The effect of the phosphor curvature in the range 0.1766-0.2589 mm-1 on the luminous efficacy of Y2.95Al5O12:0.05Ce3+ (YAG)-based white-light-emitting diodes (WLEDs) was investigated at the similar correlated color temperature (CCT) of ~6300 K by tuning the concentration of YAG phosphors in the phosphor layer ranging from 7.5 to 15 wt%. It was found that both the luminous efficacy and luminous power increased monotonically with the increasing curvature. The luminous efficacy (=82.4 lm/W) and luminous power (=297.85 mW) of the YAG-based WLED at the preferable phosphor curvature of 0.2589 mm-1 were 19.44% and 17.36%, respectively, higher than those at the curvature of 0.1766 mm-1 under 350 mA. This finding reveals that the surface curvature of phosphor layers is a critical factor which cannot be ignored for the investigation of the light output of phosphor-converted WLEDs. Moreover, the color rendering index (CRI) enhancement of YAG-based WLED with substitution of Y2.94Al5O12:0.05Ce3+, 0.01Pr3+ (YPrAG), Y2.45Gd0.5Al5O12:0.05Ce3+ (YGdAG), and Y2.95Al4.8Si0.2O11.8N0.2:0.05Ce3+ (YAlSiON) for YAG were assessed under the same phosphor curvature of 0.2589 mm-1 and the similar CCT ~6350 K. Taking the luminous efficacy, preparation cost of phosphors, and CRI into consideration, we suggest that the YGdAG is a preferable candidate for replacing the YAG for use in WLEDs among the four kinds of phosphors. Compared with the YAG (7.5 wt%)-based WLED, the YGdAG (7 wt%)-based WLED exhibited an improved CRI, less preparation cost of phosphors, and the acceptable reduction in luminous efficacy under 350 mA.
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