In order to stimulate more colors of light, scientists have been studying Quantum Dots (DQ), and a Swiss research team has discovered that quantum dots of Caesium Lead Halide can make LEDs brighter and lighter faster. .
The quantum dot is a nanocrystal semiconductor material with a diameter of only 2 to 10 nm, which is equivalent to 10 to 50 atoms. The nanocrystals developed by the Swiss research team are composed of bismuth lead halides and arranged in a perovskite lattice (Perovskite Lattice).
According to Maksym Kovalenko, a professor at the Federal Institute of Technology in Zurich, one of the researchers, the nanocrystals can be illuminated quickly by photons. By changing the composition and size of nanocrystals, Kovalenko can excite different wavelengths of visible light and apply them to LEDs and displays.
According to previous studies, after the quantum dots are excited at room temperature, they emit light after about 20 billionth of a second (Nanoseconds); while the bismuth-lead halide quantum dots are also excited at room temperature, about one billionth of a second. The second will glow. In contrast, lead-bismuth halide quantum dots react quite quickly.
David Norris, a professor of materials engineering, explains that using photons to excite nanocrystals can leave electrons out of the original lattice and create holes; while Electro-Hole Pairs are in an excited state, if electrons— The hole will return to the ground state before it will illuminate.
However, most of the quantum dot materials will be in the Dark State, and the photon state cannot be absorbed, so that the electron-hole pair cannot be restored to the ground state, so the illumination time is limited and delayed. The bismuth-lead halide quantum dots do not often have a Dark State, so they can emit light immediately. This is also why the lead-bismuth halide quantum dots react quickly and the light after excitation is also brighter.
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