WO2021039527A1

WO2021039527A1 - Laser element, laser oscillation method, and method for improving laser oscillation characteristics

Info

Publication number: WO2021039527A1
Application number: PCT/JP2020/031249
Authority: WO
Inventors: センコウシン; 安達　千波矢; 敏則松島
Original assignee: 国立大学法人九州大学
Priority date: 2019-08-27
Filing date: 2020-08-19
Publication date: 2021-03-04
Also published as: TW202124400A; JPWO2021039527A1

Abstract

This laser element containing a pseudo two-dimensional perovskite is characterized by having a quencher for quenching the excited triplet of an inorganic component constituting the pseudo two-dimensional perovskite. The quencher may use: an organic component that constitutes the pseudo two-dimensional perovskite and has an excited triplet energy level lower than the excited triplet energy level of an inorganic component; oxygen; air, etc.

Description

Laser element, laser oscillation method and method for improving laser oscillation characteristics

The present invention relates to a laser element using an organic-inorganic perovskite, a laser oscillation method, and a method for improving laser oscillation characteristics.

Organic-inorganic perovskite is composed of monovalent cations such as organic cations, ^{divalent metal ions such as Sn 2+} and Pb ²⁺ , and halogen ions, and these ions have the same crystal structure as perovskite (perovskite). It is an ionic compound regularly arranged so as to form a perovskite type structure), and three-dimensional perovskite, two-dimensional perovskite, and pseudo-two-dimensional perovskite, which are roughly classified according to the number of dimensions of the crystal arrangement space, are known. These organic-inorganic perovskites have the semiconductor characteristics of inorganic substances, the flexibility of organic substances, and the variety of molecular designs. In addition, the raw material cost is low, and film formation by the solution coating method is possible, which is advantageous in terms of cost reduction. Therefore, research and development are being actively carried out toward the realization of various elements using the material.
For example, research is being vigorously pursued to utilize organic-inorganic perovskite as the active layer of laser elements, and in such perovskite, spontaneous emission (ASE) oscillation and laser oscillation at low threshold values are performed. It has been realized. Furthermore, it has been reported that continuous wave (CW) laser oscillation in the near infrared region was observed at 140 K or room temperature for a short time of 250 seconds for _{CH 3} NH ₃ PbI ₃ , which is a three-dimensional perovskite (3D perovskite). See Non-Patent Document 1).

By the way, as described above, pseudo-two-dimensional perovskite is also known as an organic-inorganic perovskite. Pseudo-two-dimensional perovskite is a perovskite layer in which two or more octahedral two-dimensional array structures constituting a perovskite-type crystal are laminated via a monovalent cation of A site on both sides of a perovskite layer, for example, more than methylammonium. It has a structure in which a layer of organic cations with a large number of carbon atoms (organic layer) is arranged, and has advantageous features as a laser material such as high stability, large exciton binding energy, and a natural quantum well structure. It has been confirmed.
However, it is known that when a device having a pseudo-two-dimensional perovskite as an active layer is irradiated with continuous pulse excitation light, a laser death phenomenon occurs in which laser oscillation stops in the middle. Has not been clarified yet. Therefore, although the pseudo two-dimensional perovskite has the above-mentioned excellent characteristics, the actual situation is that a laser element using the material as an active layer has not been realized so far.

Under such circumstances, the present inventors have made diligent studies for the purpose of providing a perovskite laser element having better laser oscillation characteristics than before.

In order to solve the above problems, the present inventors conducted a study to elucidate the generation mechanism of the laser death phenomenon, and found that long-lived excited triplets generated in the inorganic layer accumulated and the singlet-triplet disappeared. Was found to be the main cause of the laser death phenomenon. Then, by introducing or contacting a quencher that quenches the excited triplet of the inorganic component into the pseudo-two-dimensional perovskite, it is possible to obtain the knowledge that the laser death phenomenon is suppressed and the perovskite laser element having excellent laser oscillation characteristics is realized. I arrived. The present invention has been proposed based on these findings, and specifically has the following configuration.

