JP5744468B2 - Semiconductor nanoparticle phosphor - Google Patents

Description

  The present invention relates to a semiconductor nanoparticle phosphor, and more particularly to a semiconductor nanoparticle phosphor having a laminated structure shell.

  It is known that when the nanoparticle core (hereinafter also referred to as “crystal particle”) is made as small as the exciton Bohr radius, a quantum size effect is exhibited. The quantum size effect is that when the size of a material is reduced to the same extent as the Bohr radius, electrons in it cannot move freely, and the energy of electrons can take only a specific value.

  For example, the wavelength of light generated from crystal particles having the same extent as the exciton Bohr radius becomes shorter as the size thereof becomes smaller (see Non-Patent Document 1). The phosphors made of II-VI group compound semiconductors disclosed in Non-Patent Document 1 have problems in reliability and durability, and use environmental pollutants such as cadmium and selenium. Materials have been needed.

  As an alternative to such II-VI group compound semiconductors, attempts have been made to synthesize nitride-based semiconductor microcrystals (see Patent Document 1). Patent Document 1 discloses semiconductor nanoparticles having a core-shell structure. Such semiconductor nanoparticles are coated with a coating layer made of a band gap energy larger than the band gap energy of the material constituting the semiconductor nanoparticles, thereby stabilizing the energy state of the surface and improving the light emission efficiency.

JP 2004-307679 A

C.B.Murray et al. (Journal of the American Chemical Society) 1993, 115, p. 8706-8715

  However, the semiconductor nanoparticles of the cited document 1 have a large number of crystal defects due to lattice mismatch between the core and the shell, and irregularities are generated on the surface of the core or shell. There has been a problem that the crystallinity of the shell and the shell is remarkably lowered and the luminous efficiency is lowered.

  The present invention has been made in view of the current situation as described above, and its purpose is to improve the crystallinity of the nanoparticle core by relaxing the lattice mismatch between the core and the shell, It is to increase luminous efficiency.

The semiconductor nanoparticle phosphor of the present invention comprises a nanoparticle core made of In _1-x Ga _x A (x ≧ 0, A is N or P), and a laminated shell that covers the nanoparticle core, The laminated shell has a structure in which two or more shell layers are laminated, and the composition of the n-th shell layer from the nanoparticle core is In _1-xn Ga _xn A (x _n ≧ 0, A is N or P). If the atomic ratio of gallium from the nanoparticle core to the nth shell layer is x _n and the atomic ratio of gallium from the nanoparticle core to the (n + 1) th shell layer is x _{n + 1} , x <x It is characterized by satisfying _n <x _{n + 1} .

  The nanoparticle core is preferably made of a group 13 nitride semiconductor, and more preferably made of InN or InGaN.

  The above laminated structure shell is preferably formed by bonding a modified organic molecule to the outer surface thereof or coating the modified organic molecule.

  Since the semiconductor nanoparticle phosphor of the present invention has the above-described configuration, it can relax the lattice mismatch between the nanoparticle core and the laminated structure shell, improve the crystallinity of the nanoparticle core, Therefore, luminous efficiency can be increased.

It is typical sectional drawing which shows an example of the basic structure of the semiconductor nanoparticle fluorescent substance of this invention. 6 is a schematic cross-sectional view showing the structure of a semiconductor nanoparticle phosphor of Comparative Example 1. FIG. 4 is a graph showing the light emission characteristics of the semiconductor nanoparticle phosphors of Example 1 and Comparative Example 1.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. In addition, dimensional relationships such as length, size, and width in the drawings are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensions.

<Semiconductor nanoparticle phosphor>
FIG. 1 is a schematic cross-sectional view showing the basic structure of the semiconductor nanoparticle phosphor of the present invention. As shown in FIG. 1, the semiconductor nanoparticle phosphor 10 of the present invention includes a nanoparticle core 11 made of In _1-x Ga _x A (x ≧ 0, A is N or P), and the nanoparticle core 11. And a laminated structure shell 12 having a structure in which two or more shell layers are laminated, and the composition of the nth shell layer from the nanoparticle core 11 is In _1-xn Ga _xn. A (x _n ≧ 0, A is N or P), the atomic ratio of gallium in the n-th shell layer from the nanoparticle core 11 is x _n, and the (n + 1) -th shell layer from the nanoparticle core 11 When the atomic ratio of gallium is x _{n + 1} , x <x _n <x _{n + 1} is satisfied.

  In the conventional semiconductor nanoparticle phosphor, the difference between the lattice constant of the shell layer and the lattice constant of the nanoparticle core is large, so that the crystal lattice is distorted between the nanoparticle core and the shell layer. Due to this distortion, there is a problem that defects are generated in the crystal of the nanoparticle core and the luminous efficiency is lowered.

