Quantum dot for emitting light and method for synthesizing same

Abstract

A quantum dot for emitting light under electrical stimulation has a center of a first composition and a surface of a second composition. The second composition is different than the first composition. An intermediate region extends between the center and surface and has a continuous composition gradient between the center and the surface. The quantum dot is synthesized in one pot method by controlling the rate and extent of a reaction by controlling the following parameters: (i) type and quantity of reactant, (ii) reaction time, and (iii) reaction temperature.

1 . A method for synthesizing quantum dots nanoparticle that emit light under electrical stimulation when incorporated into an emitting layer of a quantum dot light emitting diode, the quantum dot having a continuously varied composition over the nanoparticle radius from a center of the particle to a surface, comprising the steps of:
 creating a cationic mixed solution having a controlled concentration of a Zinc reactant, a Cadmium reactant and a solvent;   dissolving an anionic precursor having a controlled concentration of a Sulfur reactant, and controlled concentration of a Selenium reactant into the cationic mixed solution;   controlling the rate and extent of reaction between at least one of the Selenium reactant and the Sulfur reactant in the cationic mixed solution by varying at least one of the three parameters controlling reaction rate: (i) reaction time, (ii) reaction temperature and (iii) type of reactant; and controlling the relative amounts of the anionic reactants relative to the cationic reactants in an inert ambient.   
     
     
         2 .- 35 . (canceled) 
     
     
         36 . A quantum dot for emitting light under electrical stimulation comprising:
 a center of a first composition; and   a surface of a second composition, the second composition being different than the first composition, and an intermediate region extending between the center and surface having a continuous composition gradient between the center and the surface.   
     
     
         37 .- 52 . (canceled) 
     
     
         53 . A Quantum Dot Light Emitting Diode, having a quantum dot layer, the quantum dot layer comprising:
 a center of a first composition; and   a surface of a second composition, the second composition being different than the first composition, and an intermediate region extending between the center and surface having a continuous composition gradient between the center and the surface.   
     
     
         54 . The Quantum Dot Light Emitting Diode of  claim 53 , wherein an amount of CdSe in the center will be greater relative to an amount of ZnS in the center and an amount of CdSe in the center is greater relative to an amount of ZnSe in the center. 
     
     
         55 . The Quantum Dot Light Emitting Diode of  claim 53  wherein an amount of ZnS in the surface is greater than an amount of CdSe in the surface. 
     
     
         56 . The Quantum Dot Light Emitting Diode of  claim 53 , wherein the quantum dots has a chemical structure Cd x Zn 1-x Se y S 1-y ; wherein the center has a composition Cd x Zn 1-x Se y S 1-y  where 0<X≤0.5 and one of 0.5≤Y<1 and 0≤Y<0.5; the surface has a composition Cd x Zn 1-x Se y S 1-y  where 0<X≤0.5 and 0<Y≤0.5; and the composition approximately midway between the center and surface has a composition of Cd x Zn 1-x Se y S 1-y  where 0<X≤0.5 and one of 0.5≤Y<1 and 0≤Y<0.5. 
     
     
         57 . The Quantum Dot Light Emitting Diode of  claim 53 , having an internal quantum efficiency of between 40 to 80 percent. 
     
     
         58 . The Quantum Dot Light Emitting Diode of  claim 53 , having an electroluminescence peak when electrically activated with a full width half maximum of less than 40 nm. 
     
     
         59 . The Quantum Dot Light Emitting Diode of  claim 58 , wherein at least one of the center, surface and intermediate region has a greater relative amount of Selenium than a relative amount of Cadmium. 
     
     
         60 . The Quantum Dot Light Emitting Diode of  claim 53 , wherein a relative amount of Zinc precursor is greater than a relative amount of Selenium. 
     
     
         61 . The Quantum Dot Light Emitting Diode of  claim 53 , wherein the quantum dot has a particle size of about 7 nanometers to 8 nanometers. 
     
     
         62 . The Quantum Dot Light Emitting Diode of  claim 53 , having an emission peak at a wavelength of about 510 nm to about 540 nm. 
     
     
         63 . The Quantum Dot Light Emitting Diode of  claim 53 , wherein a luminance is about 1,000-10,000 cd/m 2 . 
     
     
         64 . The Quantum Dot Light Emitting Diode of  claim 63 , wherein the luminance is generated in response to a driving voltage of between 2.0-3.3 volts. 
     
     
         65 . (canceled) 
     
     
         66 . The Quantum Dot Light Emitting Diode of  claim 53 , wherein a peak emission occurs at a red wavelength of about 600 nm to 630 nm. 
     
     
         67 . The Quantum Dot Light Emitting Diode of  claim 53 , wherein an external quantum efficiency is about 10-14 percent. 
     
     
         68 . The Quantum Dot Light Emitting Diode of  claim 53 , wherein the first composition is Cd 1-x ZnxS. 
     
     
         69 . The Quantum Dot Light Emitting Diode of  claim 53 , wherein the center has a greater amount of ZnS relative to an amount of CdS. 
     
     
         70 . The Quantum Dot Light Emitting Diode of  claim 53 , further comprising an intermediate region extending between the center and surface, the intermediate region having a greater amount of CdS than an amount of ZnS. 
     
     
         71 . The Quantum Dot Light Emitting Diode of  claim 53 , wherein the particle size is about 12 nanometers. 
     
     
         72 . The Quantum Dot Light Emitting Diode of  claim 53 , wherein the quantum dot has a maximum power efficiency over the range of 430 to 490 nanometers. 
     
     
         73 . The Quantum Dot Light Emitting Diode of  claim 53 , having a peak power efficiency over the range of 420 to 460 nanometers. 
     
     
         74 .- 76 . (canceled)