Mechanically stable ultrathin flexible metallic Au/Pt/Au tri-layer as an alternative transparent conducting electrode for optoelectronic device applications

Abstract

Indium tin oxide (ITO) is a ubiquitous transparent conducting oxide employed in several modern optoelectronic devices. However, due to limited availability and fast depletion of indium, there is an urge to supplement its use with suitable alternatives in appropriate sheet resistance range, depending on the application requirement. In this scenario, an alternative flexible transparent conducting Au/Pt/Au ultrathin metallic tri-layer electrode sputter-deposited on PET substrate is explored. The tri-layer shows maximum transmittance of 55% at 500 nm and it presents a nearly flat behavior in the entire visible spectrum. Electrical transport properties of Au/Pt/Au layer show sheet resistance of 66 Ω/□ and mobility of 8.32 cm2V−1s−1, respectively. The contact angle measurement indicates that plain hydrophilic PET (62.6°) turns hydrophobic (94.2°) upon coating with Au/Pt/Au tri-layer. The surface properties analyzed using atomic force microscopy and optical profilometry indicate a crack-free, densely packed homogenous film. The tri-layer film shows mechanical stability up to 50,000 bending and twisting cycles. The obtained surface work function of Au/Pt/Au tri-layer film is 4.97 eV. The ultrathin flexible Au/Pt/Au tri-layer explored as top electrode in a piezoelectric generator and as top and bottom electrodes in an alternating current driven electroluminescent device exhibits appreciable performance.