[1] A laser device containing a pseudo two-dimensional perovskite, which has a quencher for quenching an excited triplet of an inorganic component constituting the pseudo two-dimensional perovskite.
[2] The quencher is an organic component constituting the pseudo two-dimensional perovskite, and the excited triplet energy level of the organic component is the excited triplet energy level of the inorganic component constituting the pseudo two-dimensional perovskite. The laser element according to [1], which is lower than.
[3] The laser element according to [2], wherein the excited triplet energy level of the organic component is 0.10 eV or more lower than the excited triplet energy level of the inorganic component constituting the pseudo two-dimensional perovskite.
[4] The laser device according to [2], wherein the organic component of the quencher is a substituted or unsubstituted naphthylalkylammonium.
[5] The laser device according to [1], wherein the quencher is a molecule having a basal triplet state or a composition containing a molecule having a basal triplet state.
[6] The laser device according to [1], wherein the quencher is oxygen that comes into contact with an inorganic component constituting a pseudo two-dimensional perovskite.
[7] The laser element according to [1], wherein the quencher is an atmosphere in contact with an inorganic component constituting a pseudo two-dimensional perovskite.
[8] The excited triplet energy level of the organic component constituting the pseudo two-dimensional perovskite is higher than the excited triplet energy level of the inorganic component constituting the pseudo two-dimensional perovskite, [5] to [7]. The laser element according to any one of the above items.
[9] The pseudo two-dimensional perovskite comprises a compound represented by the following general formula (10).
R ₂ A _n-1 B _n X _{3n + 1} (10)
[In the general formula (10), R represents a monovalent organic cation, A represents a monovalent cation, B represents a divalent metal ion, and X represents a halogen ion. n is an integer of 2 or more. ]
The laser device according to [1], wherein the inorganic layer having the composition represented by _{BX 4} of the general formula (10) constitutes the inorganic component.
[10] The quencher is an organic component composed of an organic cation represented by R in the general formula (10), and the excited triplet energy level of the organic component constitutes the pseudo-two-dimensional perovskite. The laser element according to [9], which is lower than the excited triplet energy level of the component.
[11] The organic-inorganic perovskite according to [9], wherein R of the general formula (10) is ammonium represented by the following general formula (11).
Ar (CH ₂ ) _n1 NH ₃ ⁺ (11)
[In the general formula (11), Ar represents an aromatic ring. n1 is an integer from 1 to 20. ]
[12] The laser device according to [11], wherein Ar in the general formula (11) is a benzene ring or a naphthalene ring.
[13] The laser device according to any one of [9] to [12], wherein A in the general formula (10) is formamidium or methylammonium.
[14] The laser device according to any one of [9] to [13], wherein B in the general formula (10) is Pb ^2+.
[15] The laser device according to any one of [9] to [14], wherein X in the general formula (10) is Br ^−.
[16] The compound represented by the general formula (10) is a compound represented by the following formula (A) or the following formula (B).
PEA ₂ FA _n-1 Pb _n Br _{3n + 1} equation (A)
PEA ₂ MA _n-1 Pb _n Br _{3n + 1} equation (B)
[In formulas (A) and (B), PEA represents phenylethylammonium, FA represents formamidium, and MA represents methylammonium. n is an integer of 2 or more. ]
The laser device according to [9], wherein the inorganic layer having the composition represented by _{PbBr 4} of the formula (A) or the formula (B) constitutes the inorganic component.
[17] The compound represented by the general formula (10) is a compound represented by the following formula (C) or the following formula (D).
NMA ₂ FA _n-1 Pb _n Br _{3n + 1} equation (C)
NMA ₂ MA _n-1 Pb _n Br _{3n + 1} equation (D)
[In formulas (C) and (D), NMA represents 1-naphthylmethylammonium, FA represents formamidium, and MA represents methylammonium. n is an integer of 2 or more. ]
The laser device according to [9], wherein an inorganic layer having a composition represented by _{PbBr 4} of the formula (C) or the formula (D) constitutes the inorganic component.
[18] The laser element according to any one of [1] to [17], which oscillates a laser at a temperature of 20 ° C. or higher.
[19] The laser element according to any one of [1] to [18], which has a resonator.
[20] The laser element according to [19], which is a distributed feedback type laser element.

[21] A laser oscillation method in which a laser is oscillated from the pseudo two-dimensional perovskite by quenching an excited triplet of an inorganic component constituting the pseudo two-dimensional perovskite.
[22] A method for improving laser oscillation characteristics, which improves the laser oscillation characteristics of the pseudo-two-dimensional perovskite by quenching the excited triplet of an inorganic component constituting the pseudo-two-dimensional perovskite.

According to the present invention, it is possible to realize a laser element having excellent laser oscillation characteristics. According to the laser oscillation method of the present invention, it is possible to oscillate a laser beam from a pseudo two-dimensional perovskite to obtain excellent laser oscillation characteristics. Further, according to the method for improving the laser oscillation characteristic of the present invention, the laser oscillation characteristic of the pseudo two-dimensional perovskite can be remarkably improved.

