scholarly journals A Novel Polymethyl Methacrylate Derivative Grafted with Cationic Iridium(III) Complex Units: Synthesis and Application in White Light-Emitting Diodes

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 499 ◽  
Author(s):  
Huaijun Tang ◽  
Xueyan Dong ◽  
Mingxian Chen ◽  
Qiuhong Chen ◽  
Mengran Ren ◽  
...  

A novel orange-yellow-emitting polymethyl methacrylate derivative grafted with cationic iridium(III) complex units was synthesized and used as down-conversion luminescent materials in light-emitting diodes (LEDs). The polymer had a thermal decomposition temperature (Td) of 275 °C. With the temperature increasing from 20 to 100 °C, its photoluminescent intensity decreased to 76.8% with thermal quenching activation energy (Ea) of 0.2775 eV. A series of LEDs was fabricated by 460 nm blue GaN chips and the polymer blended in silicone at different concentrations. At 4.0 wt %, a cold white LED was obtained, the correlated color temperature (CCT) was 10,050 K, color rendering index (CRI) was 71.2, luminous efficiency (ηL) was 5.3 lm·w−1, and Commission Internationale de L’Eclairage (CIE) chromaticity coordinates were (0.30, 0.24). At 5.0 wt.%, the LED emitted neutral white light, its CCT was 4938 K, CRI was 75, ηL was 13.8 lm·w−1, and the CIE value was (0.34, 0.27). At 5.5 wt %, 6.0 wt %, 7.0 wt %, and 8.0 wt %, the LEDs all emitted warm white light; their CCTs were 3446, 3093, 2557, and 2337 K, respectively; their CRIs were 73.6, 71.8, 63.8, and 59.0, respectively; their ηL were 18.1, 16.3, 14.8, and 13.7 lm·w−1, respectively; and their CIE values were (0.36, 0.30), (0.40, 0.35), (0.45, 0.38), and (0.50, 0.42), respectively. At 9.0 wt %, the blue light of GaN chip was completely absorbed by the polymer and only the orange-yellow light of the polymer emitted. The results suggested the polymer was a promising orange-yellow-emitting phosphor candidate for white LEDs, especially for warm white LEDs.

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Yen-Chang Chu ◽  
Gang-Juan Lee ◽  
Chin-Yi Chen ◽  
Shih-Hsin Ma ◽  
Jerry J. Wu ◽  
...  

Bismuth oxide photocatalysts were synthesized and coated on the front surface of phosphor-converted white light-emitting diodes to produce a safe and environmentally benign lighting source. Bismuth oxide photocatalyst powders were synthesized with a spray pyrolysis method at 500°C, 600°C, 700°C, and 800°C. Using the absorption spectrum in the blue and UV regions of the bismuth oxide photocatalysts, the blue light and UV leakage problems of phosphor-converted white LEDs can be significantly reduced. The experimental results showed that bismuth oxide photocatalyst synthesized at 700°C exhibited the most superior spectrum inhibiting ability. The suppressed ratio reached 52.33% in the blue and UV regions from 360 to 420 nm. Related colorimetric parameters and the photocatalyst decomposition ability of fabricated white-light LEDs were tested. The CIE chromaticity coordinates(x,y)were (0.349, 0.393), and the correlated color temperature was 4991 K. In addition, the coating layer of photocatalyst can act as an air purifier and diffuser to reduce glare. A value of66.2±0.60 ppmv of molecular formaldehyde gas can be decomposed in 120 mins.


RSC Advances ◽  
2017 ◽  
Vol 7 (74) ◽  
pp. 46713-46720 ◽  
Author(s):  
Yunan Zhou ◽  
Weidong Zhuang ◽  
Yunsheng Hu ◽  
Ronghui Liu ◽  
Zhouqing Jiang ◽  
...  

A newly developed orange-yellow-emitting Lu2Mg2Al2Si2O12: Ce3+ phosphor with excellent luminescent properties for warm white-LEDs.


Nanoscale ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 4686-4695 ◽  
Author(s):  
Young Chul Sim ◽  
Seung-Hyuk Lim ◽  
Yang-Seok Yoo ◽  
Min-Ho Jang ◽  
Sunghan Choi ◽  
...  

Multifaceted dodecagonal ring structures emit light of various colours with high efficiency and are demonstrated to be phosphor-free white LEDs.


2019 ◽  
Vol 48 (4) ◽  
pp. 1376-1385 ◽  
Author(s):  
Feng Hong ◽  
Haiming Cheng ◽  
Chao Song ◽  
Guixia Liu ◽  
Wensheng Yu ◽  
...  

Red phosphors (NH4)2NaInF6:Mn4+ with controllable morphology were synthesized via different synthetic methods, which can be fabricated for warm white LEDs.


2020 ◽  
Vol 8 (37) ◽  
pp. 12951-12958 ◽  
Author(s):  
Che-Yu Chang ◽  
Wei-Li Hong ◽  
Pei-Hsuan Lo ◽  
Tzu-Hsiang Wen ◽  
Sheng-Fu Horng ◽  
...  

Perovskite white light-emitting diodes with only a single emissive layer of halide perovskites and rhodamine 6G were realized with the CIE chromaticity coordinates of (0.33, 0.40).


RSC Advances ◽  
2016 ◽  
Vol 6 (3) ◽  
pp. 2155-2161 ◽  
Author(s):  
Jiyou Zhong ◽  
Weidong Zhuang ◽  
Xianran Xing ◽  
Ronghui Liu ◽  
Yanfeng Li ◽  
...  

A new blue-green-emitting garnet-type phosphor Ca3Zr2SiGa2O12:Ce3+ has been explored for n-UV pumped white light-emitting diodes.


RSC Advances ◽  
2014 ◽  
Vol 4 (62) ◽  
pp. 33114-33119 ◽  
Author(s):  
Chenglong Zhao ◽  
Zhiguo Xia ◽  
Molin Li

Eu2+-activated full-color versatile orthophosphate phosphors can find potential application in warm white LEDs.


2015 ◽  
Vol 3 (3) ◽  
pp. 607-615 ◽  
Author(s):  
Ji Hye Oh ◽  
Heejoon Kang ◽  
Yun Jae Eo ◽  
Hoo Keun Park ◽  
Young Rag Do

In this study, we synthesized and characterized narrow-band red-emitting K2SiF6:Mn4+ phosphors in order to improve the color qualities of warm white light-emitting diodes (LEDs).


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