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Research team: Quantum dots of bismuth lead halides make LEDs brighter and react faster
In order to enhance the color variety and brightness of light, scientists have been exploring quantum dots (QDs). A breakthrough has recently been made by a Swiss research team, who discovered that cesium lead halide quantum dots can significantly improve the performance of LEDs, making them brighter and more efficient.
Quantum dots are nanoscale semiconductor materials with diameters ranging from 2 to 10 nanometers—equivalent to just 10 to 50 atoms. The nanocrystals developed by the Swiss team are composed of bismuth-lead halides and arranged in a perovskite lattice structure. This unique configuration gives them remarkable optical properties.
According to Maksym Kovalenko, a professor at the Swiss Federal Institute of Technology in Zurich, these nanocrystals can be excited rapidly by photons. By adjusting their composition and size, it is possible to generate different wavelengths of visible light, which opens up new possibilities for use in LED lighting and display technologies.
Previously, quantum dots typically emitted light after about 20 billionths of a second (nanoseconds) when excited at room temperature. However, the bismuth-lead halide quantum dots show a much faster response time—emitting light within just one billionth of a second. This rapid reaction makes them particularly promising for high-speed applications.
David Norris, a professor of materials engineering, explains that when photons excite the nanocrystals, they displace electrons from their original positions, creating electron-hole pairs. These pairs exist in an excited state, and when they recombine, light is emitted.
However, most quantum dot materials tend to enter a "dark state" where they cannot efficiently return to the ground state, limiting their light emission. In contrast, bismuth-lead halide quantum dots rarely enter this dark state, allowing them to emit light almost immediately after excitation. This property not only speeds up their response but also results in brighter emissions.
These findings could pave the way for next-generation lighting and display technologies, offering improved efficiency, speed, and color quality.