TWI647173B - Manufacturing method of white-light cadmium selenide nanocrystals and white-light emitting device using the white-light cadmium selenide nanocrystals - Google Patents

Abstract

A method for preparing white light cadmium selenide nanocrystals, comprising the following steps. The first solution and the second solution are mixed into a third solution to carry out the reaction. The first solution includes a selenium powder and a trioctylphosphine solution, and the second solution includes a cadmium-containing precursor, an unsaturated fatty acid, and an organic olefin. Then, cadmium selenide powder was separated from the third solution. The present invention further provides a white light emitting device using white light cadmium selenide crystals.

Description

Preparation method of white light cadmium selenide nano crystal and white light emitting device using white light cadmium selenide nano crystal

The invention relates to a method for preparing nano crystals, in particular to a method for preparing white light cadmium selenide nanocrystals, and a white light emitting device using white light cadmium selenide crystals.

At present, a common white light emitting diode device is a blue light emitting diode chip with YAG phosphor powder. The blue light provided by the blue light emitting diode chip can excite the YAG phosphor to emit yellow light, so that the blue light absorbed by the YAG phosphor powder and the yellow light emitted by the YAG phosphor powder can be mixed into white light. However, since the excitation band of the YAG phosphor is narrow, the luminous efficiency of the white light emitting diode device is lowered as long as the light emission wavelength of the blue light emitting diode chip is slightly deviated.

Further, the white light provided by the above-described white light emitting diode device has a problem of poor color rendering property, and red phosphor powder is additionally added in order to improve the color rendering property of white light. However, reabsorption between phosphors results in reduced luminous efficiency. Moreover, since each color of the fluorescent powder has a different degree of decline, it is used. It is easy to cause color shift after a period of time. In addition, the commonly used red fluorescent powder is mostly sulfide and nitride, wherein the sulfide fluorescent powder has poor stability, and the nitride fluorescent powder has the disadvantage of being difficult to synthesize.

The invention provides a preparation method of white light cadmium selenide nanocrystal, which has the advantages of shortening the processing time, and the produced white light cadmium selenide nanocrystal has the advantages of wide light emitting band and high light conversion efficiency.

The invention further provides a white light emitting device, which has the advantages of high color rendering, good reliability and good luminous efficiency.

A method for preparing white cadmium selenide nanocrystals provided by an embodiment of the present invention includes the following steps. The first solution and the second solution are mixed into a third solution to perform a reaction, wherein the first solution includes selenium powder (Se) and a tri-n-octylphosphine (TOP) solution, and the second solution includes cadmium. Cadmium precursors, unsaturated fatty acids, and organic olefins. Then, cadmium selenide (CdSe) powder was separated from the third solution.

In an embodiment of the invention, the above method of mixing the first solution and the second solution into the third solution comprises the following steps. The cadmium-containing precursor and the unsaturated fatty acid are mixed, and then the mixed cadmium-containing precursor and unsaturated fatty acid are heated, and then the mixed cadmium-containing precursor and the unsaturated fatty acid are cooled, and then the organic olefin is added to obtain a second solution. Thereafter, the second solution is heated, and the first solution is added to the heated second solution.

In an embodiment of the invention, the step of heating the second solution heats the temperature of the second solution to between 150 degrees Celsius and 300 degrees Celsius.

In an embodiment of the invention, the second solution further includes Fatty amine.

In an embodiment of the invention, the above fatty amine comprises hexadecyl amine (HDA), octadecylamine, dodecylamine or a combination thereof.

In an embodiment of the invention, the reaction time after mixing the first solution and the second solution is between 1 second and 20 minutes.

In an embodiment of the invention, the method for preparing the white light cadmium selenide nanocrystal further comprises adding methanol to the third solution to terminate the reaction before separating the cadmium selenide powder from the third solution.

In an embodiment of the invention, the cadmium-containing precursor comprises cadmium oxide, cadmium acetate, dimethyl cadmium or a combination thereof.

In an embodiment of the invention, the unsaturated fatty acid comprises oleic acid (OA).