It is a schematic diagram for demonstrating the light emitting mechanism of the laser element of this invention. It is a schematic diagram which shows the state of the transfer of the excited triplet energy from a perovskite layer to an organic layer in a system (a) containing a triplet quencher NMA and a system (b) not containing a triplet quencher. It is the schematic sectional drawing which shows the layer structure example of the laser element of this invention. It is an ultraviolet-visible absorption spectrum and an emission spectrum of a P2F8 perovskite film and an N2F8 perovskite film. It is a graph which shows the excitation light intensity dependence of the peak intensity and the full width at half maximum of the emission peak observed in the P2F8 perovskite film and the N2F8 perovskite film. It is a graph which shows the change of the ASE intensity measured in various atmospheres about a P2F8 perovskite film and an N2F8 perovskite film. It is a graph which shows the excitation light intensity dependence of the laser intensity of the DFB laser element using the P2F8 perovskite film and the DFB laser element using the N2F8 perovskite film. 6 is a graph showing changes in laser intensity measured in air or a nitrogen atmosphere for a DFB laser element using a P2F8 perovskite film and a DFB laser element using an N2F8 perovskite film.

The contents of the present invention will be described in detail below. The description of the constituent elements described below may be based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. The numerical range represented by using "-" in the present specification means a range including the numerical values before and after "-" as the lower limit value and the upper limit value. Further, in the present specification, the term "main component" means the component having the highest content among the constituent components. Further, the isotope species of the hydrogen atom existing in the molecule of the compound used in the present invention is not particularly limited, and for example, all the hydrogen atoms in the molecule ^{may be 1} H, or part or all of them may be ² H. (Duterium D) may be used.

<Laser element>
The laser device of the present invention includes a pseudo two-dimensional perovskite and has a quencher for quenching the excited triplet of the inorganic component constituting the pseudo two-dimensional perovskite.
The "pseudo-two-dimensional perovskite" in the present invention is a layered perovskite having a perovskite layer and an organic cation layer (organic layer) in contact with the perovskite layer. The perovskite layer has a structure in which two or more layers of octahedral two-dimensional array structures constituting a perovskite-type crystal are laminated via a monovalent cation of A site. Here, in detail, the two-dimensional array structure is two-dimensionally arranged by sharing the vertices of the _{unit cell BX 6} in which the divalent metal ion B is arranged at the center of the octahedron having the halogen ion X as the apex. It refers to the structure BX _4. Further, the A site refers to a position corresponding to each vertex of the cubic crystal constituting the perovskite type crystal. The "inorganic component constituting the pseudo two-dimensional perovskite" in the present invention is a layer (inorganic layer) of the _{perovskite layer composed of an octahedral two-dimensional array structure BX 4 composed of halogen ion X and metal ion B.} The "excited triplet" of an inorganic component refers to a quantum state capable of causing phosphorescence to the inorganic component via the quantum state. Further, the "organic component" in the present specification means an "organic cation" constituting an organic layer.
The "quencher that quenches the excited triplet of an inorganic component" in the present invention refers to a substance having an action of reducing or eliminating the excited triplet of an inorganic component, for example, receiving energy from the excited triplet of an inorganic component. A substance that can be used can be used. The quencher may be a substance that constitutes a part of the pseudo two-dimensional perovskite, or may be a substance different from the pseudo two-dimensional perovskite. The quencher, which is another substance, is preferably capable of contacting the inorganic layer of the pseudo-two-dimensional perovskite. In the following description, "a quencher that quenches the excited triplet of an inorganic component" may be referred to as a "triplet quencher".
The laser device of the present invention includes a pseudo two-dimensional perovskite, and exhibits excellent laser oscillation characteristics by having a triplet quencher. This is presumed to be due to the following mechanism.
That is, when the present inventors investigated the emission lifetime characteristics of the pseudo-two-dimensional perovskite, long-lived light with a lifetime of nearly 1 microsecond was observed as the light derived from the excited triplet generated in the perovskite layer. From this, in the pseudo-two-dimensional perovskite, the excited triplet generated by the inorganic component of the perovskite layer and the excited triplet generated by receiving the excited triplet energy have a long lifetime, so that the excited triplet is dense. It is considered that the main cause of the laser death phenomenon is that the unilateral-triplet annihilation occurs and the inverted distribution of the excited singlet is eliminated. On the other hand, when the triplet quencher as described above is used, the accumulated excited triplet is reduced or eliminated, and the singlet-triplet annihilation is suppressed. As a result, it is presumed that the population inversion is maintained and excellent laser oscillation characteristics are obtained while the excitation energy is supplied.
Further, the laser element of the present invention can oscillate the laser for a long time at 20 ° C. or higher by effectively drawing out the above action. In addition, as other effects, the organic layer of the pseudo two-dimensional perovskite functions as a protective layer of the perovskite layer to stabilize the laser characteristics, and the pseudo two-dimensional perovskite is inexpensive, so that the manufacturing cost of the laser element is reduced. You can also get the effect of being done.
Hereinafter, each element constituting the laser element of the present invention will be described.

