JP7005470B2 - Semiconductor nanoparticles, their manufacturing methods and light emitting devices - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act (1) Proceedings of the 48th Chubu Chemistry Association Branch Union Autumn Meeting, November 11, 2017, Hiroki Yamauchi et al. (2) https: // confit. atlas. jp / guide / event / ecsj2018s / proceedings / list, February 23, 2018, Hiroki Yamauchi et al.

The present invention relates to semiconductor nanoparticles, a method for producing the same, and a light emitting device.

It is known that semiconductor particles exhibit a quantum size effect when the particle size is, for example, 10 nm or less, and such nanoparticles are called quantum dots (also referred to as semiconductor quantum dots). The quantum size effect refers to a phenomenon in which the bands of the valence band and the conduction band, which are considered to be continuous in bulk particles, become discrete in nanoparticles, and the band gap energy changes according to the particle size.

Since the quantum dots can absorb light and convert the wavelength into light corresponding to the bandgap energy, a white light emitting device utilizing the light emission of the quantum dots has been proposed (see, for example, Patent Documents 1 and 2). ). Specifically, it is proposed that a part of the light emitted from the light emitting diode (LED) chip is absorbed by the quantum dots to obtain white light as a mixed color of the light emitted from the quantum dots and the light emitted from the LED chip. Has been done. In these patent documents, it is proposed to use the quantum dots of the 12th group-16th group such as CdSe and CdTe, and the 14th-16th group such as PbS and PbSe. Further, in consideration of the toxicity of compounds containing Cd and Pb, semiconductor nanoparticles capable of band-end emission without containing these elements have been proposed (see, for example, Patent Documents 3 and 4).

Japanese Unexamined Patent Publication No. 2012-21286 Japanese Unexamined Patent Publication No. 2010-177656 Japanese Unexamined Patent Publication No. 2017-014476 Japanese Unexamined Patent Publication No. 2018-039971

One aspect of the present invention is to provide semiconductor nanoparticles having a low toxicity composition and capable of band-end emission, and a method for producing the same.

In the first aspect, a mixture containing an Ag salt, a salt containing at least one of In and Ga, a Se source, and an organic solvent is heat-treated at a temperature in the range of more than 200 ° C. and 370 ° C. or less. This is a method for manufacturing semiconductor nanoparticles, which comprises obtaining semiconductor nanoparticles. In the method for producing semiconductor nanoparticles, the ratio of the number of atoms of Ag to the total number of atoms of Ag, In and Ga in the mixture exceeds 0.43 and is 2.5 or less.

The second embodiment contains Ag, at least one of In and Ga, and Se, and the content of Ag in the composition is 10 mol% or more and 30 mol% or less, and the content of at least one of In and Ga is 15 mol. % Or more and 35 mol% or less, Se content is 35 mol% or more and 55 mol% or less, and the emission peak wavelength is within the range of 500 nm or more and 900 nm or less by irradiation with light having a wavelength within the range of 350 nm or more and less than 500 nm. It is a semiconductor nanoparticle that emits light having a half-value width of 250 meV or less in the emission spectrum.

The third aspect is a light emitting device including a light conversion member containing the semiconductor nanoparticles and a semiconductor light emitting device.

According to one aspect of the present invention, it is possible to provide semiconductor nanoparticles having a low toxicity composition and capable of band-end emission, and a method for producing the same.

It is a figure which shows an example of the emission spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the absorption spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the emission spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the absorption spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the emission spectrum and absorption spectrum of the semiconductor nanoparticles. It is a figure which shows an example of the X-ray diffraction pattern of a semiconductor nanoparticle. It is a figure which shows an example of the X-ray diffraction pattern of a semiconductor nanoparticle. It is a figure which shows an example of the absorption spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the emission spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the X-ray diffraction pattern of a semiconductor nanoparticle. It is a figure which shows an example of the absorption spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the emission spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the absorption spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the emission spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the absorption spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the emission spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the absorption spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the emission spectrum of a semiconductor nanoparticle. It is a figure which shows an example of the emission spectrum of a semiconductor nanoparticle.

In the present specification, the term "process" is included in this term not only as an independent process but also as long as the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes. .. Further, the content of each component in the composition means the total amount of the plurality of substances present in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below exemplify semiconductor nanoparticles and a method for producing the same, in order to embody the technical idea of the present invention, and the present invention describes the semiconductor nanoparticles and the method for producing the same. Not limited to.

Semiconductor Nanoparticles Semiconductor nanoparticles contain silver (Ag), at least one of indium (In) and gallium (Ga), and selenium (Se), and the content of Ag in the composition is 10 mol% or more and 30 mol%. Hereinafter, the content of at least one of In and Ga is 15 mol% or more and 35 mol% or less, the content of Se is 35 mol% or more and 55 mol% or less, and the wavelength of light in the range of 350 nm or more and less than 500 nm. Irradiation emits light having an emission peak wavelength in the range of 500 nm or more and 900 nm or less, or 600 nm or more and 900 nm or less, and having a half-value width of 250 meV or less in the emission spectrum.

Semiconductor nanoparticles containing Ag, at least one of In and Ga, and Se in the composition are generally said to have a composition represented by Ag (In, Ga) Se ₂ . In order to obtain semiconductor nanoparticles having a composition represented by Ag (In, Ga) Se ₂ , the charging ratios of Ag source, In source, Ga source and Se source are selected so as to correspond to the stoichiometric composition. It is common to synthesize them. The present inventor considers a semiconductor nanoparticles composed of Ag, at least one of In and Ga, and Se, or semiconductor nanoparticles containing these elements, in the case where these elements have a composition deviating from the chemical quantitative composition. We investigated the possibility of obtaining band-end emission. As a result, when the charging ratio of each element source is selected so that the ratio of the number of atoms of Ag to the sum of the number of atoms of In and Ga is more than 0.43 and 2.5 or less, the semiconductor nanoparticles are synthesized. Although it has a non-chemical quantitative composition, it has been found that semiconductor nanoparticles capable of emitting light at the band edge can be obtained.

Semiconductor nanoparticles containing Ag, at least one of In and Ga, and Se in the composition give band-end emission due to their shape and dimensions. Further, the semiconductor nanoparticles can have a composition that does not contain Cd and Pb, which are considered to be highly toxic, and can be applied to products and the like for which the use of Cd and the like is prohibited. Therefore, the semiconductor nanoparticles can be suitably used as a wavelength conversion substance for a light emitting device used in a liquid crystal display device and as a biomolecular marker.

The content of Ag in the composition of the semiconductor nanoparticles is, for example, 10 mol% or more and 30 mol% or less, preferably 15 mol% or more and 25 mol% or less. The total content of In and Ga is, for example, 15 mol% or more and 35 mol% or less, preferably 20 mol% or more and 30 mol% or less. The content of Se is, for example, 35 mol% or more and 55 mol% or less, preferably 40 mol% or more and 55 mol% or less.

The ratio of the number of atoms of In to the sum of the number of atoms of In and Ga in the composition of the semiconductor nanoparticles (In / (In + Ga)) is, for example, 0.01 or more and 1.0 or less, preferably 0.1 or more and 0 or more. It is .99 or less. The ratio of the number of atoms of Ag to the sum of the numbers of atoms of In and Ga (Ag / (In + Ga)) is, for example, 0.3 or more and 1.2 or less, preferably 0.5 or more and 1.1 or less. be. The ratio of the number of atoms of Se to the sum of the numbers of atoms of Ag, In and Ga (Se / (Ag + In + Ga)) is, for example, 0.8 or more and 1.5 or less, preferably 0.9 or more and 1.2 or less. be.

The semiconductor nanoparticles have, for example, a composition represented by the following formula (1).
Ag _x In _y Ga _(1-y) Se _{(x + 3) / 2} (1)
Here, x and y satisfy 0.20 <x ≦ 1.2 and 0 <y ≦ 1.0.

The semiconductor nanoparticles may further contain at least one alkali metal in their composition. The alkali metal includes lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and the like. Since the alkali metal can be a monovalent cation like Ag, it can replace a part of Ag in the composition of the semiconductor nanoparticles. In particular, Li has an ionic radius similar to that of Ag and is preferably used. By substituting a part of Ag in the composition of the semiconductor nanoparticles, for example, the band gap is widened and the emission peak wavelength is shifted to a short wavelength. Further, although the details are unknown, it is considered that the lattice defects of the semiconductor nanoparticles are reduced and the emission quantum yield is improved. When it contains an alkali metal, it emits light having an emission peak wavelength in the range of 500 nm or more and 900 nm or less and having a half width of 250 meV or less in the emission spectrum by irradiation with light having a wavelength in the range of 350 nm or more and less than 500 nm. ..