In an embodiment of the invention, the above organic olefin comprises octadecene (ODE), tetradecene (TDE) or decene (DE).

The invention further provides a white light emitting device comprising a substrate, a non-visible light emitting element and a packaging material, wherein the non-visible light emitting element is disposed on the substrate, and the encapsulating material covers the light emitting surface of the non-visible light emitting element, and the packaging material comprises a plurality of cladding materials The white cadmium selenide nanocrystal of the surfactant is disposed in the encapsulating material, wherein the white cadmium selenide nanocrystals comprise cadmium selenide powder.

In an embodiment of the invention, the white cadmium selenide nanocrystal has a particle diameter of less than or equal to 10 nanometers, and each white light cadmium selenide nanocrystal has an emission wavelength of 400 to 700 nanometers.

Since the method for fabricating the white light cadmium selenide nanocrystal of the embodiment of the present invention is a one-time synthesis method, it has the advantage of shortening the process time. In addition, the white cadmium selenide nanocrystals produced by the method for producing white light nanocrystals have the advantages of wide light-emitting band and high light conversion efficiency. In addition, the white light emitting device of the embodiment of the invention includes white light cadmium selenide nanocrystals, and thus has the advantages of high color rendering property, good reliability, and good light emitting efficiency.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

S110~S120‧‧‧Steps

100‧‧‧White light emitting device

110‧‧‧Substrate

120‧‧‧Non-visible light-emitting elements

121‧‧‧Lighting surface

130‧‧‧Packaging materials

131‧‧‧White light cadmium selenide nanocrystal

L1‧‧‧ non-visible light

L2‧‧‧ white light

1 is a block diagram showing the preparation of a white light cadmium selenide nanocrystal according to an embodiment of the present invention.

2 is a luminescence spectrum of white light cadmium selenide nanocrystals according to an embodiment of the present invention.

3 is a luminescence spectrum of white light cadmium selenide nanocrystals according to another embodiment of the present invention.

4 is a luminescence spectrum of white light cadmium selenide nanocrystals according to still another embodiment of the present invention.

Figure 5 is a graph showing the luminescence spectrum of white light cadmium selenide nanocrystals according to still another embodiment of the present invention.

Figure 6 is a schematic illustration of a white light emitting device in accordance with an embodiment of the present invention.

1 is a white light cadmium selenide nanocrystal according to an embodiment of the present invention; A block diagram of the process of the preparation process. Referring to FIG. 1, the preparation method of the white light cadmium selenide nanocrystal of the embodiment comprises the steps of: step S110, mixing the first solution and the second solution into a third solution to carry out the reaction. The first solution includes a selenium powder and a trioctylphosphine solution, and the second solution includes a cadmium-containing precursor, an unsaturated fatty acid, and an organic olefin. In this embodiment, the cadmium-containing precursor includes, for example, cadmium oxide, cadmium acetate, dimethyl cadmium or a combination thereof. The unsaturated fatty acid includes, for example, oleic acid, and the organic olefin includes, for example, octadecene as a surfactant. In other embodiments, the organic olefin may also be one of a heptadecene to a decene, such as a tetradecene or a decene, and is not limited thereto. Further, in another embodiment of the present invention, the second solution may include a fatty amine in addition to the organic olefin, the cadmium-containing precursor, and the unsaturated fatty acid described above. The fatty amine is, for example, hexadecylamine, octadecylamine, dodecylamine or a combination thereof, but is not limited thereto.

In this embodiment, the method of mixing the first solution and the second solution into the third solution is, for example, first mixing the cadmium-containing precursor with the unsaturated fatty acid. Then, the mixed cadmium-containing precursor and unsaturated fatty acid are heated to form a clear yellow transparent homogeneous solution. In one embodiment, the mixed cadmium-containing precursor and unsaturated fatty acid may be heated to between 150 degrees Celsius and 300 degrees Celsius, such as 180 degrees Celsius, 190 degrees Celsius, 210 degrees Celsius, 240 degrees Celsius. Or 270 degrees Celsius, etc. Next, the mixed cadmium-containing precursor and the unsaturated fatty acid are cooled, for example, to room temperature, and then the organic olefin is added to obtain a second solution.