  In the present invention, by forming the laminated structure shell 12 in which the atomic ratio of gallium is adjusted as described above, the lattice constant gradually decreases from the nanoparticle core 11 to the surface of the laminated structure shell 12. For this reason, the lattice mismatch at the interface between the nanoparticle core 11 and the laminated structure shell 12 is relaxed, and defects due to the difference in lattice constant generated between the nanoparticle core 11 and the laminated structure shell 12 can be reduced. it can. Therefore, the crystallinity of the nanoparticle core 11 is enhanced, and the light emission efficiency can be improved.

  Furthermore, the semiconductor nanoparticle phosphor 10 of the present invention is preferably formed by coating the outer surface of the laminated shell 12 with a modified organic molecule 13 as shown in FIG. By covering the laminated structure shell 12 with the modified organic molecules 13 in this way, the deactivation of excitation energy on the surface of the laminated structure shell 12 can be suppressed, and the luminous efficiency can be improved.

  The semiconductor nanoparticle phosphor 10 of the present invention preferably has an average particle size of 0.1 nm to 100 nm, more preferably 0.5 nm to 50 nm, and even more preferably 1 nm to 20 nm. The average particle size is as follows. By using the semiconductor nanoparticle phosphor 10 having such an average particle diameter, scattering of excitation light can be suppressed on the surface layer of the nanoparticle core 11, and the excitation light can be absorbed by the nanoparticle core 11. The semiconductor nanoparticle phosphor 10 of the present invention is usually estimated to have an average particle diameter of about 2 to 6 nm from the spectrum half width of the X-ray diffraction measurement.

  If the average particle size of the semiconductor nanoparticle phosphor 10 is less than 0.1 nm, the particle size is too small, so that aggregation is likely to occur. If the average particle size exceeds 100 nm, the excitation light scatters and the luminous efficiency decreases. Therefore, it is not preferable.

  When the semiconductor nanoparticle phosphor 10 of the present invention is irradiated with excitation light, the nanoparticle core 11 and / or the laminated structure shell 12 absorb the energy of the excitation light. Here, since the average particle diameter of the nanoparticle core 11 is small enough to have a quantum size effect, the nanoparticle core 11 can take a plurality of discrete energy levels, but may have one level. .

  The light energy absorbed and excited by the nanoparticle core 11 and / or the laminated structure shell 12 transitions between the ground level of the conduction band and the ground level of the valence band of the nanoparticle core 11, It emits light having a wavelength corresponding to energy. At this time, the laminated structure shell 12 contributes to the confinement effect of excited carriers in the nanoparticle core 11 and improves the light emission efficiency. Hereinafter, each structure of the semiconductor nanoparticle phosphor 10 of the present invention will be described.

<Nanoparticle core>
In the present invention, the nanoparticle core 11 becomes a nucleus of growth when the laminated structure shell 12 is crystal-grown. That is, a group 13 element and a group 15 element having a dangling bond are arranged on the surface of the nanoparticle core 11, and the first shell layer 1 of the first layer of the laminated shell 12 is arranged in the dangling hand. The elements used as raw materials are combined.

The nanoparticle core 11 is a semiconductor having a band gap energy that emits visible light, and is specifically a nanoparticle made of In _1-x Ga _x A (x ≧ 0, A is N or P). . Here, the “nanoparticle” means a particle having a diameter of several nm or more and several thousand nm or less. The nanoparticle core 11 is preferably made of a group 13 nitride semiconductor, more preferably InN. By controlling the average particle diameter of the nanoparticle core 11 and the mixed crystal ratio thereof, the emission wavelength of the semiconductor nanoparticle phosphor 10 can be adjusted to a wavelength in an arbitrary visible light region.

The material used for the nanoparticle core 11 may contain an unintended impurity other than InGaN or InGaP, and may have a concentration of 1 × 10 ¹⁶ cm ⁻³ or more and 1 × 10 ²¹ cm ⁻³ or less. Impurities may be intentionally added. When impurities are intentionally added to the nanoparticle core 11, it is preferable to use any one of group 2 elements (Be, Mg, Ca, Sr, Ba), Zn, or Si as a dopant, and among these, Mg It is more preferable to use any one of Zn, Zn, and Si as a dopant.

  The band gap of the material used for the nanoparticle core 11 is preferably 1.8 eV or more and 2.8 eV or less, although it varies depending on the emission wavelength of the desired semiconductor nanoparticle phosphor 10. More specifically, when the semiconductor nanoparticle phosphor 10 is used as a red phosphor, the band gap of the semiconductor used for the nanoparticle core 11 is preferably 1.85 eV or more and 2.5 eV or less. When the semiconductor nanoparticle phosphor 10 is used as a green phosphor, the band gap of the semiconductor used for the nanoparticle core 11 is preferably 2.3 eV or more and 2.5 eV or less. When the semiconductor nanoparticle phosphor 10 is used as a blue phosphor, the band gap of the semiconductor used for the nanoparticle core 11 is preferably 2.65 eV or more and 2.8 eV or less.

