High Stability Carbon Dots Phosphor and Ultra-High Color Rendering Index White Light-Emitting Diodes

A new kind of carbon dots based phosphor is developed for light emitting diodes (LED) by adsorbing carbon dots to starch particles. The bonding mechanism is based on hydrogen bonding of surface functional groups of carbon dots and starch particles. Aggregation-induced quenching is avoided and the thermal stability of the carbon dots phosphor is enhanced. The carbon dots phosphor is used as color convert material for white LED devices. The white LED device fabricated has an ultra-high color rendering index of 93.9, almost pure white CIE coordinate at (0.332, 0.336) and moderate CCT at 5498 K. The photoluminescence intensity (PL) under constant temperature and alternative condition is both tested to study the thermal stability of the phosphor. The PL intensity shows no obvious change after 3 days of aging; only 4% of PL loss after 10 cycles of 25 °C /85 °C alternation. Based on its good PL properties and thermal stability, this carbon dots phosphor has great potential for white LED lighting.