Then, the second solution is heated, and the first solution is quickly added to the heated second solution to carry out the reaction, thereby producing cadmium selenide. The first solution and the second solution after mixing are the third solution described above. The step of heating the second solution may heat the temperature of the second solution to between 150 degrees Celsius and 300 degrees Celsius, for example, 180 degrees Celsius, 190 degrees Celsius, 210 degrees Celsius. Degree, 240 degrees Celsius or 270 degrees Celsius. Further, the reaction time after the first solution is mixed with the second solution is, for example, between 1 second and 20 minutes, for example, 30 seconds, 60 seconds, 300 seconds, 600 seconds. The heating temperature and the reaction time may depend on the degree of the reaction, and the present invention does not limit the temperature of the second solution after heating and the reaction time after the first solution is mixed with the second solution. Further, the first solution is reacted with the second solution, for example, under an argon atmosphere to avoid oxidation of the reactants in the process due to contact with oxygen. In other embodiments, it may be selected to be carried out under a nitrogen atmosphere or after evacuating the container used for the reaction, and the invention is not limited thereto.

After the first solution is reacted with the second solution for a period of time, it can be naturally cooled to room temperature or added with methanol to cool down to terminate the reaction. The methanol to be added is, for example, hot methanol having a temperature higher than room temperature. In one embodiment, the temperature of the hot methanol is, for example, about 65 degrees Celsius.

Next, in step S120, the cadmium selenide powder is separated from the third solution. In this embodiment, for example, cadmium selenide in the third solution is separated by centrifugation to obtain a cadmium selenide powder. The cadmium selenide powder is white cadmium selenide crystal. In the foregoing step, the timely addition of methanol to terminate the reaction prevents the crystal of the cadmium selenide powder from being excessively large, and the emission band is narrowed.

The above-described method for preparing white light cadmium selenide nanocrystals has the advantage of shortening the processing time because it is a one-time synthesis method. In addition, the prepared white light cadmium selenide nanocrystals have a particle diameter of, for example, less than or equal to 10 nanometers, and can emit light having a wavelength between 400 nm and 700 nm, and have the advantage of wide light-emitting wavelength, and white light. The quantum efficiency of cadmium selenide nanocrystals can be greater than or equal to 20%, and has the advantage of high light conversion efficiency.

2 is a luminescence spectrum of white cadmium selenide nanocrystals prepared according to the method for preparing white cadmium selenide nanocrystals according to an embodiment of the present invention. Specifically, in the present embodiment, 0.3 millimoles (mmole) of selenium powder, 0.2 milliliters (ml) of trioctylphosphine solution (concentration of 90%), 0.3 millimoles of cadmium oxide, 2.4 millimeters are selected. Mohr (0.8 ml) of oleic acid and 12.5 mmol (4 ml) of octadecene, and the temperature of the second solution after heating was 180 degrees Celsius. In addition, the several curves of FIG. 2 are the luminescence measured by white light cadmium selenide nanocrystals (cadmium selenide powder) obtained by photoexcitation reaction time of 0 seconds, 30 seconds, 60 seconds, 300 seconds, and 600 seconds, respectively. spectrum. It can be seen from Fig. 2 that the white light cadmium selenide nanocrystal has an emission wavelength of between 400 and 700 nm, and has the advantage of a wide emission band.

3 is a luminescence spectrum of white cadmium selenide nanocrystals prepared according to the above-described preparation method of white cadmium selenide nanocrystals according to another embodiment of the present invention. Referring to FIG. 3, in the present embodiment, 0.3 millimoles (mmole) of selenium powder, 0.2 milliliters (ml) of trioctylphosphine solution (concentration of 90%), 0.3 millimoles of cadmium oxide, 1.2 are selected. Millol (0.4 ml) of oleic acid and 12.5 mmol (4 ml) of octadecene, and the temperature of the second solution after heating was 180 degrees Celsius. The graphs of Fig. 3 are measured by white light cadmium selenide nanocrystals (cadmium selenide powder) obtained by photoexcitation reaction times of 0 seconds, 30 seconds, 60 seconds, 180 seconds, 300 seconds, and 600 seconds, respectively. Luminescence spectrum. It can be seen from Fig. 3 that the white light cadmium selenide nanocrystal has an emission wavelength of between 400 and 650 nm.

