Example 1
Selenium is dispersed in trioctylphosphine (TOP) to obtain a Se/TOP stock solution.
Indium acetate, zinc acetate, and palmitic acid are dissolved in 1-octadecene in a 200 milliliter (mL) reaction flask, subjected to a vacuum state at 120° C. for one hour. A mole ratio of indium:zinc:palmitic acid is 1:1:3. The atmosphere in the flask is exchanged with N2. After the reaction flask is heated to 200° C., a trioctylphosphine (TOP) solution of tris(trimethylsilyl)phosphine (TMS3P) and the Se/TOP stock solution is quickly injected, and the reaction proceeds at 300° C. for 10 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 InPZnS cores.
The amount of the selenium is about 0.2 moles per one mole of zinc. The results of the TEM analysis confirm that the size of the InPZnS cores thus obtained is about 2.5 nm on average.
For the InPZnS cores, an ICP-AES analysis and a UV-Vis absorption spectroscopic analysis are conducted and the results are shown in Table 1 and
In a 200 mL reaction flask, indium acetate, zinc acetate, and palmitic acid are dissolved in 1-octadecene and the resulting solution is subjected to vacuum at 120° C. for 10 minutes. A ratio of the indium with respect to the palmitic acid is 1:3. The atmosphere in the flask is replaced with N2. While the resulting solution is heated to about 200° C., a trioctylphosphine (TOP) solution of tris(trimethylsilyl)phosphine (TMS3P) is quickly injected.
Then, a temperature is raised to 270° C. and kept for 10 minutes to synthesize a core. Then, the Se/TOP stock solution is injected thereto and a temperature of the reaction flask is kept at 300° C. for 10 minutes to form a ZnSe shell on the synthesized core.
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 selenium is about 0.2 moles per one mole of zinc. The results of the TEM analysis confirm that the size of the core thus obtained is about 2.3 nm on average.
For the InP/ZnSe particles, an ICP-AES analysis and a UV-Vis absorption spectroscopic analysis are conducted and the results are shown in Table 1 and
The results of Table 1 and
Alloy Core/Shell Quantum Dot
Example 2
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 alloy core prepared in Example 1 is injected thereto and the Se/TOP stock solution and the S/TOP stock solution are injected into the reaction flask. A reaction is carried out to obtain a reaction solution including a particle having a ZnSeS shell disposed on the alloy core.
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 based shell disposed on the ZnSeS shell.
An excess amount of ethanol is added to the final reaction mixture including the InPZnSe/ZnSeS/ZnS quantum dots, which are 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).
For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 2. A photoluminescence spectroscopic analysis is made for the QD solution, and the results are shown in Table 3.
A ZnSeS/ZnS shell is formed in the same manner as in Example 2 except for using a core prepared in the same manner of Comparative Example 1. For the obtained QD solution, an ICP-AES analysis is made and the results are shown in Table 2. A photoluminescence spectroscopic analysis is made for the QD solution, and the results are shown in Table 3.
The results of Table 3 confirm that the quantum dots of Example 2 show significantly improved QY in comparison with the quantum dots of Comparative Example 2.
Example 3
A toluene dispersion of the alloy core prepared in Example 1 is added to a monomer/oligomer mixture prepared as below to obtain a composition, 1 gram (g) of which is drop casted on a glass substrate:
30 parts by weight of a lauryl methacrylate monomer, 36 parts by weight of a tricyclodecane dimethanol diacrylate monomer, 4 parts by weight of a trimethylol propane triacrylate monomer, 20 parts by weight of an epoxy diacrylate oligomer (purchased from Sartomer) are mixed to obtain a monomer/oligomer mixture. 1 part by weight of 1-hydroxy-cyclohexyl-phenyl-ketone, and 1 part by weight of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide are added thereto to obtain a final mixture, which is then defoamed under vacuum.
The casted composition is covered with a poly(ethylene terephthalate) (PET) film and is UV-cured with a light intensity of 100 milliwatts per square centimeter (mW/cm2) for four minutes to produce a semiconductor-polymer composite film. For the obtained film, brightness is measured and the results are summarized in Table 4.
A quantum dot polymer composite is prepared in the same manner as in Example 3 except for using the core-shell quantum dots prepared in Comparative Example 1.