  In the present invention, the nanoparticle core 11 preferably has an average particle diameter that is not more than twice the Bohr radius. Thereby, the emitted light intensity of the semiconductor nanoparticle fluorescent substance 10 can be improved extremely. Here, the “Bohr radius” indicates the spread of the existence probability of excitons, and is expressed by the following formula (1).

y = 4πεh ² · me ² Formula (1)
Here, each symbol in the formula (1) is y: Bohr radius, ε: dielectric constant, h: Planck constant, m: effective mass, e: elementary charge. When the Bohr radius is calculated based on this formula, the Bohr radius of GaN is about 3 nm, and the Bohr radius of InN is about 7 nm.

  When the average particle diameter of the nanoparticle core 11 is less than twice the exciton Bohr radius, the optical band gap tends to widen due to the quantum size effect. Even in this case, the band gap of the material constituting the nanoparticle core 11 is preferably within the above-described range.

  The average particle diameter of the nanoparticle core 11 can be calculated by directly observing the lattice image of the nanoparticle core 11 with a high-magnification observation image using a transmission electron microscope (TEM). it can.

<Laminated structure shell>
In the present invention, the laminated structure shell 12 has a structure in which two or more shell layers are laminated. Since the laminated structure shell 12 inherits the crystal structure of the nanoparticle core 11 and is formed on the surface of the nanoparticle core 11, the shell layers are chemically bonded to each other. In such a laminated structure shell 12, the composition of the nth shell layer from the nanoparticle core is expressed as In _1-xn Ga _xn A (x _n ≧ 0, A is N or P). When the atomic ratio of gallium from the nanoparticle core 11 to the nth shell layer is x _n and the atomic ratio of gallium from the nanoparticle core 11 to the (n + 1) th shell layer is x _{n + 1} , x <X _n <x _{n + 1} is satisfied.

  By adjusting the gallium atomic ratio of the multilayer shell 12 so as to satisfy the above formula, the atomic ratio of gallium in the innermost shell layer of the multilayer shell 12 becomes the atomic ratio of gallium in the nanoparticle core 11. Get closer. For this reason, distortion of the crystal lattice between the nanoparticle core 11 and the laminated structure shell 12 is reduced. Thereby, the crystallinity of the nanoparticle core is improved, and the luminous efficiency can be increased.

  Such a laminated structure shell 12 is preferably 0.1 to 10 nm thick. If it is less than 0.1 nm, the surface of the nanoparticle core 11 cannot be sufficiently covered, and it is difficult to form a uniform protective layer. On the other hand, when the thickness exceeds 10 nm, it is difficult to make the laminated shell 12 uniformly and defects increase, which is not desirable in terms of raw material costs. The laminated shell 12 covers part or all of the nanoparticle core 11, but the thickness is not necessarily uniform, and the thickness may be distributed. The thickness of the laminated structure shell 12 can be measured by X-ray diffraction, and can also be estimated by observing a lattice image with a high magnification observation image using a TEM.

In the present invention, the laminated structure shell 12 is preferably made of either InGaN or InGaP. Such a laminated structure shell 12 may contain unintentional impurities, and impurities are intentionally added at a low concentration of 1 × 10 ¹⁶ cm ⁻³ or more and 1 × 10 ²¹ cm ⁻³ or less. Also good. When impurities are intentionally added, it is preferable to use any one of group 2 elements (Be, Mg, Ca, Sr, Ba), Zn, or Si as a dopant. Among these, any of Mg, Zn, or Si It is more preferable to use as a dopant.

<Modified organic molecule>
In the present invention, it is preferable that the modified organic molecule 13 is bonded to the outer surface of the laminated shell 12 or the laminated shell 12 is covered with the modified organic molecule 13. When the modified organic molecules 13 cover the surface of the semiconductor nanoparticle phosphor 10 in this manner, the semiconductor nanoparticle phosphors 10 are easily separated from each other, have good dispersibility, and are used when the semiconductor nanoparticle phosphor 10 is applied. It is easy to handle.

  Such a modified organic molecule 13 is preferably a compound having a hydrophilic group and a hydrophobic group in the molecule. As a result, the laminated shell 12 is covered with both a chemical bond in which heteroatoms are coordinated and a bond by physical adsorption.

  The modified organic molecule 13 is bonded to a metal element having dangling bonds arranged on the surface of the laminated structure shell 12. With this configuration, dangling bonds on the surface of the laminated shell 12 are efficiently capped. Thus, since the surface defect of the laminated structure shell 12 is suppressed by the modified organic molecule 13 capping the surface of the laminated structure shell 12, the light emission efficiency of the semiconductor nanoparticle phosphor 10 can be further improved.

