Low‐Temperature Solution‐Processed Transparent QLED Using Inorganic Metal Oxide Carrier Transport Layers

Abstract Quantum dot light‐emitting diodes (QLEDs) represent an exciting new technology that has many desirable attributes when compared to existing organic LEDs (OLEDs) including increased brightness, contrast, and response time. Solution‐based fabrication approaches have the advantage of being able to produce large‐area electronic systems at reduced costs and critical in applications such as large display fabrication and electronics on curved surfaces including low‐profile augmented reality glasses. In this paper, for the first time, a fully solution‐processed transparent inorganic QLED is described. Traditional QLED fabrication methodologies require the use of air‐sensitive materials that make fabrication of these devices challenging and expensive. Instead of using air‐sensitive organic materials, in the approach, nickel oxide (NiO) is used as the hole transport layer and is deposited using a sol‐gel method. Copper doping of the NiO to reduce the turn‐on voltage of the QLED device is investigated. Importantly, the post‐annealing temperature of the sol‐gel process is below 275 °C, which permits the fabrication of QLEDs on a wide range of substrates. The experimental results are concordant with the COMSOL simulation data and demonstrate the feasibility of fabricating fully transparent inorganic QLED devices using a solution‐based process.