In order to produce more vibrant colors of light, scientists have been exploring quantum dots (QDs), and a team from Switzerland has made a breakthrough. They discovered that cesium lead halides, when structured as quantum dots, can create brighter and faster LEDs.
Quantum dots are nanoscale semiconductor crystals, typically between 2 to 10 nanometers in size—equivalent to about 10 to 50 atoms. The nanocrystals developed by the Swiss researchers are composed of bismuth-lead halides arranged in a perovskite lattice structure. This unique arrangement gives them exceptional optical properties.
Maksym Kovalenko, a professor at ETH Zurich, explained that these nanocrystals respond rapidly to photon excitation. By adjusting their composition and size, it's possible to generate different wavelengths of visible light, making them highly suitable for use in next-generation LEDs and display technologies.
Green-emitting perovskite quantum dot sample excited by blue laser
Previous studies showed that typical quantum dots emit light after about 20 billionths of a second (nanoseconds) when excited at room temperature. However, the bismuth-lead halide quantum dots emit light much faster—within just one billionth of a second. This rapid response makes them ideal for high-speed applications.
David Norris, a materials engineering professor, explains that when photons hit the nanocrystals, they energize electrons, 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 the electron-hole pairs 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 their response time but also enhances their brightness.
Editor: Yan Zhixiang
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