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.

Plasmonic metal oxides and their biological applications

“…Sol-gel method. Complementary to the commonly adopted synthesis pathways discussed above, the ''sol-gel'' method is another popular approach for transparent MO thin film synthesis and optoelectronics, 126,127 though it is rarely reported in plasmonic MO fabrication. The ''sol-gel'' method describes the approach of the formation of a liquid-phase network (gel) from colloidal suspension (sol), which usually features arbitrary architectures while maintaining the unique properties of nano-sized materials.…”

A Review on Quantum Dot Light‐Emitting Diodes: From Materials to Applications

“…[3] The energy band level of some of the material that has been reported in QLED is shown in Figure 6. [10,105,106,[110][111][112][113][114] Recently, it was found that the carrier transport behavior in blue QLEDs has changed due to the wider bandgap of the blue QDs, leading to a more complicated charge balance problem in blue QLEDs. On the one hand, the deeper valence band maximum (VBM) of QDs increase the hole injection barrier of HTL/QDs.…”

Tailored ZnO Functional Nanomaterials for Solution‐Processed Quantum‐Dot Light‐Emitting Diodes

“…Therefore, low‐temperature (typically <100 °C) solution‐precipitation synthetic methods for the preparation of amorphous TMO thin films are desired, especially in printed plastic optoelectronic domains. [ 27 ]…”

“…Therefore, low-temperature (typically <100 °C) solution-precipitation synthetic methods for the preparation of amorphous TMO thin films are desired, especially in printed plastic optoelectronic domains. [27] Specifically, in the synthesis processes of ZnO NPs, the widely used precursors are zinc acetate dihydrate (ZnAc 2 •2H 2 O) [28] and zinc nitrate hydrate (Zn(NO 3 ) 2 •xH 2 O) in alcoholic or aqueous solvents, to achieve sub-10 nm NPs. [29] The ZnO NPs are eventually dispersed and stored in polar solvents.…”