When the semiconductor nanoparticles contain an ^alkali metal (hereinafter, may be abbreviated as Ma) in the composition, the content of the alkali metal in the composition of the semiconductor nanoparticles is, for example, greater than 0 mol% and less than 30 mol%. It is preferably 1 mol% or more and 25 mol% or less. Further, the ratio of the number of atoms of the alkali metal ( ^Ma ) to the total number of atoms of the alkali metal ( ^Ma ) and the total number of atoms of Ag in the composition of the semiconductor nanoparticles ( ^Ma / ( ^Ma + Ag)) is, for example,. It is less than 1, preferably 0.8 or less, and more preferably 0.2 or less. The ratio is, for example, greater than 0, preferably 0.05 or more, and more preferably 0.1 or more. The total content of Ag and alkali metal ( ^Ma ) in the composition of the semiconductor nanoparticles is, for example, 10 mol% or more and 30 mol% or less.

The semiconductor nanoparticles further containing an alkali metal in the composition have, for example, a composition represented by the following formula (2).
(Ag _p ^Ma _(1-p) ) _q In _r Ga _(1-r) Se _{(q + 3) / 2} (2)
Here, p, q and r satisfy 0 <p <1.0, 0.20 <q ≦ 1.2, 0 <r ≦ 1.0. ^Ma represents an alkali metal.

The semiconductor nanoparticles may contain sulfur (S) in their composition. Sulfur (S) is contained, for example, by substituting a part of selenium (Se) in the composition of semiconductor nanoparticles. The content of S in the composition of the semiconductor nanoparticles is, for example, greater than 0 mol% and less than 50 mol%, preferably 1 mol% or more and 45 mol% or less, and more preferably 15 mol% or more and 42 mol% or less. .. The total content of sulfur (S) and selenium (Se) in the composition of the semiconductor nanoparticles is, for example, 35 mol% or more and 55 mol% or less, preferably 40 mol% or more and 55 mol% or less. Further, the ratio of the number of atoms of sulfur (S) to the total number of atoms of sulfur (S) and the number of atoms of selenium (Se) in the composition of the semiconductor nanoparticles (S / (S + Se)) is, for example, less than 1. It is preferably 0.95 or less, more preferably 0.9 or less, still more preferably 0.85 or less, still more preferably 0.8 or less, still more preferably 0.7 or less. The ratio is, for example, greater than 0, preferably 0.1 or more. When sulfur is contained, irradiation with light having a wavelength in the range of 350 nm or more and less than 500 nm emits light having an emission peak wavelength in the range of 500 nm or more and 900 nm or less and having a half width of 250 meV or less in the emission spectrum.

The semiconductor nanoparticles further containing sulfur (S) in the composition have, for example, a composition represented by the following formula (3a) or (3b).
(Ag _p ^Ma _(1-p) ) _q In _r Ga _(1-r) (Se _(1-s) + S _s ) _{(q + 3) / 2} (3a)
Here, p, q, r and s satisfy 0 <p ≦ 1.0, 0.20 <q ≦ 1.2, 0 <r ≦ 1.0, 0 <s <1.0. Here, ^Ma represents an alkali metal.
Ag _q In _r Ga _(1-r) (Se _(1-s) + S _s ) _{(q + 3) / 2} (3b)
Here, q, r and s satisfy 0.20 <q ≦ 1.2, 0 <r ≦ 1.0, 0 <s <1.0.

The composition of semiconductor nanoparticles is identified by, for example, energy dispersive X-ray analysis (EDX), X-ray fluorescence spectrometry (XRF), inductively coupled plasma (ICP) emission spectroscopy, and the like. Ag / (In + Ga), Se / (Ag + In + Ga) and the like are calculated based on the composition identified by any of these methods.

In the composition of the semiconductor nanoparticles, Ag may be partially substituted and contain at least one element of Cu and Au, but it is preferably composed substantially of Ag. Here, "substantially" means that the ratio of the element other than Ag to Ag is, for example, 10 mol% or less, preferably 5 mol% or less, and more preferably 1 mol% or less.

In the composition of the semiconductor nanoparticles, at least one of In and Ga may be partially substituted with at least one element of Al and Tl, but is substantially composed of at least one of In and Ga. Is preferable. Here, "substantially" means that the ratio of elements other than In or Ga to In and Ga is, for example, 10 mol% or less, preferably 5 mol% or less, and more preferably 1 mol% or less. Means.

In the composition of the semiconductor nanoparticles, Se may be partially substituted and contain at least one element of S and Te, or may be substantially composed of Se. Here, "substantially" means that the ratio of the element other than Se to Se is, for example, 10 mol% or less, preferably 5 mol% or less, and more preferably 1 mol% or less.

The semiconductor nanoparticles may be composed substantially of at least one of Ag, In and Ga, and Se only. Further, the semiconductor nanoparticles may be substantially composed of at least one of Ag, an alkali metal, In and Ga, and Se only. Further, the semiconductor nanoparticles may be composed substantially of at least one of Ag, In and Ga, and Se and S only. Here, the term "substantially" is used in consideration of the fact that elements other than Ag, alkali metal, In, Ga, Se and S are inevitably contained due to the inclusion of impurities and the like.

The crystal structure of the semiconductor nanoparticles contains at least tetragonal crystals, and may further include at least one selected from the group consisting of hexagonal crystals and orthorhombic crystals. Semiconductor nanoparticles containing Ag, In and Se and whose crystal structure is tetragonal, hexagonal or orthorhombic are generally represented by the composition formula of AgInSe ₂ in the literature and the like. Introduced. It can be considered that the semiconductor nanoparticles according to the present embodiment are, for example, a part of In, which is a Group 13 element, replaced with Ga, which is also a Group 13 element. The composition of the semiconductor nanoparticles is, for example, Ag-In-Ga-Se, ^Ag -Ma-In-Ga-Se, ^Ag -Ma-In-Ga-Se-S, Ag-In-Ga-Se-S, etc. It may be represented by.

The semiconductor nanoparticles represented by the composition formula such as Ag-In-Ga-Se having a hexagonal crystal structure are wurtzite type, and the semiconductor having a tetragonal crystal structure is calcopyrite. It is a type. The crystal structure is identified, for example, by measuring the XRD pattern obtained by X-ray diffraction (XRD) analysis. Specifically, the XRD pattern obtained from the semiconductor nanoparticles is compared with the XRD pattern known as that of the semiconductor nanoparticles represented by the composition of AgInSe ₂ or the XRD pattern obtained by simulation from the crystal structure parameters. do. If any of the known patterns and simulation patterns match the pattern of the semiconductor nanoparticles, it can be said that the crystal structure of the semiconductor nanoparticles is the crystal structure of the matching known or simulation pattern.

In the aggregate of semiconductor nanoparticles, semiconductor nanoparticles having different crystal structures may coexist. In that case, in the XRD pattern, peaks derived from a plurality of crystal structures are observed.

The semiconductor nanoparticles have, for example, an average particle size of 50 nm or less. The average particle size may be, for example, 20 nm or less, 10 nm or less, or less than 10 nm. When the average particle size is 50 nm or less, the quantum size effect tends to be easily obtained, and the band end emission tends to be easily obtained. The lower limit of the average particle size is, for example, 1 nm.

The particle size of the semiconductor nanoparticles can be determined from, for example, a TEM image taken using a transmission electron microscope (TEM). Specifically, it is a line segment connecting arbitrary two points on the outer circumference of a particle observed in a TEM image of a certain particle, and is the length of the longest line segment among the line segments passing inside the particle. The particle size of the particles.

However, when the particles have a rod shape, the length of the minor axis is regarded as the particle size. Here, the rod-shaped particles have a minor axis and a major axis orthogonal to the minor axis in the TEM image, and the ratio of the length of the major axis to the length of the minor axis is larger than 1.2. .. The rod-shaped particles are observed in the TEM image as, for example, a rectangular shape including a rectangular shape, an elliptical shape, a polygonal shape, or the like. The shape of the cross section, which is a plane orthogonal to the long axis of the rod shape, may be, for example, a circle, an ellipse, or a polygon. Specifically, for rod-shaped particles, the length of the major axis refers to the length of the longest line segment among the line segments connecting any two points on the outer circumference of the particle in the case of an elliptical shape. , Rectangular or polygonal, refers to the length of the longest line segment that is parallel to the longest side that defines the outer circumference and connects any two points on the outer circumference of the particle. .. The length of the minor axis refers to the length of the longest line segment orthogonal to the line segment defining the length of the major axis among the line segments connecting arbitrary two points on the outer circumference.

