Designing pH-Functionalized carbon dots as white light emitting phosphor for cool white LED application

Carbon Dots (CDs) are zero dimensional carbon rich nanoparticles that exhibit promising photoluminescent properties due to quantum confinement effect. Furthermore, their ease of synthesis, reduced toxicity and customizable properties have gained considerable focus. In the present era of advanced lighting technology, achieving single white light emitting CDs which could serve as white phosphors with high efficiency is essential due to their cost-effective application in Light Emitting Diodes (LEDs). Though various rare earth doped phosphors produce white light emission; their tedious synthetic process, high cost, potential toxicity imposes challenges in real world applications. In response to this, we explored reproducible one-step hydrothermal synthesis of white light emitting CDs from l-leucine and l-tryptophan under pH assisted reaction conditions. They exhibited wide photoluminescence emission spectrum reaching maximum intensity at 450 nm. These CDs were embedded into polyvinyl alcohol (PVA) matrix to attain colour conversion phosphor layer, which prevents aggregation induced self-quenching and were subsequently incorporated onto 365 nm UV LED. The fabricated CDs film was stable up to 300 days under room temperature storage conditions with a longer decay time of 18.6 ns. Intriguingly, a high Colour Rendering Index (CRI) of 86 % was achieved, exhibiting cool white light emission characterized by chromaticity coordinates of (0.302, 0.318) and Correlated Colour Temperature (CCT) of 7236 K positioned near the Planckian locus curve. These results highlight the potential of the synthesized CDs as efficient, metal-free phosphors for the development of cost effective cool white LEDs.