Photon Up-Conversion Materials

Abstract

To provide a photon up-conversion material that ensures triplet energy movement from excited sensitizing molecules in triplet state (T1) to light-emitting molecules and can increase the use efficiency of energy of the sensitizing molecules excited into the triplet state (T1).SOLUTION: The inventive photon up-conversion material contains particles containing organic light-emitting molecules and organic sensitizing molecules. The particles form a monocrystalline structure or a polycrystalline structure in which the plurality of monocrystals aggregate, which is a solid body in which the organic sensitizing molecules are solid-dissolved in the mother crystals of the organic light-emitting molecules, thus ensuring the thermomechanical stability of the material, so that a photon up-conversion material suitable for long-term use can be provided.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a photon upconversion material, and more particularly to a photon upconversion material using triplet-triplet annihilation. [Background technology]

[0002] In order to convert solar energy into secondary energy such as electricity or hydrogen using solar cells or water-splitting photocatalysts, it is necessary to improve the conversion efficiency because the density of the solar energy that reaches the earth's surface is low.

[0003] In the above-mentioned system for converting solar energy into secondary energy, the spectrum corresponding to photons with energies below a threshold energy (also called a band gap) specific to the system, i.e., light with wavelengths longer than the threshold wavelength, is not used for conversion into secondary energy.

[0004] Photon up-conversion (hereinafter sometimes referred to as "photon UC") has been proposed as a method for utilizing such currently unused long-wavelength light for the above conversion.

[0005] The photon UC described above converts two low-energy photons into one higher-energy photon using a process called triplet-triplet annihilation; in other words, it is a method of converting long-wavelength light into short-wavelength light.

[0006] Non-Patent Document 1 describes a fine crystalline powdery organic solid that is precipitated by rapidly evaporating a solution containing a relatively high concentration of organic luminescent molecules and a relatively low concentration of organic sensitizer molecules on a substrate.

[0007] This organic solid has rapid solid precipitation, so that the organic sensitizer molecules are finely dispersed in the solid of the organic light-emitting molecules before the organic light-emitting molecules and the organic sensitizer molecules are almost separated from each other, making it possible to increase the content of the sensitizer molecules without causing aggregation.

[0008] Therefore, it is disclosed that triplet energy transfer from the organic sensitizer molecule to the organic light-emitting molecule is facilitated, enabling highly efficient photo-UC. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] Efficient triplet-triplet annihilation upconversion in binary crystalline solids fabricated via solution casting and operated in air ;Mater. Horiz., 2017,4, 83 Summary of the Invention [Problem to be solved by the invention]

[0010] However, the organic solid described in Non-Patent Document 1 was prepared using a strong non-equilibrium property, and this organic solid has not yet reached a thermodynamically stable state. Therefore, it is difficult to perform photo-UC without changing the properties for a long period of time.

[0011] The present invention has been made in consideration of the problems associated with the conventional techniques, and an object of the present invention is to provide a photon upconversion material that does not rely on non-equilibrium, in other words, has high equilibrium and thermodynamic stability, and has a form in which a small amount of sensitizing molecules are thermodynamically stable solid-dissolved in an organic crystal of a light-emitting molecule. [Means for solving the problem]

[0012] As a result of intensive research to achieve the above object, the present inventors came up with an original idea of ​​utilizing the solid solution phase in the thermodynamic equilibrium phase diagram of a finite soluble eutectic system and a mixture of two molecules, which has not been used in photon upconversion technology until now, as shown in Figure 1. The inventors have pursued this idea and succeeded in realizing it. The solid solution phase is shown as "α phase" in Figure 1, which is a thermodynamically stable phase in which a small amount of organic sensitizing molecules are dissolved in a mother crystal of organic luminescent molecules.

