Positive aging in InP-based QD-LEDs encapsulated with epoxy: the role of thiol molecules and post-annealing treatment

In this study, we uncover remarkable aging behavior in InP-based quantum dot light-emitting diodes (QD-LEDs) encapsulated with epoxy, where the current efficiency increases over time. Our investigation reveals that positive aging is driven by the diffusion of thiol molecules among the components of epoxy resin. As the aging process progresses, the epoxy components not only mitigate the photoluminescence loss in the QDs caused by the presence of ZnMgO nanoparticles and the Al electrode on top of the QD layer but also reduce the electron injection into the QD layer, leading to improved efficiency. Moreover, we found that the post-annealing treatment has a significant impact on the performance of the device. By carefully modulating the diffusive behavior, the optimal aging process results in significant enhancement in the overall performance of the green InP-based QD-LED. With a maximum luminance of 15 340 cd m-2 and a maximum external quantum efficiency of 5.13%, the improvement is approximately 30-fold. This study sheds light on the intricate interplay between the aging process, thiol molecules, and post-annealing treatment in QD-LEDs and opens avenues for further optimization and improvement. The diffusion of thiol molecules present in epoxy resin promotes positive aging in InP-based QD-LEDs. Subsequent annealing treatment enable thiol molecules migration into lower layers, leading to a remarkable performance enhancement.