The average particle size of the semiconductor nanoparticles is measured by measuring the particle size of all measurable particles observed in the TEM image of 50,000 times or more and 150,000 times or less, and used as the arithmetic mean of those particle sizes. Here, the "measurable" particles are those in which the entire particles can be observed in the TEM image. Therefore, in the TEM image, a part of the TEM image is not included in the imaging range, and particles that are "cut" are not measurable. When the number of measurable particles contained in one TEM image is 100 or more, the average particle size is obtained using the TEM image. On the other hand, when the number of measurable particles contained in one TEM image is less than 100, the imaging location is changed to further acquire the TEM image, and 100 or more measurable particles included in two or more TEM images are possible. The particle size of the particles is measured to obtain the average particle size.

Semiconductor nanoparticles are capable of band-end emission. The semiconductor nanoparticles emit light having a emission peak wavelength in the range of 500 nm or more and 900 nm or less by irradiating with light having a wavelength in the range of 350 nm or more and less than 500 nm. The half width in the emission spectrum of the semiconductor nanoparticles is 250 meV or less, preferably 200 meV or less, and more preferably 150 meV or less. The lower limit of the half width is, for example, 30 meV or more. When the half-value width is 250 meV or less, the half-value width is 73 nm or less when the emission peak wavelength is 600 nm, the half-value width is 100 nm or less when the emission peak wavelength is 700 nm, and the emission peak wavelength is 800 nm. In the case, it means that the half width is 130 nm or less, and it means that the semiconductor nanoparticles emit light at the band end.

The semiconductor nanoparticles may give other emission, for example, defect emission, as well as band-end emission. Defect emission generally has a long emission lifetime, has a broad spectrum, and has its peak on the longer wavelength side than the band-end emission. When both the band edge emission and the defect emission are obtained, it is preferable that the intensity of the band edge emission is larger than the intensity of the defect emission.

The peak position of the band end emission of the semiconductor nanoparticles can be changed by changing at least one of the shape and the average particle size of the semiconductor nanoparticles, particularly the average particle size. For example, if the average particle size of the semiconductor nanoparticles is made smaller, the bandgap energy becomes larger due to the quantum size effect, and the peak wavelength of the band-end emission can be shifted to the short wavelength side.

Further, the band edge emission of the semiconductor nanoparticles can change the emission peak wavelength by changing the composition of the semiconductor nanoparticles. For example, the emission peak wavelength of band-end emission is shifted to the short wavelength side by increasing the Ga ratio (Ga / (In + Ga)), which is the ratio of the number of atoms of Ga to the sum of the number of atoms of In and Ga in the composition. Can be done. Further, for example, Li or the like is selected as the alkali metal, and the Ma ratio ( ^Ma / ( ^Ag + ^M ), which is the ratio of the number of atoms of the alkali metal (Ma) to the sum of the number of atoms of Ag and the alkali metal (Ma) in the composition. By increasing ^a )), the emission peak wavelength of band-end emission can be shifted to the short wavelength side. Further, for example, by substituting a part of Se in the composition with S and increasing the S ratio (S / (Se + S)), which is the ratio of the number of atoms of S to the sum of the numbers of atoms of Se and S, the band end emission is emitted. The emission peak wavelength of can be shifted to the short wavelength side.

It is preferable that the absorption spectrum of the semiconductor nanoparticles shows an exciton peak. The exciton peak is a peak obtained by exciton generation, and the fact that it is expressed in the absorption spectrum means that the semiconductor nanoparticles are composed of particles suitable for band-end emission with a small particle size distribution and few crystal defects. It means that it has been done. Further, the steeper the exciton peak, the more particles having the same particle size and less crystal defects are contained in the aggregate of semiconductor nanoparticles. Therefore, if the exciton peak is steep, the half-value width of light emission is expected to be narrowed, and the light emission efficiency is expected to improve. In the absorption spectrum of semiconductor nanoparticles, exciton peaks are observed, for example, in the range of 350 nm or more and 900 nm or less.

The semiconductor nanoparticles emit light having an emission peak wavelength on the longer wavelength side than the exciton peak of the absorption spectrum due to the Stokes shift. When the absorption spectrum of the semiconductor nanoparticles shows an exciton peak, the energy difference between the exciton peak and the emission peak wavelength is, for example, 100 meV or less.

The semiconductor nanoparticles may have a core-shell structure in which a shell is arranged on the surface. The shell is a semiconductor having a band gap energy larger than that of the semiconductor constituting the core, and is composed of a semiconductor containing a group 13 element and a group 16 element. Group 13 elements include B, Al, Ga, In and Tl, and Group 16 elements include O, S, Se, Te and Po. The semiconductor constituting the shell may contain only one kind or two or more kinds of Group 13 elements, and may contain only one kind or two or more kinds of Group 16 elements.

The shell may be substantially composed of a semiconductor composed of Group 13 elements and Group 16 elements. Here, "substantially" means that the ratio of elements other than Group 13 elements and Group 16 elements is, for example, 10% or less when the total number of atoms of all the elements contained in the shell is 100%. , It is preferably 5% or less, and more preferably 1% or less.

The shell may be configured by selecting its composition or the like according to the bandgap energy of the semiconductor constituting the core described above. Alternatively, if the composition of the shell or the like is determined in advance, the core may be designed so that the bandgap energy of the semiconductor constituting the core is smaller than that of the shell. For example, a semiconductor made of Ag-In-Se has a bandgap energy of about 1.1 eV or more and 1.3 eV or less.

Specifically, the semiconductor constituting the shell may have, for example, a bandgap energy of 2.0 eV or more and 5.0 eV or less, particularly 2.5 eV or more and 5.0 eV or less. Further, the bandgap energy of the shell is, for example, 0.1 eV or more and 3.0 eV or less, particularly 0.3 eV or more and 3.0 eV or less, more particularly 0.5 eV or more and 1.0 eV or less, more than the band gap energy of the core. It may be large. When the difference between the bandgap energy of the semiconductor constituting the shell and the bandgap energy of the semiconductor constituting the core is equal to or more than the above lower limit value, the proportion of light emitted from the core other than the band-end emission is reduced, and the band The rate of edge emission tends to be large.

Further, the bandgap energy of the semiconductors constituting the core and the shell is selected so that the bandgap energy of the shell provides the bandgap energy of type-I that sandwiches the bandgap energy of the core in the heterojunction of the core and the shell. Is preferable. By forming the band alignment of type-I, the band end emission from the core can be obtained better. In type-I alignment, it is preferable that a barrier of at least 0.1 eV is formed between the band gap of the core and the band gap of the shell, for example, a barrier of 0.2 eV or more, or 0.3 eV or more. May be formed. The upper limit of the barrier is, for example, 1.8 eV or less, and particularly 1.1 eV or less. When the barrier is at least the above lower limit value, the ratio of light emission other than band-end light emission tends to decrease and the ratio of band-end light emission tends to increase in light emission from the core.

The semiconductor constituting the shell may contain In or Ga as a Group 13 element. Further, the shell may contain S as a group 16 element. A semiconductor containing In or Ga, or containing S, tends to be a semiconductor having a bandgap energy larger than that of the core described above.

The shell may have a crystal system of the semiconductor familiar to the crystal system of the semiconductor of the core, and its lattice constant may be the same as or close to that of the semiconductor of the core. A shell made of semiconductors that is familiar to the crystal system and has a close lattice constant (here, the one whose lattice constant is close to the grid constant of the core is also close to the lattice constant) has a good circumference of the core. May be covered. For example, the above-mentioned core is generally a tetragonal system, and examples of the crystal system familiar to this system include a tetragonal system and an orthorhombic system. When Ag-In-Se is a tetragonal system, its lattice constants are 0.61038 nm (6.14 Å), 0.61038 nm (6.104 Å), and 1.171 18 nm (11.71 Å), which are covered. The shell is preferably a tetragonal system or a cubic system, and its lattice constant or a multiple thereof is preferably close to a lattice constant such as Ag-In-Se. Alternatively, the shell may be amorphous.

Whether or not an amorphous shell is formed can be confirmed by observing semiconductor nanoparticles having a core-shell structure with HAADF-STEM. When an amorphous shell is formed, specifically, a portion having a regular pattern (for example, a striped pattern, a dot pattern, etc.) is observed in the center, and a regular pattern is observed around the portion. Parts that are not observed as having a pattern are observed in HAADF-STEM. According to HAADF-STEM, substances having a regular structure such as crystalline substances are observed as images with regular patterns, and substances having no regular structure such as amorphous substances are observed. It is not observed as an image with a regular pattern. Therefore, when the shell is amorphous, the shell is observed as a part clearly different from the core (which has a crystal structure such as a tetragonal system as described above) observed as an image having a regular pattern. be able to.

Also, when the shell consists of GaS, the shell tends to be observed as a darker image than the core in the image obtained by HAADF-STEM because Ga is a lighter element than Ag and In contained in the core. ..

