Selecting a Suitable Remote Phosphor Configuration for Improving Color Quality of White Led

García-Delgado²,

Morales³

2023

IJMS

Artificial lighting is ubiquitous in modern society, with detrimental effects on sleep and health. The reason for this is that light is responsible not only for vision but also for non-visual functions, such as the regulation of the circadian system. To avoid circadian disruption, artificial lighting should be dynamic, changing throughout the day in a manner comparable to natural light in terms of both light intensity and associated color temperature. This is one of the main goals of human-centric lighting. Regarding the type of materials, the majority of white light-emitting diodes (WLEDs) make use of rare-earth photoluminescent materials; therefore, WLED development is at serious risk due to the explosive growth in demand for these materials and a monopoly on sources of supply. Photoluminescent organic compounds are a considerable and promising alternative. In this article, we present several WLEDs that were manufactured using a blue LED chip as the excitation source and two photoluminescent organic dyes (Coumarin 6 and Nile Red) embedded in flexible layers, which function as spectral converters in a multilayer remote phosphor arrangement. The correlated color temperature (CCT) values range from 2975 K to 6261 K, while light quality is preserved with chromatic reproduction index (CRI) values superior to 80. Our findings illustrate for the first time the enormous potential of organic materials for supporting human-centric lighting.

Section: Resultsmentioning

confidence: 99%

Human-Centric Lighting: Rare-Earth-Free Photoluminescent Materials for Correlated Color Temperature Tunable White LEDs

García-Delgado²,

Morales³

2023

IJMS

“…Most white LEDs on the market use blue LED chips manufactured from GaN-based materials and a phosphor coating placed either directly on the chips or separated from the chip (remote phosphor configuration) [15]. A phosphor is defined as a luminescent material that absorbs and reemits energy over time, which is associated with the lifetime of the excited electron.…”

Section: Methodsmentioning

confidence: 99%

“…Description of the WLEDs(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) and their optical properties.…”

mentioning

confidence: 99%

Light Pollution and Circadian Misalignment: A Healthy, Blue-Free, White Light-Emitting Diode to Avoid Chronodisruption

Morales²,

García-Delgado³

2022

IJERPH

Sunlight has participated in the development of all life forms on Earth. The micro-world and the daily rhythms of plants and animals are strongly regulated by the light–dark rhythm. Human beings have followed this pattern for thousands of years. The discovery and development of artificial light sources eliminated the workings of this physiological clock. The world’s current external environment is full of light pollution. In many electrical light bulbs used today and considered “environmentally friendly,” such as LED devices, electrical energy is converted into short-wavelength illumination that we have not experienced in the past. Such illumination effectively becomes “biological light pollution” and disrupts our pineal melatonin production. The suppression of melatonin at night alters our circadian rhythms (biological rhythms with a periodicity of 24 h). This alteration is known as chronodisruption and is associated with numerous diseases. In this article, we present a blue-free WLED (white light-emitting diode) that can avoid chronodisruption and preserve circadian rhythms. This WLED also maintains the spectral quality of light measured through parameters such as CRI (color reproduction index).

“…Most white LEDs on the market use blue LED chips made from GaN-based materials and some type of phosphor coating, placed either directly on the chips or separated from the chip (remote phosphor configuration) [ 24 ]. These WLED sources emit light with characteristic spectral distributions, which depend on the nature of the excitation source and the phosphors used.…”

Section: Methodsmentioning

confidence: 99%

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

Morales²,

García-Delgado³

2022

Materials

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.