Active Locating Exciton- and Charge-Initialized Degradation in Quantum-Dot Light-Emitting Diodes.

For quantum-dot light-emitting diodes (QLED), electrical aging commonly introduces collective aging sources across all layers, making it difficult to isolate the impact of each layer on electroluminescence (EL) degradation. In this work, a layer-selective aging method using active photoexcitation is proposed, in which the photoexcitation wavelength is used to selectively target specific layers for exciton generation, and an electrical bias is applied to induce photocurrent and create charges. An iterative aging-sampling (A-S) procedure is used to link aging conditions to EL degradation. It is found that photo-aging leads to strong but reversible quenching of EL intensity, which is interpreted as being caused by electrical field screening due to trapped charges in the quantum dot (QD) layer and requires electrical activation before the sampling (S) step. Repeated A-S cycles in a model red QLED system show that excitations in the QD layer result in negligible EL degradation. In contrast, aging of the hole-transport (HT) layer enables an acceleration of aging rate by 3 orders of magnitude compared to standard aging and is interpreted as a result of photo-charge accumulation in the HT layer, particularly related to electrons and low electron mobility.
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