  Here, the modified organic molecule 13 in the present invention uses a structure having a nitrogen-containing functional group, a sulfur-containing functional group, an acidic group, an amide group, a phosphine group, a phosphine oxide group, a hydroxyl group, a linear alkyl group, or the like. Can do. Examples of such modified organic molecules 13 include sodium hexametaphosphate, sodium laurate, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, triethanolamine lauryl sulfate, lauryl diethanolamide, dodecyltrimethylammonium chloride, trioctylphosphine, and trioctyl. A phosphine oxide etc. can be mentioned.

  Such a modified organic molecule 13 is preferably an amine which is a compound having a nonpolar hydrocarbon terminal as a hydrophobic group and an amino group as a hydrophilic group. When the hydrophilic group of the modified organic molecule 13 is an amine, the amine can be firmly bonded to the metal element on the surface of the laminated structure shell 12.

  Effective amines as the modified organic molecule 13 are, for example, butylamine, t-butylamine, isobutylamine, tri-n-butylamine, triisobutylamine, triethylamine, diethylamine, hexylamine, dimethylamine, laurylamine, octylamine, tetradecylamine, Examples include hexadecylamine, oleylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, and triundecylamine.

  The modified organic molecule 13 preferably has a hetero atom. When the modified organic molecule 13 has a hetero atom, an electric polarity between the hetero atom and the carbon atom is generated, and the modified organic molecule 13 can be firmly bonded to the outer surface of the laminated structure shell 12. Here, “heteroatom” means all atoms except hydrogen atom and carbon atom. The thickness of the modified organic molecule 13 can be estimated by observing a high-magnification observation image using TEM.

<Method for producing semiconductor nanoparticle phosphor>
The manufacturing method of the semiconductor nanoparticle phosphor of the present embodiment can be any manufacturing method without any particular limitation, but it is a simple method and uses a chemical synthesis method from the viewpoint of low cost. Is preferred. In the chemical synthesis method, a target product can be obtained by dispersing a plurality of starting materials containing constituent elements of the product in a medium and reacting them. Specific examples of such chemical synthesis methods include sol-gel method (colloid method), hot soap method, reverse micelle method, solvothermal method, molecular precursor method, hydrothermal synthesis method, flux method and the like.

  Hereinafter, a method for producing a semiconductor nanoparticle phosphor by a hot soap method using chemical synthesis in a liquid phase will be described. The hot soap method is suitable for producing a nanoparticle core made of a compound semiconductor material.

(Step of synthesizing nanoparticle core)
First, the nanoparticle core 11 is liquid-phase synthesized. For example, when the nanoparticle core 11 made of InN is manufactured, a flask or the like is filled with 1-octadecene as a synthesis solvent, and tris (dimethylamino) indium and hexadecylamine (HDA) are mixed. This mixed solution is sufficiently stirred and then reacted at a synthesis temperature of 180 to 500 ° C., whereby the modified organic molecule composed of HDA is bonded to the nanoparticle core 11 composed of InN. The modified organic molecule may be added to the solution after growing a laminated structure shell described later.

  Here, the synthetic solvent used in the hot soap method is preferably a compound solution composed of carbon atoms and hydrogen atoms (hereinafter referred to as “hydrocarbon solvent”). If a solvent other than the hydrocarbon solvent is used as the synthesis solvent, water and oxygen will be mixed in the synthesis solvent, which is not preferable because the nanoparticle core 11 is oxidized. Here, examples of the hydrocarbon solvent include n-pentane, n-hexane, n-heptane, n-octane, cyclopentane, cyclohexane, cycloheptane, benzene, toluene, o-xylene, m-xylene, and p-xylene. Etc.

  In the hot soap method, in principle, the longer the reaction time, the larger the particle diameter of the nanoparticle core 11 grows. Therefore, the nanoparticle core 11 made of InN can be controlled to a desired size by performing liquid phase synthesis while monitoring the particle diameter by photoluminescence, light absorption, dynamic light scattering, or the like.

(Step of synthesizing the laminated shell)
A reaction reagent that is a raw material of the first shell layer 1 that is the innermost layer of the laminated shell 12 is added to the solution containing the nanoparticle core 11 described above, and the first shell layer 1 is formed on the surface of the nanoparticle core 11 by heating reaction. Are chemically bonded. Thus, a solution in which the semiconductor nanoparticle phosphor having a structure in which the surface of the nanoparticle core 11 is covered with the first shell layer 1 and the surface of the first shell layer 1 is covered with the modified organic molecules 13 is manufactured. Since the first shell layer 1 is grown by taking over the crystal structure of the nanoparticle core 11, the nanoparticle core 11 receives stress from the first shell layer 1.

