Example 1
Indium acetate and palmitic acid are dissolved in 1-octadecene in a 200 milliliters (mL) reaction flask, subjected to a vacuum state at 120° C. for one hour. A molar ratio of indium to palmitic acid is 1:3. The atmosphere in the flask is exchanged with N2. After the reaction flask is heated to 280° C., a mixed solution of tris(trimethylsilyl)phosphine (TMS3P) and trioctylphosphine (TOP) is quickly injected, and the reaction proceeds for a predetermined time (e.g., for 20 minutes). The reaction mixture then is rapidly cooled to room temperature and acetone is added thereto to produce nanocrystals, which are then separated by centrifugation and dispersed in toluene to obtain a toluene dispersion of the InP core nanocrystals. The amount of the TMS3P is about 0.5 moles per one mole of indium. A size of the InP core thus obtained is about 3 nm.
1. Synthesis of Quantum Dots and Characterization Thereof
(1) Selenium and sulfur are dispersed in trioctylphosphine (TOP) to obtain a Se/TOP stock solution and a S/TOP stock solution, respectively.
In a 200 mL reaction flask, zinc acetate and oleic acid are dissolved in trioctyl amine and the solution is subjected to vacuum at 120° C. for 10 minutes. The atmosphere in the flask is replaced with N2. While the resulting solution is heated to about 320° C., a toluene dispersion of the InP semiconductor nanocrystal core is injected thereto and a predetermined amount of Se/TOP stock solution is injected into the reaction flask over three times. A reaction is carried out to obtain a reaction solution including a particle having a ZnSe shell disposed on the InP core. A total of reaction time is 80 minutes and a total amount of the Se as used per one mole of the indium is about 4 moles.
Then, at the aforementioned reaction temperature, the S/TOP stock solution is injected to the reaction mixture. A reaction is carried out to obtain a resulting solution including a particle having a ZnS shell disposed on the ZnSe shell. A total of reaction time is 80 minutes and a total amount of the S as used per one mole of the indium is about 9 moles.
An excess amount of ethanol is added to the final reaction mixture including the resulting InP/ZnSe/ZnS semiconductor nanocrystals, which is then centrifuged. After centrifugation, the supernatant is discarded and the precipitate is dried and dispersed in chloroform to obtain a quantum dot solution (hereinafter, QD solution).
(2) For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 1. A UV-vis absorption spectroscopic analysis and a photoluminescence spectroscopic analysis are made for the QD solution, and the results are shown in Table 2.
2. Production of a Quantum Dot Polymer Composite and a Pattern Thereof
(1) Preparation of Quantum Dot-Binder Dispersion
A chloroform solution of the quantum dots prepared above is mixed with a solution of a binder polymer, which is a four membered copolymer of methacrylic acid, benzyl methacrylate, hydroxyethyl methacrylate, and styrene, (acid value: 130 milligrams (mg) per gram of KOH (mg KOH/g), molecular weight: 8,000 g/mol, acrylic acid:benzyl methacrylate:hydroxyethyl methacrylate:styrene (molar ratio)=61.5:12:16.3:10.2) (solvent: propylene glycol monomethyl ether acetate, PGMEA, a concentration of 30 percent by weight, wt %) to form a quantum dot-binder dispersion.
(2) Preparation of a Photosensitive Composition
To the quantum dot-binder dispersion prepared above, a hexaacrylate having the following structure (as a photopolymerizable monomer), ethylene glycol di-3-mercaptopropionate (hereinafter, 2T, as a multi-thiol compound), an oxime ester compound (as an initiator), TiO2 as a metal oxide fine particle, and PGMEA (as a solvent) are added to obtain a composition.
Based on a total solid content, the prepared composition includes 40 wt % of quantum dots, 12.5 wt % of the binder polymer, 25 wt % of 2T, 12 wt % of the photopolymerizable monomer, 0.5 wt % of the photoinitiator, and 10 wt % of the metal oxide fine particle. The total solid content is about 25%.
(3) Formation of Quantum Dot-Polymer Composite Pattern and Heat Treatment Thereof
The composition obtained above is spin-coated on a glass substrate at 150 revolutions per minute (rpm) for 5 seconds (s) to provide a film. The obtained film is pre-baked at 100° C. (PRB). The pre-baked film is exposed to light (wavelength: 365 nanometers (nm), intensity: 100 millijoules, mJ) under a mask having a predetermined pattern (e.g., a square dot or stripe pattern) for 1 second (s) (EXP) and developed with a potassium hydroxide aqueous solution (conc.: 0.043%) for 50 seconds to obtain a pattern of a quantum dot polymer composite (thickness: 6 μm).