[0013] In other words, the focus of the present invention is not to use techniques accompanied by strong non-equilibrium, such as rapid drying or rapid solidification, used in conventional techniques for uniformly mixing organic sensitizing molecules and organic light-emitting molecules, but to utilize one of the thermodynamically stable phases defined by a thermodynamic equilibrium phase diagram, which is the polar opposite of these techniques. In order to realize this idea, the amount of organic sensitizing molecule added is set to an amount that allows it to be dissolved in the host crystal of the light-emitting molecules, so that the excess organic sensitizing molecules do not form aggregates, i.e., a stable crystalline material is formed, typically in which one organic sensitizing molecule is surrounded by organic light-emitting molecules, thereby completing the present invention.

[0014] That is, the photon up-conversion material of the present invention contains particles including organic light-emitting molecules and organic sensitizing molecules. The particles form single crystals or polycrystals formed by assembling a plurality of the single crystals, a solid solution in which the organic sensitizing molecule is dissolved in a host crystal of the organic light-emitting molecule, The organic light-emitting molecules are anthracene-based organic light-emitting molecules having a dioxaborane group and / or An organic light-emitting molecule represented by the following structural formula (3) and / or an organic light-emitting molecule represented by the following structural formula (4): It is characterized in that: [ka] [ka]

[0015] The method for producing a photon up-conversion material of the present invention is characterized by including a precipitation step of precipitating, from a solution in which organic light-emitting molecules and organic sensitizer molecules are dissolved, particles that form single crystals that are a solid solution in which the organic sensitizer molecules are dissolved in a mother crystal of the organic light-emitting molecules, or particles that form a polycrystal in which a plurality of such single crystals are aggregated. Effect of the Invention

[0016] According to the present invention, organic sensitizer molecules are dissolved in a host crystal of organic light-emitting molecules, thereby ensuring the thermodynamic stability of the material and providing a photon upconversion material suitable for long-term use. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a thermodynamic equilibrium phase diagram for a two-molecule mixture system, sometimes called a finitely miscible eutectic system, which represents the solid solution phase utilized in the present invention. [Diagram 2] FIG. 1 is a diagram illustrating the principle of optical UC. [Diagram 3] FIG. 1 is a diagram illustrating how a triplet state (T1), which is one type of excited state, i.e., triplet excitons, move randomly in a crystal of a luminescent molecule. [Figure 4] FIG. 2 is a schematic diagram illustrating a luminescence measurement system. [Diagram 5] 1 shows a microscope image, a polarizing microscope image, and a graph of a UC emission spectrum of the photon upconversion material of Example 1. [Figure 6] 1 shows a microscope image, a polarizing microscope image, and a graph of a UC emission spectrum of the photon upconversion material of Example 2. [Figure 7] 1 shows a microscope image, a polarizing microscope image, and a graph of a UC emission spectrum of the photon upconversion material of Example 3. [Figure 8] 1 shows a microscope image, a polarizing microscope image, and a graph of a UC emission spectrum of the photon upconversion material of Example 4. [Figure 9]1 shows a microscope image, a polarizing microscope image, and a graph of a UC emission spectrum of the photon upconversion material of Comparative Example 1. [Figure 10] 1 is a graph showing a microscope image, a polarizing microscope image, and a UC emission spectrum of the photon upconversion material of Comparative Example 2. [Figure 11] 1 is a graph showing a microscope image, a polarizing microscope image, and a UC emission spectrum of the photon upconversion material of Comparative Example 3. [Figure 12] 1 is a graph showing a microscope image, a polarizing microscope image, and a UC emission spectrum of the photon upconversion material of Comparative Example 4. [Figure 13] FIG. 1 is a spectrum diagram of UC emission of Example 1 after annealing. [Figure 14] 1 is a graph showing changes in emission spectrum when excitation light is continuously irradiated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] <Photon up-conversion materials> The photon upconversion material of the present invention will now be described in detail. The photon up-conversion material uses polycyclic aromatic π-conjugated molecules that have high optical activity in the visible to near-infrared range, and contains particles that include organic light-emitting molecules and organic sensitizing molecules. The particles form single crystals or polycrystals consisting of multiple aggregates of the single crystals, and are a solid solution in which the organic sensitizing molecules (hereinafter sometimes referred to as "sensitizing molecules") are dissolved in the mother crystal domain of the organic luminescent molecules (hereinafter sometimes referred to as "luminescent molecules").