  The step of synthesizing the shell layer is repeated in the same manner as the step of synthesizing the first shell layer except that the composition ratio of gallium is increased. In this way, the laminated structure shell 12 in which two or more shell layers are coated on the surface of the nanoparticle core 11 is formed. In the laminated structure shell 12 formed in this way, the atomic ratio of gallium gradually increases from the nanoparticle core 11 side toward the outermost surface, so that the lattice constant gradually decreases toward the outer shell. For this reason, the stress which the nanoparticle core 11 receives by the laminated structure shell 12 is relieved, and the semiconductor nanoparticle phosphor 10 with few crystal defects can be obtained by the protective effect of the laminated structure shell 12. The semiconductor nanoparticle phosphor of the present invention can be obtained by the above steps.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
In this example, a semiconductor nanoparticle phosphor having the structure shown in FIG. 1 was produced by a hot soap method. Specifically, a semiconductor nanoparticle phosphor 10 including a laminated structure shell 12 having a configuration shown in Table 1 was prepared for a nanoparticle core 11 having an average particle diameter of 5 nm. The “lattice constant” in Table 1 can be confirmed (measured) by observing a lattice image with a TEM. Below, the manufacturing method is demonstrated concretely.

  First, a nanoparticle core 11 made of InN was synthesized by thermally decomposing 1 mmol of indium iodide and 10 mmol of sodium amide in 30 ml of 1-octadecene solution containing 1 mmol of hexadecanethiol (HDT). .

  Next, 3 ml of 1 containing 0.4 mmol of indium iodide and 0.1 mmol of gallium iodide and 5 mmol of sodium amide as a raw material of the first shell layer 1 in the solution containing the nanoparticle core 11 described above. -The 1st shell layer 1 was formed in the surface of the nanoparticle core 11 by adding and reacting an octadecene solution.

  Next, as a raw material of the second shell layer 2, 3 ml of 1-octadecene solution containing 0.3 mmol of indium iodide and 0.2 mmol of gallium iodide and 5 mmol of sodium amide is added and reacted. A second shell layer 2 was formed on the surface of the first shell layer 1.

  Then, 3 ml of 1-octadecene solution containing 0.2 mmol of indium iodide and 0.3 mmol of gallium iodide and 5 mmol of sodium amide as a raw material of the third shell layer 3 is added and reacted. A third shell layer 3 was formed on the surface of the two shell layer 2.

  Further, as a raw material of the fourth shell layer 4, 3 ml of 1-octadecene solution containing 0.1 mmol of indium iodide and 0.4 mmol of gallium iodide and 5 mmol of sodium amide was added and reacted. A fourth shell layer 4 was formed on the surface of the three shell layer 3.

  Finally, 3 ml of 1-octadecene solution containing 0.5 mmol of gallium iodide and 5 mmol of sodium amide as a raw material for the fifth shell layer 5 is added and reacted to form a surface of the fourth shell layer 4. A fifth shell layer 5 was formed. The surface of the fifth shell layer 5 was covered with a modified organic molecule 13 made of HDT. Thus, the modified organic molecules 13 were uniformly coated on the surface, so that the semiconductor nanoparticle phosphors were not agglomerated and had a uniform size and high dispersibility.

Semiconductor nano configuration in this way InN (nanoparticle core _{11) / In 0.8 Ga 0.2 N} / In 0.6 Ga 0.4 N / In 0.4 Ga 0.6 N / In 0.2 Ga 0.8 N / GaN / HDT ( modified organic molecules 13) A particle phosphor 10 was produced. In addition, when written as “A / B”, it means A covered with B.

  It has been found that the semiconductor nanoparticle phosphor produced in this manner can use a blue light emitting element made of a group 13 nitride as an excitation light source, and efficiently absorbs 405 nm light having a particularly high external quantum efficiency. Moreover, since the average particle diameter of the semiconductor nanoparticle phosphor is adjusted so as to emit light having a wavelength of 620 nm, it can be used as a red phosphor.

(Example 2)
In this example, a semiconductor nanoparticle phosphor having the same structure as that of Example 1 was prepared, except that the particle diameter of the nanoparticle core and the modified organic molecules were different. Specifically, a semiconductor nanoparticle phosphor 10 including a laminated structure shell 12 having a configuration shown in Table 1 was prepared for a nanoparticle core 11 having an average particle diameter of 4 nm. Below, the manufacturing method is demonstrated concretely.

  First, a nanoparticle core 11 composed of InN is synthesized by thermally decomposing 1 mmol of indium iodide and 10 mmol of sodium amide in 30 ml of 1-octadecene solution containing 1 mmol of hexadecylamine (HDA). did. Subsequently, the laminated structure shell 12 was produced by the same method as in Example 1.

The surface of the multilayer structure shell 12 produced in this way was covered with a modified organic molecule 13 made of HDA. Was prepared InN (nanoparticle _{core) / In 0.8 Ga 0.2 N /} In 0.6 Ga 0.4 N / In 0.4 Ga 0.6 N / In 0.2 Ga 0.8 N / semiconductor nanoparticle phosphor 10 configured as GaN / HDA in this way . Thus, the modified organic molecules 13 were uniformly coated on the surface, so that the semiconductor nanoparticle phosphors were not agglomerated and had a uniform size and high dispersibility.

