Passivation of CsPbBr3 nanocrystals with nitrogen-doped graphene quantum dots for white LEDs

Perovskite nanocrystals (PNCs) are promising luminescent materials for display applications owing to their exceptional optoelectronic characteristics. Nevertheless, their practical deployment is hindered by intrinsic high defect densities, which lead to insufficient photoluminescence quantum yields (PLQYs) and accelerated material degradation. In this study, a one-pot strategy was proposed by using nitrogen-doped graphene quantum dots (NGQDs) as surface ligands. Coupled with a polymethyl methacrylate (PMMA) coating, the NGQDs facilitate the formation of a robust composite architecture. Under optimized NGQD incorporation, the fabricated CsPbBr 3 /NGQDs/PMMA composite films display an ultra-narrow green emission peaked at 522 nm, with a full width at half maximum (FWHM) as narrow as 16 nm. More importantly, the composite exhibits significantly enhanced stability, maintaining 70% of its initial PL intensity after 7 days of water immersion or 1 h of thermal treatment at 100 °C. Such improvements are ascribed to effective defect passivation by the NGQDs and the beneficial role of their nitrogen-rich sites in promoting perovskite crystallization. As a demonstration of their potential, white light-emitting diodes (WLEDs) based on the composite realize a wide color gamut, covering 131% of the NTSC standard and 98% of the Rec. 2020 standard. This work thus proposes a novel one-pot in situ passivation approach, providing an effective route to concurrently address the efficiency and stability issues of PNCs.