Core-shell particle, method of producing core shell particle, and film

Abstract

An object of the present invention is to provide a core shell particle having high luminous efficacy and excellent durability; a method of producing the same; and a film formed of the core shell particle. The core shell particle of the present invention includes: a core which contains a Group III element and a Group V element; a first shell which covers at least a part of a surface of the core; and a second shell which covers at least a part of the first shell, in which the core shell particle includes a protective layer containing a metal oxide that covers at least a part of the second shell, and at least a part of a surface of the protective layer includes coordination molecules.

Claims

1. A core shell particle comprising: a core which contains a Group III element and a Group V element; a first shell which covers at least a part of a surface of the core, wherein the first shell is a Group III-V semiconductor which contains Ga as a Group III element and P as a Group V element; and a second shell which covers at least a part of the first shell, wherein the core shell particle includes a protective layer containing a metal oxide that covers at least a part of the second shell, at least a part of a surface of the protective layer includes coordination molecules, and among the core, the first shell, and the second shell, a band gap of the core is the smallest, and the core and the first shell respectively have a type 1 band structure.

2. The core shell particle according to claim 1, wherein the metal oxide is an oxide containing a Group 12 or Group 13 metal element in the periodic table.

3. The core shell particle according to claim 1, wherein the metal oxide is an oxide containing at least one metal element selected from the group consisting of zinc, indium, and gallium.

4. The core shell particle according to claim 1, wherein the metal oxide is an oxide containing indium.

5. The core shell particle according to claim 1, wherein the Group III element contained in the core is In, and the Group V element contained in the core is any of P, N, or As.

6. The core shell particle according to claim 1, wherein the Group III element contained in the core is In, and the Group V element contained in the core is P.

7. The core shell particle according to claim 1, wherein the core further contains a Group II element.

8. The core shell particle according to claim 7, wherein the Group II element contained in the core is Zn.

9. The core shell particle according to claim 1, wherein the second shell is a Group II-VI semiconductor which contains a Group II element and a Group VI element or a Group III-V semiconductor which contains a Group III element and a Group V element.

10. The core shell particle according to claim 9, wherein the second shell is the Group II-VI semiconductor, the Group II element is Zn, and the Group VI element is S.

11. The core shell particle according to claim 1, wherein the core, the first shell, and the second shell respectively have a crystal system having a zinc blende structure.

12. A method of producing a core shell particle for synthesizing the core shell particle according to claim 1, the method comprising: a first step of heating and stirring a solution obtained by adding a Group III raw material which contains a Group III element to a solvent containing coordination molecules; a second step of forming a core by adding a Group V raw material which contains a Group V element to the solution after the first step; a third step of forming a first shell by adding a raw material of the first shell to the solution after the second step, wherein the first shell is a Group III-V semiconductor which contains Ga as a Group III element and P as a Group V element; a fourth step of adding a raw material of a second shell to the solution after the third step to form the second shell and synthesizing a core shell particle; and a fifth step of adding a metal raw material to the solution after the fourth step and heating the solution.

13. The method of producing a core shell particle according to claim 12, wherein a thiol compound is further added in the fifth step.

14. The method of producing a core shell particle according to claim 12, wherein the metal raw material is a fatty acid metal salt.

15. The method of producing a core shell particle according to claim 12, wherein the metal raw material is a carboxylate of indium.

16. The method of producing a core shell particle according to claim 12, wherein the heating temperature in the fifth step is in a range of 140 C. to 220 C.

17. The method of producing a core shell particle according to claim 12, wherein the heating temperature in the fifth step is in a range of 160 C. to 220 C.

18. A film which contains the core shell particle according to claim 1.

Description

EXAMPLES

(1) Hereinafter, the present invention will be described in more detail based on examples. The materials, the use amounts, the ratios, the treatment contents, and the treatment procedures described in the following examples can be changed as appropriate within the range not departing from the gist of the present invention. Therefore, the scope of the present invention should not be limitatively interpreted by the following examples.

Examples 1 to 4

(2) 32 mL of octadecene, 140 mg (0.48 mmol) of indium acetate, 48 mg (0.26 mmol) of zinc acetate, and 485 mg (1.89 mmol) of palmitic acid were added to a flask, heated and stirred at 110 C. in a vacuum, and degassed while the raw materials were sufficiently dissolved.

(3) Next, the flask was heated to 300 C. in a nitrogen flow, and 0.18 mmol of tristrimethylsilylphosphine dissolved in approximately 4 mL of octadecene was added to the flask in a case where the temperature of the solution was stabilized. Thereafter, the flask was held for 120 minutes in a state in which the temperature of the solution was set to 230 C. It was confirmed that the solution was colored red and particles (cores) were formed.