  It has been found that the semiconductor nanoparticle phosphor of this example can use a blue light-emitting element made of a group 13 nitride as an excitation light source, and particularly efficiently absorbs 405 nm light having a high external quantum efficiency. Moreover, since the average particle diameter of the semiconductor nanoparticle phosphor is adjusted so as to emit light having a wavelength of 520 nm, it can be used as a green phosphor.

(Example 3)
In this example, a semiconductor nanoparticle phosphor was prepared by the same method as in Example 1 except that the composition of the nanoparticle core and the structure and composition of the laminated shell were different. Specifically, a semiconductor nanoparticle phosphor including a laminated structure shell having the configuration shown in Table 1 was prepared for a nanoparticle core having an average particle diameter of 5 nm. Below, the manufacturing method is demonstrated concretely.

First, in 30 ml of 1-octadecene solution containing 1 mmol of hexadecanthiol (HDT), 0.3 mmol of indium iodide and 0.7 mmol of gallium iodide and 10 mmol of sodium amide are subjected to a thermal decomposition reaction. A nanoparticle core 11 composed of In _0.3 Ga _0.7 N was synthesized.

  Next, 3 ml of 1-octadecene containing 0.1 mmol of indium iodide and 0.4 mmol of gallium iodide and 5 mmol of sodium amide as raw materials for the first shell layer is added to the solution containing the nanoparticle core. A first shell layer was formed on the surface of the nanoparticle core by adding the solution and reacting.

  Next, as a raw material of the second shell layer 2, 3 ml of 1-octadecene solution containing 0.05 mmol of indium iodide and 0.45 mmol of gallium iodide and 5 mmol of sodium amide is added and reacted. A second shell layer was formed on the surface of the first shell layer.

Finally, as a raw material for the third shell layer, 3 ml of 1-octadecene solution containing 0.5 mmol of gallium iodide and 5 mmol of sodium amide is added and reacted to form a third shell layer on the surface of the second shell layer. A shell layer was formed. The surface of the third shell layer was covered with a modified organic molecule made of HDT. There was thus prepared an In _0.3 Ga _0.7 N (nanoparticle _{core) / In 0.2 Ga 0.8 N /} In 0.1 Ga 0.9 N / GaN / HDT ( modified organic molecules) semiconductor nanoparticle phosphor 10 configured as. Thus, by uniformly covering the surface with the modified organic molecules, the semiconductor nanoparticle phosphors did not aggregate with each other, and the dispersibility was high with a uniform size.

  It has been found that the semiconductor nanoparticle phosphor of this example can use a blue light-emitting element made of a group 13 nitride as an excitation light source, and particularly efficiently absorbs 405 nm light having a high external quantum efficiency. Moreover, since the average particle diameter of the semiconductor nanoparticle phosphor is adjusted so as to emit light having a wavelength of 480 nm, it can be used as a blue phosphor.

Example 4
In this example, a semiconductor nanoparticle phosphor was produced by the same method as in Example 1, except that the composition of the nanoparticle core and the structure and composition of the laminated shell were different. Specifically, a semiconductor nanoparticle phosphor including a laminated structure shell having the structure shown in Table 1 was prepared for a nanoparticle core having an average particle diameter of 3 nm. Below, the manufacturing method is demonstrated concretely.

  First, in a 30 ml 1-octadecene solution containing 1 mmol of hexadecylamine (HDA), 1 mmol of indium chloride and 1 mmol of tris (trimethylsilylphosphine) are thermally decomposed to form a nanoparticle core made of InP. Synthesized.

  Next, 3 ml of 0.4 ml of indium chloride and 0.1 mmol of gallium chloride, and 0.5 mmol of tris (trimethylsilylphosphine) are contained in the solution containing the nanoparticle core as a raw material for the first shell layer. A 1-octadecene solution was added and reacted to form a first shell layer on the surface of the nanoparticle core.

  Next, 3 ml of 1-octadecene solution containing 0.3 mmol of indium chloride and 0.2 mmol of gallium chloride and 0.5 mmol of tris (trimethylsilylphosphine) is added and reacted as a raw material for the second shell layer. Thus, the second shell layer was formed on the surface of the first shell layer.

  By adding 3 ml of 1-octadecene solution containing 0.2 mmol of indium chloride and 0.3 mmol of gallium chloride and 0.5 mmol of tris (trimethylsilylphosphine) as a raw material for the third shell layer, the reaction is performed. A third shell layer was formed on the surface of the second shell layer.

  Furthermore, as a raw material for the fourth shell layer, 3 ml of 1-octadecene solution containing 0.1 mmol of indium chloride and 0.4 mmol of gallium chloride and 0.5 mmol of tris (trimethylsilylphosphine) was added and reacted. A fourth shell layer was formed on the surface of the third shell layer.

