Liquid-crystal-modulated correlated color temperature tunable light-emitting diode with highly accurate regulation

Abstract

A precise correlated color temperature (CCT) tuning method for light-emitting diodes (LEDs) has been developed and is demonstrated in this article. By combining LEDs and a liquid crystal (LC) cell, a light source with continuous CCT variation along a straight track on the chromaticity diagram is achieved. Moreover, the manner of CCT variation can be modulated by choosing appropriate LEDs and phosphors to yield a variation going from 3800 K to 6100 K with the track near the black-body locus. By adapting various developed LC technologies for diverse demands, the performance and applications of LEDs can be greatly improved.

Novel liquid crystal photonic devices enabled by two-photon polymerization [Invited]

“…Nowadays, liquid crystal displays (LCDs) have become ubiquitous in our daily lives [7,8]; their applications span from smartphones, pads, computer screens, to large-sized TVs. In addition to displays, LC devices have also found useful applications in beam steering [9][10][11], optical communications [12][13][14], lighting applications [15][16][17], smart windows [18][19][20], tunable metasurfaces [21][22][23], and augmented reality and virtual reality systems [24][25][26], just to name a few. To manipulate electro-optical properties and thus accomplish different device functions, strategies including special electrode designs, compound structures, and spatially variant alignment can be utilized.…”

Widely color-temperature low-luminosity-loss electrochromic-tuned white light-emitting diodes

“…Table 1 shows the luminous flux measured by the photometric integrating sphere with respect to different driving voltage on the EC cell. Before the EC cell was driven, the luminous flux stood at about 130.86 lm, which dropped to about 110.03 lm, for a difference of 15.9%, after the driving voltage rose to 2.4 V. By contrast, the LC cells applied in our previous work [16], equipped with patterned polarizers, absorbed 90% of the light in the working region, leading to significant reduction of the brightness of LEDs. Therefore, the low consumption of light suggests that EC cells may pose as a better option in CCT tuning method.…”

“…In our previous work, we introduced a method based on a liquid crystal (LC) cell for manipulating the CCT of white LEDs electrically, but with noticeable loss of luminosity due to the polarizers in the LC cell system [16]. The drawback was improved by adding dichroic dye to the LC cell, which utilizes the LC molecules to align the doped dye in different directions electrically [15].…”

P-114: A Tunable Correlated-Color-Temperature Lighting with Two Blue LEDs and a Quantum-Dot Enhancement Film

“…However, such device requires complicated and individual electronic setup, which boosts up the cost and limits its widespread applications in especially consumer electronics. Recently, LC film is proposed to realize real-time CCT tuning [5,6]. By applying different voltages to the LC film, it shows good color rendering index (CRI), wide CCT tuning range (>2500 K) and small chromaticity offset [7].…”