In order to stimulate more color light, scientists have been studying quantum dots (Quantum, Dots, DQ), and the Swiss research team found that cesium lead halide (Caesium Lead Halide) of the quantum dots can make LED more light and light is faster.
Quantum dot is a kind of micro nano crystal (Nanocrystal) semiconductor material, its diameter is only 2~10nm, equivalent to 10~50 atoms width. The Swiss research team developed the micro nano crystal is composed of cesium lead halide, and the perovskite lattice (Perovskite Lattice) arrangement.
One of the researchers of the Zurich Federal Institute of Technology Professor Maksym Kovalenko said that the nano microcrystal by photon excitation can quickly light. Kovalenko by the composition and size by changing the nano micro crystal, can produce different wavelengths of visible light, and applied to LED and display.
The green emitting perovskite quantum dot samples excited by blue laser
According to previous studies, quantum dots are excited at room temperature, about one in 20 billion seconds (Nanoseconds) after light; and cesium lead halide quantum dots were also excited at room temperature after only about 1/1000000000 seconds light. In contrast, cesium halide quantum dots lead very fast reaction.
Materials engineering professor David Norris explained by photon (Photon) generated hole excitation nanocrystals can make electron lattice body leaving the original position; and electron hole pair (Electron-Hole Pair) in the excited state, if the electron hole back to the ground state (Ground State) shine.
But most of the quantum dots are in Dark State, will not be able to absorb the photon state, the electron hole can not be restored to the ground state, so the light time is limited and delayed. The cesium lead halide QDs have not always Dark State, so you can immediately light. This is why cesium halide lead quantum dot reaction speed, after being excited light is bright. (text: LEDinside Annie)