Finally, as a raw material for the fifth shell layer, 3 ml of 1-octadecene solution containing 0.5 mmol of gallium chloride and 0.5 mmol of tris (trimethylsilylphosphine) is added and reacted to thereby form the surface of the fourth shell layer. A fifth shell layer was formed. The surface of the fifth shell layer was covered with a modified organic molecule made of HDA. As described above, the surface of the organic nanoparticle phosphor was not aggregated by uniformly coating the surface with the modified organic molecules, and the dispersibility was high with a uniform size. In this way, a configuration of InP (nanoparticle core) / In _0.8 Ga _0.2 P / In _0.6 Ga _0.4 P / In _0.4 Ga _0.6 P / In _0.2 Ga _0.8 P / GaP (laminated structure shell) / HDA (modified organic molecule) A semiconductor nanoparticle phosphor was prepared.

  It has been found that the semiconductor nanoparticle phosphor produced in this manner can use a blue light emitting element made of a group 13 nitride as an excitation light source, and efficiently absorbs 405 nm light having a particularly high external quantum efficiency. Moreover, since the average particle diameter of the semiconductor nanoparticle phosphor is adjusted so as to emit light having a wavelength of 650 nm, it can be used as a red phosphor.

(Example 5)
In this example, a semiconductor nanoparticle phosphor was produced by the same method as in Example 1, except that the composition of the nanoparticle core and the structure and composition of the laminated shell were different. Specifically, a semiconductor nanoparticle phosphor including a laminated structure shell having the structure shown in Table 1 was prepared for a nanoparticle core having an average particle diameter of 3 nm. Below, the manufacturing method is demonstrated concretely.

First, in 30 ml of 1-octadecene solution containing 1 mmol of hexadecylamine (HDA), 0.7 mmol of indium chloride and 0.3 mmol of gallium chloride are thermally decomposed with 1 mmol of tris (trimethylsilylphosphine). Thus, a nanoparticle core made of In _0.7 Ga _0.3 P was synthesized.

  Next, 3 ml of the above solution containing the nanoparticle core contains 0.3 mmol of indium chloride and 0.2 mmol of gallium chloride and 0.5 mmol of tris (trimethylsilylphosphine) as the raw material of the first shell layer. A 1-octadecene solution was added and reacted to form a first shell layer on the surface of the nanoparticle core.

  Next, 3 ml of 1-octadecene solution containing 0.2 mmol of indium chloride and 0.3 mmol of gallium chloride and 0.5 mmol of tris (trimethylsilylphosphine) is added and reacted as a raw material for the second shell layer. Thus, the second shell layer was formed on the surface of the first shell layer.

  Then, by adding 3 ml of 1-octadecene solution containing 0.1 mmol of indium chloride and 0.4 mmol of gallium chloride and 0.5 mmol of tris (trimethylsilylphosphine) as a raw material for the third shell layer, the reaction is performed. A third shell layer was formed on the surface of the second shell layer.

Finally, as a raw material of the fourth shell layer, 3 ml of 1-octadecene solution containing 0.5 mmol of gallium chloride and 0.5 mmol of tris (trimethylsilylphosphine) is added and reacted, whereby the third shell layer A fourth shell layer was formed on the surface. The surface of the fourth shell layer was covered with a modified organic molecule made of HDA. As described above, the surface of the organic nanoparticle phosphor was not aggregated by uniformly coating the surface with the modified organic molecules, and the dispersibility was high with a uniform size. Thus, a semiconductor nanoparticle phosphor having a configuration of In _0.7 Ga _0.3 P (nanoparticle core) / In _0.6 Ga _0.4 P / In _0.4 Ga _0.6 P / In _0.2 Ga _0.8 P / GaP / HDA (modified organic molecule) is obtained. Produced.

  It has been found that the semiconductor nanoparticle phosphor produced in this manner can use a blue light emitting element made of a group 13 nitride as an excitation light source, and efficiently absorbs 405 nm light having a particularly high external quantum efficiency. Moreover, since the average particle diameter of the semiconductor nanoparticle phosphor is adjusted so as to emit light having a wavelength of 600 nm, it can be used as a red phosphor.

(Comparative Example 1)
The comparative example 1 is different in that the surface of the nanoparticle core 21 made of InN having an average particle diameter of 5 nm is not covered with a laminated structure shell but is covered with one shell layer 22 made of GaN as shown in FIG. Others produced the semiconductor nanoparticle phosphor 20 by the same method as in Example 1. FIG. 2 is a cross-sectional view schematically showing the structure of the semiconductor nanoparticle phosphor of Comparative Example 1. Below, the manufacturing method is demonstrated concretely.

