Sputter-deposited highly flexible noble metal multi-layer electrode viable for energy and luminescent devices

Abstract

Transparent conducting Indium tin oxide (ITO) electrode is predominantly utilized currently in most of the display and energy harvesting devices. However, its sustained usage is an imminent imperil due to its low availability, dwindling supply and recycling issues. There is a dire need to supplement the usage of ITO with appropriate alternatives in desired resistance scale, depending on the device necessity. At this juncture, an analogous viable transparent conducting ultrathin Au/Cu/Ag/Pt/Au noble metallic multi-layer electrode sputtered onto PET substrate is investigated. The multi-layer presents highest transmittance of 44% (at 500 nm) with a nearly uniform trend over the complete visible region of the electromagnetic spectrum. Electrical transport measurements of the multi-layer yielded 60 Ω/□ sheet resistance and a carrier mobility of 2.02 cm2 V−1 s−1. The transition of bare PET from hydrophilic (73.85°) to hydrophobic (99.83°) upon depositing the metallic multi-layer is indicated from contact angle measurements. The surface features studied using atomic force microscope and optical profiler show a uniform topography, free from cracks. The metallic multi-layer exhibits high mechanical strength up to 50,000 bending - twisting sequences. The measured surface work function of Au/Cu/Ag/Pt/Au metallic multi-layer is 5.01 eV. The ultrathin pliable metallic multi-layer tested in a piezoelectric nanogenerator device and alternating current-operated electroluminescent device as top electrode and bottom electrode, displays significant performance.