Whether or not an amorphous shell is formed can also be confirmed by observing the semiconductor nanoparticles having the core-shell structure of the present embodiment with a high-resolution transmission electron microscope (HRTEM). In the image obtained by HRTEM, the core part is observed as a crystal lattice image (an image having a regular pattern), the shell part is not observed as a crystal lattice image, and black and white contrast is observed, but it is regular. The pattern is observed as an invisible part.

On the other hand, it is preferable that the shell does not form a solid solution with the core. When the shell forms a solid solution with the core, the two become one, and the mechanism of the present embodiment, in which the core is covered with the shell and the surface state of the core is changed to obtain band-end emission, cannot be obtained.

The shell may include, but is limited to, a combination of In and S, a combination of Ga and S, or a combination of In and Ga and S as a combination of Group 13 and Group 16 elements. is not it. The combination of In and S may be in the form of indium sulfide, the combination of Ga and S may be in the form of gallium sulfide, and the combination of In, Ga and S may be indium gallium sulfide. good. The indium sulfide constituting the shell does not have to have a stoichiometric composition (In ₂ S ₃ ), and in that sense, indium sulfide is expressed in the formula InS _x (x is an arbitrary number not limited to an integer). , For example, 0.8 or more and 1.5 or less). Similarly, gallium sulfide does not have to have a stoichiometric composition (Ga ₂ S ₃ ), and in that sense, gallium sulfide is referred to herein as GaS _x (x is any number not limited to an integer, for example. It may be expressed as 0.8 or more and 1.5 or less). The indium gallium sulfide may have a composition represented by In _{2 (1-y)} Ga _2y S ₃ (y is any number greater than 0 and less than 1), or In _a Ga _1- . It may be represented by _a S _b (a is an arbitrary number larger than 0 and less than 1 and b is an arbitrary number not limited to an integer).

The bandgap energy of indium sulfide is 2.0 eV or more and 2.4 eV or less, and the lattice constant of indium sulfide having a cubic crystal system is 1.0775 nm (10.775 Å). The bandgap energy of gallium sulfide is about 2.5 eV or more and 2.6 eV or less, and the lattice constant of gallium sulfide having a tetragonal crystal system is 0.5215 nm (5.215 Å). However, the crystal systems and the like described here are all reported values, and the shell does not always satisfy these reported values in the semiconductor nanoparticles having an actual core-shell structure.

Indium sulfide and gallium sulfide are preferably used as semiconductors constituting a shell arranged on the surface of the core. In particular, gallium sulfide is preferably used because it has a larger bandgap energy. When gallium sulfide is used, stronger band-end emission can be obtained as compared with the case where indium sulfide is used.

In semiconductor nanoparticles having a core-shell structure, the core may have an average particle size of, for example, 10 nm or less, particularly 8 nm or less. The average particle size of the core may be in the range of 2 nm or more and 10 nm or less, particularly in the range of 2 nm or more and 8 nm or less. When the average particle size of the core is not more than the upper limit, the quantum size effect can be easily obtained.

The thickness of the shell may be in the range of 0.1 nm or more and 50 nm or less, in the range of 0.1 nm or more and 10 nm or less, and particularly in the range of 0.3 nm or more and 3 nm or less. When the thickness of the shell is not less than the lower limit, the effect of the shell covering the core can be sufficiently obtained, and the band end emission can be easily obtained.

The surface of the semiconductor nanoparticles may be modified with any compound. Compounds that modify the surface of semiconductor nanoparticles are also called surface modifiers. The surface modifier has, for example, a function of stabilizing semiconductor nanoparticles to prevent aggregation or growth of semiconductor nanoparticles, a function of improving dispersibility of semiconductor nanoparticles in a solvent, and compensation for surface defects of semiconductor nanoparticles. It has at least one function of improving light emission efficiency.

The surface modifier is, for example, a nitrogen-containing compound having a hydrocarbon group having 4 to 20 carbon atoms, a sulfur-containing compound having a hydrocarbon group having 4 to 20 carbon atoms, and an oxygen-containing compound having a hydrocarbon group having 4 to 20 carbon atoms. It may be a compound or the like. Hydrocarbon groups having 4 to 20 carbon atoms include saturated aliphatic hydrocarbon groups such as butyl group, isobutyl group, pentyl group, hexyl group, octyl group, ethylhexyl group, decyl group, dodecyl group, hexadecyl group and octadecyl group; Unsaturated aliphatic hydrocarbon groups such as oleyl group; alicyclic hydrocarbon groups such as cyclopentyl group and cyclohexyl group; aromatic hydrocarbon groups having 6 to 10 carbon atoms such as phenyl group and naphthyl group; benzyl group and naphthylmethyl Examples thereof include an arylalkyl group such as a group, and among these, a saturated aliphatic hydrocarbon group and an unsaturated aliphatic hydrocarbon group are preferable. Examples of the nitrogen-containing compound include amines and amides, examples of the sulfur-containing compound include thiols and the like, examples of the oxygen-containing compound include fatty acids and the like, and examples of the phosphorus-containing compound include phosphine and phosphine oxide. Kind and the like.

As the surface modifier, a nitrogen-containing compound having a hydrocarbon group having 4 to 20 carbon atoms is preferable. Examples of such nitrogen-containing compounds include alkylamines such as butylamine, isobutylamine, pentylamine, hexylamine, octylamine, ethylhexylamine, decylamine, dodecylamine, hexadecylamine and octadecylamine, and alkenylamines such as oleylamine. ..

As the surface modifier, a sulfur-containing compound having a hydrocarbon group having 4 to 20 carbon atoms is also preferable. Examples of such sulfur-containing compounds include butanethiol, isobutanethiol, pentanthiol, hexanethiol, octanethiol, ethylhexanethiol, decanethiol, dodecanethiol, hexadecanethiol, octadecanethiol and the like.

The surface modifier may be used alone or in combination of two or more different types. For example, one compound selected from the nitrogen-containing compounds exemplified above (for example, oleylamine) and one compound selected from the sulfur-containing compounds exemplified above (for example, dodecanethiol) may be used in combination. ..

When the semiconductor nanoparticles have a core-shell structure, the shell surface may be modified with a surface modifier containing phosphorus (P) having a negative oxidation number (hereinafter, also referred to as “specific modifier”). Since the surface modifier of the shell contains the specific modifier, the quantum efficiency in the band end emission of the semiconductor nanoparticles of the core shell structure is further improved.

The specific modifier contains P having a negative oxidation number as a Group 15 element. The oxidation number of P becomes -1 when one hydrogen atom or alkyl group is bonded to P, and becomes +1 when one oxygen atom is bonded by a single bond, and changes in the substitution state of P. For example, the oxidation number of P in trialkylphosphine and triarylphosphine is -3, and that in trialkylphosphine oxide and triarylphosphine oxide is -1.

The specific modifier may contain other Group 15 elements in addition to P having a negative oxidation number. Examples of other Group 15 elements include N, As, Sb and the like.

The specific modifier may be, for example, a phosphorus-containing compound having a hydrocarbon group having 4 or more and 20 or less carbon atoms. Hydrocarbon groups having 4 or more and 20 or less carbon atoms include n-butyl group, isobutyl group, n-pentyl group, n-hexyl group, octyl group, ethylhexyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group and octadecyl. Linear or branched saturated aliphatic hydrocarbon groups such as groups; Linear or branched unsaturated aliphatic hydrocarbon groups such as oleyl groups; Alicyclic hydrocarbon groups such as cyclopentyl groups and cyclohexyl groups; Aromatic hydrocarbon groups such as phenyl group and naphthyl group; arylalkyl groups such as benzyl group and naphthylmethyl group are mentioned, and among them, saturated aliphatic hydrocarbon group and unsaturated aliphatic hydrocarbon group are preferable. When the specific modifier has a plurality of hydrocarbon groups, they may be the same or different.

Specifically, as the specific modifier, tributylphosphine, triisobutylphosphine, tripentylphosphine, trihexylphosphine, trioctylphosphine, tris (ethylhexyl) phosphine, tridecylphosphine, tridodecylphosphine, tritetradecylphosphine, trihexadecyl Phosphine, trioctadecylphosphine, triphenylphosphine, tributylphosphine oxide, triisobutylphosphine oxide, tripentylphosphine oxide, trihexylphosphine oxide, trioctylphosphine oxide, tris (ethylhexyl) phosphine oxide, tridecylphosphine oxide, tridodecylphosphine oxide , Tritetradecylphosphine oxide, trihexadecylphosphine oxide, trioctadecylphosphine oxide, triphenylphosphine oxide and the like, and at least one selected from the group consisting of these is preferable.

Method for manufacturing semiconductor nanoparticles In the method for manufacturing semiconductor nanoparticles, a mixture containing an Ag salt, a salt containing at least one of In and Ga, a Se source, and an organic solvent is mixed at a temperature of more than 200 ° C and 370 ° C or less. Including heat treatment at a temperature within the range of to obtain semiconductor nanoparticles. In the production method, the ratio of the number of atoms of Ag to the total number of atoms of In and Ga in the mixture is more than 0.43 and 2.5 or less. The salt containing at least one of In and Ga may contain at least one of In salt and Ga salt.

