Design of a MoOx/Au/MoOx transparent electrode for high-performance OLEDs

A MoO_x(top)/Au/MoO_x(bottom) multilayer was systematically designed for transparent electrodes in green OLEDs in terms of optical transmission and series resistance of the device. The enhancement in optical transmission of MoO_x/Au/MoO_x (MAM) structures is a result of a series of events, including the optical interference within the multilayers and the interaction of light with surface plasmon polaritons in the metal layer. For the maximum transmission, the optical interference occurring within the multilayers was simulated using a transfer matrix model to determine the optimum thickness of MoO_x layers, and then the thickness of the Au interlayer was experimentally optimized for extraordinary optical transmission. In addition, the series resistance added by the top MoO_x was characterized to confirm its negligible impact on the performance of the device. The optimum MoO_x (40 nm)/Au (10 nm)/MoO_x (40 nm) structure showed much higher transmission in the green-red region and lower sheet resistance than indium tin oxide (ITO). We have fabricated MAM-based OLEDs the driving voltage of which was significantly reduced to ∼5.5 V at a current density of 20 mA/cm², and the current efficiency (11.46 Cd/A) was higher than that (10.91 Cd/A) of ITO-based OLEDs, demonstrating that the MAM electrode is a potential replacement for ITO in optical devices.