(4) Next, 30 mg (0.18 mmol) of gallium chloride and 188 L (0.6 mmol) of oleic acid which were dissolved in 8 mL of octadecene were added to the solution in a state in which the solution was heated to 200 C., and the solution was further heated for approximately 1 hour, thereby obtaining a dispersion liquid of a core shell particle precursor including InP (core) doped with Zn and GaP (first shell).

(5) Next, the dispersion liquid was cooled to room temperature, 0.93 mmol of zinc oleate was added thereto, the dispersion liquid was heated to 240 C., and the state thereof was maintained for approximately 4 hours. Next, 0.55 mL (2.3 mmol) of dodecanethiol was added to the dispersion liquid and the state of the resulting dispersion liquid was maintained for 2 hours, thereby obtaining a dispersion liquid of core shell particles including InP (core) doped with Zn, GaP (first shell) covering the surface of the core, and ZnS (second shell) covering the surface of the first shell.

(6) Next, the obtained dispersion liquid was cooled to the heating temperature (heating temperature *1) in the fifth step listed in Table 1, 1 mL of dodecanethiol was added thereto, 0.8 mmol of zinc stearate was added thereto, and the state of the resulting dispersion liquid was maintained for approximately 4 hours.

(7) Thereafter, the dispersion liquid was held, cooled, or heated to the heating temperature (heating temperature *2) in the fifth step listed in Table 1, 2.16 mmol of indium myristate (a solution prepared by dissolution in 10 mL of octadecene in advance) was added thereto, and the state thereof was held for 2 hours. Next, the dispersion liquid was cooled to room temperature, acetone was added thereto, and centrifugation was performed on the dispersion liquid so that particles were precipitated. The supernatant was disposed of and the resultant was dispersed in a toluene solvent.

(8) In this manner, a toluene dispersion liquid of core shell particles including InP (core) doped with Zn, GaP (first shell) covering the surface of the core, ZnS (second shell) covering the surface of the first shell, and indium oxide (In.sub.2O.sub.3) in a part of the surface of the second shell was obtained.

Example 5

(9) A toluene dispersion liquid of core shell particles including InP (core) doped with Zn, GaP (first shell) covering the surface of the core, ZnS (second shell) covering the surface of the first shell, and indium oxide (In.sub.2O.sub.3) in a part of the surface of the second shell was obtained according to the same method as that in Example 1 except that indium palmitate was added in place of indium myristate.

Example 6

(10) A toluene dispersion liquid of core shell particles including InP (core) doped with Zn, GaP (first shell) covering the surface of the core, ZnS (second shell) covering the surface of the first shell, and indium oxide (In.sub.2O.sub.3) in a part of the surface of the second shell was obtained according to the same method as that in Example 1 except that octanethiol was added in place of dodecanethiol.

Examples 7 to 9

(11) A toluene dispersion liquid of core shell particles including InP (core) doped with Zn, GaP (first shell) covering the surface of the core, ZnS (second shell) covering the surface of the first shell, and indium oxide (In.sub.2O.sub.3) in a part of the surface of the second shell was obtained according to the same method as that in Example 1 except that the presence or absence of a thiol compound and a zinc-based metal material were changed as listed in Table 1.

Comparative Example 1

(12) 32 mL of octadecene, 140 mg (0.48 mmol) of indium acetate, 48 mg (0.26 mmol) of zinc acetate, and 364 mg (1.44 mmol) of palmitic acid were added to a flask, heated and stirred at 110 C. in a vacuum, and degassed for 90 minutes while the raw materials were sufficiently dissolved.

(13) Next, the flask was heated to 300 C. in a nitrogen flow, and 0.24 mmol of tristrimethylsilylphosphine dissolved in approximately 4 mL of octadecene was added to the flask in a case where the temperature of the solution was stabilized. Thereafter, the flask was heated for 120 minutes in a state in which the temperature of the solution was set to 230 C. It was confirmed that the solution was colored red and particles (cores) were formed.

(14) Next, 20 mg (0.12 mmol) of gallium chloride and 125 L (0.4 mmol) of oleic acid which were dissolved in 8 mL of octadecene were added to the solution in a state in which the solution was heated to 200 C., and the solution was further heated for approximately 1 hour, thereby obtaining a dispersion liquid of a core shell particle precursor including InP (core) doped with Zn and GaP (first shell).

(15) Next, the dispersion liquid was cooled to room temperature, 220 mg (1.2 mmol) of zinc acetate was added thereto, the dispersion liquid was heated to 230 C., and the state of the dispersion liquid was maintained for 4 hours. Subsequently, 479 L (2.0 mmol) of dodecane thiol was added thereto, and the state of the solution was maintained at 230 C. for 2 hours. The obtained dispersion liquid was cooled to room temperature, ethanol was added thereto, and centrifugation was performed on the dispersion liquid so that particles were precipitated. The supernatant was disposed of and the resultant was dispersed in a toluene solvent.