In this production method, the salt of Ag, In and so that the ratio of the number of atoms of Ag to the total number of atoms of In and Ga (Ag / (In + Ga)) exceeds 0.43 and becomes 2.5 or less. It is characterized in that a salt containing at least one of Ga and a Se source are charged into an organic solvent. The above-mentioned Ag-In-Ga-Se semiconductor nanoparticles can be obtained by inputting the supply source of each element so that Ag / (In + Ga) is within the above range. That is, one of the features of the production method of this embodiment is that semiconductor nanoparticles are produced by setting the charging ratio of the source of each element to a specific ratio that is not according to the stoichiometric composition ratio.

The mixture before heat treatment in the method for producing semiconductor nanoparticles may further contain an alkali metal salt, if necessary. When the mixture contains an alkali metal salt, the ratio of the number of atoms of the alkali metal ( ^Ma ) to the total number of atoms of Ag and the alkali metal ( ^Ma ) in the mixture ( ^Ma / ( ^Ma + Ag)) is, for example, It is less than 1, preferably 0.85 or less, or 0.35 or less. The ratio is, for example, greater than 0, preferably 0.1 or more, or 0.15 or more. That is, one of the features of the production method of this embodiment is that a part of Ag in the composition is replaced with an alkali metal to generate semiconductor nanoparticles.

The mixture before heat treatment in the method for producing semiconductor nanoparticles may further contain a sulfur (S) source, if necessary. When the mixture contains an S source, the ratio of the number of atoms of S to the total number of atoms of S and Se in the mixture (S / (Se + S)) is, for example, less than 1, preferably 0.95 or less, or It is 0.9 or less. The ratio is, for example, greater than 0, preferably 0.1 or more, or 0.4 or more. That is, one of the features of the production method of this embodiment is that a part of Se in the composition is replaced with S to generate semiconductor nanoparticles.

The semiconductor nanoparticles include, for example, a salt of Ag, a salt containing at least one of In and Ga, a Se source, an organic solvent, and optionally at least one of an alkali metal salt and an S source. A preparatory step for preparing a mixture in which the ratio of the atomic number of Ag to the total atomic number of In and Ga is more than 0.43 and 2.5 or less, and the prepared mixture is more than 200 ° C and 370 ° C or less. It is manufactured by a manufacturing method including a heat treatment step of heat-treating at a temperature within the range of.

For semiconductor nanoparticles, a salt containing Ag, a salt containing at least one of In and Ga, a Se source, and optionally at least one of an alkali metal salt and an S source are added to an organic solvent at a time to prepare a mixture. It may be produced by preparing and heat-treating it. According to this method, semiconductor nanoparticles can be synthesized with good reproducibility in one pot by a simple operation. Further, the organic solvent and the salt of Ag are reacted to form a complex, and then the organic solvent and the salt of In are reacted to form a complex, and these complexes are reacted with the Se source. The obtained reaction product may be produced by a method of growing crystals. In this case, the heat treatment is carried out at the stage of reacting with the Se source and, if necessary, the included S source.

The salt of Ag, the salt containing at least one of In and Ga, and the alkali metal salt may be either an organic acid salt or an inorganic acid salt. Specifically, examples of the salt include nitrates, acetates, sulfates, hydrochlorides, sulfonates, acetylacetonate salts and the like, and preferably at least one selected from the group consisting of these. More preferably, it is an organic acid salt such as an acetate. This is because the organic acid salt has a high solubility in an organic solvent and the reaction can proceed more uniformly.

Examples of the Se supply source include elemental selenium; Se-containing compounds such as selenourea, selenoacetamide, and alkylselenol.

Examples of the S supply source include sulfur alone, thiourea, alkylthiourea, thioacetamide, alkylthiol, 2,4-bis (4-methoxyphenyl) -1,3,2,4-dithiadiphosphetan-2. , 4-Disulfide, β-dithiones such as 2,4-pentanedithione, dithiols such as 1,2-bis (trifluoromethyl) ethylene-1,2-dithiol, S-containing compounds such as diethyldithiocarbamidase Can be mentioned. Of these, thioacetamide is preferable from the viewpoint of quantum yield.

The mixture comprises a salt of Ag, a salt containing at least one of In and Ga, a Se source and optionally at least one of an alkali metal salt and an S source, which do not react with each other. It may be included as a complex formed from these. Further, the mixture may contain an Ag complex formed from a salt of Ag, a complex formed from a salt containing at least one of In and Ga, a complex formed from a Se source, and the like. Complex formation is carried out, for example, by mixing a salt of Ag, a salt containing at least one of In and Ga, and a Se source in a suitable solvent.

Examples of the organic solvent include amines having a hydrocarbon group having 4 to 20 carbon atoms, particularly alkyl amines or alkenyl amines having 4 to 20 carbon atoms, and thiols having a hydrocarbon group having 4 to 20 carbon atoms, particularly carbon atoms. Examples thereof include alkyl thiol or alkenyl thiol having 4 to 20 and phosphine having a hydrocarbon group having 4 to 20 carbon atoms, particularly alkyl phosphine or alkenyl phosphine having 4 to 20 carbon atoms, and the like is selected from the group consisting of these. It is preferable to contain at least one kind. These organic solvents may, for example, finally surface-modify the resulting semiconductor nanoparticles. The organic solvent may be used in combination of two or more, and in particular, selected from at least one selected from thiols having a hydrocarbon group having 4 to 20 carbon atoms and an amine having a hydrocarbon group having 4 to 20 carbon atoms. A mixed solvent may be used in combination with at least one of the above. These organic solvents may also be used in combination with other organic solvents. When the organic solvent contains the thiol and the amine, the volume ratio of the thiol to the amine (thiol / amine) is, for example, greater than 0 and 1 or less, preferably 0.007 or more and 0.2 or less.

In the mixture, the ratio of the number of atoms of Ag to the total number of atoms of In and Ga contained as the composition (Ag / (In + Ga)) is, for example, more than 0.43 and 2.5 or less, preferably 0. It is 5.5 or more and 1.0 or less, more preferably 0.6 or more and 0.8 or less. Further, in the composition of the mixture, the ratio of the number of atoms of In to the total number of atoms of In and Ga (In / (In + Ga)) is, for example, 0.1 or more and 1.0 or less, preferably 0.25 or more. It is 0.99 or less. Further, in the composition of the mixture, the ratio of the number of atoms of Ag to the total number of atoms of Se (Ag / Se) is, for example, 0.27 or more and 1.0 or less, preferably 0.35 or more and 0.5 or less. Is. By using the source of each element so that the composition of the mixture satisfies these conditions, it is possible to generate semiconductor nanoparticles that easily give band-end emission.

The heat treatment step comprises heat treating the mixture at a first temperature in the range above 200 ° C and below 370 ° C. The first temperature in the heat treatment is preferably 220 ° C. or higher, more preferably 250 ° C. or higher, and preferably less than 370 ° C., for example, when the mixture contains a salt of Ag, a salt of In and a Se source. Yes, more preferably 350 ° C. or lower. Further, for example, when the mixture contains a salt of Ag, a salt of In, a salt of Ga, and a Se source, the temperature is preferably 270 ° C or higher, more preferably 300 ° C or higher, and preferably less than 370 ° C. It is more preferably 350 ° C. or lower. Further, for example, when the mixture contains a salt of Ag, a salt of In, a salt of Ga, a Se source, and an S source, the temperature is preferably 270 ° C or higher, more preferably 280 ° C or higher, still more preferable. Is 300 ° C. or higher, preferably less than 370 ° C., more preferably 350 ° C. or lower, still more preferably 320 ° C. or lower. The heat treatment time at the first temperature is, for example, 1 minute or longer, preferably 5 minutes or longer, more preferably 8 minutes or longer, still more preferably 10 minutes or longer. The heat treatment time at the first temperature is, for example, 180 minutes or less, preferably 120 minutes or less, and more preferably 60 minutes or less. Further, for example, the heat treatment time at the first temperature may be 20 minutes or less.

The heat treatment time is defined as the start time of the heat treatment when the temperature reaches a predetermined temperature, and the end time of the heat treatment at the predetermined temperature when the operation for lowering the temperature or raising the temperature is performed. The rate of temperature rise until reaching a predetermined temperature is, for example, 1 ° C./min or more and 100 ° C./min or less, or 1 ° C./min or more and 50 ° C./min or less. The temperature lowering rate after the heat treatment is, for example, 1 ° C./min or more and 100 ° C./min or less, and may be cooled as needed, or the heat source may be stopped and allowed to cool.

