KR101360073B1 - Quantum dot for light emitting diode and white light emission device using the same - Google Patents

Abstract

Disclosed are a quantum dot for a light emitting diode and a white light emitting device using the same. The quantum dot according to the present invention is a quantum dot for converting the excitation light of the light emitting diode to generate wavelength converted light, Cu _1-x In _1-y Ga _y S ₂ / ZnS core / shell quantum dot (0.5≤x≤0.95, 0 ≤ y <1). Copper-deficient Cu _1-x In _1-y Ga _y S ₂ / ZnS core / shell quantum dots (0.5 ≦ _x ≦ 0.95, 0 ≦ y <1) may be used to implement a wide yellow emission band. Accordingly, even if one type of quantum dot is used, the white LED can be realized by combining with the blue LED. Accordingly, the Cu _1-x In _1-y Ga _y S ₂ / ZnS core / shell quantum dots (0.5 ≦ _x ≦ 0.95, 0 ≦ y <1) according to the present invention may replace bulk phosphors such as YAG: Ce. .

Description

Quantum dot for light emitting diode and white light emission device using the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to quantum dots (QDs) for light emitting diodes that wavelength convert an excitation light of a light emitting diode to generate wavelength converted light. More specifically, the present invention relates to a quantum dot capable of emitting white light in combination with a blue light emitting diode. And it relates to a white light emitting device using the same.

Quantum dots refer to nanoparticles of a few tens of nanometers (nm) in size with semiconductor characteristics, and are a key material of great interest because they exhibit different characteristics from bulk-sized particles due to quantum confinement effects. When the quantum dots absorb light from an excitation source and reach an energy excited state, the quantum dots emit energy corresponding to the energy band gap of the quantum dots to emit light. Therefore, when the size or material composition of the quantum dot is adjusted, the band gap can be adjusted to use energy of various levels of wavelength bands. In general, the quantum dots show a phenomenon in which the band gap increases as the size of the particles decreases. As a result, the emission wavelength is blue-shifted as the size of the particles decreases. In addition, the extreme reduction in particle size increases the proportion of atoms or ions on the surface of the material, which can lead to bulky particles due to the size of extremely small particles, such as lower melting points and lower crystal lattice constants. It shows new optical, electrical and physical properties that could not be seen. Therefore, researches for applying in the fields of display, light emitting diode (LED), biotechnology, etc. using the quantum dots having the above characteristics are actively underway.

Demand for white LEDs is high in the LED field. In the method of manufacturing a white LED, there is a method of combining white LEDs with LED chips of various colors, or combining LED chips emitting light of a specific color and phosphors emitting fluorescence of a specific color. The current commercially available white LED is applied with the latter method to obtain a white LED package by dispensing YAG: Ce bulk yellow phosphor on a blue LED chip.

In order to replace the bulk phosphor used in the LED field, it is also known to apply various kinds of quantum dots that can emit light of different wavelengths on a blue LED chip. Jang et al. Reported the combination of green- and red-emitting CdSe / multi-shell quantum dots with blue InGaN LEDs yielded a luminous efficiency of 41 lm / W at an operating current of 20 mA [2010 Adv. Mater. 22 3076]. According to Wang et al., The combination of green-, yellow- and red-emitting CdSe / multi-shell quantum dots with a blue LED results in luminous efficiency of 32 lm / W at an operating current of 40 mA and a color index of 88 [2011 J]. Mater. Chem. 21 8558].

As such, quantum dot-based LEDs have been actively studied, but an example of implementing a white LED using a single type of quantum dots is not known so far, and no excellent quantum dots have been developed to replace YAG: Ce bulk yellow phosphors.

The problem to be solved by the present invention is to provide a quantum dot excellent enough to replace the YAG: Ce bulk yellow phosphor and its manufacturing method.

Another object of the present invention is to provide a white light emitting device that emits white light even when using a single type of quantum dot by using such a quantum dot, and a method of manufacturing the same.

In order to solve the above problems, the quantum dot according to the present invention is a quantum dot that converts the excitation light of the light emitting diode to generate wavelength converted light, and includes a Cu _1-x In _1-y Ga _y S ₂ / ZnS core / shell quantum dot ( 0.5 ≦ x ≦ 0.95, 0 ≦ y <1).

