An optimal spectral model for phosphor‐converted white light‐emitting diodes used in the mesopic vision

Abstract

AbstractWhite light‐emitting diodes (WLEDs) for road lighting are required to have both the high scotopic to photopic ratio (S/P) and color rendering index (CRI). However, there is a trade‐off between S/P and CRI, and WLEDs commonly having the S/P of 1.68‐2.38 usually exhibit a low CRI. In this work, to provide a best solution to the trade‐off problem we proposed an optimal spectral model for the phosphor‐converted WLEDs (pc‐WLEDs) aiming to figure out the optimal phosphor combination. The Monte Carlo Algorithms combined with the Genetic Algorithm were adopted to obtain the optimization of CRI and S/P by varying the spectral power distributions of WLEDs through adjusting the spectral parameters. Considering the spectral requirements of pc‐WLEDs based on the mesopic vision, we chose CaAlSiN3:Eu2+ and Y3(Ga,Al)5O12:Ce3+ as the red‐ and green‐emitting phosphors to prepare WLEDs with both high S/P and CRI, respectively. The simulation based on the optimal spectral model led to an optimal pc‐WLED with a high S/P of 2.0‐2.14, Ra > 80 and correlated color temperature (CCT) of 4000‐5000 K, which matches very well with the experimental results of S/P = 2.064, Ra = 93.9, and CCT = 4981 K for the two‐phosphor converted WLEDs. It implies that the optimal spectral model would be used effectively for the spectral design and phosphor selection for WLEDs.