Direct blending of multicolor carbon quantum dots into fluorescent films for white light emitting diodes with an adjustable correlated color temperature

“…White LED is the current mainstream green lighting source which has the advantages of energy saving, eco-friendly, long lifetime and high reliability, etc [1]. With the improvement of living standards, in different environments, human beings have different requirements for the photometric or colorimetric parameters of the light source such as luminance, CCT, CRI, etc [2,3].…”

Section: Introductionmentioning

confidence: 99%

Research on adjustable correlated color temperature COB-LED light source based on flip chips and screen printing technology

Zhang¹,

Wen²,

Li³

et al. 2021

Preprint

View full text Add to dashboard Cite

Using the characteristic of flip light emitting diode (LED) chips without front-side welding wires, before applying fluorescent glue throughout the luminous surface, a part of the chips are directionally and quantitatively coated fluorescent glue by screen printing process, a chip on board (COB) white LED light source is developed with adjustable correlated color temperature (CCT). A part of the blue LED chips in the light source excites the fluorescent glue to produce a warm white light (CCT = 2631K), and the other part produces cool white light (CCT = 6181K). When changing the driving current ratio of the two parts of the chips, the CCT of COB LED light source can be continuously adjusted between warm and cool white light. According to the measured data, the relationship between the CCT and the driving current ratio of the two parts is obtained by fitting. Within the adjustable range of the CCT (2631 K to 6181 K), the color rendering index (CRI) is about 90. The minimum is 89.3 and the maximum is 93.1. While achieving adjustable CCT and high CRI, the LED light source has a luminous flux of 1938.76 lm on a circular surface with a diameter of 11 mm. The overall luminous efficiency is close to 100 lm/W.

show abstract

“…Common white light-emitting diodes (WLEDs) containing blue light-emitting chips and yellow light-emitting phosphor have high luminous efficiencies (LEs) but low color rendering indexes (CRIs) because of the lack of red light. , Quantum dots (QDs) as luminescent nano-semiconductor materials have shown excellent advantages in wavelength turnability and color rendering capability in the application of WLEDs. − A phosphor and QDs-converted WLED (PQ-WLED) can achieve high LE and CRI, simultaneously. − During the packaging of PQ-WLEDs, QDs and phosphor are uniformly mixed in a polymer such as silicone with a certain viscosity and behave differently: phosphor with a diameter of several microns undergoes sinking in the viscous silicone, , but the nanometer-sized QDs stay in suspension. After several minutes, phosphor is distributed in a gradient concentration in silicone but QDs are still distributed uniformly.…”

Section: Introductionmentioning

confidence: 99%

Quantum Dots Electrostatically Adsorbed on the Surface of SiO₂ Nanoparticle-Decorated Phosphor Particles for White Light-Emitting Diodes with a Stable Optical Performance

Zhou

et al. 2020

ACS Appl. Nano Mater.

View full text Add to dashboard Cite

White light-emitting diodes (WLEDs) based on phosphor and quantum dots (QDs) have attracted worldwide attention. Phosphor and QDs with different physical characteristics are distributed unevenly in a polymer matrix, resulting in the spectrum changes of the phosphor-QD-based WLEDs (PQ-WLEDs). Aiming for a similar distribution of QDs and phosphor in the matrix, we proposed the phosphor/SiO2/QD (PSQ) composite particles in which negatively charged QDs are electrostatically adsorbed on the surface of phosphor particles decorated with positively charged SiO2. The PSQ composite particles retained a high quantum yield of 77.6%. PSQ-WLEDs with varied standing times of the uncured PSQ-added silicone showed stable spectra with stable optical parameters. For comparison, the spectra of PQ-WLEDs with untreated phosphor and QDs obviously changed with the standing time. Specifically, the LE, CCT, and CRI of PSQ-WLEDs using Dow corning OE 180 silicone only changed by 1.7, 3.3, and 3.9%, respectively, after a long sufficient standing time; however, the LE, CCT, and CRI of PQ-WLEDs using the same silicone changed by 9, 5.4, and 10%, respectively. This optical instability in PQ-WLEDs resulted from the difference between the distribution of phosphor and QDs in the mixed silicone matrix after standing. However, the distribution of phosphor and QDs in PSQ-WLEDs was always the same with each other due to the composite structure. Applying the PSQ composite particles in WLEDs, we can easily attain highly optical consistent phosphor-QD-based WLEDs and provide an efficient control of product quality.

show abstract

Direct blending of multicolor carbon quantum dots into fluorescent films for white light emitting diodes with an adjustable correlated color temperature

Abstract: The synthesis and luminescence origin of multicolour long wavelength CQDs and solid state luminous red-green-blue CQD films for CQD phosphor-based WLEDs with a high CRI and an adjustable CCT.

Cited by 69 publications

References 37 publications

Investigation on the chirality mechanism of chiral carbon quantum dots derived from tryptophan

Investigation on the chirality mechanism of chiral carbon quantum dots derived from tryptophan

Research on adjustable correlated color temperature COB-LED light source based on flip chips and screen printing technology

Quantum Dots Electrostatically Adsorbed on the Surface of SiO₂ Nanoparticle-Decorated Phosphor Particles for White Light-Emitting Diodes with a Stable Optical Performance

Contact Info

Product

Resources

About

Direct blending of multicolor carbon quantum dots into fluorescent films for white light emitting diodes with an adjustable correlated color temperature

Abstract: The synthesis and luminescence origin of multicolour long wavelength CQDs and solid state luminous red-green-blue CQD films for CQD phosphor-based WLEDs with a high CRI and an adjustable CCT.

Cited by 69 publications

References 37 publications

Investigation on the chirality mechanism of chiral carbon quantum dots derived from tryptophan

Investigation on the chirality mechanism of chiral carbon quantum dots derived from tryptophan

Research on adjustable correlated color temperature COB-LED light source based on flip chips and screen printing technology

Quantum Dots Electrostatically Adsorbed on the Surface of SiO2 Nanoparticle-Decorated Phosphor Particles for White Light-Emitting Diodes with a Stable Optical Performance

Contact Info

Product

Resources

About

Quantum Dots Electrostatically Adsorbed on the Surface of SiO₂ Nanoparticle-Decorated Phosphor Particles for White Light-Emitting Diodes with a Stable Optical Performance