The heat treatment step may include heat treatment at a second temperature in the range of 30 ° C. or higher and 190 ° C. or lower prior to the heat treatment of the mixture at the first temperature. That is, in the heat treatment step, the mixture is heat-treated at a second temperature in the range of 30 ° C. or higher and 190 ° C. or lower (also referred to as “first-stage heat treatment”), and the mixture heat-treated at the second temperature is 200 ° C. It may be a two-step heat treatment step including heat treatment at a first temperature in the range of 370 ° C. or lower (also referred to as “second step heat treatment”). By carrying out the heat treatment in two steps, it is possible to produce semiconductor nanoparticles having relatively high intensity of band-end emission with better reproducibility. Here, the heat treatment at the second temperature and the heat treatment at the first temperature may be continuously performed, or the heat treatment may be performed by lowering the temperature after the heat treatment at the second temperature and then raising the temperature to the first temperature. good.

The second temperature is preferably 30 ° C. or higher, more preferably 100 ° C. or higher. The second temperature is preferably 200 ° C. or lower, more preferably 180 ° C. or lower. The heat treatment time at the second temperature is, for example, 1 minute or longer, preferably 5 minutes or longer, and more preferably 10 minutes or longer. The heat treatment time at the second temperature is, for example, 120 minutes or less, preferably 60 minutes or less, and more preferably 30 minutes or less.

The atmosphere in the heat treatment step is preferably a rare gas atmosphere such as argon or an inert atmosphere such as a nitrogen atmosphere. By heat-treating in an inert atmosphere, it is possible to suppress the by-product of oxides and the oxidation of the surface of the obtained semiconductor nanoparticles.

The semiconductor nanoparticles obtained by the heat treatment may be separated from the organic solvent, and may be further purified if necessary. Separation of semiconductor nanoparticles is performed, for example, by subjecting an organic solvent containing semiconductor nanoparticles to centrifugation after completion of the heat treatment step, and taking out the supernatant liquid containing the nanoparticles. Purification involves, for example, adding an organic solvent such as alcohol to the supernatant, subjecting it to centrifugation, and removing the semiconductor nanoparticles as a precipitate. The precipitate may be removed by itself or by removing the supernatant. The removed precipitate may be dried by, for example, vacuum degassing or natural drying, or a combination of vacuum degassing and natural drying. The natural drying may be carried out, for example, by leaving it in the air at normal temperature and pressure, and in that case, it may be left for 20 hours or more, for example, about 30 hours.

Alternatively, the removed precipitate may be dispersed in an organic solvent. The purification process including the addition of alcohol and centrifugation may be carried out multiple times as needed. As the alcohol used for purification, lower alcohols such as methanol, ethanol and propanol may be used. When the precipitate is dispersed in an organic solvent, a halogen-based solvent such as chloroform or a hydrocarbon-based solvent such as toluene, cyclohexane, hexane, pentane, or octane may be used as the organic solvent.

[Light emitting device]
The light emitting device includes a light conversion member and a semiconductor light emitting device, and the light conversion member includes the semiconductor nanoparticles described above. According to this light emitting device, for example, a part of the light emitted from the semiconductor light emitting device is absorbed by the semiconductor nanoparticles to emit light having a longer wavelength. Then, the light from the semiconductor nanoparticles and the balance of the light emitted from the semiconductor light emitting device are mixed, and the mixed light can be used as the light emission of the light emitting device.

Specifically, if a semiconductor light emitting device that emits bluish-purple light or blue light having a peak wavelength of about 400 nm or more and 490 nm or less is used, and a semiconductor nanoparticle that absorbs blue light and emits yellow light is used. A light emitting device that emits white light can be obtained. Alternatively, a white light emitting device can be obtained by using two types of semiconductor nanoparticles, one that absorbs blue light and emits green light and the other that absorbs blue light and emits red light.

Alternatively, even when a semiconductor light emitting element that emits ultraviolet rays having a peak wavelength of 400 nm or less is used and three types of semiconductor nanoparticles that absorb ultraviolet rays and emit blue light, green light, and red light, respectively, are used, a white light emitting device is used. Can be obtained. In this case, it is desirable that all the light from the light emitting element is absorbed by the semiconductor nanoparticles and converted so that the ultraviolet rays emitted from the light emitting element do not leak to the outside.

Alternatively, if a device that emits blue-green light having a peak wavelength of 490 nm or more and 510 nm or less is used, and a device that absorbs the above-mentioned blue-green light and emits red light is used as the semiconductor nanoparticles, a device that emits white light is used. Obtainable.

Alternatively, if a semiconductor light emitting element that emits red light having a wavelength of 700 nm or more and 780 nm or less is used, and a semiconductor nanoparticles that absorbs red light and emits near infrared rays is used, a light emitting device that emits near infrared rays. You can also get.

The semiconductor nanoparticles may be used in combination with other semiconductor quantum dots, or may be used in combination with other non-quantum dot phosphors (eg, organic or inorganic phosphors). The other semiconductor quantum dots are, for example, the binary semiconductor quantum dots described in the background technology section. As a phosphor that is not a quantum dot, a garnet-based phosphor such as an aluminum garnet-based phosphor can be used. Examples of the garnet phosphor include a cerium-activated yttrium-aluminum-garnet-based fluorescent substance and a cerium-activated lutetium-aluminum-garnet-based fluorescent substance. In addition, a nitrogen-containing calcium aluminosilicate-based phosphor activated with europium and / or chromium, a silicate-based phosphor activated with europium, a β-SiAlON-based phosphor, a nitride-based phosphor such as CASN-based or SCANS-based, Rare earth nitride-based phosphors such as LnSi 3N ₁₁ -based or LnSiAlON-based, BaSi ₂ O ₂ N ₂ : Eu _- based or Ba ₃ Si ₆ O ₁₂ N ₂ : Acid nitride-based phosphors such as Eu-based, CaS-based, SrGa ₂ S4 series, SrAl ₂ O ₄ series, ZnS series and other sulfide-based phosphors, chlorosilicate-based phosphors, SrLiAl ₃ N ₄ : Eu phosphors, SrMg ₃ SiN ₄ : Eu phosphors, activated with manganese. As the fluoride complex phosphor, K ₂ SiF ₆ : Mn phosphor or the like can be used.

In the light emitting device, the light conversion member containing the semiconductor nanoparticles may be, for example, a sheet or a plate-shaped member, or may be a member having a three-dimensional shape. An example of a member having a three-dimensional shape is that in a surface mount type light emitting diode, when the semiconductor light emitting element is arranged on the bottom surface of the recess formed in the package, the recess is used to seal the light emitting element. It is a sealing member formed by filling with a resin.

Another example of the light conversion member is a resin member formed so as to surround the upper surface and the side surface of the semiconductor light emitting device with a substantially uniform thickness when the semiconductor light emitting device is arranged on a flat substrate. be. Alternatively, another example of the light conversion member is that the semiconductor light emitting device is filled with a resin member containing a reflective material so that the upper end thereof forms the same plane as the semiconductor light emitting device. It is a resin member formed in a flat plate shape with a predetermined thickness on the upper part of the resin member including the semiconductor light emitting element and the reflective material.

The light conversion member may be in contact with the semiconductor light emitting device or may be provided away from the semiconductor light emitting device. Specifically, the optical conversion member may be a pellet-shaped member, a sheet member, a plate-shaped member or a rod-shaped member arranged away from the semiconductor light-emitting element, or a member provided in contact with the semiconductor light-emitting element, for example. , A sealing member, a coating member (a member that covers a light emitting element provided separately from the mold member), or a mold member (including, for example, a member having a lens shape).

Further, when two or more types of semiconductor nanoparticles exhibiting light emission of different wavelengths are used in the light emitting device, the two or more types of semiconductor nanoparticles may be mixed in one light conversion member, or Two or more optical conversion members containing only one type of quantum dot may be used in combination. In this case, the two or more types of optical conversion members may form a laminated structure or may be arranged as a dot-shaped or striped pattern on a plane.

Examples of the semiconductor light emitting device include an LED chip. The LED chip may include one or more semiconductor layers selected from the group consisting of GaN, GaAs, InGaN, AlInGaP, GaP, SiC, ZnO and the like. The semiconductor light emitting device that emits blue-purple light, blue light, or ultraviolet light is, for example, a GaN-based device whose composition is represented by In _X Al _Y Ga _1-XY N (0 ≦ X, 0 ≦ Y, X + Y <1). The compound is provided as a semiconductor layer.

