In a study published in Light Science & Applications, a team of scientists led by Professor Xingliang Dai and Professor Zhizhen Ye from the State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, China, created a copper iodide nanocluster using a one-step solution synthesis-deposition process.
Preparation and characterization of the nanocluster films. Image Credit: Light: Science & Applications (2024). DOI: 10.1038/s41377-024-01427-z
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.
Image Credit: Toru Kimura/Shutterstock.com
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