The method for preparing such quantum dots includes mixing and heating a precursor and a solvent to grow Cu _1-x In _1-y Ga _y S ₂ core quantum dots (0.5 ≦ _x ≦ 0.95, 0 ≦ y <1); And applying a ZnS shell stock solution on the Cu _1-x In _1-y Ga _y S ₂ core quantum dots to perform ZnS coating.

When such a quantum dot is combined with a blue light emitting diode, a light emitting device that emits white light while using a single type of quantum dot can be manufactured.

In order to couple the quantum dot to the blue light emitting diode, a method of preparing a quantum dot paste by adding a thermosetting silicone resin and a curing agent and then dispensing the quantum dot on the blue light emitting diode may be used.

Instead, a polymer solution is prepared by dissolving a polymer in an organic solvent, and then mixing the quantum dots with the polymer solution and drying them to form a polymer thin film, and then forming an inorganic oxide protective film on at least one side of the polymer thin film. A polymer composite plate may be prepared, and then a method of adhering the quantum dot-polymer composite plate onto the blue light emitting diode may be used.

Lighting white LEDs are typically manufactured by combining yellow bulk phosphors (YAG: Ce or silicate-based compositions) on a blue LED chip. An example is the use of quantum dots for wavelength conversion for LED manufacturing. However, to realize white light, various kinds of quantum dots having different wavelength windows must be used.

In contrast, according to the present invention, a wide yellow emission band can be realized by using Cu _1-x In _1-y Ga _y S ₂ / ZnS core / shell quantum dots (0.5 ≦ _x ≦ 0.95, 0 ≦ y <1), which lack copper. have. Accordingly, even if one type of quantum dot is used, the white LED can be realized by combining with the blue LED. Thus, the Cu _1-x In _1-y Ga _y S ₂ / ZnS core / shell quantum dots according to the present invention may replace bulk phosphors such as YAG: Ce.

An example of implementing a white LED using a single kind of quantum dot is not known yet. In the case of using a single type of quantum dot, there is an advantage in that a device with good reproducibility can be manufactured because the variable to be controlled is reduced as compared with the case of using several types of quantum dots. White light emitting devices, such as white LEDs manufactured according to the present invention, exhibit a color rendering index greater than 72 and a luminous efficiency greater than 63 lm / W under a current of 20 mA.

FIG. 1 (a) shows absorption spectra of CIS quantum dots for various Cu / In ratios, FIG. 1 (b) shows normalized emission spectra and fluorescence images of the CIS quantum dots, and FIG. 1 (c) shows various Absorption spectra of CIS / ZnS quantum dots are shown for the Cu / In ratio, and FIG. 1 (d) shows normalized emission spectra and fluorescence images of CIS / ZnS quantum dots.
FIG. 2 (a) is the EL spectrum under 20 mA forward current of the LED combined with CIS / ZnS quantum dots when Cu / In is 1/1, 1/2 and 1/4, and FIG. 2 (b) is the CIE color Coordinates. FIG. 2 (c) is a photograph before and after applying a forward current of 20 mA in an LED combined with a CIS / ZnS quantum dot when Cu / In is 1/4.
FIG. 3 is an EL spectrum measured with increasing forward current from 5 mA to 100 mA in an LED combined with CIS / ZnS quantum dots when Cu / In is 1/4.
Figure 4 (a) is the CIE color coordinates measured by increasing the forward current from 5 mA to 100 mA in the LED combined with CIS / ZnS quantum dots when Cu / In is 1/4, Figure 4 (b) is CRI 4C is a light emission efficiency / light conversion efficiency graph.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you.

In the present invention, to implement a white LED, Cu _1-x In _1-y Ga _y S ₂ / ZnS core / shell quantum dots (0.5 ≦ _x ≦ 0.95, 0 ≦ y <1) are used as yellow light emitting phosphors.

Cu _1-x In _1-y Ga _y S ₂ (0.5≤x≤0.95, 0≤y <1) In addition to the hot colloid method and the solvent thermal method, the quantum dots may be heated or It can be prepared by hot-injection. ZnS coating on Cu _1-x In _1-y Ga _y S ₂ (0.5≤x≤0.95, 0≤y <1) cores improves PL (photoluminescence) and quantum efficiency (QY). ZnS coating may also be carried out by a cation exchange process, a solvent heat method, or the like.

Generally known CuInS ₂ quantum dots have a characteristic of being dependent on internal defects and thus exhibit a wide emission band. Thus, it is not suitable for use in display applications that require a narrow bandwidth for a particular color. However, CuInS ₂ quantum dots are advantageous in implementing white LEDs because phosphors of a wide emission band are preferred to secure a wide spectral region.

