Circadian-effect engineering of solid-state lighting spectra for beneficial and tunable lighting

Abstract

Optimization of solid-state lighting spectra is performed to achieve beneficial and tunable circadian effects. First, the minimum spectral circadian action factor (CAF) of 2700 K white light-emitting diodes (LEDs) is studied for applications where biologically active illumination is undesirable. It is found that white-LEDs based on (i) RGB chips, (ii) blue & red chips plus green phosphor, and (iii) blue chip plus green & red phosphors are the corresponding minimum-CAF solutions at color-rendering index (CRI) requirements of 80, 90, and 95, respectively. Second, maximum CAF tunability of LED clusters is studied for dynamic daylighting applications. A dichromatic phosphor-converted blue-centered LED, a dichromatic phosphor-converted green-centered LED, and a monochromatic red LED are grouped to obtain white spectra between 2700 K and 6500 K. A maximum CAF tunability of 3.25 times is achieved with CRI above 90 and luminous efficacy of radiation of 313 - 373 lm/W. We show that our approaches have advantages over previously reported solutions on system simplicity, minimum achievable CAF value, CAF tunability range, and light source efficacy.

Realization of wide circadian variability by quantum dots-luminescent mesoporous silica-based white light-emitting diodes

“…As a comparison, a theoretical CAF variability of 3.11 times (ranging from 0.351-1.038) can be achieved at a color fidelity index of 90, based on four channels of LED chips spectral optimization [26]. Based on three-channel tunable LED cluster spectral optimization, the theoretical CAF can be tuned by 3.25 times (ranging from 0.294-0.957) while maintaining a CRI of 90 [27]. Therefore, our QDs-WLEDs can reduce the number of tunable channels and achieve wider CAF variability.…”

Towards 10 Gb/s orthogonal frequency division multiplexing-based visible light communication using a GaN violet micro-LED

“…For generation of white light for illumination, the use of violet-emitting LEDs exciting tricolor (red, green, and blue) phosphors also offers advantages over the widely used method of combining blue direct LED emission with a yellow-emitting phosphor. These include much superior color rendering indices [9,10] and the absence of a direct blue component, which has proven to be disruptive to the human circadian rhythm [11]. The micro-LED die shapes employed in this work are also expected to be advantageous for efficient light extraction, by analogy with previous designs employing non-circular emitting areas [12].…”

Emerging Perovskite Nanocrystals-Enhanced Solid-State Lighting and Liquid-Crystal Displays

“…At very early stages, numerous researches have been devoted to optimizing SSL's energy efficiency and color rendering performance [69][70][71][72][73][74]. However, as the biological impacts of light have been studied extensively [75][76][77][78][79], researches started to take human-health effect into SSL design [80][81][82][83]. Under ambient light, the intrinsically photosensitive retinal ganglion cells (ipRGCs) innervating the suprachiasmatic nucleus (SCN) can influence the melatonin secretion, and thus affect the circadian rhythm [84].…”