title: Correlated color temperature tunable white LED with a dynamic color filter.
abstract: We proposed a new device structure to dynamically tune the correlated color temperature (CCT) of a white light-emitting-diode (WLED). The key component is a dynamic color filter, consisting of a liquid crystal (LC) cell sandwiched between two cholesteric LC films whose Bragg reflection band covers the blue wavelength of the WLED. When a voltage is applied to the LC cell, the transmittance of blue light is changed, while the longer wavelength part remains unaffected, resulting in a tunable CCT. Validated by experiment, our design exhibits several advantages, such as reasonably wide tuning range (6916K to 3253K), low operation voltage (~3.2 V), simple device configuration, and low cost. It is a strong contender for next generation smart lighting.
authors.forename: Haiwei
authors.initials: H
authors.lastname: Chen
authors.forename: Ruidong
authors.initials: R
authors.lastname: Zhu
authors.forename: Yun-Han
authors.initials: YH
authors.lastname: Lee
authors.forename: Shin-Tson
authors.initials: ST
authors.lastname: Wu