The inventors found that the CuInS ₂ / ZnS core / shell quantum dots had to be chemically aligned towards the lack of copper in the core quantum dot CuInS ₂ to be used as a yellow light emitting phosphor. In other words, Cu and In are not in a 1: 1 ratio, and Cu should have a less stoichiometric composition than In. According to the present invention, such copper-deficient Cu _1-x InS ₂ (0.5≤x≤0.95, i.e., the ratio of Cu and In is 1/20 to 1/2) is excellent by more than 70% through the hot colloid method or the solvent heat method. It can be manufactured to have a quantum efficiency and a wide emission half width of 104 nm or more. When the yellow light-emitting copper-deficient CIS / ZnS quantum dots according to the present invention are applied to the blue LEDs, blue and yellow light emission are combined to realize a quantum dot-based white LED made of a single type of quantum dots. If the ratio of Cu and In is larger than 1/20, the use as a yellow phosphor is not a problem, and if the ratio of Cu and In is larger than 1/2, it does not become a yellow phosphor.

Meanwhile, Cu _1-x (In, Ga) S ₂ / ZnS core / shell quantum dots (0.5 ≦ _x ≦ 0.95), in which Ga is partially substituted at In sites in the copper-deficient CIS / ZnS quantum dots according to the present invention, are also yellow. Because it emits light nearby, it is very suitable as a color conversion material for white LEDs. Accordingly, the quantum dot according to the present invention has a chemical formula of Cu _1-x In _1-y Ga _y S _{2 /} ZnS (0.5 ≦ _x ≦ 0.95, 0 ≦ y <1).

An example of implementing a white LED using a single type of quantum dot as in the present invention is not known yet. In the case of using a single type of quantum dot, there is an advantage in that a device with good reproducibility can be manufactured because the variable to be controlled is reduced as compared with the case of using several types of quantum dots. A white light emitting device such as a white LED manufactured according to the present invention has a color rendering index greater than 72 and a luminous efficiency greater than 63 lm / W under a current of 20 mA.

Hereinafter, the present invention will be described in more detail with reference to specific experimental examples.

<CIS and CIS / ZnS quantum dot synthesis and quantum dot based LED manufacturing method>

The amount of the indium precursor was fixed and the amount of the copper precursor was changed to prepare CIS quantum dots having different Cu / In compositions of 1/1, 1/2, and 1/4. To prepare a CIS quantum dot with a Cu / In composition of 1/1, 0.5 mL (0.095 g) of CuI, 0.5 mmol (0.146 g) of In (Ac) ₃ , and 5 mL of DDT were added to a 50 mL flask. into a neck flask). The reaction mixture was degassed while heating to 100 ° C. and backfilled with Ar and then heated to 230 ° C. in 10 minutes. After 5 minutes at this temperature, CIS core quantum dots were grown. The CIS quantum dots having a Cu / In composition of 1/2 and 1/4 were prepared in the same manner as in this method, except that the amount of CuI was 0.25 mmol and 0.125 mmol, respectively.

 In order to obtain a quantum dot in which Ga is partially substituted at an In site, a quantum dot may be formed by mixing a copper precursor, an indium precursor, a gallium precursor, and a solvent as described above.

ZnS shell stock solutions were prepared for ZnS shell coating. A ZnS shell stock solution was prepared by mixing 4 mmol (2.528 g) of Zn stearate, 1 mL of DDT, and 4 mL of ODE followed by heating to 190 ° C. using a hot plate. This shell stock solution was dripped at the rate of 0.91.0 mL / min in the solution in which the CIS core of 230 degreeC was formed. It was then heated to 240 ° C. to maintain the optimum time needed for the coating. The optimal time was 60-70 minutes. CIS core and CIS / ZnS core / shell quantum dots were precipitated with excess ethanol and then repeatedly purified by centrifugation using a solvent of chloroform / ethanol combination (7000 rpm / 10 minutes), and finally dispersed in chloroform. I was.

A method of manufacturing a quantum dot-based LED by combining a surface mount InGaN-based blue light emitting LED and a CIS / ZnS quantum dot-silicon resin mixture is as follows.

