scholarly journals Facile Preparation of Stable Solid-State Carbon Quantum Dots with Multi-Peak Emission

Nanomaterials ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 303 ◽  
Author(s):  
Yanning Zheng ◽  
Jingxia Zheng ◽  
Junli Wang ◽  
Yongzhen Yang ◽  
Taiping Lu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Solid State ◽  
Carbon Quantum Dots ◽  
Color Temperature ◽  
Light Emitting ◽  
One Step ◽  
White Light Emitting Diodes ◽  
Color Rendering ◽  
Peak Emission

Aggregation-caused quenching (ACQ) effect, known as the main cause to restrain solid-state luminescence of carbon quantum dots (CQDs), hinders further application of CQDs in white light-emitting diodes (WLED). Here, a complex of CQDs and phthalimide crystals (CQDs/PC) was prepared through a one-step solvothermal method. CQDs/PC prevented CQDs from touching directly by embedding the CQDs in phthalimide crystal matrix in situ, which effectively reduced the ACQ effect. Furthermore, CQDs/PC exhibited multi-peak fluorescence spectra that span the green, yellow and orange spectral regions. Finally, a WLED fabricated based on CQDs/PC achieved a color-rendering index of 82 and a correlated color temperature of 5430 K. This work provides a quick and effective strategy to apply CQDs to WLED.

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

2019 ◽  
Vol 7 (6) ◽  
pp. 1502-1509 ◽  
Author(s):  
Yuanfei Ding ◽  
Jingxia Zheng ◽  
Junli Wang ◽  
Yongzhen Yang ◽  
Xuguang Liu
Keyword(s):  
Quantum Dots ◽  
Solid State ◽  
White Light ◽  
Light Emitting Diodes ◽  
Carbon Quantum Dots ◽  
Color Temperature ◽  
Light Emitting ◽  
Long Wavelength ◽  
White Light Emitting Diodes

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.

53% Efficient Red Emissive Carbon Quantum Dots for High Color Rendering and Stable Warm White‐Light‐Emitting Diodes

2017 ◽  
Vol 29 (37) ◽  
pp. 1702910 ◽  
Author(s):  
Zifei Wang ◽  
Fanglong Yuan ◽  
Xiaohong Li ◽  
Yunchao Li ◽  
Haizheng Zhong ◽  
...  
Keyword(s):  
Quantum Dots ◽  
White Light ◽  
Light Emitting Diodes ◽  
Carbon Quantum Dots ◽  
Light Emitting ◽  
Warm White Light ◽  
White Light Emitting Diodes ◽  
Color Rendering

scholarly journals Light Output, Thermal Properties, and Reliability of Using Glass Phosphors in WLED Packages

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 239
Author(s):  
Chin-Chuan Huang ◽  
Tsung-Han Weng ◽  
Chun-Liang Lin ◽  
Yan-Kuin Su
Keyword(s):  
Thermal Properties ◽  
Yttrium Aluminum Garnet ◽  
Saturated Vapor ◽  
Light Output ◽  
Junction Temperature ◽  
Color Temperature ◽  
Light Emitting ◽  
Chromaticity Coordinate ◽  
White Light Emitting Diodes ◽  
Color Rendering

White-light-emitting diodes (WLED) based on yttrium aluminum garnet (YAG) phosphors sintered with glass (PiG) and with silicone (PiS) are compared in terms of their light properties, temperature properties and reliability.The complete YAG phosphor was doped with an encapsulant traditional WLED (PiS WLED), and the WLED was covered with PiG (PiG WLED). PiG was made by sintering glass powder and YAG phosphor at the ratio of 87:13 (%), and the correlated color temperature (CCT) was 5564 K. The CCT of the PiG WLED with the YAG doping concentration of 8.5 wt.% approximated 5649 K. The initial light output of the PiG WLED was 6.4% lower than that of the PiS WLED. Under 1008 h and 350 mA aging, PiG WLED and PiS WLED’ light output, CCT and color rendering index variation rates were all within 1%. In the saturated vapor-pressure test, no sample exhibited red ink infiltration, light nor peeling between the encapsulant and the lead-frame. Compared with that of the PiS WLED, the junction temperature of the PiG WLED reduced from 88.4 °C to 81.3 °C. Thermal resistance dropped from 37.4 °C/W to 35.6 °C/W. The PiG WLED presented a better CIE (Commission Internationale de l’Eclairage) 1931 chromaticity coordinate (x,y) concentration and thermal properties than the PiS WLED.