4 is a luminescence spectrum of white cadmium selenide nanocrystals prepared according to the above-described preparation method of white cadmium selenide nanocrystals according to still another embodiment of the present invention. Please refer to FIG. 4. Specifically, in the present embodiment, 0.3 millimoles (mmole) of selenium powder, 0.2 milliliters (ml) of trioctylphosphine solution (concentration of 90%), 0.3 millimolar are used. Cadmium oxide, 2.4 mM (0.8 ml) of oleic acid, 6.2 mmol (2 ml) of octadecene and 6.7 mmol of hexadecylamine, and the temperature of the second solution after heating is 180 degrees Celsius. In addition, the number in Figure 4 The curves are luminescence spectra measured by white light cadmium selenide nanocrystals (cadmium selenide powder) obtained by photoexcitation reaction times of 0 seconds, 30 seconds, 60 seconds, 180 seconds, 300 seconds, and 600 seconds, respectively. It can be seen from Fig. 4 that the white light cadmium selenide nanocrystal has an emission wavelength between 400 and 700 nm.

5 is a luminescence spectrum of white cadmium selenide nanocrystals prepared according to the above-described method for preparing white cadmium selenide nanocrystals according to still another embodiment of the present invention. Please refer to FIG. 5. Specifically, in the present embodiment, 0.3 millimoles (mmole) of selenium powder, 0.2 milliliters (ml) of trioctylphosphine solution (concentration of 90%), 0.3 millimolar are selected. Cadmium oxide, 2.4 mM (0.8 ml) of oleic acid, 9.38 mmol (3 ml) of octadecene and 3.12 mmol of hexadecylamine, and the temperature of the second solution after heating is 180 degrees Celsius. The graphs of Fig. 5 are luminescence spectra measured by white light cadmium selenide nanocrystals (cadmium selenide powder) obtained by photoexcitation reaction times of 0 seconds, 30 seconds, 60 seconds, 300 seconds, and 600 seconds, respectively. . It can be seen from Fig. 5 that the white light cadmium selenide nanocrystal has an emission wavelength between 400 and 700 nm.

Figure 6 is a schematic illustration of a white light emitting device in accordance with an embodiment of the present invention. Referring to FIG. 6 , the white light emitting device 100 of the present embodiment includes a substrate 110 , a non-visible light emitting device 120 and an encapsulating material 130 , wherein the invisible light emitting device 120 is disposed on the substrate 110 , and the encapsulating material 130 covers the invisible light emitting device 120 . Light emitting surface 121. The encapsulating material 130 includes a plurality of white cadmium selenide crystallites 131 prepared by the above method, and is disposed in the encapsulating material 130, wherein each white cadmium selenide crystallite 131 is coated with a surfactant.

In this embodiment, the encapsulating material 130 is, for example, a light-permeable colloid, but is not limited thereto. The particle diameter of each white light cadmium selenide crystallite 131 is, for example, less than or equal to 10 nanometers, and the light emission wavelength of each white light cadmium selenide crystallite 131 is, for example, between 400 and 700 nanometers. The non-visible light emitting element 120 is for example Non-visible light having a wavelength of less than 470 nm can be emitted. Specifically, the non-visible light-emitting element 120 is, for example, an ultraviolet light-emitting element such as an ultraviolet light-emitting diode chip. When the non-visible light emitting element 120 emits the non-visible light L1 to excite the white light cadmium selenide nanocrystal 131 disposed in the encapsulating material 130, the white light cadmium selenide nanocrystal 131 is excited to emit light having a wavelength of 400 to 700 nm. The light of this band is in the visible light band, so that the white light emitting device 100 can emit white light L2.

