Spectral optimization of color temperature tunable white LEDs with excellent color rendering and luminous efficacy.

Abstract

The optimization model of limited luminous efficacy (LLE) for correlated color temperature (CCT) tunable phosphor-coated white light-emitting diodes (pc-W LEDs) consisting of blue chips, green and yellow phosphors, and red chips, including downconversion energy loss, has been developed under the constraint of a designated color-rendering index (CRI) and a special CRI of R9 for strong red. The optimal spectra of pc-W LEDs are obtained with a nonlinear program for maximizing LLE under conditions of both CRI and R9 above 90, 95, and 98 at CCTs of 2700-6500 K. The pc-W LEDs with LLE>301 lm/W for both CRI and R9 above 90, LLE>290 lm/W for both CRI and R9 above 95, and LLE>276 lm/W for both CRI and R9 above 98 could be achieved at CCTs of 2700-6500 K. The recommended peak wavelengths and full widths at half-maximum (FWHMs) for the current LEDs and phosphors and their photometric and colorimetric performances are presented.