[0019] The photon up-conversion material is composed of a solid solution of the sensitizer molecules in the host crystal of the luminescent molecules, and the sensitizer molecules are dispersed in the host crystal of the luminescent molecules without agglomeration. This solid solution corresponds to the α phase, which is defined as a thermodynamically stable phase in the thermodynamic equilibrium phase diagram shown in Figure 1. The photon upconversion material of the present invention, which is composed of such an α-phase solid solution, has excellent stability desired for long-term use, and can perform photo-induced UC stably over a long period of time.

[0020] In the present invention, the term "sensitizer molecules are dissolved in a solid solution in a mother crystal of luminescent molecules" means that no aggregates or aggregated regions consisting of only sensitizer molecules are observed in the material by observation with an optical microscope, and does not mean, for example, that there are absolutely no locations in the mother crystal of luminescent molecules where two sensitizer molecules are adjacent to each other.

[0021] In such a photon upconversion material, the content of the sensitizing molecule is preferably less than the solid solubility limit in the light-emitting molecule at 100°C.

[0022] The solid solubility limit of the sensitizing molecule in the crystal phase of the luminescent molecule can be known from a thermodynamic equilibrium phase diagram of a two-molecule mixture system, such as that shown diagrammatically in FIG. 1, for the luminescent molecule and sensitizing molecule used. When the molar ratio of the luminescent molecule to the sensitizing molecule is within a range in which the sensitizing molecule forms a solid-solution phase in the mother crystal of the luminescent molecule, the solid-solution state can be maintained for a long period of time. The thermodynamic equilibrium phase diagram of a mixture of two molecules can be prepared according to an experimental method for preparing a phase diagram that is generally used by those skilled in the art.

[0023] For example, if the photon upconversion material is one in which the luminescent molecules and the sensitizer molecules do not phase separate but maintain a solid-solution state when kept at 100°C for three days, photo-UC can be performed for a long period of time in many practical applications.

[0024] In addition, the photon upconversion material of the present invention has the feature that a small amount of sensitizer molecules are dissolved in the crystalline phase of the luminescent molecule, which is the parent phase. Therefore, each sensitizer molecule is surrounded by luminescent molecules, and during photo-UC, triplet energy transfer (hereinafter sometimes referred to as "TET") from the sensitizer molecules to the luminescent molecules is carried out with high efficiency, thereby reducing energy loss during the TET process.

[0025] The process of photo-UC described above is as follows: As shown in Figure 2, first, the sensitized molecule in the ground state (S0) absorbs the incident light, which is long-wavelength light, and goes into a singlet excited state (S1), and then immediately goes into a lower-energy triplet state (T1) through intersystem crossing, and then TET occurs from this sensitized molecule to the luminescent molecule in the ground state (S0).

[0026] When two luminescent molecules in the triplet state (T1) approach each other, one of the organic luminescent molecules transitions to the higher energy singlet excited state (S1), while the other organic luminescent molecule falls to the ground state (S0), causing triplet-triplet annihilation (hereinafter sometimes referred to as "TTA"). As a result, the organic luminescent molecule in the singlet excited state (S1) emits a photon as it returns to the ground state (S0). Through the above process, the absorbed long-wavelength light is converted to short-wavelength light.

[0027] The organic solid consisting of fine crystalline regions described in Non-Patent Document 1 differs from isolated solute molecules that dissolve in a solvent and move around in a Brownian motion in that the organic sensitizer molecules and the organic luminescent molecules are fixed in close proximity to each other. This has the advantage that TET does not require collisions between the organic sensitizer molecules and the organic luminescent molecules through motion, enabling rapid and efficient TET.

