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White LED represents the next generation of green, solid-state lighting technology. Developing high-performance white LED materials and techniques is of great importance for sustainable lighting solutions. Semiconductor nanocrystals are emerging as a promising class of luminescent materials due to their unique properties such as solution processability, tunable emission spectra, high quantum efficiency, and ease of dispersion. These characteristics make them a strong candidate to reduce the industry's reliance on rare earth materials, overcome foreign patent barriers, and enhance existing LED technologies.
CuInSâ‚‚ nanocrystals, in particular, are a new type of non-rare-earth, non-heavy-metal luminescent material. They offer advantages such as small size, adjustable wavelength, broad emission spectrum, low self-absorption, and cost-effectiveness, making them highly suitable for white LED applications.
Associate Professor Zhong Haizheng from the School of Materials has been researching the synthesis of CuInS₂ and CuInSe₂ nanocrystals for many years, achieving international recognition in this field. Supported by the National Natural Science Foundation of China and the Ministry of Science and Technology 973 Program, he utilized the School of Materials Science and the Micronano Technology Center to systematically investigate the optical properties of these nanocrystals based on their size and composition. By employing a combination of control strategies, he successfully developed fluorescent nanocrystals with an adjustable emission range between 500–700 nm and an absolute quantum yield of 75%.
Building on this achievement, a small-scale test device was established to overcome the challenges in synthesizing fluorescent nanocrystals, enabling the preparation of nanocrystals at the one-hundred-gram level. Additionally, collaborations with multiple research groups both domestically and internationally have expanded the potential applications of these materials in areas such as display, sensing, and detection.
Recently, Associate Professor Zhong has focused on developing white LEDs using CuInSâ‚‚-based nanocrystal phosphors. By combining red and green nanocrystal phosphors, he has created patches and high-power white LED devices (see Figure 1a), achieving a color rendering index above 90, a maximum luminous efficacy of nearly 70 lm/W, and an adjustable color temperature ranging from 3000K to 11000K. Compared to other white LED technologies currently available, the performance of these devices is at an advanced level (see Figure 1b).
Currently, his research is focusing on surface interface engineering of nanocrystals to identify more suitable packaging substrates. If the service life can exceed 10,000 hours, these materials are expected to meet the requirements of lighting and display applications, offering significant market potential.
The research has led to the publication of 11 SCI papers in high-impact journals such as Advanced Functional Materials, ACS Nano, Journal of Physical Chemistry Letters, Nanoscale, and Optics Express. These works have been cited over 200 times, and four core patents have been filed, with one already authorized. The findings have been presented more than 10 times at national and international conferences, with seven of them being invited talks.
The results have gained recognition from both domestic and international researchers. In 2012, Professor Prashant Kamat, Editor-in-Chief of the Journal of Physical Chemistry Letters, invited a Perspective essay. The ACS website also published a video interview with him, available at http://pubs.acs.org/page/jpclcd/zou.html. After the paper was published, it became one of the most-read papers of that month. At the recent 13th National Conference on Luminescence Science, Professor Zhong delivered an academic talk titled “Non-Rare-Earth Nanocrystal Phosphor Fine Control and Its LED Application,†and was awarded the 6th Xu Zuoyi Excellent Luminescence Academic Paper Award.