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. 2022 Feb 23;15(5):1680.
doi: 10.3390/ma15051680.

Sunlike White Light-Emitting Diodes Based on Rare-Earth-Free Luminescent Materials

Amador Menéndez-Velázquez  1 , Dolores Morales  1 , Ana Belén García-Delgado  1
Affiliations

Sunlike White Light-Emitting Diodes Based on Rare-Earth-Free Luminescent Materials

Amador Menéndez-Velázquez et al. Materials (Basel). .

Abstract

Solid-state lighting (SSL) sources based on light-emitting diodes represent the new generation of highly efficient illumination systems that significantly impact energy-saving. The development of white light-emitting diodes (WLEDs) with a combination of high color rendering index (CRI) and high deep-red color rendering R9 is an important challenge in the field of solid-state lighting. On the other hand, most WLEDs use rare-earth inorganic luminescent materials. The annual demand for rare-earth metals has doubled to 125,000 tons in 15 years, and the demand is projected to reach 315,000 tons in 2030. The explosion in demand for these materials, combined with a monopolistic supply source, represents a real risk for the development of WLEDs in the next few years. Luminescent organic materials are a relevant and promising alternative. Here, we report a WLED with a very high CRI of 95.7 and R9 of 78.7, obtained using a combination of a blue LED chip (excitation source) and two organic luminescent dyes (Coumarin 6 and Lumogen Red) acting as spectral converters in a multilayer remote phosphor configuration. To the best of our knowledge, this is the first rare-earth-free WLED with such high values of CRI and R9.

Keywords: color rendering index (CRI); luminescent organic materials; rare-earth-free luminescent materials; solid-state lighting (SSL); spectral converters; white light-emitting diode (WLED).

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Spectral power distribution (SPD) chart of the selected blue LED.
Figure 2
Figure 2
Photoluminescent excitation (a) and emission (b) spectra of Coumarin 6 green-emitting converter embedded in a PMMA matrix.
Figure 3
Figure 3
Three-dimensional photoluminescent spectra under the excitation wavelengths from 410 nm to 500 nm.
Figure 4
Figure 4
Photoluminescent excitation (a) and emission (b) spectra of Lumogen Red red-emitting converter embedded in a PMMA matrix.
Figure 5
Figure 5
Three-dimensional photoluminescent spectra under the excitation wavelengths from 410 nm to 740 nm.
Figure 6
Figure 6
Spectral power distribution (SPD) chart (a) and CRI points (b) of WLED-2.
Figure 7
Figure 7
Spectral power distribution (SPD) chart (a) and CRI points (b) of WLED-11.
Figure 8
Figure 8
Spectral power distribution (SPD) chart (a) and CRI points (b) of WLED-11-I.
Figure 9
Figure 9
(a) Photoluminescent red-emitting and green-emitting converters embedded in a PMMA matrix and coated on glass under exposure to blue light. (b) White light emitted by the WLED-11-I device.
See this image and copyright information in PMC

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