Healthy lighting technology is becoming increasingly popular. Traditional solid-state lighting sources use photoluminescence down conversion technology to provide a perfect white emission. Blue LEDs specifically stimulate yellow phosphors, whereas ultraviolet LEDs excite three primary color phosphors.
This technique unavoidably includes strong blue-violet components in the emission, which are damaging to the human body. Furthermore, differences in emitter degradation rates cause instability in emission spectra, and rare-earth metals (e.g., Y, Ce) or poisonous metals (e.g., Cd, Pb) are always utilized in phosphors.
Thus, creating electroluminescent systems with ultrabroad and spectra-stable emission based on environmentally benign emitters is critical for future healthy lighting, but it remains an unparalleled difficulty.
The as-prepared nanocluster film demonstrates good ambient and thermal stability, consistent and compact shape, high luminous efficiency (up to 60%), and ultra-broadband emission by careful ligand design and solvent selection.
Broadband nanocluster LEDs fabricated using this novel material exhibit stable emission spectra under varying voltages, high quantum efficiency (13%) and luminance (50,000 nits), a long operating half-life (137 h), and nearly identical performance in air or inert atmospheres. These LEDs are made using a convenient solution process.
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The findings demonstrate copper halide nanoclusters’ potential for use in next-generation, healthy lighting. These scientists provided an overview of their study's characteristics.
The authors noted, “Compared to the mainstream lighting technology, they possess the following advantages: 1) the emission spectra omit intense blue light components, which are beneficial to human body; 2) copper iodide nanocluster plays the single broadband emitter to generate spectra-stable emission, thus avoiding the color shift caused by different degradation rates of multiple emitters in the traditional technology; 3) the nanocluster consists of copper iodide and organic ligands, making them environment-friendly and low-cost.”
They further added, “Besides, the corresponding LEDs are fabricated by solution process, resulting in low production costs and ease of large-scale manufacture. Due to the high structural rigidity of the nanocluster in the excited state, our LEDs exhibit excellent environmental stability and thermal stability. In addition, the dual-mode emission consists of phosphorescence and thermal activated delayed fluorescence endows the LEDs decent efficiency roll-off, which ensures high efficiency at high luminance. These properties are also crucial for lighting applications.”
The authors concluded, “The superiority in the rigidity of nanoclusters combined with the earth-rich and environmentally-friendly nature of CuI manifests the bright prospect of CuI nanoclusters to achieve broadband LED for lighting. We anticipate that the device efficiency and operational stability of the CuI nanocluster-based LEDs can be further optimized through rational ligand design.”
Journal Reference:
Zhang, D., et. al. (2024) Efficient and bright broadband electroluminescence based on environment-friendly metal halide nanoclusters. Light Science & Applications. doi.org/10.1038/s41377-024-01427-z