On the impact of the temperature dependency of the phosphor quantum efficiency on correlated color temperature stability in phosphor converted LEDs

Since phosphors are prone to a temperature dependent loss of luminescence intensity, an appropriate thermal management in phosphor converted light-emitting diodes (LEDs) is indispensable to maintain the desired correlated color temperature (CCT) value. This can be achieved either by improving the thermal stability of the phosphor material itself or by enhancing the thermal conductivity of the color conversion element (phosphor embedded in a transparent matrix) of the LED. Based on optical simulations we give a comprehensive discussion on the related coherences. We compare our results with the related research goals of the US Department of Energy with respect to phosphor development. We show that the thermal stability performance target of the phosphor as predicted for 2020 will be beneficial with regard to color stability.

However, an improvement of the thermal conductivity of the matrix materials which encapsulate the phosphor particles would have a similar impact, even for phosphors with current state of the art performance. Besides investing in the progress of phosphor materials, research should also focus on novel concepts and materials to enhance the thermal conductivity of color conversion elements in phosphor converted LEDs.