Properties of transparent and conductive Al:ZnO/Au/Al:ZnO multilayers on flexible PET substrates

• Transparent, low resistive AZO/Au/AZO layers were sputtered on PET substrates.
• AZO/Au/AZO has higher figure of merit than ITO for specific Au thicknesses.
• The resistance of AZO/Au/AZO is stable against repetitive substrate bending.
• AZO/Au/AZO electrode performance is comparable to ITO in light emitting diodes.

We investigate the structural, electrical and optical properties of transparent electrodes, consisting of Al-doped ZnO (AZO) and ultrathin Au layers, sputtered on polyethylene terephthalate (PET). These electrodes are relevant for optoelectronic devices and thin film photovoltaics. When deposited on AZO, Au films as thin as 3 nm form electrically conductive, meandering structures, whereas uniform Au films are obtained from a thickness of 5 nm. The sheet resistance decreases with Au thickness, reaching 7 Ω for 11 nm-thick Au. AZO/Au/AZO trilayers combine lowest resistance with highest transparency, while their resistance stability against bending fatigue is superior to the Sn-doped In2O3 (ITO) electrode. The figure of merit of AZO/Au/AZO is larger than of ITO for Au thickness equal to or larger than 9 nm. To demonstrate the applicability of the AZO/Au/AZO transparent electrode, simple organic light emitting diodes were fabricated and tested in comparison to PET/ITO standard substrates.