Enhancing electrically driven excitonic emission stability in WSe₂ monolayer through contact engineering with HfN electrode

Abstract

Two-dimensional (2D) monolayered (ML) transition-metal dichalcogenides (TMDCs) show strong potential for compact optoelectronic devices, such as light-emitting devices (LEDs). Among all, ML WSe2 can potentially offer the highest external quantum efficiency (EQE) under ambient conditions. However, ML TMDC LEDs with conventional noble metal electrodes face challenges like heat accumulation and intensity quenching. We addressed these limitations by incorporating semi-metal HfN electrodes into AC-driven ML WSe2 LEDs. Replacing standard silver electrodes with HfN nearly doubled the EL intensity and reduced the quenching rate by 83%. After 2 & times;109 times of AC pulses injected, HfN could still help maintain over 80% of intensity magnitude, while Ag-electrode LEDs were almost burned out. Furthermore, HfN-electrode LEDs demonstrated superior excitonic EL stability and distinct defect-state recombination suppression after high-temperature treatment. These results highlight HfN electrodes' potential for durable TMDC LEDs and broader applications in 2D photodetectors, modulators, and integrated optoelectronic systems in the future.