Local Surface Plasmon–Graphene Synergy for Efficient Quantum Dot Color Conversion in Micro-LEDs

Exciting quantum dots (QDs) with short-wavelength micro-LEDs (μLEDs) are one of the most promising approaches for achieving full-color μLED displays. However, the low color conversion efficiency (CCE) caused by surface carrier loss in QDs remains a major barrier to large-scale application. In this work, we propose a novel color conversion layer structure incorporating a graphene interlayer and nanogapped gold nanoparticles (AuNNPs) within the QD layer to realize efficient color conversion in GaN-based blue μLEDs. The AuNNPs can boost the radiative recombination of the QDs via localized surface plasmon resonance (LSPR), which further improves the quantum yield. Meanwhile, the graphene layer functions as a carrier transport channel, facilitating the transfer of photogenerated carriers to adjacent QDs, thereby promoting the carrier population and radiative recombination within the QDs. Detailed physical analysis and optical measurements confirm the feasibility of this strategy. The results show that the synergistic effects of AuNNPs and graphene enable a high CCE of over 91%, with a 25% improvement compared to conventional structures at a current density of 200 A/cm2. This QD/AuNNP-Graphene-QD/AuNNP multilayer structure demonstrates significant potential for full-color display applications in μLED technology.