The light emitting device is preferably incorporated in the liquid crystal display device as a light source. Since band-end emission by semiconductor nanoparticles has a short emission lifetime, a emission device using this is suitable as a light source for a liquid crystal display device that requires a relatively high response speed. Further, the semiconductor nanoparticles of the present embodiment may exhibit emission peaks having a small half-value width energy as band-end emission. Therefore, in the light emitting device:
-A blue semiconductor light emitting device is used to obtain blue light having a peak wavelength in the range of 420 nm or more and 490 nm or less, and semiconductor nanoparticles are used to obtain green light having a peak wavelength in the range of 510 nm or more and 550 nm or less, preferably 530 nm or more and 540 nm or less. To obtain light and red light having a peak wavelength in the range of 600 nm or more and 680 nm or less, preferably 630 nm or more and 650 nm or less;
-In the light emitting device, the semiconductor light emitting element is used to obtain ultraviolet light with a peak wavelength of 400 nm or less, and the semiconductor nanoparticles are used to obtain blue light having a peak wavelength of 430 nm or more and 470 nm or less, preferably 440 nm or more and 460 nm or less, and a peak wavelength of 510 nm. A dark color filter is used by obtaining green light having a peak wavelength of 600 nm or more and 540 nm or less, and red light having a peak wavelength in the range of 600 nm or more and 680 nm or less, preferably 630 nm or more and 650 nm or less. A liquid crystal display device with good color reproducibility can be obtained. The light emitting device is used, for example, as a direct type backlight or an edge type backlight.

Alternatively, a sheet, plate-shaped member, or rod made of resin, glass, or the like containing semiconductor nanoparticles may be incorporated in the liquid crystal display device as a light conversion member independent of the light emitting device.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

(Example 1)
0.10 mmol silver acetate (AgOAc), 0.15 mmol acetylacetonatoindium (In (CH ₃ COCHCOCH ₃ ) ₃ ; In (acac) ₃ ), and 0.25 mmol selenourea as a selenium source, 0.1 cm. It was put into a mixed solution of 1-dodecanethiol of ³ and oleylamine of 2.9 cm ³ and dispersed. The dispersion is placed in a test tube together with a stirrer, replaced with nitrogen, and then the contents in the test tube are stirred under a nitrogen atmosphere for 10 minutes at 150 ° C. as the first stage heat treatment. As the heat treatment, a heat treatment at 250 ° C. for 10 minutes was carried out. After the heat treatment, the obtained suspension was allowed to cool, and then subjected to centrifugation (radius 146 mm, 4000 rpm, 5 minutes), and the dispersion liquid as the supernatant was taken out. Methanol was added to this until the semiconductor nanoparticles were precipitated, and the mixture was subjected to centrifugation (radius 146 mm, 4000 rpm, 5 minutes) to precipitate the semiconductor nanoparticles. The precipitate was taken out and dispersed in chloroform to obtain a semiconductor nanoparticle dispersion liquid. Table 1 shows the preparation composition of the raw materials.

(Examples 2, 3, 4, Comparative Example 1)
A semiconductor nanoparticle dispersion liquid was obtained in the same manner as in Example 1 except that the charging composition of the raw materials was changed as shown in Table 1.

(Example 5)
0.10 mmol of silver acetate (AgOAc), 0.11 mmol of acetylacetonatoindium (In (CH ₃ COCHCOCH ₃ ) ₃ ; In (acac) ₃ ), 0.038 mmol of acetylacetonato gallium (Ga (CH ₃ COCHCOCH ₃ )) ) ₃ ; Ga (acac) ₃ ) and 0.25 mmol of selenourea as a source of selenium were added to a mixture of 0.1 cm ³ of 1-dodecanethiol and 0.29 cm of ³ of oleylamine and dispersed. The dispersion is placed in a test tube together with a stirrer, replaced with nitrogen, and then the contents in the test tube are stirred under a nitrogen atmosphere for 10 minutes at 150 ° C. as the first stage heat treatment. As the heat treatment, a heat treatment at 300 ° C. for 10 minutes was carried out. After the heat treatment, the obtained suspension was allowed to cool, and then subjected to centrifugation (radius 146 mm, 4000 rpm, 5 minutes), and the dispersion liquid as the supernatant was taken out. Methanol was added to this until the semiconductor nanoparticles were precipitated, and the mixture was subjected to centrifugation (radius 146 mm, 4000 rpm, 5 minutes) to precipitate the semiconductor nanoparticles. The precipitate was taken out and dispersed in chloroform to obtain a semiconductor nanoparticle dispersion liquid. Table 2 shows the preparation composition of the raw materials.

(Examples 5 to 8, Comparative Examples 2 and 3)
A semiconductor nanoparticle dispersion was obtained in the same manner as in Example 1 except that the composition of the raw materials and the heat treatment temperature (first temperature) of the second stage were changed as shown in Table 2.

(Average particle size)
The shape of the obtained semiconductor nanoparticles is observed using a transmission electron microscope (TEM, manufactured by Hitachi High-Technologies Corporation, trade name H-7650), and the average particle size is 80,000 to 200,000 times. It was measured from the TEM image of. Here, as the TEM grid, the trade name High-Resolution Carbon HRC-C10 STEM Cu100P Grid (Oken Shoji Co., Ltd. was used. The shape of the obtained particles was spherical or polygonal. The average particle size was 3? Select the above TEM images and select all the nanoparticles contained in them that are measurable, that is, all the particles except those in which the image of the particles is cut off at the edge of the image. The particle size was determined by a method of measuring the particle size and calculating the arithmetic average. In all the examples including this example and the comparative example, the particle size of a total of 100 or more nanoparticles was determined using 3 or more TEM images. The average particle size measured is shown in Table 3.

(Light emission characteristics)
The absorption spectrum and emission spectrum of the obtained semiconductor nanoparticles were measured. The absorption spectrum was measured using a diode array spectrophotometer (manufactured by Agilent Technologies, trade name Agent 8453A) with a wavelength of 190 nm or more and 1100 nm or less. The emission spectrum was measured at an excitation wavelength of 365 nm using a multi-channel spectroscope (manufactured by Hamamatsu Photonics Co., Ltd., trade name PMA11). The emission spectra of Examples 1 to 4 and Comparative Example 1 are shown in FIG. 1, and the absorption spectra are shown in FIG. The emission spectra of Examples 5 and 6 and Comparative Examples 2 and 3 are shown in FIG. 3, and the absorption spectra are shown in FIG. The absorption spectra and emission spectra of Examples 7 and 8 are shown in FIG. It is obtained from the emission spectrum from the emission peak wavelength (band-end emission), half-value width, emission quantum yield, and Stokes shift (energy value of the absorption peak obtained from the absorption spectrum) of the steep emission peak observed in each emission spectrum. The energy value of the emission peak is subtracted) is shown in Table 3.

(X-ray diffraction pattern)
X-ray diffraction (XRD) patterns were measured for the semiconductor nanoparticles obtained in Examples 1 to 4 and Comparative Example 1 and compared with the tetragonal (chalcopyrite type) AgInSe ₂ and the orthorhombic AgInSe ₂ . .. The measured XRD pattern is shown in FIG. X-ray diffraction (XRD) patterns were measured for the semiconductor nanoparticles obtained in Examples 5, 7 and 8 and compared with tetragonal (chalcopyrite type) AgInSe ₂ and AgGaSe ₂ and orthorhombic AgInSe ₂ . .. The measured XRD pattern is shown in FIG. The XRD pattern was measured using a powder X-ray diffractometer (trade name: SmartLab) manufactured by Rigaku Corporation.

Obtained in Examples 1 to 4 containing Ag, In and Se, the charging ratio of Ag to In at the time of synthesis exceeded 0.43, and the first temperature, which is the heat treatment temperature of the second stage, was 250 ° C. The semiconductor nanoparticles showed band-end emission with a half-value width of 250 meV or less. On the other hand, the semiconductor nanoparticles obtained in Comparative Example 1 in which the charging ratio of Ag to In was 0.43 or less did not show band-end emission and showed wide defect emission.
Examples 5 and 6 containing Ag, In, Ga and Se, the charging ratio of Ag to In and Ga at the time of synthesis exceeds 0.43, and the first temperature, which is the heat treatment temperature of the second stage, exceeds 200 ° C. The semiconductor nanoparticles obtained in 1 above showed band-end emission with a half-value width of 250 meV or less. On the other hand, the semiconductor nanoparticles obtained in Comparative Examples 2 and 3 having a first temperature of 200 ° C. or lower did not show band-end emission and showed wide defect emission.
In the case of semiconductor nanoparticles containing Ag, In, Ga, and Se, when the charging ratio of In to In and Ga became small, the emission peak wavelength shifted to a short wavelength while maintaining band-end emission.