[0028] However, the results shown in Non-Patent Document 1 suggest that some of the organic sensitizer molecules are microscopically aggregated in the organic solid phase mainly composed of organic light-emitting molecules, and in such aggregates, TET to the organic light-emitting molecules is not efficiently carried out, and there is a possibility that energy transfer within the aggregate is accompanied by a loss of excitation energy. In addition, phosphorescence (light with a longer wavelength than the absorbed light) is generated from the sensitizer molecules excited to the triplet state (T1), making further highly efficient conversion difficult.

[0029] In the photon upconversion material of the present invention, the sensitizer molecules are dissolved in the host crystal of the luminescent molecules, and the luminescent molecules and the sensitizer molecules are close to each other, but the sensitizer molecules are not adjacent to each other. Therefore, the energy of the sensitizer molecules excited to the triplet state (T1) is transferred from the sensitizer molecules to the luminescent molecules without transferring between the sensitizer molecules, and the energy is prevented from being dissipated as phosphorescence.

[0030] The shape of the single crystals constituting the particles of the photon upconversion material may be any shape, for example, a regular tetrahedron, an ellipsoid, a pyramid, or other polyhedron, as well as a needle, branch, net, scale, or other shape, but it is preferable that the longest dimension among the vertical, horizontal, and thickness directions is 1 μm or more.

[0031] If the size of the single crystal is 1 μm or more, more efficient optical UC is possible. As shown in Figure 2, in optical UC, TET must be followed by TTA. In the crystal, as shown in Figure 3, the excitation energy of an emissive molecule in the triplet state (T1) is transferred to an adjacent emissive molecule in the ground state (S0), and the excited triplet state (T1), i.e., the position of the triplet exciton, moves randomly within the crystal, resulting in two triplet excitons meeting each other to produce TTA.

[0032] The photon upconversion material of the present invention is formed as a single crystal, and the molecules are closely spaced and regularly aligned, allowing triplet excitons to move randomly within the crystal.

[0033] However, in the case of a single crystal with excessively small dimensions, there is a high possibility that each exciton will encounter the crystal surface before meeting each other, and the crystal surface is a place where the periodicity is interrupted and can function as a type of defect, causing the exciton energy transfer between organic light-emitting molecules to be interrupted there, resulting in the exciton being deactivated.

[0034] Previous reports have shown that the diffusion distance of triplet excitons in organic molecular crystals is on the order of several tens to several hundreds of nm. Therefore, by making the dimensions of the above single crystal 1 μm or more, the exciton energy transfer between light-emitting molecules is less likely to be interrupted, increasing the probability of TTA occurring, and thus enabling the efficient optical UC.

[0035] As described above, the probability of TTA occurring increases with increasing size of the single crystal, so the lower limit of the size of the single crystal is preferably 1 μm, more preferably 10 μm or more, even more preferably 20 μm or more, and most preferably 50 μm or more. Furthermore, there is no particular upper limit to the size of the single crystal, but based on the experimental results of the inventors to date, for example, growing the crystal to 5000 μm or more can easily cause the crystal structure to become disordered, so the size is preferably 4000 μm or less, more preferably 3000 μm or less, and even more preferably 2000 μm or less.

[0036] The particle size of the photon upconversion material varies greatly depending on the application. For example, when used as a paint, the particle size is preferably 1 μm to 5 μm from the viewpoint of dispersibility in the coating resin.

[0037] As the organic light-emitting molecules, polycyclic aromatic π-conjugated molecules conventionally known as photon up-conversion materials can be used, and anthracene-based organic light-emitting molecules and perylene-based organic light-emitting molecules can be used.

[0038] Examples of the anthracene-based organic luminescent molecules include luminescent molecules having a dioxaborolane group, a phenyl group, a hydrocarbon group, and any combination thereof. Specific examples of the luminescent molecules include those represented by the following structural formulas (1) to (3).

