Enhanced Electron Charging Induces Positive Aging of QD-LEDs: An Electrically Excited Transient Absorption Study

Quantum dot light-emitting diodes (QD-LEDs) require encapsulation to extend their storage and operational lifetime. However, acidic encapsulants commonly used usually induce an anomalous positive aging phenomenon─the device performance improves rather than decreases in the initial days. These uncontrollable gains hinder the commercialization of QD-LEDs, yet no study to date has directly probed the in situ evolution of charge carriers during this process. Here, we employ electrically excited transient absorption (EETA) spectroscopy to investigate how encapsulants influence charge carrier dynamics in QD-LEDs. Taking red QD-LEDs as a model system, we demonstrate that positive aging is accompanied by enhanced electron charging in the quantum dot (QD) layer and accelerated electron injection into the emissive layer. Furthermore, we show that acid-induced progressive passivation of surface defects on ZnMgO nanoparticles improves electron injection efficiency. This work reveals that enhanced electron charging induces positive aging in QD-LEDs.