Green And Red Quantum Dots With Thick Shell And Its Application Research On Display Backlight

Own to their excellent optical properties,semiconductor quantum dots?QDs?have great potential to be used in display and lighting.This paper mainly focused on several kinds of core/shell QDs and studied the influence of shell thickness on the optical properties of QDs as well as the mechanism of photo stability.Then we put forward the possibility of application in display backlight.The original works are organized as follows:First,CdSe/CdS core/shell QDs with 3,6,10 and 14 monolayers?MLs?were prepared by a flash synthesis method and strong violet illumination experiment on these QDs were conducted.The results of photo stability were analyzed by comparing the evolution of photoluminescence?PL?intensity and PL lifetime of these QDs.Experimental results shows that a thicker shell can effectively prevent surface related recombination,increasing the photo stability of CdSe/CdS core/shell QDs.Second,CdZnSeS alloy cores with narrow line widths?²1 nm?were prepared and CdZnSeS/ZnS core/shell QDs with 3,11 and 17 MLs ZnS shell were synthesized by using the flash synthesis method.The photo stabilities of these QDs were studied by applying spectro-electrochemistrymethodandultravioletilluminationexperiment.Spectro-electrochemistry studies indicate that exciton recombination of the QDs is mainly affected by surface electronic defects,and the interaction between exciton recombination centers and surface defects significantly weakened with the increase of shell thickness.The ultraviolet illumination results show that the photo stabilities of the samples improve remarkably with increasing shell thickness.But when the shell thickness further increases to 17 MLs,the photo stability of the QDs decreases obviously instead.The results from spectro-electrochemical experiments indicate that the photo stability decrease is due to the relaxed lattice strain as a result of lattice dismatch in sample with 17 MLs ZnS shell,which can be proved by the HRTEM and the XRD patterns data.Then,we explored the feasibility of application of QDs-based display back light by integrating stable CdSe/CdS QDs and green-emitting alloy QDs with a blue light-emitting diode?LED?chip.The white LED device shows a color gamut⁹8%relative to NTSC color space after applying the commercial color filters to the white emission.Further,we calculated the mass of green and red QDs used for QDs fluorescent films based white LED backlight,which provides a theoretical guidance for preparation of QDs fluorescent film.Based on the theory calculation,white backlight based on red and green QDs fluorescent films was encapsulated and its color gamut reached 130%NTSC.And its related parameters of colorimetry and photometry were discussed.Besides,we explored the Cd-free core/shell QDs for future display application.CuInS₂/ZnS QDs with four different Cu/In molar ratios?1/1,1/2,1/4 and 1/8?and three typical shell thicknesses?2MLs,5MLs and 9MLs ZnS shell?were prepared and photo stabilities of these samples were studied.With the decrease of Cu/In ratio and the increase of shell thickness,the photo stabilities of the CuInS₂/ZnS QDs improved.The time-resolved photoluminescence study indicates that the PL emission consists of the contribution from two kinds of DAPs with different emission energies.The one with higher emission energy which is located at the interface of the core/shell QDs is easier to be affected than the other one?located in the core?in the thin shell CuInS₂/ZnS QDs.The shell's overcoating,which would keep the higher energy DAPs away from the surroundings,could improve the photo-stability of the QDs.By doping Mn ions into CuInS₂/ZnS QDs,bicolor QDs with green and orange emission as well as thses QDs based white LED were successfully realized.