Elucidating a complete picture of exciton dynamics in operating quantum-dot light-emitting diodes

Quantum-dot light-emitting diodes (QLEDs) are promising as energy-saving, color-pure, and flexible light sources for display, lighting, and communication techniques. At present, the performance of QLEDs is hindered by the efficiency roll-off at high currents and the device degradation in long-term operations. Further development of QLEDs demands an in-depth understanding of the fundamental processes in device operations. However, due to the lack of in-situ/operando characterization methods, the ultrafast charge and exciton dynamics in operating QLEDs is still not clear. Here, the project aims to go beyond the state-of-the-art methodologies, and create a set of ultrafast spectroscopic toolkits to elucidate a spatio-temporal resolved picture of exciton dynamics in operating QLEDs. I will realize a) operando time-resolved transient absorption (TA), b) operando spatio-temporal TA microscopy, and c) electrically-pumped time-resolved TA measurements on full stacks of QLEDs. I will gain quantitative insights into exciton dissociation, exciton diffusion, and electron injection dynamics. Finally, new mechanistic interpretations on the efficiency roll-off and degradation of QLEDs will be provided. The project covers the disciplines of optics, material science, and device physics, combining the host group's expertise in ultrafast spectroscopy, and the
researcher's expertise in QLEDs. The fellow will acquire complementary skills and knowledge to reach professional maturity. The outcomes will increase the fundamental understanding of nanomaterials and LEDs, facilitating the optimization of QLEDs towards practical requirements. The project will yield a widely-applicable toolkit for various LEDs. Successful implementation of this project will promote the competitiveness of the host organization in the field of optoelectronics. In the long run, the potential commercialization of QLEDs is expected to reduce electricity consumption and promote sustainable development in Europe.