The obtained pattern is heat-treated at a temperature of 180° C. for 30 minutes under a nitrogen atmosphere (FOB).
For the obtained pattern film, a photoluminescent peak wavelength, a blue light absorption rate, and a photoconversion efficiency are measured and the results are shown in Table 3.
1. An InP/ZnSe/ZnS quantum dot is prepared in the same manner as set forth in Example 1, except that per one mole of indium, a total amount of the Se and a total amount of the S as used are 9 moles and 27 moles, respectively. For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 1. A UV-vis absorption spectroscopic analysis and a photoluminescence spectroscopic analysis are made for the QD solution, and the results are shown in Table 2.
2. A quantum dot polymer composite is prepared in the same manner as set forth in Example 1 except for using the quantum dot as obtained above. For the obtained film pattern, a photoluminescent peak wavelength, a blue light absorption rate, and a photoconversion efficiency are measured and the results are shown in Table 3.
Example 2
An InZnP core is prepared in the same manner as set forth in Reference Example 1 except that Zinc acetate is further used in an amount of one mole per one mole of the indium precursor. A size of the InZnP core thus obtained is about 2 nm.
Red Quantum Dots
1. An InP/ZnSe/ZnS quantum dot is prepared in the same manner as set forth in Example 1, except that per one mole of indium, a total amount of the Se and a total amount of the S as used are 3 moles and 6 moles, respectively. For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 1. A UV-vis absorption spectroscopic analysis and a photoluminescence spectroscopic analysis are made for the QD solution, and the results are shown in Table 2.
2. A quantum dot polymer composite is prepared in the same manner as set forth in Example 1 except for using the quantum dot as obtained above. For the obtained film pattern, a photoluminescent peak wavelength, a blue light absorption rate, and a photoconversion efficiency are measured and the results are shown in Table 3.
1. An InP/ZnSe/ZnS quantum dot is prepared in the same manner as set forth in Example 1, except that per one mole of indium, a total amount of the Se as used is 3 moles, a total amount of the S as used is 6 moles, and the reaction time for the formation of the first semiconductor shell is 30 minutes. For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 1. A UV-vis absorption spectroscopic analysis and a photoluminescence spectroscopic analysis are made for the QD solution, and the results are shown in Table 2.
2. A quantum dot polymer composite is prepared in the same manner as set forth in Example 1 except for using the quantum dot as obtained above. For the obtained film pattern, a photoluminescent peak wavelength, a blue light absorption rate, and a photoconversion efficiency are measured and the results are shown in Table 3.
A quantum dot including a ZnSeS shell on the InP core is prepared in the same manner as set forth in Example 1, except that per one mole of indium, a total amount of the Se and a total amount of the S as used are 5 moles and 33 moles, respectively, and a mixture of the S precursor and the Se precursor is first injected and then the S precursor is injected. For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 1. A UV-vis absorption spectroscopic analysis and a photoluminescence spectroscopic analysis are made for the QD solution, and the results are shown in Table 2.
The results of the tables confirm that when the value of In/(Se+S) is greater than or equal to 0.06 and less than or equal to 0.3, the red light emitting QD may exhibit enhanced optical properties and improved stability. The prepared quantum dot may exhibit enhanced blue light absorption, which may contribute the increase in the luminous efficiency of the quantum dot polymer composite.
Green Quantum Dots
Example 3
1. An InZnP/ZnSe/ZnS quantum dot is prepared in the same manner as set forth in Example 1, except that the InZnP core prepared in Reference Example 2 is used and per one mole of indium, a total amount of the Se and a total amount of the S as used are 13 moles and 36 moles, respectively. For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 4. A UV-vis absorption spectroscopic analysis and a photoluminescence spectroscopic analysis are made for the QD solution, and the results are shown in Table 5.
2. A quantum dot polymer composite is prepared in the same manner as set forth in Example 1 except for using the quantum dot as obtained above. For the obtained film pattern, a photoluminescent peak wavelength, a blue light absorption rate, and a photoconversion efficiency are measured and the results are shown in Table 6.
