Jaehoon Kim

Sol–gel-processed zinc oxide (ZnO) is indispensable in various optoelectronic applications, such as quantum dot light-emitting diodes (QLEDs), due to its high electron transport capability and adjustable oxygen vacancy characteristics. However, its commercialization has been delayed by defect-related issues and a high sensitivity to fabrication conditions. ZnO exhibits complex aging behaviors, notably ‘shelf-aging,’ where device properties change unpredictably over time even without external stimuli. Recent studies suggest that this shelf-aging in QLEDs might relate to the resistive switching (RS) behavior in ZnO, affecting the current conduction mechanism through external bias and internal oxygen dynamics. Despite its significance, systematic studies on the shelf-aging effects in ZnO-based RS structures have been lacking. In this study, we fabricate RS devices using sol–gel-processed ZnO and aluminum-doped ZnO (AZO) as dielectric layers, employing indium tin oxide (ITO) and aluminum (Al) as electrodes—materials commonly utilized in QLEDs. Notably, the I_on/I_off ratio increased during the initial storage period, reaching the highest measured values after two days for ZnO and three days for AZO, followed by a decrease at later storage times. Further electrical measurements revealed storage-associated changes, while qualitative time-of-flight secondary ion mass spectrometry (TOF-SIMS) profiles showed differences between pristine and archived aged specimens. These observations suggest possible interfacial or defect-related contributions. Overall, this study documents electrical evolution in simplified oxide/Al-containing RS structures during ambient storage with repeated measurements and generates hypotheses for future investigation into complete QLEDs.

Maskless and simple laser fabrication produces porous laser-induced graphene (LIG) that serves as an excellent platform for integrating PbS quantum dots into high-performance heterostructure photodetectors.

Sol–gel-processed zinc oxide (ZnO) and magnesium-doped zinc oxide (ZnMgO) are widely used in quantum dot light-emitting diodes (QLEDs) due to their excellent charge transport properties, ease of fabrication, and tunable film characteristics. In particular, the ZnMgO/ZnO bilayer structure has attracted considerable attention for its dual functionality: defect passivation by ZnMgO and efficient charge transport by ZnO. However, while the effects of resistive switching (RS) in individual ZnO and ZnMgO layers on the aging behavior of QLEDs have been studied, the RS characteristics of sol–gel-processed ZnMgO/ZnO bilayers remain largely unexplored. In this study, we systematically analyzed RS properties of an indium tin oxide (ITO)/ZnMgO/ZnO/aluminum (Al) device, demonstrating superior performance compared to devices with single layers of either ZnMgO or ZnO. We also investigated the shelf-aging characteristics of RS devices with single and bilayer structures, finding that the bilayer structure exhibited the least variation over time, thereby confirming its enhanced uniformity and reliability. Furthermore, based on basic current–voltage measurements, we estimated accuracy variations in MNIST pattern recognition using a two-layer perceptron model. These results not only identify a promising RS device architecture based on the sol–gel process but also offer valuable insights into the aging behavior of QLEDs incorporating ZnMgO/ZnO bilayers, ITO, and Al electrodes.

Recent advancements and challenges in scaling up quantum dot light-emitting diodes are highlighted, particularly with respect to the metal oxide nanoparticle and organic electron transport layers.

To achieve a simplified method instead of resin-induced post-treatment, 2-hydroxyethyl methacrylate, a component of the resin, was pre-mixed with ZnMgO nanoparticles, leading to enhanced efficiency and lifetime.

Colloidal quantum dots (QDs) exhibit tremendous potential in display technologies owing to their unique optical properties, such as size‐tunable emission wavelength, narrow spectral linewidth, and near‐unity photoluminescence quantum yield. Significant efforts in academia and industry have achieved dramatic improvements in the performance of quantum dot light‐emitting diodes (QLEDs) over the past decade, primarily owing to the development of high‐quality QDs and optimized device architectures. Moreover, sophisticated patterning processes have also been developed for QDs, which is an essential technique for their commercialization. As a result of these achievements, some QD‐based display technologies, such as QD enhancement films and QD‐organic light‐emitting diodes, have been successfully commercialized, confirming the superiority of QDs in display technologies. However, despite these developments, the commercialization of QLEDs is yet to reach a threshold, requiring a leap forward in addressing challenges and related problems. Thus, representative research trends, progress, and challenges of QLEDs in the categories of material synthesis, device engineering, and fabrication method to specify the current status and development direction are reviewed. Furthermore, brief insights into the factors to be considered when conducting research on single‐device QLEDs are provided to realize active matrix displays. This review guides the way toward the commercialization of QLEDs.

The quantum dot light‐emitting diode (QLED) represents one of the strongest display technologies and has unique advantages like a shallow emission spectrum and superior performance based on the cumulative studies of state‐of‐the‐art quantum dot (QD) synthesis and interfacial engineering. However, research on managing the device's light extraction has been lacking compared to the conventional LED field. Moreover, relevant studies on top‐emitting QLEDs (TE‐QLEDs) have been severely lacking compared to bottom‐emitting QLEDs (BE‐QLEDs). This paper demonstrates a novel light extraction structure called the randomly disassembled nanostructure (RaDiNa). The RaDiNa is formed by detaching polydimethylsiloxane (PDMS) film from a ZnO nanorod (ZnO NR) layer and laying it on top of the TE‐QLED. The RaDiNa‐attached TE‐QLED shows significantly widened angular‐dependent electroluminescence (EL) intensities over the pristine TE‐QLED, confirming the effective light extraction capability of the RaDiNa layer. Consequently, the optimized RaDiNa‐attached TE‐QLED achieves enhanced external quantum efficiency (EQE) over the reference device by 60%. For systematic analyses, current–voltage–luminance (J–V–L) characteristics are investigated using scanning electron microscopy (SEM) and optical simulation based on COMSOL Multiphysics. It is believed that this study's results provide essential information for the commercialization of TE‐QLEDs.