(16) In this manner, a toluene dispersion liquid of core shell particles including InP (core) doped with Zn, GaP (first shell) covering the surface of the core, and ZnS (second shell) covering the surface of the first shell was obtained.

(17) In regard to the presence of indium oxide (In.sub.2O.sub.3) as a metal oxide in the core shell particles contained in each of the prepared dispersion liquids, the detection intensity (In.sub.3O.sup.+/.sup.113In.sup.+) of In.sub.3O.sup.+ with respect to .sup.113In.sup.+ detected under the above-described measurement conditions was calculated, and it was determined that the metal oxide was contained in the core shell particles in a case where the detection intensity of the sample was 0.05 or greater. The results are listed in Table 1.

(18) Further, the results obtained by calculating the detection intensities (In.sub.3O.sup.+/.sup.113In.sup.+) of Examples 1, 7, and 8 and Comparative Example 1 are listed in Table 1.

(19) [Luminous Efficacy]

(20) <Initial Stage>

(21) The emission intensity of each of the prepared dispersion liquids was measured using an absolute PL quantum yield spectrometer C11347 (manufactured by Hamamatsu Photonics K.K.) by adjusting the concentration thereof such that the absorbance at an excitation wavelength of 450 nm was set to 0.04. Further, the luminous efficacy was calculated by performing relative comparison with a quantum dot sample whose luminous efficacy was known. The obtained luminous efficacy was calculated as a ratio of the number of emission photons to the number of absorption photons from excitation light. The results are listed in Table 1.

(22) <After Irradiation with Ultraviolet Rays>

(23) Each of the prepared dispersion liquids was irradiated with ultraviolet rays by fixing a mercury lamp (wavelength of 365 nm) at a position of 1 mW/cm.sup.2 in the atmosphere. Further, the time for irradiating each solution with ultraviolet rays was set to 105 minutes and the irradiation amount was set to 6.3 J/cm.sup.2.

(24) Thereafter, the luminous efficacy was measured in the same manner as that for the initial stage. The results are listed in Table 1.

(25) TABLE-US-00001 TABLE 1 Fifth step Presence or Luminous efficacy (%) Heating Metal raw Heating Metal raw absence of After irradiation temperature Thiol material temperature material metal oxide TOF-SIMS Initial with ultraviolet *1 compound (zinc-based) *2 (indium-based) (In.sub.2O.sub.3) In.sub.3O.sup.+/.sup.113In.sup.+ stage rays Example 1 180 C. Dodecanethiol Zinc stearate 180 C. Indium myristate Present 0.07 79.5 76.5 Example 2 180 C. Dodecanethiol Zinc stearate 140 C. Indium myristate Present 78.8 74.9 Example 3 180 C. Dodecanethiol Zinc stearate 220 C. Indium myristate Present 80.1 76.3 Example 4 180 C. Dodecanethiol Zinc stearate 240 C. Indium myristate Present 79.2 74.9 Example 5 180 C. Dodecanethiol Zinc stearate 180 C. Indium palmitate Present 78.8 75.6 Example 6 180 C. Octanethiol Zinc stearate 180 C. Indium myristate Present 79.0 75.9 Example 7 180 C. None None 180 C. Indium myristate Present 0.22 70.5 65.3 Example 8 180 C. Dodecanethiol None 180 C. Indium myristate Present 0.12 75.9 71.8 Example 9 180 C. None Zinc stearate 180 C. Indium myristate Present 74.6 70.2 Comparative Absent 0.03 53.0 29.6 Example 1 *1 heating time during addition of thiol compound *2 heating temperature during addition of indium-based metal raw material

(26) Based on the results listed in Table 1, it was understood that the luminous efficacy was decreased, the luminous efficacy after the irradiation with ultraviolet rays was decreased by 20% or greater, and the durability was low in a case where the fifth step was not performed and the metal oxide protective layer was not formed on the surface of the core shell particle (Comparative Example 1).

(27) Further, it was understood the luminous efficacy was high, the luminous efficacy after the irradiation with ultraviolet rays was also high, and the durability excellent in a case where a metal raw material was added in the fifth step to form a metal oxide protective layer on the surface of the core shell particle (Examples 1 to 9).

(28) Particularly, based on the comparison between Examples 1 and 8, it was understood that the luminous efficacy was increased and the durability was improved in a case where a zinc-based metal raw material was used together with an indium-based metal raw material.

(29) Further, based on the comparison between Examples 1 and 9, it was understood that the luminous efficacy was increased and the durability was improved in a case where a thiol compound was used in the fifth step.