical Engineering and Materials Science, Rice University, 6100 Main Street MS 321, Houston, TX 77005, USA
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  • Zheng Jia,

    1. Department of Mechanical Engineering and Maryland Nano Center, University of Maryland, 2181 Glenn L. Martin Hall, College Park, MD 20742, USA
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  • Henry Neilson,

    1. Department of Mechanical Engineering and Materials Science, Rice University, 6100 Main Street MS 321, Houston, TX 77005, USA
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  • Teng Li,

    Corresponding author
    1. Department of Mechanical Engineering and Maryland Nano Center, University of Maryland, 2181 Glenn L. Martin Hall, College Park, MD 20742, USA
    • Department of Mechanical Engineering and Maryland Nano Center, University of Maryland, 2181 Glenn L. Martin Hall, College Park, MD 20742, USA.
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  • Jun Lou

    Corresponding author
    1. Department of Mechanical Engineering and Materials Science, Rice University, 6100 Main Street MS 321, Houston, TX 77005, USA
    • Department of Mechanical Engineering and Materials Science, Rice University, 6100 Main Street MS 321, Houston, TX 77005, USA.
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  • This work is supported by NSF Collaborative Research Grants (Nos. 0928278 and 0928297). T.L. also acknowledges the support of NSF (Grant No. 0856540). Z.J. acknowledges UMD Future Faculty Program and a student travel award from Haythornthwaite Foundation.

Abstract

Indium Tin Oxide (ITO) films are widely used as transparent electrodes in electronic displays and solar cells. However, the small fracture strain of brittle ITO films poses significant challenge to their applications in flexible electronics devices that often undergo large deformation. Inspired by recent development of inorganic/organic hybrid permeation barriers for flexible electronics, we design and fabricate ITO-based multilayer electrodes with enhanced electro-mechanical durability. In situ electro-mechanical experiments of five structural designs of ITO-based multilayer electrodes are performed to investigate the evolution of crack density and the corresponding variance of electrical resistance of such electrodes. A coherent mechanics model is established to determine the driving force for crack propagation in the ITO layer in these electrodes. The mechanics model suggests that a top protective polymeric coating above and an intermediate polymeric layer below the ITO layer can effectively enhance the mechanical durability of the ITO electrodes by reducing the crack driving force up to 10-folds. The modeling results offer mechanistic understanding of the in situ experimental measurements of the critical fracture strains of the five types of ITO-based multilayer electrodes. The findings in this work provide quantitative guidance for the material selection and structural optimization of ITO-based multilayer transparent electrodes of high mechanical durability.

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