Influence of Shelf-Aging on Resistive Switching Characteristics of Sol–Gel-Processed ZnO and Al-Doped ZnO Structures

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 Ion/Ioff 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.