The results of Table 4 confirm that the quantum dots of Example 1 may show increased brightness and improved chemical stability in a composite film.
Example 4
(1) A dispersion of the quantum dots prepared in Example 2 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 grams per mole (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.
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 photosensitive 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%.
(2) Preparation of a Pattern of a Quantum Dot Polymer Composite and a Thermal Treatment Thereof
The photosensitive composition obtained as 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 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 micrometers (μm)).
The obtained pattern is heat-treated at a temperature of 180° C. for 30 minutes under a nitrogen atmosphere. (POB)
For the obtained pattern film, a luminous efficiency of a pattern and maintenance of light emission after FOB (i.e., in comparison with the PRB) are measured and the results are shown in Table 5.
A quantum dot polymer composite pattern is prepared in the same manner as in Example 4 except for using the core-shell quantum dots prepared in Comparative Example 2 instead of the quantum dots of Example 2.
The results of Table 5 confirm that the quantum dots of Example 2 have greatly improved stability in comparison with the quantum dots of Comparative Example 2.
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 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.
Example 1
Seed Synthesis:
Selenium is dispersed in trioctylphosphine (TOP) to obtain a Se/TOP stock solution. In a 300 milliliter (mL) reaction flask containing trioctylamine, an organic ligand including oleic acid is put and then, heated at 120° C. under vacuum. After about 1 hour, an atmosphere in the reactor is converted into inert gas. While the temperature of the reactor is increased up to 300° C., diethylzinc, diphenylphosphine oxide, and the Se/TOP stock solution are injected thereinto. After completing the injection, a reaction is performed for 40 minutes.
When the reaction is complete, acetone is added to the reaction solution, which is rapidly cooled down to room temperature, and a precipitate obtained by centrifuging the mixture is dispersed in toluene to obtain a ZnSe seed. The ZnSe seed has an average size of about 2.5 nm.
Amounts of the Zn precursor and the Se precursor used herein are 0.9 millimoles (mmol), and 0.45 mmol, respectively.
Formation of Quantum Well Layer Including an Alloy Semiconductor Nanocrystal:
An organic ligand including oleic acid is placed in a 300 mL reaction flask containing octadecene (ODE) and vacuum-treated at 120° C. The atmosphere in the flask is changed into nitrogen (N2). While the temperature of the reactor is increased to 300° C., toluene dispersion of the ZnSe seed is rapidly put in the reaction flask, and subsequently, indium laurate, tris(trimethylsilyl)phosphine (hereinafter, also referred to as ‘TMSP’), and a trioctyl phosphine dispersion of gallium chloride are injected thereto. Then, a reaction is performed for 30 minutes to form a quantum well layer on the seed.
When the reaction is complete, the reaction solution is rapidly cooled down to room temperature and ethanol is added thereto, and a precipitate is separated by centrifuging and is dispersed in toluene.
A used amount of the indium precursor is about 0.5 moles per one mole of selenium. A mole ratio among the indium, the phosphorus, and the gallium is about 1:1:0.4.
For the particle thus prepared, an ICP analysis is made and the results are summarized in Table 1. A transmission electron microscopy analysis is made for the prepared particle and the results confirm that the particle size having the formed quantum well layer is about 3.15 nm.
A particle having the quantum well layer on the seed is prepared in the same manner as in Example 1 except for not using the gallium precursor. For the particle thus prepared, an ICP analysis is made and the results are summarized in Table 1. A transmission electron microscopy analysis is made for the prepared particle and the results confirm that the thickness of the quantum well layer as formed is about 3.01 nm.
Thus, the particle prepared in Example 1 has a volume increased by 15% in comparison with the particle prepared in Comparative Example 1.
Example 2
A particle having the quantum well layer on the seed is prepared in the same manner as in Example 1 except for increasing the amount of the gallium by two times. For the particle thus prepared, an ICP analysis is made and the results are summarized in Table 1.
A particle having the quantum well layer on the seed is prepared in the same manner as in Example 1 except for increasing the amount of the gallium by two times. For the particle thus prepared, an ICP analysis is made and the results are summarized in Table 1.
The results of Table 1 confirm that the introduction of the gallium into the emission layer may suppress the stokes shift and the PL wavelength may decrease.
