Color‐tunable white leds with single chip realized through phosphor pattern and thermal‐modulating optical film

Abstract

In this paper, a new method to regulate the correlated color temperature (CCT) of white light‐emitting diodes (LEDs) is proposed for the single‐chip packaging structure, in which the blue light distribution emitted from the chip in the red/yellow phosphor layer was modulated through changing the paraffin‐polydimethylsiloxane (PDMS) film transparence and haze. The results show that the transmittance of the paraffin‐PDMS film can be modulated from 49.76% to 97.64%, while the haze of that ranges from 88.19% to 63.10%. When the thickness of paraffin‐PDMS film is 0.6 mm, and the paraffin‐PDMS film concentration is 30 wt%, the CCT of white LED decreases from 15177 K to 3615 K with the increase of thermal load in the paraffin‐PDMS film. The modulating range of its CCT reaches 11562 K. The maximum CCT variation at the same test condition is only 536 K in the repeated experiments within one week.