First, CIS / ZnS quantum dot chloroform dispersion solution was mixed with 1.23 g of a thermosetting silicone resin (OE-6630 B, Dow Corning Co.). The CIS / ZnS quantum dot chloroform dispersion solution had an optical density of about 3.0 at 450 nm, and the approximate concentration was 43 mg / mL. It was then heated at 90 ° C. for 1 hour to remove chloroform in the mixture.

An equivalent amount (1.23 g) of curing agent (OE-6630 A) was then added to the CIS / ZnS quantum dot-silicone resin mixture to produce the final quantum dot paste, which was dispensed onto a blue LED chip mold. The dispensed quantum dot paste was heat-treated in an oven for 2 hours at 70 ° C. for 30 minutes and 120 ° C. for 1 hour.

<Fluorescence Characteristics of CIS and CIS / ZnS Quantum Dots>

FIG. 1 (a) shows absorption spectra of CIS quantum dots when Cu / In is 1/1, 1/2 and 1/4, and FIG. 1 (b) shows normalized PL spectrum. The excitation wavelength for the PL measurement was 450 nm. Fluorescence under 365 nm UV irradiation of CIS quantum dots dispersed in chloroform is shown in the inset in FIG.

Referring to Figure 1 (a), the greater the degree of copper shortage, the more blue shift or higher band gap in absorption is confirmed. As such, the band gap in the CID quantum dots depends on the Cu / In composition.

As shown in FIG. 1 (b), all the core quantum dots emit light in the far red region (peak wavelength is 717 nm when Cu / In is 1/1 and peak wavelength is 665 nm when Cu / In is 1/4). The half width of light emission is wide at 128-141 nm. The emission quantum efficiencies of the CIS quantum dots were measured to be 8.6, 11.3, and 12.7% for the case of Cu, In, 1/1, 1/2, and 1/4.

ZnS coatings were performed on CIS core quantum dots with Cu / In of 1/1, 1/2 and 1/4.

FIG. 1 (c) is normalized absorption spectrum of CIS / ZnS quantum dots when Cu / In is 1/1, 1/2 and 1/4, and FIG. 1 (d) is normalized PL spectrum. The excitation wavelength for the PL measurement was 450 nm. Fluorescence under 365 nm UV irradiation of CIS / ZnS quantum dots dispersed in chloroform is shown in the inset in FIG.

Referring to FIG. 1 (c), it can be seen that the absorption peaks of all the CIS / ZnS quantum dots are shifted toward shorter wavelengths than the first CIS core quantum dots.

Referring to FIG. 1 (d), as the band gap of the CIS core in the CIS / ZnS quantum dot increases, the emission spectrum of the CIS / ZnS quantum dot is shifted blue as compared to the original CIS core quantum dot, and Cu / In is 1/1, 1/2 and 1/4 showed red (623 nm), orange (598 nm) and yellow (564 nm) luminescence, respectively. The luminescence quantum efficiency also increased dramatically.

As surface protection is effectively achieved by the ZnS shell layer, the quantum efficiency of CIS / ZnS quantum dots has risen to 68, 74 and 78% for Cu / In of 1/1, 1/2 and 1/4, respectively. And these results were reproducible.

For the most useful yellow light emission in white LED implementations, 78% quantum efficiency is a significant improvement over previous results. In addition, the CIS / ZnS of the composition according to the present invention also showed a quantum efficiency of more than 80%, such as 85%.

<Electroluminescence Characteristics of CIS / ZnS Quantum-Based LEDs>

In order to manufacture quantum dot-based LEDs, each CIS / ZnS quantum dot when Cu / In is 1/1, 1/2, and 1/4 is dispersed in silicon resin, and has a luminous efficiency of 15.7 lm / W at 20 mA. Dispensed over a blue LED.

FIG. 2 (a) is the EL spectrum under 20 mA forward current of the LED combined with CIS / ZnS quantum dots when Cu / In is 1/1, 1/2 and 1/4, and FIG. 2 (b) is the CIE color Coordinates.

In FIG. 2 (a), the EL spectrum of the blue InGaN LED without the phosphor was included as a reference, and a cross-sectional view of the light emitting device manufactured by this method was also presented.

As shown in FIG. 2 (b), the quantum dot-based LED manufactured from quantum dots that emit red color when Cu / In is 1/1 shows color coordinates of (0.270, 0.128), and orange when Cu / In is 1/2. The quantum dot-based LEDs manufactured from the quantum dots emitting light showed color coordinates of (0.327, 0.182), which were far from white light emission.