(Examples 9 and 10)
Silver acetate (AgOAc), lithium acetate (LiOAc), indium acetate (In (OAc) ₃ ), and selenourea ((NH ₂ ) ₂ CSe) were collected in test tubes as shown in the table below. To this, 0.1 cm ³ of 1-dodecanethiol and 2.9 cm ³ of oleylamine were added as solvents. A stirrer is placed in the test tube to replace it with nitrogen, and the contents in the test tube are stirred in a nitrogen atmosphere at 150 ° C. for 10 minutes as the first stage heat treatment and 300 ° C. for 10 minutes as the second stage heat treatment. The heat treatment was carried out. After the heat treatment, the obtained suspension was allowed to cool, and then subjected to centrifugation (radius 146 mm, 4000 rpm, 5 minutes) to separate into a supernatant and a precipitate. The supernatant and the precipitate were washed with 3 mL of methanol and 3 mL of ethanol, respectively, and subjected to centrifugation (radius 146 mm, 4000 rpm, 5 minutes) again to precipitate the semiconductor nanoparticles. The precipitate was taken out and dispersed in chloroform to obtain a semiconductor nanoparticle dispersion liquid.

The average particle size, emission characteristics, and X-ray diffraction (XRD) pattern of the obtained semiconductor nanoparticles were measured in the same manner as described above. The results are shown in Table 5. Further, FIG. 8 shows an absorption spectrum normalized at 400 nm, FIG. 9 shows an emission spectrum (excitation light 365 nm), and FIG. 10 shows an XRD pattern.

From the absorption spectrum of FIG. 8, when the Li ratio (Li / (Ag + Li)) in the preparation increases, the absorption edge wavelength shifts to a shorter wavelength. Therefore, it is considered that the alkali metal (Li) and Ag could be solid-dissolved. In the emission spectrum of Example 10 shown in FIG. 9, a peak near 1000 nm, which seems to be defective emission, was not observed. From the XRD pattern of FIG. 10, it was confirmed that the peak shifts to the high angle side as the Li ratio in the preparation increases. It is considered that this allowed the solid dissolution of the alkali metal (Li) and Ag.

(Examples 11 to 13)
Silver acetate (AgOAc), acetylacetonatoindium (In (acac) ₃ ), acetylacetonato gallium (Ga (acac) ₃ ), powdered sulfur (S), selenourea ((NH ₂ ) ₂ CSe) are shown in the table below. Weighed into a test tube as per, and 2.75 mL of oleylamine and 0.25 mL of 1-dodecanethiol were added to replace the inside of the test tube with nitrogen. The mixture was heated and stirred at 300 ° C. for 10 minutes and allowed to cool to room temperature. Centrifugation (4000 rpm, 5 minutes) was performed, and the obtained supernatant was filtered through a 20 μm mesh membrane filter. Methanol was added to this until the semiconductor nanoparticles were precipitated, and the mixture was subjected to centrifugation (radius 146 mm, 4000 rpm, 5 minutes) to precipitate the semiconductor nanoparticles. The precipitate was taken out and dispersed in chloroform to obtain a semiconductor nanoparticle dispersion liquid.

The average particle size and emission characteristics of the obtained semiconductor nanoparticles were measured in the same manner as above. The results are shown in Table 7. Further, FIG. 11 shows an absorption spectrum normalized at 365 nm, and FIG. 12 shows an emission spectrum (excitation light 365 nm).

(Examples 14 to 16)
The semiconductor nanoparticles prepared in the same manner as in Example 1 and the semiconductor nanoparticles obtained in Examples 11 and 12 were separated by 1.0 × ^10-5 mmol, respectively, and the solvent was dried under reduced pressure. Acetylacetonatogallium (Ga (acac) ₃ ) 5.33 × ^10-5 mmol and thiourea 5.33 × ^10-5 mmol were weighed, and 3.0 mL of oleylamine was added to replace the inside of the test tube with nitrogen. The mixture was heated and stirred at 300 ° C. for 15 minutes and allowed to cool to room temperature. Centrifuge (4000 rpm, 5 minutes) to remove the precipitate. The supernatant was filtered through a 20 μm mesh membrane filter. Methanol was added and centrifuged (4000 rpm, 5 minutes), and ethanol was added to the obtained precipitate and centrifuged (4000 rpm, 5 minutes) to obtain core-shell type semiconductor nanoparticles as a precipitate. Chloroform was then added to the precipitate to disperse the core-shell semiconductor nanoparticles.

The average particle size and emission characteristics of the obtained semiconductor nanoparticles were measured in the same manner as above. The results are shown in Table 8. Further, for Examples 15 and 16, the absorption spectrum normalized at 365 nm is shown in FIG. 13, and the emission spectrum (excitation light 365 nm) is shown in FIG.

(Examples 17 and 18)
Silver acetate (AgOAc), acetylacetonatoindium (In (acac) ₃ ), acetylacetonato gallium (Ga (acac) ₃ ), powdered sulfur (S), selenourea ((NH ₂ ) ₂ CSe) are shown in the table below. Weighed into a test tube as per, and 2.75 mL of oleylamine and 0.25 mL of 1-dodecanethiol were added to replace the inside of the test tube with nitrogen. The mixture was heated and stirred at 300 ° C. for 10 minutes and allowed to cool to room temperature. Centrifugation (4000 rpm, 5 minutes) was performed to separate the supernatant and the precipitate, and the supernatant was filtered through a 20 μm mesh membrane filter. Methanol was added to this until the semiconductor nanoparticles were precipitated, and the mixture was subjected to centrifugation (radius 146 mm, 4000 rpm, 5 minutes) to precipitate the semiconductor nanoparticles. The precipitate was taken out and dispersed in chloroform to obtain a semiconductor nanoparticle dispersion liquid.

The average particle size and emission characteristics of the obtained semiconductor nanoparticles were measured in the same manner as above. The results are shown in Table 10. Further, FIG. 15 shows an absorption spectrum normalized at 400 nm, and FIG. 16 shows an emission spectrum (excitation light 365 nm).

(Examples 19 to 20)
Core-shell type semiconductor nanoparticles were obtained in the same manner as in Example 14 except that the semiconductor nanoparticles obtained in Examples 17 and 18 were used.

With respect to the semiconductor nanoparticles obtained in Examples 19 and 20, the average particle size and the light emission characteristics were measured in the same manner as described above. The results are shown in Table 11. Further, FIG. 17 shows an absorption spectrum normalized at 400 nm, and FIG. 18 shows an emission spectrum (excitation light 365 nm).

(Example 21)
For the core-shell type semiconductor nanoparticles obtained in Example 20, the concentration of the dispersion was adjusted so that the absorbance at 500 nm was 1.5. To 1.5 mL of the dispersion having an adjusted concentration, 1.5 mL of trioctylphosphine (TOP) was added in a glove box in a nitrogen atmosphere, and the mixture was sufficiently stirred. The semiconductor nanoparticles were TOP-treated by allowing them to stand in a light-shielded state for one day.

The emission characteristics of the semiconductor nanoparticles obtained in Example 21 were measured in the same manner as above. FIG. 19 shows an emission spectrum (excitation light 365 nm).

Claims (6)

A mixture containing Ag salt, In salt, Ga salt, Se source, and organic solvent and not containing S source is heat-treated at a temperature in the range of more than 200 ° C and 370 ° C or less. Including obtaining semiconductor nanoparticles,
A method for producing semiconductor nanoparticles in which the ratio of the atomic number of Ag to the total atomic number of In and Ga in the mixture is 0.07 or more and 2.5 or less. The first aspect of claim 1 is that the mixture is heat-treated at a temperature in the range of 30 ° C. or higher and 190 ° C. or lower for 1 minute or more and 15 minutes or less, and then further heat-treated at a temperature in the range of more than 200 ° C. and 370 ° C. or lower. The method for producing semiconductor nanoparticles according to the above. The mixture further comprises an alkali metal salt and
The method for producing semiconductor nanoparticles according to claim 1 or 2, wherein the ratio of the number of atoms of the alkali metal to the total number of atoms of the alkali metal and Ag in the mixture is less than 1. A mixture of Ag salt, In salt, Ga salt, Se source, S source, and organic solvent is heat-treated at a temperature in the range of more than 200 ° C and 370 ° C to achieve semiconductor nanoparticles. Including getting particles
The ratio of the number of atoms of Ag to the total number of atoms of In and Ga in the mixture is more than 0.43 and 2.5 or less.
A method for producing semiconductor nanoparticles in which the ratio of the number of atoms of S to the total number of atoms of Se contained in the Se source and the number of atoms of S contained in the S source in the mixture is 0.4 or more and less than 1. According to claim 4, the mixture is heat-treated at a temperature in the range of 30 ° C. or higher and 190 ° C. or lower for 1 minute or more and 15 minutes or less, and then further heat-treated at a temperature in the range of more than 200 ° C. and 370 ° C. or lower. The method for producing semiconductor nanoparticles according to the above. The mixture further comprises an alkali metal salt and
The method for producing semiconductor nanoparticles according to claim 4 or 5, wherein the ratio of the number of atoms of the alkali metal to the total number of atoms of the alkali metal and Ag in the mixture is less than 1.

Images