Comparisons of the Mechanical Behaviors of Poly (3, 4-ethylenedioxythiophene) (PEDOT) and ITO on Flexible Substrates
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Comparisons of the Mechanical Behaviors of Poly (3, 4-ethylenedioxythiophene) (PEDOT) and ITO on Flexible Substrates Khalid Alzoubi1, Gihoon Choi1, Mohammad M. Hamasha1, Atif S Alkhazali2, John DeFranco3, Susan Lu2, Bahgat Sammakia4, and Charles Westgate1 1 Center for Autonomous Solar Power (CASP), State University of New York at Binghamton, Binghamton, NY 13905 2 Deaprtment of Systems Science and Industrial Engineering, State University of New York at Binghamton, Binghamton, NY 13905 3 Orthogonal Inc, Ithaca, NY 14850 4 Deaprtment of Mechanical Engineering, State University of New York at Binghamton, Binghamton, NY 13905 ABSTRACT Indium Tin Oxide (ITO) has been widely used as a Transparent Conductive Oxide (TCO) layer in the photovoltaic solar technology because of its excellent electrical and optical properties. However, ITO is brittle, and its conductivity decreases significantly as the ITO films are exposed to stretching or bending strains especially in flexible/foldable solar cell applications. The cracks in ITO appear at very low strains which might cause failure in the conductive layer because of the combination of a very thin film of brittle ceramic material applied to a polymer substrate. Poly (3, 4-ethylenedioxythiophene), abbreviated PEDOT, is of increasing interest as a competitive candidate to ITO. PEDOT has found its way in many applications such as transparent electrode materials and transparent conductive layers in photovoltaic solar cells. In this work, the mechanical behavior of PEDOT was studied under high cycle bending fatigue in which the effects of bending diameter and bending frequency were considered and compared to ITO. High magnification optical images were used to study cracking in the PEDOT as well as the ITO layers. In flexible solar cells, the web will be exposed to folding/bending many times during manufacturing and installation. Therefore, the thin film substrate structure will be exposed to cyclic loading cyclic tensile and compressive strains. Therefore, this work was designed to mechanically fatigue the structure and study its behavior. It was found that bending diameters as well as material (PEDOT or ITO) have a great influence on the electrical conductivity of the thin films. INTRODUCTION Indium Tin Oxide (ITO) has been widely used as a transparent conductive oxide in solar cell structures because of its superior electrical and optical properties. The deposition of ITO on glass substrates requires high temperatures to obtain low sheet resistance and high transparency, which is not suitable for flexible electronics applications. When electronic systems are fabricated on flexible platforms, ITO thin films cannot withstand even small strains. Therefore, this research is to identify alternative materials that can withstand greater mechanical and thermal strains without significant degradation in their electrical and optical properties. Organic conductive materials have been investigated, although the electrical and optical properties of organic conductive materials are not as attract
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