However, quantum dot-based LEDs manufactured from quantum dots that emit yellow when Cu / In was 1/4 showed color coordinates of (0.347, 0.288) and a color index of 72. Therefore, white light emission was obtained by the combination of the blue light from the LED and the yellow light from the quantum dot.

Under 20 mA forward current, the luminous efficiencies of the CIS / ZnS quantum dots of red, orange and yellow luminescence were 14.8, 27.6 and 63.4 lm / W, respectively. This is due in part to the higher quantum efficiency of the yellow quantum dots than others.

FIG. 2 (c) is a photograph before and after applying a forward current of 20 mA in an LED combined with a CIS / ZnS quantum dot when Cu / In is 1/4. As described above, according to the present invention, a single type of quantum dot can be used to manufacture a white light emitting quantum dot-based LED.

FIG. 3 is an EL spectrum measured with increasing forward current from 5 mA to 100 mA in an LED combined with CIS / ZnS quantum dots when Cu / In is 1/4. Referring to FIG. 3, as the forward bias increases, the blue light emission and the quantum dot light emission monotonously increase.

Figure 4 (a) is the CIE color coordinates measured by increasing the forward current from 5 mA to 100 mA in the LED combined with CIS / ZnS quantum dots when Cu / In is 1/4, Figure 4 (b) is CRI 4C is a light emission efficiency / light conversion efficiency graph.

4 (a) and 4 (b), the color coordinates are (0.334-0.348, 0.273-0.291), the CRI is 72-75, and the CCT is in the range of 4447-5380 K. This confirms that quantum dot-based LEDs are very stable against forward current changes.

Light conversion efficiency is defined as the ratio of blue light emission consumed to be converted into quantum dot light emission converted in a quantum dot based LED package. Referring to FIG. 4C, it can be seen that the light conversion efficiency at 5 mA gradually decreases from 75.2% to 62.0% at 100 mA. The light conversion efficiency of 74.7% at 20 mA is higher than 72% recorded in conventional quantum dot based LEDs (green light emitting CdSe / various shell quantum dots with nearly 100% quantum efficiency). Compared with the light conversion efficiency, the luminous efficiency decreases more rapidly from 79.3 lm / W at 5 mA to 28.1 lm / W at 100 mA. It is well known that internal quantum efficiency decreases with increasing injection current in nitride based LEDs. The luminous efficiency at each operating current was also measured for blue LEDs without phosphors, decreasing from 19.9 lm / W at 5 mA to 7.6 lm / W at 100 mA. Since the efficiency reduction in the blue LED without the phosphor is about 62% and the efficiency reduction in the quantum dot based LED according to the present invention is about 65%, the efficiency reduction in the quantum dot based LED according to the present invention is the quantum dot saturation It is not the cause but the inherent property that the internal quantum efficiency decreases with increasing injection current in nitride-based LEDs.

On the other hand, to combine the quantum dot according to the present invention to a blue LED, as described above, in addition to the method of dispensing the blue quantum dot paste by adding a thermosetting silicone resin and a curing agent on the blue LED, the following method can also be used.

First, prepare a polymer by dissolving it in an organic solvent. The polymer is intended to serve as a matrix for uniformly dispersing and fixing Cu _1-x In _1-y Ga _y S ₂ core / shell quantum dots (0.5 ≦ _x ≦ 0.95, 0 ≦ y <1), and may be selected from chloroform or toluene ( A polymer that can be dissolved in an organic solvent such as toluene and is transparent to visible light is possible. For example, polyurethane (PU), polyetherurethane, polyurethane copolymers, cellulose acetate, cellulose acetate butylate, cellulose acetate propionate, polymethylacrylate (PMA), polymethylmethacrylate (PMMA), Polyacryl copolymer, polyvinylacetate (PVAc), polyvinylacetate copolymer, polyperfuryl alcohol (PPFA), polylauryl methacrylate (PL MA), polystyrene (PS), polystyrene copolymer, polyethylene oxide (PEO) ), Polypropylene oxide (PPO), polyethylene oxide copolymer, polypropylene oxide copolymer, polycarbonate (PC), polyvinyl chloride (PVC), polycaprolactone (PCL), polyvinylcarbazole (PVK), polyvinyl Any one selected from the group consisting of lithium fluoride (PVdF), polyvinylidene fluoride copolymer and polyamide There must be water. The organic solvent may be any one or mixture thereof selected from the group consisting of chloroform, toluene, octane, heptane, hexane, pentane, trichloroethylene, dimethylformamide (DMF) and tetrahydrofuran (THF). Dissolution may be by means of stirring with a magnetic bar, for example for 24 hours.

