Abstract
White light emitting diode (LED) systems, capable of lowering the color temperature of emitted light on dimming, have been reported in the literature. These systems all use multiple color LEDs and complex control circuitry. Here we present a novel responsive lighting system based on a single white light emitting LED and a thermoresponsive scattering coating. The coated LED automatically emits light of lower correlated color temperature (CCT) when the power is reduced. We also present results on the use of multiple phosphors in the white light LED allowing for the emission of warm white light in the range between 2900 K and 4150 K, and with a chromaticity complying with the ANSI standards (C78.377). This responsive warm white light LED-system with close-to-ideal emission characteristics is highly interesting for the lighting industry.
Highlights
Driven by advances in R&D in the field of light-emitting diodes (LEDs) [1–3], the lighting industry is expected to shift towards intelligent lighting systems in the coming years [4]
We present a novel responsive lighting system based on a single white light emitting LED and a thermoresponsive scattering coating
We present results on the use of multiple phosphors in the white light LED allowing for the emission of warm white light in the range between 2900 K and 4150 K, and with a chromaticity complying with the ANSI standards (C78.377)
Summary
Driven by advances in R&D in the field of light-emitting diodes (LEDs) [1–3], the lighting industry is expected to shift towards intelligent lighting systems in the coming years [4]. The intensity-related heat generated by white-light LEDs controls the correlated color temperature (CCT) of the LED-emitted light. A white light emitting LED package contains a blue light emitting LED embedded in a matrix material containing a photoluminescent material (with the lighting nomenclature addressed as the phosphor). The CCT of the light emitted by the LED package depends on the type of blue LED and the type and quantity of phosphor in the package. A scattering coating on top of such an LED package facilitates more of the aforementioned light conversion from blue to another color by redirecting the emitted light back to the phosphor where it can be absorbed and subsequently re-emitted at another wavelength [9]. If the applied coating can be switched between a scattering and a transparent state, the CCT of the emitted light can be addressed [Fig. 1]
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