[0039] [ka]

[0040] [ka]

[0041] [ka]

[0042] Moreover, the perylene-based organic luminescent molecule may be represented by the following structural formula (4).

[0043] [ka]

[0044] As the organic sensitizer molecule, polycyclic aromatic π-conjugated molecules conventionally known as photon upconversion materials can be used. For example, organic sensitizer molecules represented by the following structural formulas (5) and (6) can be used.

[0045] [ka]

[0046] [ka]

[0047] The molar ratio of the luminescent molecules to the sensitizer molecules (sensitizer molecules / luminescent molecules) is 1 / 10, depending on the types of luminescent molecules and sensitizer molecules and their combination. 6 1 / 10 3 It is preferable that it is less than 1000 .mu.m.

[0048] From the inventor's experience when carrying out the following examples, 6 At less than 1 / 10, there are few sensitizing molecules, making it difficult to perform meaningful photoUC. 3 If the concentration exceeds this range, the solubility limit may be exceeded, which may lead to the formation of aggregates of the sensitizer molecule, or the UC efficiency may decrease due to re-collisions of triplet excitons with the sensitizer molecule, which may be unsuitable.

[0049] <Method of manufacturing photon upconversion materials> The method for producing a photon up-conversion material of the present invention is a method for producing the above-mentioned photon up-conversion material.

[0050] The above-mentioned manufacturing method includes a precipitation step of dissolving organic light-emitting molecules and organic sensitizer molecules in a solvent, and then precipitating crystals of a solid solution in which the organic sensitizer molecules are solid-dissolved in a mother crystal of the organic light-emitting molecules. The single crystal precipitated in the above precipitation step grows and forms an aggregate with a plurality of adjacent single crystals, resulting in a polycrystalline body.

[0051] The precipitation step may include a recrystallization method, an evaporation diffusion method, and a reprecipitation method. These methods can gently change the environment during the precipitation process to precipitate crystals, and can form solid solution crystals with large particle size while dissolving the organic sensitizing molecules in the host crystals of the organic light-emitting molecules without agglomeration.

[0052] In addition, the molar ratio of the luminescent molecules to the sensitizing molecules in the solid solution, i.e., the amount of the sensitizing molecules dissolved in the mother crystal of the luminescent molecules, can be adjusted by the type of solvent in which they are dissolved and the concentrations of the luminescent molecules and the sensitizing molecules.

[0053] Specifically, if the concentration of the sensitizing molecule in the solvent is the same, the amount of the sensitizing molecule dissolved in the mother crystal of the luminescent molecule decreases when a solvent with high solubility for the sensitizing molecule is used, and the amount of solid solution increases when a solvent with low solubility for the sensitizing molecule is used. Also, if the solubility of the sensitizing molecule in the solvent is the same, the amount of solid solution of the luminescent molecule in the mother crystal increases when the concentration of the sensitizing molecule in the solvent is high, and the amount of solid solution decreases when the concentration of the sensitizing molecule is low. However, when selecting a solvent and adjusting the concentrations of the luminescent molecules and the sensitizing molecules, care must be taken to prevent the sensitizing molecules from precipitating independently.

[0054] Examples of the solvent that dissolves the organic luminescent molecules and the organic sensitizing molecules include toluene, ethylbenzene, cyclohexane, and acetonitrile. In the evaporation diffusion method and the reprecipitation method, ethanol, hexane, etc. can be used as a poor solvent for precipitating the organic light-emitting molecules and the organic sensitizing molecules dissolved in the solvent. EXAMPLES

[0055] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

[0056] [Example 1] In 3.1 mL of toluene, 0.68 mg (3 × 10 -4 M) and 20 mg (1.5 × 10 -2 M) was added and heated to 100°C until completely dissolved, then the mixture was gradually cooled to room temperature and left to stand for about a day to obtain a photon upconversion material.

