Decoupling Transparency and Electron Injection in Ultrathin Ag Electrodes Using an Al/MoO3 Double Seed Layer for Transparent Quantum Dot Light-Emitting Diodes

Abstract

There is growing interest in transparent quantum dot light-emitting diodes (Tr-QLEDs) for window-type displays. For such devices, the top transparent electrode must simultaneously provide high optical transmittance, low sheet resistance, and efficient charge injection. Ultrathin Ag films are promising because of their high conductivity and transparency, but they tend to grow via the Volmer-Weber mode, resulting in poor continuity and increased resistance. Although seed layers have been widely used to improve Ag film continuity, their influence on charge injection in practical devices has received limited attention. Here, an Al/MoO3 double seed layer is introduced, in which MoO3 provides high transmittance and low sheet resistance, while Al enhances electron injection. This strategy enables continuous 10 nm Ag films with a transmittance of 63.48% and a sheet resistance of 7.35 Omega sq-1. Tr-QLEDs incorporating the Al/MoO3 double seed layer exhibit a twofold increase in external quantum efficiency and a threefold improvement in operational lifetime compared with devices employing a MoO3 single seed layer. Furthermore, large-area Tr-QLEDs are demonstrated on a 2 & times; 2 inch substrate, highlighting the potential of this electrode strategy for scalable transparent displays.