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

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 degrees 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.