scholarly journals Naturally Derived Organic Dyes for LED Lightings of High Color Rendering and Fidelity Index

2021 ◽  
Author(s):  
Yunping Huang ◽  
Theodore A. Cohen ◽  
Christine K. Luscombe
Keyword(s):  
Excited State ◽  
Organic Dyes ◽  
Continuous Emission ◽  
Light Emitting ◽  
Organic Hybrid ◽  
Industry Standard ◽  
Color Rendering Index ◽  
The Cost ◽  
Color Rendering ◽  
Excellent Color

<p>Light-emitting diodes (LEDs) are a lighting technology with a huge and ascending market. Typically, LED backlights are often paired with inorganic phosphors made from rare-earth elements (REEs) to tune the emission lineshapes for different applications. However, REE production is a resource-intensive process with many negative environmental impacts. Herein we develop organic hybrid LEDs using organic dyes synthesized from an abundant and non-toxic natural product (theobromine) to replace REE phosphors. The resulting hybrid LED generates continuous emission from 400 – 740 nm, resulting in high color rendering index (the current industry standard) of 90 and color fidelity index (the most advanced and comprehensive standard) of 92, challenging commercial LEDs based on REE phosphors. In addition, the light-converting composite is made from 99 wt% SBS, an inexpensive industrial polymer, and 1wt% theobromine dyes, reducing the cost of the light converter to ¢1.30 for a 1 W LED, compared to approximately ¢ 19.2 of commercial products. The light converting efficiency of the dye-SBS composite is 82%. Excited state kinetics experiments were also conducted to provide guidance to further increase the light-converting efficiency of the theobromine dyes while maintaining excellent color rendering and fidelity. </p>

scholarly journals Naturally Derived Organic Dyes for LED Lightings of High Color Rendering and Fidelity Index

2021 ◽  
Author(s):  
Yunping Huang ◽  
Theodore A. Cohen ◽  
Christine K. Luscombe
Keyword(s):  
Excited State ◽  
Organic Dyes ◽  
Continuous Emission ◽  
Light Emitting ◽  
Organic Hybrid ◽  
Industry Standard ◽  
Color Rendering Index ◽  
The Cost ◽  
Color Rendering ◽  
Excellent Color

<p>Light-emitting diodes (LEDs) are a lighting technology with a huge and ascending market. Typically, LED backlights are often paired with inorganic phosphors made from rare-earth elements (REEs) to tune the emission lineshapes for different applications. However, REE production is a resource-intensive process with many negative environmental impacts. Herein we develop organic hybrid LEDs using organic dyes synthesized from an abundant and non-toxic natural product (theobromine) to replace REE phosphors. The resulting hybrid LED generates continuous emission from 400 – 740 nm, resulting in high color rendering index (the current industry standard) of 90 and color fidelity index (the most advanced and comprehensive standard) of 92, challenging commercial LEDs based on REE phosphors. In addition, the light-converting composite is made from 99 wt% SBS, an inexpensive industrial polymer, and 1wt% theobromine dyes, reducing the cost of the light converter to ¢1.30 for a 1 W LED, compared to approximately ¢ 19.2 of commercial products. The light converting efficiency of the dye-SBS composite is 82%. Excited state kinetics experiments were also conducted to provide guidance to further increase the light-converting efficiency of the theobromine dyes while maintaining excellent color rendering and fidelity. </p>

scholarly journals Excellent color rendering index single system white light emitting carbon dots for next generation lighting devices

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Manasa Perikala ◽  
Asha Bhardwaj
Keyword(s):  
White Light ◽  
Carbon Dots ◽  
Quantum Yields ◽  
Single System ◽  
Light Emitting ◽  
Color Rendering Index ◽  
Different Color ◽  
Color Rendering ◽  
Excellent Color ◽  
Emission Bandwidth

AbstractRecently, quantum dots (QDs) are finding enormous application in white light emitting diodes (WLEDs) and WLEDs with high color rendition are in high demand. QD-WLEDs use different color (Red, Blue, Green) emitting QDs to obtain white light. Use of different color emitting QDs affect purity of white light due to self-absorption losses and QD degradation, in the long run affecting color rendering index (CRI) of WLEDs. Herein, we report low cost, environment friendly, open air atmosphere synthesis of single system white light emitting carbon dots (CDs) with broad emission bandwidth ranging 116 –143 nm and quantum yields (QY) ~ 5 – 13 % in colloidal state by modifying CD surface. Furthermore, carbon dot polymer phosphor (CD-PDMS phosphor) is fabricated which emits white light under UV illumination with a record emission bandwidth of ~ 154 nm and QY ~ 16 % in solid state. Moreover, CD-PDMS phosphor exhibit excellent color rendering index (CRI) ~ 96, the highest reported so far with CIE co-ordinates (0.31, 0.33) that are quite akin to pure white light. Such high performances are achieved due to high quality of CDs and CD-PDMS polymer phosphors by precise control in passivation/functionalization of nanoparticle surface. This work will set platform for the application of CD-phosphor based WLEDs in lighting systems.

Combination of carbon dot and polymer dot phosphors for white light-emitting diodes

Nanoscale ◽  
2015 ◽  
Vol 7 (28) ◽  
pp. 12045-12050 ◽  
Author(s):  
Chun Sun ◽  
Yu Zhang ◽  
Kai Sun ◽  
Claas Reckmeier ◽  
Tieqiang Zhang ◽  
...  
Keyword(s):  
Energy Transfer ◽  
White Light ◽  
Light Emitting Diodes ◽  
Color Stability ◽  
Light Emitting ◽  
Color Rendering Index ◽  
Carbon Based Nanomaterials ◽  
White Light Emitting Diodes ◽  
Color Rendering ◽  
Excellent Color

The white light-emitting diodes with high color rendering index (85–96) and widely variable color temperatures(2805–7786 K) were fabricated from carbon-based nanomaterials with weak reabsorption and no energy transfer crosstalk and showed excellent color stability.

scholarly journals Efficient, stable and high color rendering index white polymer light-emitting diodes by restraining the electron trapping

2020 ◽  
Author(s):  
Jin Xu
Keyword(s):  
Light Emitting Diodes ◽  
Color Stability ◽  
Electron Trapping ◽  
Light Emitting ◽  
Color Rendering Index ◽  
Electron Transporting Layer ◽  
Operating Current ◽  
Polymer Light Emitting Diodes ◽  
Color Rendering ◽  
Excellent Color

Superior solid-state light source should possess not only a high device efficiency but also high color rendering index (CRI) and excellent color stability. Here, we obtained efficient, stable and high CRI white polymer light- emitting diodes (WPLEDs) through applying the well-chosen trichromatic polymers and restraining the electron trapping. The trichromatic polymers all possess the similar mainchain units, their EL spectra shows an equidistant distribution. Detailed studies revealed that the part of green and red emission in the WPLED derive from the electron trapping which led to the current-dependent spectra. Applied proper electron transporting layer can enhance the direct electron injection which resulted in the electron trapping being restrained and improving the color stability. The optimized WPLED got a LEmax of 10.17 cd A 1 and CRI of 92, the CIE coordinates (0.346, 0.345) almost keep the same with the operating current density increasing from 10.53 mA cm 2 to 263.16 mA cm 2.

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