In order to create more vibrant colors of light, scientists have been exploring quantum dots (QDs), and a team from Switzerland has made a breakthrough by developing lead halide-based quantum dots that can produce brighter and faster LED emissions.
Quantum dots are semiconductor nanocrystals with diameters ranging from 2 to 10 nm—roughly the size of 10 to 50 atoms. The nanocrystals developed by the Swiss researchers consist of bismuth-lead halides arranged in a perovskite lattice structure, which gives them unique optical properties.
Maksym Kovalenko, a professor at the Swiss Federal Institute of Technology in Zurich, explained that these nanocrystals respond rapidly to photons. By adjusting their composition and size, he is able to generate different wavelengths of visible light, making them highly suitable for use in LEDs and advanced display technologies.
Green-emitting perovskite quantum dot sample excited by blue laser
Previous studies showed that typical quantum dots emit light after about 20 nanoseconds when excited at room temperature. However, the bismuth-lead halide quantum dots developed by the Swiss team glow within just one nanosecond, showing a much faster response time. This rapid emission makes them ideal for high-speed lighting and display applications.
David Norris, a materials engineering professor, explains that when photons excite the nanocrystals, electrons are promoted to higher energy levels, creating electron-hole pairs. When these pairs recombine, they release energy in the form of light.
However, many quantum dot materials tend to get trapped in a "dark state," where they cannot efficiently return to the ground state, causing delays in light emission. Bismuth-lead halide quantum dots rarely enter this dark state, allowing them to emit light almost instantly. This property not only speeds up the response time but also enhances the brightness of the emitted light.
Editor: Yan Zhixiang
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