An InZnP/ZnSe/ZnS quantum dot is prepared in the same manner as set forth in Example 1, except that the InZnP core prepared in Reference Example 2 is used, per one mole of indium, a total amount of the Se and a total amount of the S as used are 26 moles and 39 moles, respectively, and the duration for the formation of the 1st semiconductor shell is about 120 minutes. For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 4. A UV-vis absorption spectroscopic analysis and a photoluminescence spectroscopic analysis are made for the QD solution, and the results are shown in Table 5.
A quantum dot polymer composite is prepared in the same manner as set forth in Example 1 except for using the quantum dot as obtained above. For the obtained film pattern, a photoluminescent peak wavelength, a blue light absorption rate, and a photoconversion efficiency are measured and the results are shown in Table 6.
Example 4
1. An InZnP/ZnSe/ZnS quantum dot is prepared in the same manner as set forth in Example 1, except that the InZnP core prepared in Reference Example 2 is used and per one mole of indium, a total amount of the Se and a total amount of the S as used are 10 moles and 33 moles, respectively. For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 4. A UV-vis absorption spectroscopic analysis and a photoluminescence spectroscopic analysis are made for the QD solution, and the results are shown in Table 5.
2. A quantum dot polymer composite pattern is prepared in the same manner as set forth in Example 1 except for using the quantum dot as obtained above. For the obtained film pattern, a photoluminescent peak wavelength, a blue light absorption rate, and a photoconversion efficiency are measured and the results are shown in Table 6.
An InZnP/ZnSe/ZnS quantum dot is prepared in the same manner as set forth in Example 1, except that the InZnP core prepared in Reference Example 2 is used, per one mole of indium, a total amount of the Se and a total amount of the S as used are 3 moles and 18 moles, respectively, and the duration for the formation of the 1st semiconductor shell is about 120 minutes. For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 4.
A quantum dot polymer composite is prepared in the same manner as set forth in Example 1 except for using the quantum dot as obtained above. For the obtained film pattern, a photoluminescent peak wavelength, a blue light absorption rate, and a photoconversion efficiency are measured and the results are shown in Table 6.
Example 5
An InZnP/ZnSe/ZnS quantum dot is prepared in the same manner as set forth in Example 1, except that the InZnP core prepared in Reference Example 2 is used, per one mole of indium, a total amount of the Se and a total amount of the S as used are 5 moles and 30 moles, respectively, and the duration for the formation of the 1st semiconductor shell is about 120 minutes. For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 4. A UV-vis absorption spectroscopic analysis and a photoluminescence spectroscopic analysis are made for the QD solution, and the results are shown in Table 5.
A quantum dot polymer composite is prepared in the same manner as set forth in Example 1 except for using the quantum dot as obtained above. For the obtained film pattern, a photoluminescent peak wavelength, a blue light absorption rate, and a photoconversion efficiency are measured and the results are shown in Table 6.
An InZnP/ZnSe/ZnS quantum dot is prepared in the same manner as set forth in Example 1, except that the InZnP core prepared in Reference Example 2 is used, per one mole of indium, a total amount of the Se and a total amount of the S as used are 14 moles and 51 moles, respectively, and the duration for the formation of the 1st semiconductor shell is about 120 minutes. For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 4. A UV-vis absorption spectroscopic analysis and a photoluminescence spectroscopic analysis are made for the QD solution, and the results are shown in Table 5.
The results of the tables confirm that when the value of In/(Se+S) is greater than or equal to 0.027 and less than or equal to 0.1, the green light emitting QD may exhibit enhanced optical properties and improved stability. The prepared quantum dot may exhibit enhanced blue light absorption, which may contribute the increase in the luminous efficiency of the quantum dot polymer composite.
While this disclosure has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Example 6
An InZnP/ZnSe/ZnS quantum dot is prepared in the same manner as set forth in Example 1, except that the InZnP core prepared in Reference Example 2 is used, per one mole of indium, a total amount of the Se and a total amount of the S as used are 12 moles and 36 moles, respectively, and the duration for the formation of the 1st semiconductor shell is about 120 minutes. For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 4. A UV-vis absorption spectroscopic analysis and a photoluminescence spectroscopic analysis are made for the QD solution, and the results are shown in Table 5.
A quantum dot polymer composite is prepared in the same manner as set forth in Example 1 except for using the quantum dot as obtained above. For the obtained film pattern, a photoluminescent peak wavelength, a relative blue light absorption, and a photoconversion efficiency are measured and the results are shown in Table 6.
