Spectral Optimization of Candle-Like White Light-Emitting Diodes With High Color Rendering Index and Luminous Efficacy

The tradeoff between the color rendering index (CRI) and the luminous efficacy (LE) for candle-like three-hump white light-emitting diodes (LEDs), which consist of blue InGaN chip, yellowaluminate phosphors, and redAlGaInP chip, has been investigated. Spectralmodels have been separately developed for the optimization process after experimentally measuring spectral power distributions of phosphor materials and semiconductor chips. By filtering billions of defective spectral data with a nonlinear program, optimal values of LE of 272 lm/W and CRI of 96 (CRI No. 9 of 98) at a correlated color temperature of 2000 K can be achieved, while LE and CRI are 0.1 lm/W and 83 for candles. These three-humps LEDs are capable of achieving excellent photometric and chromatic performances of candle-like white light. Finally, this study can serve as a critical guide for manufacturing high-CRI candle-like white LEDs.