  First, nanoparticle core 21 made of InN was synthesized by thermally decomposing 1 mmol of tris (dimethylamino) indium in 30 ml of 1-octadecene solution containing 1 mmol of hexadecylamine (HDA).

  Next, 30 ml of 1-octadecene solution containing 1 mmol of tris (dimethylamino) gallium and 1 mmol of hexadecylamine as a raw material of the shell layer 22 is added to the solution containing the nanoparticle core 21 and reacted. Thus, the shell layer 22 was formed on the surface of the nanoparticle core 21. The surface of the shell layer 22 was covered with a modified organic molecule 23 made of HDA. Thus, a semiconductor nanoparticle phosphor 20 having a configuration of InN (nanoparticle core 21) / GaN (shell layer 22) / HDA (modified organic molecule 23) was produced.

  The semiconductor nanoparticle phosphor thus produced efficiently absorbed 405 nm light having a particularly high external quantum efficiency, emitted light having a wavelength of 620 nm, and exhibited red light emission.

<Evaluation results and discussion>
As a result of performing X-ray diffraction measurement on the semiconductor nanoparticle phosphors produced in Examples 1 to 5 and Comparative Example 1, the average particle diameter of the semiconductor nanoparticle phosphors estimated by the half width of the spectrum is as follows. The result shown in the column of “Particle size” in FIG. For this reason, it turned out that the semiconductor nanoparticle fluorescent substance of Examples 1-5 showed a quantum size effect and has high luminous efficiency. The following Scherrer equation (2) was used to calculate the average particle size of the semiconductor nanoparticle phosphor.
B = λ / cos θ · R (2)

  Here, each symbol in the formula (2) represents B: X-ray half width [deg], λ: X-ray wavelength [nm], θ: Bragg angle [deg], and R: particle diameter [nm], respectively. .

  The semiconductor nanoparticle phosphors obtained in Examples 1 to 5 have a structure of nanoparticle core / laminated structure shell / modified organic molecule, and the gallium composition gradually increases from the nanoparticle core toward the outer shell of the laminated structure shell. It is getting bigger. For this reason, the lattice constant gradually decreased from the nanoparticle core toward the outer shell of the laminated structure shell, the crystallinity of the nanoparticle core 11 was high, and the light emission efficiency was high.

  On the other hand, since the semiconductor nanoparticle phosphor obtained in Comparative Example 1 has a large difference between the lattice constant of the nanoparticle core and the lattice constant of the shell layer, the stress is caused by lattice mismatch between the nanoparticle core and the shell layer. As a result, the crystallinity of the nanoparticle core was low and the luminous efficiency was also low.

  FIG. 3 is a graph showing the light emission characteristics of the semiconductor nanoparticle phosphors of Example 1 and Comparative Example 1. The vertical axis of the graph of FIG. 3 represents the intensity (unit: arbitrary unit) of red emission (wavelength 620 nm) of the semiconductor nanoparticle phosphor. From the results shown in FIG. 3, it is clear that the semiconductor nanoparticle phosphor of Example 1 has significantly superior light emission characteristics than that of Comparative Example 1.

  In the present invention, the semiconductor nanoparticle fluorescent material described above in the preferred embodiment is not limited to the above, and may have a configuration other than the above.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  Since the semiconductor nanoparticle phosphor of the present invention is excellent in luminous efficiency and dispersibility, it is suitably used for, for example, blue LEDs.

  DESCRIPTION OF SYMBOLS 1 1st shell layer, 2nd shell layer, 3rd shell layer, 4th shell layer, 5th shell layer, 10,20 semiconductor nanoparticle fluorescent substance, 11,21 nanoparticle core, 12 laminated structure shell , 13, 23 Modified organic molecule, 22 shell layer.

Claims (5)

A nanoparticle core composed of In _1-x Ga _x A (x ≧ 0, A is N or P);
A laminated shell covering the nanoparticle core,
The laminated structure shell is a structure in which two or more shell layers are laminated,
The composition of the nth shell layer from the nanoparticle core is In _1-xn Ga _xn A (x _n ≧ 0, A is N or P),
When the atomic ratio of gallium in the n-th shell layer from the nanoparticle core is x _n and the atomic ratio of gallium in the (n + 1) -th shell layer from the nanoparticle core is x _{n + 1} , x Semiconductor nanoparticle phosphor satisfying <x _n <x _{n + 1} .   The semiconductor nanoparticle phosphor according to claim 1, wherein the nanoparticle core is made of a group 13 nitride semiconductor.   The semiconductor nanoparticle phosphor according to claim 2, wherein the nanoparticle core is made of InN.   The semiconductor nanoparticle phosphor according to claim 2, wherein the nanoparticle core is made of InGaN.   5. The semiconductor nanoparticle phosphor according to claim 1, wherein the laminated structure shell is formed by bonding a modified organic molecule to an outer surface thereof, or being coated with the modified organic molecule.

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