Indium-free transparent TiOx/Ag/WO3 stacked composite electrode with improved moisture resistance
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Amorphous TiOx, WO3 and Ag mid-layer films were deposited on polyethersulfone (PES) and soda-lime glass via electron beam evaporation at room temperature. The crystallinity, microstructure and surface morphology of asymmetric TiOx/Ag/WO3 multilayers (TAW) and symmetric WO3/Ag/WO3 (WAW) multilayers were investigated. The polygrains oriented along the (111) planes in the inserted Ag thin films were adopted to supply carriers into both of the dielectric layers and reduce the sheet resistance of the multilayer. The TAW multilayer with a sufficiently large Ag thickness (>15 nm) exhibited low resistance, and highly visible transmittance, low infra-red transmittance, to serve as a transparent conductive electrode and a good heat mirror. The dependence of the Ag and TiOx thickness on the optical and electrical properties of TAW multilayers was also explored. A figure of merit (FOM) was used to find an optimal layer structure for a TAW multilayer with superior conductivity and highly visible transparency. A high FOM of 1.2 × 10−1 (Ω−1) was achieved at the visible wavelength of 550 nm for a asymmetric TAW stacked layer on PES with a 15-nm-thick Ag layer, a 40-nm-thick TiOx and a 40 nm-thick WO3 layer. The moisture resistances of the TAW stacking layer showed more robustness than that of the WAW sample after damp heat exposure.
KeywordsAg2O Transparent Conductive Oxide TiOx Organic Light Emit Diode Visible Transmittance
One of authors (P. S. Chen) acknowledges that this work is supported by the Minister of Science and Technology through Grant No. MOST 104-2221-E-159-008.
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