On the Thermal Load of the Color‐Conversion Elements in Phosphor‐Based White Light‐Emitting Diodes

For further improvements to the reliability and the white light quality of phosphor‐converted light‐emitting diodes (LEDs), it is imperative to understand how the compositional, optical, and thermal properties of the materials constituting the color‐conversion elements (CCEs) affect their respective thermal loads. By means of a combined optical and thermal simulation procedure, a comprehensive discussion is given on the underlying coherences of the absorption profile of the blue LED light, the phosphor concentration, the quantum efficiency of the phosphor, and the thermal conductivities of the CCEs. Some general strategies of material composition and design are deduced in order to minimize the thermal load of the CCEs, which is a prerequisite for correlated color temperature maintenance and long‐term material reliability of phosphor‐converted white LEDs. Recent developments in high‐power LED technology allow the junction temperatures in phosphor‐converted LEDs to be kept at comparably low levels. Still challenging is effective heat removal from the phosphor layer. An appropriate design and composition of the respective materials also turns out as a promising strategy to keep the thermal load of the phosphor layer at a moderate level.