[0057] In addition, the solvent was replaced with 3.1 mL of ethylbenzene to prepare the photon upconversion material, and 0.11 mg (5 × 10 -5 M) and 15 mg (1.2 × 10 -2 M) When the photon upconversion material was prepared by dissolving the toluene, the photon upconversion material obtained was similar to the photon upconversion material prepared using the toluene described above.

[0058] [Example 2] Add 0.11 mg (5 × 10) of the organic sensitizer molecule of formula (5) to 0.3 mL of toluene. -4 M) and 5 mg (5 × 10 -2The open container containing this solution was placed in a closed container containing 2 mL of a poor solvent (ethanol) for organic light-emitting molecules for 1 to 2 weeks, and the toluene and poor solvent were mixed through the gas phase to obtain a photon upconversion material.

[0059] [Example 3] Add 0.12 mg (5 × 10) of the organic sensitizer molecule of formula (5) to 0.32 mL of toluene. -4 M) and 12 mg (1 × 10 -1 A photon upconversion material was obtained in the same manner as in Example 2, except that M) was dissolved.

[0060] [Example 4] Add 0.09 mg (2 × 10) of the organic sensitizer molecule of formula (6) to 0.48 mL of toluene. -4 M) and 2.4 mg (2 × 10 -2 A photon upconversion material was obtained in the same manner as in Example 1, except that M) was dissolved.

[0061] [Comparative Example 1] Concentration is 5×10 -4 4 μL of the toluene solution of the organic sensitizer molecule of structural formula (5) M was dropped into an aluminum cell (open container) attached to a differential scanning calorimeter, and the toluene was evaporated by vacuum heating at 60° C. for 1 hour, and the organic sensitizer molecule was attached to the wall of the aluminum cell. 3.4 mg of the organic luminescent molecule of structural formula (3) (organic sensitizer molecule / organic luminescent molecule: 1 / 5000) was added to this aluminum cell and sealed. This was heated at a rate of 10°C / min, and the temperature was raised by 15°C from the temperature at which a melting signal of the organic luminescent molecule was obtained by differential thermal analysis, and the temperature was maintained for 5 minutes to mix the luminescent molecule and the sensitizer molecule. The mixture was then cooled at a rate of 5°C / min, and the molecules were solidified to obtain the photon upconversion material.

[0062] [Comparative Example 2] A photon upconversion material was obtained in the same manner as in Comparative Example 1, except that after heating and maintaining the temperature, the material was immersed in liquid nitrogen for 5 minutes to rapidly cool it.

[0063] [Comparative Example 3] A photon up-conversion material was obtained in the same manner as in Comparative Example 1, except that 3.9 mg of the organic luminescent molecule of structural formula (2) was used.

[0064] [Comparative Example 4] A photon upconversion material was obtained in the same manner as in Comparative Example 3, except that after heating and maintaining the temperature, the material was immersed in liquid nitrogen for 5 minutes to rapidly cool it.

[0065] <Evaluation> The photon upconversion materials of Examples 1 to 4 and Comparative Examples 1 to 4 were evaluated by the following methods. The evaluation results are shown in Table 1.

[0066] (Emission spectrum) Using the luminescence measurement system shown in Figure 4, the photon upconversion material was irradiated with a specific monochromatic light (excitation light), and the luminescence intensity ratio between UC luminescence and phosphorescence was measured. The emission spectrum diagrams of Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Figs. 5 to 12, respectively.

[0067] In addition, the UC luminescence was measured after annealing at 100° C. for 3 days. The spectrum of UC emission of Example 1 after annealing is shown in FIG.

[0068] (Photon upconversion material form) Polarized light microscopy images of the photon upconversion material particles were used to observe the morphology, crystalline domain size, and the presence or absence of aggregates of organic sensitizer molecules within the crystalline domains. Microscopic images and polarizing microscope images of Examples 1 to 4 and Comparative Examples 1 to 4 are shown in FIGS. 5 to 12 together with their respective emission spectrum diagrams.