The white light emitting device 100 of the present embodiment includes the white light cadmium selenide nanocrystal 131 obtained by the above method, and the white light cadmium selenide crystal 131 has an emission band of 400 to 700 nm, and has a wide emission band. The advantages. In addition, since there is no need to add different colors of phosphor powder to increase color rendering, and there is no need to mix a plurality of different colors of phosphor powder, but the respective decay rates are different, resulting in color shift, so the color rendering is better. High, reliable, and luminous efficiency.

In summary, the method for producing white light cadmium selenide nanocrystal of the present invention has the advantage of shortening the processing time because of the one-time synthesis method. In addition, the white cadmium selenide nanocrystals obtained by the method for producing white light cadmium selenide nanocrystals of the invention have the advantages of wide light-emitting band and high light conversion efficiency. In addition, the white light emitting device of the present invention includes white light cadmium selenide nanocrystals, and the white light cadmium selenide nanocrystal has an emission band of 400 to 700 nm, since no additional fluorescent color of different colors is required. Powder to increase the color rendering property, and also does not need to mix a plurality of different colors of phosphor powder, but the respective decay rates are different, resulting in color shift. Therefore, the white light emitting device of the present invention has high color rendering property, good reliability, and light emission. The advantage of better efficiency.

Although the present invention has been disclosed in the above preferred embodiments, it is not intended to limit the invention, and those skilled in the art, without departing from the invention. In the spirit and scope, the scope of protection of the present invention is defined by the scope of the appended claims.

Claims (12)

A method for preparing white light cadmium selenide nanocrystals, comprising: mixing a first solution and a second solution into a third solution to perform a reaction, wherein the first solution comprises a selenium powder and a trioctylphosphine a solution comprising a cadmium-containing precursor, an unsaturated fatty acid, and an organic olefin; and separating cadmium selenide powder from the third solution. The method for preparing white cadmium selenide nanocrystals according to claim 1, wherein the method of mixing the first solution and the second solution into the third solution comprises: mixing the cadmium-containing precursor with the An unsaturated fatty acid; the cadmium-containing precursor and the unsaturated fatty acid after heating and mixing; adding the mixed cadmium precursor and the unsaturated fatty acid to the organic olefin to obtain the second solution; and heating the first The second solution is added to the heated second solution. The method for preparing white cadmium selenide nanocrystals according to claim 2, wherein in the step of heating the second solution, the temperature of the second solution is heated to between 150 degrees Celsius and 300 degrees Celsius between. The method for preparing white cadmium selenide nanocrystals according to claim 1, wherein the second solution further comprises a fatty amine. The method for preparing white cadmium selenide nanocrystals according to claim 4, wherein the fatty amine comprises hexadecylamine, octadecylamine, dodecylamine or a combination thereof. The method for preparing white cadmium selenide nanocrystals according to claim 1, wherein the reaction time after mixing the first solution with the second solution is between 1 second and 20 minutes. The method for preparing white cadmium selenide nanocrystals according to claim 1, further comprising adding a methanol to the third solution to terminate the reaction before separating the cadmium selenide powder from the third solution. The method for preparing white cadmium selenide nanocrystals according to claim 1, wherein the cadmium-containing precursor comprises cadmium oxide, cadmium acetate, dimethyl cadmium or a combination thereof. The method for preparing white light cadmium selenide nanocrystals according to claim 1, wherein the unsaturated fatty acid comprises oleic acid. The method for preparing white cadmium selenide nanocrystals according to claim 1, wherein the organic olefin comprises octadecene, tetradecene or decene. A white light emitting device comprising: a substrate; a non-visible light emitting element disposed on the substrate; a packaging material covering a light emitting surface of the invisible light emitting element; And a plurality of white cadmium selenide nanocrystals prepared by the preparation method according to any one of claims 1 to 10, wherein the surfactant-coated white cadmium selenide nanocrystals are disposed in the package Within the material, the white cadmium selenide nanocrystals comprise cadmium selenide powder. The white light emitting device of claim 11, wherein each of the white light cadmium selenide nanocrystals has a particle diameter of less than or equal to 10 nanometers, and each of the white light cadmium selenide nanocrystals has an emission wavelength. At 400~700 nm.