Recently, the team of Professor Zeng Haibo from Nanjing University of Science and Technology has made new progress in quantum dot display research, and the related research results were published online in "Advanced Functional Materials" on February 29 (Adv. Funct. Mater., 2016, DOI: 10.1002 /adfm.201600109). In this study, a method of supersaturated crystallization at room temperature of all-inorganic perovskite quantum dots was developed. The mechanism behind the superiority of photoluminescence was put forward. Backlight LED light source with adjustable color rendering index and wide color gamut was demonstrated. The application of quantum dot television provides the necessary foundation.
First of all, for the synthesis of the problem, the team doctoral student Li Xiaoming developed a high-quality synthesis method at room temperature. Based on the principle of supersaturation, the ion transfer between good and poor solvents, the synthesis of CsPbX3 perovskite single crystal structure at room temperature has been achieved. It can be quickly completed in a few seconds without any harsh conditions such as heating, inert gas protection and injection operation The composition of X was adjustable between chlorobromine and iodine, and the size of more than 3 nm was adjustable, which verified the amplification and synthesis of 10 liters quantum dot inks and 5-gram quantum dots powder. Commendable is that a substantial decrease in the synthesis temperature does not reduce the quality of the quantum dots of light, still showing the photochromic multicolor, high quantum efficiency, high monochromaticity and other advantages, the emission peak 430-670 nm adjustable, red Green and blue trichromatic quantum efficiency of up to 70% -95%, half-width width to 15 nm. In addition, the stability was also tested, and the quantum efficiency of the emitted light remained 95% after 30 days of the ambient atmosphere and was still stimulated after 70,000 pulses of laser excitation.
Secondly, in view of the unexpectedly superior mechanism of luminescence properties, the authors proposed the discovery of the superiority of luminescence as high exciton binding energy, self-passivation of halogen surface, quasi-quantum well Band structure, the synergy of the three. By X-ray photoelectron spectroscopy, it was found that the surface of the quantum dots is rich in halogen, and formed a good passivation effect on defects such as surface dangling bonds. In addition, this structure also formed CsPbX3 / X-like quantum well core-shell structure, making the excited state electrons are confined to the perovskite quantum dots. By temperature-dependent luminescence spectroscopy, higher exciton binding energy (40 meV, greater than room temperature thermal disturbance energy, 26 meV) and lower phonon perturbation energy were calculated. These effects greatly inhibit the non-radiative recombination of the perovskite quantum dots and improve the radiation recombination probability.
Finally, a composite white light-emitting LED device incorporating a blue LED chip and a perovskite quantum dot is also demonstrated. On the one hand, the high color rendering index of white light emission with color coordinate (0.33, 0.30), (Ra = 90, R9 = 95) can be obtained due to the multi-color tunable property of the perovskite quantum dots. 2500-11500 K) A wide range of color temperature control is expected to be used as a healthy light source to simulate sunlight. On the other hand, due to the very narrow luminescence peaks of the three primary colors, the half-height widths of red, green and blue are 35, 20, and 18 nm, respectively. The color purity is high, and the backlight source has a very wide red, green and blue color.
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