An Electrode Based on Ca:Au Alloy and Atomic Layer Deposition for a Transparent Flexible OLED Device

Transparent organic light-emitting diodes (OLEDs) have the advantages of excellent visual experience and low power consumption, and can be applied to flexible display technology, completely breaking from traditional display technology. Transparent conductive electrodes (TCEs) are an important component for realizing high-performance OLEDs. At present, cathode materials widely used in transparent OLEDs include Mg:Ag alloys and Ca:Ag alloys; however, their low transmittance makes the light extraction rate relatively low. In this study, a composite transparent conductive cathode with a ZnO/Ca:Au/Al₂O₃ structure was fabricated by atomic layer deposition (ALD), achieving excellent optical transmittance, mechanical flexibility, and lateral conductivity. The ZnO layer prepared by ALD was used as the seed layer of the ultrathin Ca:Au alloy layer, while ensuring the low work function of the entire structure, and the Al₂O₃ layer prepared by ALD was used as an anti-reflection layer and encapsulation layer to improve the optical transmittance and the overall structure of the device lifetime. The luminance and external quantum efficiency (EQE) of the transparent OLED prepared in this work were significantly improved over the traditional Ca:Ag electrode, achieving values of 40,000 cd/m² and 31.2% at 5 V, respectively, and the average transmittance of the device in the visible light range was 53%.