Example 3
1. Zinc acetate and oleic acid are placed in a 300 mL reaction flask containing TOA and then, vacuum-treated at 120° C. The flask is internally substituted with nitrogen (N2). While the reaction temperature of the reactor is increased to 320° C., toluene dispersion of the particles having the quantum well layer injected to the reaction flask, then the Se/TOP stock solution are injected thereto, and subsequently, a S/TOP stock solution together with zinc acetate is injected thereto, as well. A reaction is performed for predetermined time, and a ZnSe/ZnS shell layer is formed on the quantum well layer.
An amount, e.g., mole, ratio between a Zn precursor and an Se precursor is about 1:2:1 and an amount, e.g., mole, ratio of the Zn precursor used for the synthesis of the seed: the Zn precursor used for the formation of the shell is about 1:3:1.
When the reaction is complete, ethanol is added to the reaction solution, which is rapidly cooled down to room temperature, and a precipitate obtained by centrifuging the mixture is dispersed in toluene to obtain toluene dispersion of QW quantum dots.
An UV-Vis absorption spectroscopy analysis is performed for the prepared QW quantum dots, and the results are shown in
A photoluminescent spectroscopy analysis is performed for the prepared QW quantum dots, and the results are shown in table 2. For the QW quantum dots thus prepared, an ICP analysis is made and the results are summarized 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 prepared 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 grams per mole (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.
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 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 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 (EXP) and developed with a potassium hydroxide aqueous solution (concentration: 0.043 wt %) for 50 seconds to obtain a pattern of a quantum dot polymer composite.
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 blue light absorption rate and a photoconversion efficiency are measured and the results are shown in Table 2.
The QW quantum dots of Example 1 have a narrower FWHM than those of Comparative Example 1, and the results of Table 1 show that the QW quantum dots of Example 1 have improved absorption and enhanced luminance efficiency.
A QW quantum dot is prepared in the same manner as in Example 3 except for using the particle prepared in Comparative Example 1. For the particle thus prepared, an ICP analysis is made and the results are summarized in Table 1.
A photoluminescent spectroscopy analysis is performed for the prepared QW quantum dots, and the results are shown in table 2. For the QW quantum dots thus prepared, an ICP analysis is made and the results are summarized in Table 2.
An UV-Vis absorption spectroscopy analysis is performed for the prepared QW quantum dots, and the results are shown in
A quantum dot polymer composite pattern is prepared in the same manner as in Example 2 except for using the prepared QW quantum dot. For the obtained pattern film, a light absorption rate and a light conversion efficiency are measured and the results are shown in Table 2.
Example 4
A QW quantum dot is prepared in the same manner as in Example 3 except for using the particle prepared in Example 2. For the particle thus prepared, an ICP analysis is made and the results are summarized in Table 1.
A photoluminescent spectroscopy analysis is performed for the prepared QW quantum dots, and the results are shown in table 2. For the QW quantum dots thus prepared, an ICP analysis is made and the results are summarized in Table 2.
An UV-Vis absorption spectroscopy analysis is performed for the prepared QW quantum dots, and the results are shown in
A quantum dot polymer composite pattern is prepared in the same manner as in Example 2 except for using the prepared QW quantum dot. For the obtained pattern film, a light absorption rate and a light conversion efficiency are measured and the results are shown in Table 2.
A QW quantum dot is prepared in the same manner as in Example 3 except for using the particle prepared in Comparative Example 2. For the particle thus prepared, an ICP analysis is made and the results are summarized in Table 1.
A photoluminescent spectroscopy analysis is performed for the prepared QW quantum dots, and the results are shown in table 2. For the QW quantum dots thus prepared, an ICP analysis is made and the results are summarized in Table 2.
An UV-Vis absorption spectroscopy analysis is performed for the prepared QW quantum dots, and the results are shown in
A quantum dot polymer composite pattern is prepared in the same manner as in Example 2 except for using the prepared QW quantum dot. For the obtained pattern film, a light absorption rate and a light conversion efficiency are measured and the results are shown in Table 2.
The results of Table 2 show that the QW quantum dots of Examples may suppress the red shift phenomenon and the quantum dot composite of the examples may exhibit improved absorption and enhanced luminance efficiency in comparison with the QW quantum dots and the quantum dot composite of Comparative Examples.
The quantum dots of the embodiment may exhibit a structure of a quantum well structure and may show improved conversion rate at a relatively short wavelength.
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, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
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.
