Photometric optimization and comparison of hybrid white LEDs for mesopic road lighting.

The photometric model for the mesopic luminous efficacy (LE) of hybrid white LEDs, including the radiant efficiency of both blue and red LEDs as well as the overall quantum efficiency of the phosphor layer or the quantum dot (QD) film, was developed. The optimal spectral parameters of integrated with quantum dots (QD-WLED), phosphor-converted white LED (pc-WLED) with red LEDs instead of red phosphor (pc/R WLED) for both color fidelity index (R) and color rendering index (R) above 70, 80, and 90 at correlated color temperatures of 2700-6500 K were obtained by maximizing the average LE of four road lighting standards. By comparing among pc-WLED, QD-WLED, and pc/R WLED, it was suggested that the pc/R WLEDs make strong candidates for mesopic road lighting. The requirements of the overall efficiency of QD film were presented if the QD-WLEDs were competitive to the pc-WLEDs. Finally, the three real pc/R WLEDs with both R and R about 80 at CCTs of 2982 K, 4560 K, and 5683 K were demonstrated.