Abstract
We demonstrate an electro-optic method to tune the correlated color temperature (CCT) of white light-emitting-diode (WLED) with a color conversion film, consisting of fluorescent dichroic dye doped in a liquid crystal host. By controlling the molecular reorientation of dichroic dyes, the power ratio of the transmitted blue and red lights of the white light can be accurately manipulated, resulting in different CCT. In a proof-of-concept experiment, we showed that the CCT of a yellow phosphor-converted WLED can be tuned from 3200 K to 4100 K. With further optimizations, the tuning range could be enlarged to 2500 K with fairly good color performance: luminous efficacy of radiation (LER) > 300 lm/W, color rendering index (CRI) > 75, and Duv < 0.005. Besides, the operation voltage is lower than 5 V and good angular color uniformity is achieved with remote-phosphor coating. This approach is promising for next generation smart lighting.
Highlights
Smart solid-state lighting is emerging and has potential to become generation lighting technology [1, 2]
We demonstrate an electro-optic method to tune the correlated color temperature (CCT) of white light-emitting-diode (WLED) with a color conversion film, consisting of fluorescent dichroic dye doped in a liquid crystal host
The tuning range could be enlarged to 2500 K with fairly good color performance: luminous efficacy of radiation (LER) > 300 lm/W, color rendering index (CRI) > 75, and Duv < 0.005
Summary
Smart solid-state lighting is emerging and has potential to become generation lighting technology [1, 2]. A main feature of smart lighting is real-time tunable spectrum, resulting in tunable correlated color temperature (CCT). There is great demand for real-time CCT tunable white light-emitting diode (WLED) depending on the use and time of the day in a variety of settings, such as indoor or outdoor. To realize this goal, several approaches have been proposed. Once the applied voltage exceeds a threshold, the dichroic dyes will be reoriented with the LC directors [13] Based on this principle, in this paper, we demonstrate a real-time CCT tunable WLED with a dichroic fluorescent dye. The power consumption is really low because LC is a voltage device, and the operation voltage is lower than 5 V
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