Example 1
An indium precursor (indium laurate), a zinc precursor (zinc oleate), and a sulfur precursor (dodecane thiol) each dissolved in 1-octadecene are added to a 200 milliliter (mL) reaction flask and then, heated at 90° C. under vacuum. An atmosphere of the reactor is converted into nitrogen after one hour, and while the reactor is heated to about 280° C., triethyl gallium and tris(trimethylsilyl)phosphine (TMS3P) each dispersed in trioctylphosphine are injected thereinto and then, the temperature of the reactor is increased to 300° C. to carry out a reaction for 3 hours. Subsequently, zinc oleate (Zn(OA)2) as a zinc precursor is injected into the reactor.
The reaction solution is cooled down to room temperature, acetone is added thereto and then, centrifuged, and precipitates are dispersed again in toluene.
The amount of TMS3P and the amount of the sulfur are 1.5 moles and 1 mole per one mole of indium. The amount of the gallium and the Zn per one mole of indium are 0.6 moles and 2 moles, respectively.
A size of the obtained core is about 2.2 nm and a first absorption peak is about 430 nm. An ICP analysis is made and the results are compiled in Table 1.
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 reaction flask is replaced with N2. While the resulting solution is heated to about 320° C., a toluene dispersion of the semiconductor nanocrystal core prepared in Example 1-1 is injected thereto and a predetermined amount of the Se/TOP stock solution is injected into the reaction flask several times and then a predetermined amount of the STOP stock solution is injected into the reaction flask several times, respectively to form quantum dots having a ZnSe/ZnS shell disposed on the semiconductor nanocrystal core.
An excess amount of ethanol is added to the final reaction mixture including the quantum dots, which is then centrifuged. After centrifugation, the supernatant is discarded and the precipitate is dried and dispersed in chloroform or toluene to obtain a quantum dot solution (hereinafter, QD solution).
Total amounts of the Se and the S as used per one mole of the indium is about 8 moles and about 18 moles, and a total reaction time is about 3 hours.
For the obtained QD, an ICP-AES analysis is made and the results are shown in Table 2. A UV-Vis absorption spectroscopic analysis and a photoluminescence spectroscopic analysis are made for the QD, and the results are shown in Table 3.
2. Production of a Quantum Dot Polymer Composite and a Pattern Thereof
(1) Preparation of Quantum Dot-Binder Dispersion
The prepared chloroform solution of the quantum dots 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) of KOH per gram (mg KOH/g), molecular weight: 8,000 g/mol, methacrylic acid:benzyl methacrylate:hydroxyethyl methacrylate:styrene (mole 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 prepared quantum dot-binder dispersion, 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.
(ethylene glycol di-3-mercaptopropionate)
(hexaacrylate)
wherein
based on a total solid content, the prepared composition includes 43 wt % of quantum dots, 12.5 wt % of the binder polymer, 24 wt % of 2T, 10 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 wt %.
(3) Formation of Quantum Dot-Polymer Composite Pattern and Heat Treatment Thereof
The obtained composition 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 (concentration: 0.043 weight %) for 50 seconds to obtain a pattern of a quantum dot polymer composite (thickness: 6 micrometers (μm)).
The obtained pattern is heat-treated at a temperature of 180° C. for 30 minutes under a nitrogen atmosphere (post-baked (POB)).
For the obtained pattern film, a blue light absorption and a photoconversion rate are measured and the results are shown in Table 4.
1-1. Indium laurate and a zinc precursor (zinc oleate) each dissolved in 1-octadecene are added to a 200 milliliters (mL) reaction flask, subjected to a vacuum state at 120° C. for one hour. In one hour, the atmosphere in the reaction 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 about 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. The amount of the TMS3P is about 1 mole per one mole of indium. A size of the obtained core is about 1.9 nm and a first absorption peak is about 430 nm. An ICP analysis is made and the results are compiled in Table 1.
1-2. A core shell quantum dot is prepared in the same manner as Example 1-2 except for using the prepared core.
1-3. A quantum dot polymer composite and pattern thereof are prepared in the same manner as set forth in Example 1-2 except for using the obtained quantum dots. For the obtained pattern film, a blue light absorption and a photoconversion rate are measured and the results are shown in Table 4.
Example 2
A core is manufactured according to the same method as Example 1-1 except that 0.4 moles of gallium per 1 mole of indium is used. A size of the obtained core is about 2.1 nm and a first absorption peak is about 430 nm. An ICP analysis is made and the results are compiled in Table 1.
1. A core shell quantum dot having a ZnSe/ZnS shell is prepared in the same manner as Example 1-2 except for using the core prepared in Example 2-1.
2. A quantum dot polymer composite and pattern thereof are prepared in the same manner as set forth in Example 1-2 except for using the obtained quantum dots. For the obtained pattern film, a blue light absorption and a photoconversion rate are measured and the results are shown in Table 4.
A core is manufactured according to the same method as Example 2-1 except for not using a zinc precursor. During the synthesis, precipitation occurs and the product does not show, e.g., exhibit, an absorption peak. An ICP analysis is made and the results are compiled in Table 1.
Example 3
A core is manufactured according to the same method as Example 2-1 except for not using a sulfur precursor. During the synthesis, precipitation occurs and the product does not show, e.g., exhibit, an absorption peak. An ICP analysis is made and the results are compiled in Table 1.
Example 4
A core is manufactured according to the same method as Example 2-1 except for using gallium acetylacetonate as a gallium precursor. A size of the obtained core is about 2.0 nm and a first absorption peak is about 439 nm. An ICP analysis is made and the results are compiled in Table 1.
Example 5
A core is manufactured according to the same method as Example 2-1 except for using gallium chloride as a gallium precursor. A size of the obtained core is about 2.1 nm and a first absorption peak is about 455 nm. An ICP analysis is made and the results are compiled in Table 1.
The results of Table 1 show that in Examples 1-1 and 2-1, the InGaZnPS alloy semiconductor nanocrystals having a size of about 2 nm, In+Ga+Zn:P+S of about 1.2:1-1.7:1, and P:In of greater than 1:1 are prepared. The results of Comparative Examples 2-4 show that the ICP compositions are outside an appropriate range and an excessive amount is precipitated, failing to form a nanocrystal (i.e., an alloy semiconductor nanocrystal is not formed).
The results of Table 3 and Table 4 confirm that the quantum dots prepared in Examples 1-2 and 2-2 have a high level of luminous efficiency in an individual quantum dot or in a composite form and show, e.g., exhibit, an improved absorption.
While this disclosure has been described in connection with what is presently considered to be practical example embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