Next, a certain amount of quantum dots are mixed with the polymer solution obtained above. After mixing, dispersion may be performed by sonication. Then, the solution is dried, for example, in a vacuum state for 12 hours, and then further dried in the air for 12 hours to remove the organic solvent, thereby obtaining a polymer thin film containing quantum dots.

Next, a polymer adhesive layer is formed on the polymer thin film. When the polymer thin film is dip-coated with ethanol solution in which PVP or PVA is dissolved and dried at 60 ° C. for 1 hour, a polymer adhesive layer may be formed on both sides of the polymer thin film. The polymer adhesive layer serves as a buffer to uniformly coat the inorganic oxide protective film formed thereafter. The thickness of the polymer adhesive layer may be controlled by controlling the number of coatings.

Next, an inorganic oxide protective film is formed. The inorganic oxide protective film is for blocking quantum dots from contact with oxygen or moisture, and is preferably formed by a simple solution coating process, and is selected from the group consisting of SiO ₂ , TiO ₂ , Al ₂ O _3, and mixtures thereof. It may be a thin film of. Such an inorganic oxide protective film has a lower gas permeability than an organic material to prevent shortening of the quantum dot life and is very advantageous in terms of device stability. When the inorganic oxide protective film is a SiO ₂ thin film, the polymer thin film may be dip-coated on the silica sol solution and dried at 60 ° C for 1 hour, for example. The thickness of the inorganic oxide protective film may be controlled by controlling the number of coatings.

After that, it is possible to easily apply a process of bonding a quantum dot-polymer composite plate with a desired size to the LED with an adhesive (σ-cyanoacrylate ester) on an individual LED to easily encapsulate it. Of course, it is also possible to apply a quantum dot-polymer composite plate on a wafer-level semiconductor laminate, and then cut the semiconductor laminate and the quantum dot-polymer composite plate together to form individual elements. The semiconductor laminate may be one that emits blue excitation light, and may be applied as a white LED according to the combination of the two because it uses a quantum dot as a yellow phosphor.

According to this encapsulation method, it is possible to prevent the aggregation phenomenon of the quantum dots to be generated when using a conventionally used silicone resin and epoxy resin. In order to prevent agglomeration of quantum dots generated when mixing a quantum dot with a hydrophobic surface and a silicone resin or an epoxy resin, polymers are used in an organic solvent to more uniformly disperse the quantum dots, thereby minimizing light scattering and high transmittance. This is because a quantum dot-polymer composite plate is used to maintain the.

An inorganic oxide protective film may be formed on the surface of the polymer thin film including the quantum dots to prevent surface oxidation and ligand detachment of the quantum dots by moisture and oxygen in the atmosphere. In addition, the manufacture of a quantum dot-polymer composite plate, which is a remote type in which quantum dots and LEDs are separated from each other, can reduce quantum dot deterioration due to heat generation of the LED chip itself. Accordingly, even when driving for a long time, the characteristics of the LED are not changed so that the stability of the device according to the driving time of the quantum dot-based white LED can be improved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation in the embodiment in which said invention is directed. It will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the appended claims.

Claims (6)

delete delete A light emitting device in which a blue light emitting diode emits white light by combining a Cu _1-x In _1-y Ga _y S ₂ / ZnS core / shell quantum dot (0.5 ≦ _x ≦ 0.95, 0 ≦ y <1). delete delete Preparing a polymer solution by dissolving the polymer in an organic solvent;
Mixing Cu _1-x In _1-y Ga _y S ₂ / ZnS core / shell quantum dots (0.5 ≦ _x ≦ 0.95, 0 ≦ y <1) with the polymer solution;
The _{Cu 1-x In 1-y} Ga y S 2 / ZnS core / shell quantum dots of drying the mixed polymer solution containing the _{Cu 1-x In 1-y} Ga y S 2 / ZnS core / shell quantum dots polymer thin film Forming a;
Preparing a Cu _1-x In _1-y Ga _y S ₂ / ZnS core / shell quantum dot-polymer composite plate by forming an inorganic oxide protective film on at least one surface of the polymer thin film; And
Bonding the Cu _1-x In _1-y Ga _y S ₂ / ZnS core / shell quantum dot-polymer composite plate onto a blue light emitting diode.

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