scholarly journals Solvent regulation synthesis of single-component white emission carbon quantum dots for white light-emitting diodes

2021 ◽  
Vol 10 (1) ◽  
pp. 465-477
Author(s):  
Longshi Rao ◽  
Qing Zhang ◽  
Mingfu Wen ◽  
Zhongfa Mao ◽  
Huaxian Wei ◽  
...  
Keyword(s):  
Quantum Dots ◽  
White Light ◽  
Light Emitting Diodes ◽  
Carbon Quantum Dots ◽  
Single Component ◽  
Great Promise ◽  
Solvent Engineering ◽  
Light Emitting ◽  
White Emission ◽  
White Light Emitting Diodes

Abstract White light-emitting diodes (WLEDs) hold great promise in lighting, display, and visible light communication devices, and single-component white emission carbon quantum dots (SCWE-CQDs) as the key component of WLEDs have many outstanding advantages. However, rapid and efficient synthesis of SCWE-CQDs with high photoluminescence quantum yield (PLQY) and stability remains challenging. Here, we report a novel solvent engineering strategy to obtain highly photoluminescent SCWE-CQDs by controlling the dilution ratios between N,N-dimethylformamide (DMF) and pristine red carbon quantum dots (RCQDs) solution. By optimizing synthesis conditions, the relative PLQY of the SCWE-CQDs solution reached 53%. Morphological, structural, and optical property characterizations indicate that the combined action of the hydrogen bond (HB) effect and the size effect leads to the blue shift of RCQDs, but the HB effect is more dominant than the particle size in causing large spectral shifts. In addition, the WLEDs with high color rendering index of 89 and remarkable reliability were obtained based on the highly photoluminescent SCWE-CQDs. This facile solvent engineering approach for synthesizing tunable emission CQDs will promote the progress of carbon-based luminescent materials for applications in optoelectronic devices.

Reduced Working Temperature of Quantum Dots-Light-Emitting Diodes Optimized by QDs@Silica-on-Chip Structure

2018 ◽  
Author(s):  
Bin Xie ◽  
Haochen Liu ◽  
Xiao Wei Sun ◽  
Xingjian Yu ◽  
Kai Wang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Light Emitting Diodes ◽  
Temperature Stability ◽  
Phosphor Layer ◽  
Light Emitting ◽  
Yellow Phosphor ◽  
Working Temperature ◽  
On Chip ◽  
White Light Emitting Diodes ◽  
Color Rendering

White light-emitting diodes (WLEDs) composed of blue LED chip, yellow phosphor, and red quantum dots (QDs) are considered as a potential alternative for next-generation artificial light source with their high luminous efficiency (LE) and color-rendering index (CRI). While, QDs’ poor temperature stability and the incompatibility of QDs/silicone severely hinder the wide utilization of QDs-WLEDs. To relieve this, here we proposed a separated QSNs/phosphor structure, which composed of a QSNs-on-chip layer with a yellow phosphor layer above. A silica shell was coated onto the QDs surface to solve the compatibility problem between QDs and silicone. With CRI > 92 and R9 > 90, the newly proposed QDs@silica nanoparticles (QSNs) based WLEDs present 16.7 % higher LE and lower QDs working temperature over conventional mixed type WLEDs. The reduction of QDs’ temperature can reach 11.5 °C, 21.3 °C and 30.3 °C at driving current of 80 mA, 200 mA and 300 mA, respectively.

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