[0069] It is seen that the photon up-conversion materials of Examples 1 to 4 have no aggregates of the organic sensitizer molecules, and the organic sensitizer molecules are in a solid solution in the organic light-emitting molecules.

[0070] (molar ratio of organic sensitizer molecules to organic luminescent molecules) The photon upconversion material was dissolved in acetonitrile, and the signal obtained by high performance liquid chromatography (HPLC) was compared with a calibration curve to estimate the molar ratio of organic sensitizer molecules to organic emissive molecules.

[0071] [Table 1]

[0072] From Table 1 and Figures 5 to 8, it can be seen that the phosphorescence spectrum is hardly detected in the photon upconversion material of the present invention, and triplet energy is transferred from the organic sensitizer molecule to the organic light-emitting molecule with high efficiency. Furthermore, from Table 1 and Figures 9 to 12, it can be seen that although optical UC occurs in the sample in which the organic sensitizer molecules are aggregated, phosphorescence occurs, which indicates that part of the excitation energy of the organic sensitizer molecules (is not transferred to the light-emitting molecules) does not contribute to the UC emission.

[0073] From the comparison of the emission spectra before and after annealing in FIG. 13, it can be seen that the photon upconversion material of the present invention does not change in emission spectrum upon annealing, is thermodynamically stable, and can undergo photo-UC for a long period of time.

[0074] FIG. 14 shows the change in emission spectrum when the photon upconversion material of the present invention (Example 3) and the amorphous sample (Comparative Example 3) were continuously irradiated with the excitation light (monochromatic light) shown in Table 1 for several minutes. The photon upconversion material of the present invention stably generates UC light with high emission intensity, whereas in the comparative example, strong UC light was generated at the beginning of irradiation with excitation light, but the intensity quickly decreased and the phosphorescence intensity increased, and the intensity ratio of the UC light changed simply by irradiating light. These results show that the photon upconversion material of the present invention is stable under long-term light irradiation, whereas the glass sample of the comparative example is unstable.

Claims

1. A photon up-conversion material containing particles including organic light-emitting molecules and organic sensitizer molecules, The particles form single crystals or polycrystals formed by assembling a plurality of the single crystals, a solid solution in which the organic sensitizing molecule is dissolved in a host crystal of the organic light-emitting molecule, A photon upconversion material, characterized in that the organic light-emitting molecule is an anthracene-based organic light-emitting molecule having a dioxaborane group and / or an organic light-emitting molecule represented by the following structural formula (3) and / or an organic light-emitting molecule represented by the following structural formula (4). 【Chemistry 1】 【Chemistry 2】

2. The photon upconversion material as described in claim 1, characterized in that the anthracene-based organic luminescent molecule having the dioxaborane group is an organic luminescent molecule represented by the following structural formula (1) and / or an organic luminescent molecule represented by the following structural formula (2): 【Chemistry 3】 【Chemistry 4】

3. A photon upconversion material as described in claim 1, characterized in that the longest dimension of the single crystal in the vertical, horizontal and thickness directions is 1 μm or more.

4. A photon upconversion material as described in claim 1, characterized in that when the particles are maintained at 100°C for three days, the organic luminescent molecules and the organic sensitizer molecules maintain a solid solution state.

5. A method for producing the photon up-conversion material according to any one of claims 1 to 4, which contains particles comprising organic light-emitting molecules and organic sensitizer molecules, comprising: A method for producing a photon upconversion material, comprising a precipitation step of precipitating from a solution in which the organic luminescent molecules and the organic sensitizer molecules are dissolved, particles that form a single crystal that is a solid solution in which the organic sensitizer molecules are solid-dissolved in a mother crystal of the organic luminescent molecules, or particles that form a polycrystal in which a plurality of such single crystals are aggregated.

6. A method for producing a photon upconversion material as described in claim 5, characterized in that the particle precipitating process uses at least one method selected from the group consisting of a recrystallization method, an evaporation diffusion method, and a reprecipitation method.

Images