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

Abstract

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.

A supramolecular assembly strategy towards organic luminescent materials

“…With the increasing demand for ecofriendly materials, organic molecules with white light emission (WLE) are used in lighting 20 and sensing. 21 The majority of reported ways to achieve WLE entail mixing several components that produce light in complementary colors, which causes issues in stability, reproducibility, and device fabrication.…”

A Novel Photopharmacological Tool: Dual-Step Luminescence for Biological Tissue Penetration of Light and the Selective Activation of Photodrugs

“…Once inside, the light can be spectrally converted to specific wavelengths in the UV-visible range for the activation of specific photodrugs. Spectral conversion techniques have already found applications in fields such as photovoltaics [35][36][37][38][39], LED lighting [40][41][42], greenhouses [43,44], ophthalmology [45], anti-counterfeiting [46][47][48], etc. The photopharmacology sector could also benefit from these spectral conversion techniques.…”

Engineering linkers to regulate solid-state emission of spirodifluorene-based conjugated porous polymers for white light-emitting devices

“…Light-conversion materials are mainly divided into inorganic 5 and organic materials. 6 Inorganic materials contain rare earth ion-doped materials; 7,8 inorganic metal compounds are currently the mainstream use of lightconversion materials with high brightness, good stability, rich color, and other characteristics. However, there are some pro-blems in the preparation of LED devices, such as film-related difficulties, process complexity, and the need for precious metals or rare earth elements that make it impossible to produce sustainably.…”