[Triplet Quencher]
As described above, the triplet quencher may form a part of the pseudo two-dimensional perovskite, or may be a substance different from the pseudo two-dimensional perovskite.
Hereinafter, each type of triplet quencher will be specifically described.

(Triplet quencher that forms part of a pseudo-two-dimensional perovskite)
As a triplet quencher that constitutes a part of the pseudo-two-dimensional perovskite, for example, an excited triplet of an organic component that constitutes the pseudo-two-dimensional perovskite and whose excited triplet energy level constitutes an inorganic component that constitutes the pseudo-two-dimensional perovskite. An organic cation lower than the term energy level, in other words, an organic cation having both a function as an organic component of a pseudo two-dimensional perovskite and a function of a triplet quencher can be used. By using the organic component as a triplet quencher, it is not necessary to bring another substance into contact with the triplet quencher, which facilitates the design of the laser element and influences the laser characteristics of the other substance. The effect of avoiding is obtained.
The light emission mechanism of a laser device that uses an organic component as a triplet quencher is represented by NMA ₂ FA _n-1 Pb _n Br _{3n + 1} (NMA stands for 1-naphthylmethylammonium and FA stands for formamidium). A case where a pseudo two-dimensional perovskite (hereinafter referred to as “N2F8”) of No. 8 is used will be described as an example with reference to FIGS. 1 and 2.
Here, quasi-two-dimensional perovskite by N2F8 is a layered perovskite having a perovskite layer comprising an inorganic layer 8 layers (two-dimensional array structure of PbBr ₆ ^-4), and an organic layer NMA placing on both sides. The pseudo two-dimensional perovskite that can be used in the present invention is not limitedly interpreted by this specific example. Further, here, it is represented by PEA ₂ FA _n-1 Pb _n Br _{3n + 1} (PEA represents phenylethylammonium and FA represents formamidium, respectively), and n is 8 in a pseudo-two-dimensional perovskite (hereinafter, “P2F8””. The quencher function of the organic component will be described with reference to (referred to as), but P2F8 can also constitute the laser element of the present invention by contacting and using a triplet quencher as another substance, and the present invention It is not excluded from the pseudo-two-dimensional perovskite used in.
FIG 1, N2F8 and a schematic diagram of a quasi-two-dimensional perovskite structure P2F8, (two-dimensional array structure of PbBr ₆ ^-4) each pseudo 2D perovskite inorganic components PbBr ₄ and the organic component NMA, the energy level of the PEA A position diagram is shown, and FIG. 2 schematically shows a pseudo two-dimensional perovskite structure of N2F8 and P2F8 and an exciter generated in the perovskite layer. In the energy level diagram of Fig. 1, E _S represents the emission excitation singlet energy level of the inorganic component, E _T represents the triplet energy level of the inorganic component. E _S1 represents the emission excitation singlet energy level of the organic component, E _T1 represents a triplet energy level of an organic component. The organic component is a triplet quencher, the excited triplet energy level E _T1 is lower than the excited triplet energy level E _T of the inorganic component, that is, satisfies the condition that the E _T> E _T1. In the specific example shown in FIG. 1, _{E S} of the inorganic component is 3.01eV, _{E T} is 2.99 eV, _{E S1} of NMA is 4.1 eV, _{E T} is 2.6 eV, _{E S1} of PEA is 4 .4eV, the _{E T} is 3.3eV. Therefore, here, NMA constitutes a triplet quencher, and PEA is an organic component that does not exhibit the function of the triplet quencher.
First, when each pseudo-two-dimensional perovskite is irradiated with excitation light equal to or higher than the threshold value, a luminescence-excited singlet and an excitation triplet are generated in the inorganic components constituting the perovskite layer. Among them, the energy of the emission-excited singlet is used for forming a population inversion and used for laser oscillation.
Meanwhile, excited triplet generated in the inorganic component, as shown in FIG. 1 the right side and 2 (b), system that does not include triplet quencher, that is, when it is E _T ≦ E _T1, the excited triplet never term energy is transferred to an excited triplet energy level E _T1 of the organic layer, also, for the transition from an excited triplet to the ground singlet is spin forbidden transition, it is directly stored in triplet It becomes dense. As a result, the high-density excitation triplet and the excitation singlet forming the inversion distribution cause singlet-triplet annihilation, the inversion distribution of the excitation singlet is eliminated, and the laser oscillation stops. ..
In contrast, as shown in FIG. 1 the left side and FIG. 2 (a), the system comprising an organic component NMA as triplet quencher, i.e. in a system is E _T> E _T1, excitation generated in the inorganic layer by triplet is lost from the inorganic layer to move to the excited triplet energy level E _T1 of the organic layer, singlet as described above - triplet annihilation can be suppressed. As a result, the population inversion of the excited singlet is maintained and excellent laser oscillation characteristics are exhibited.

Here, the case of using an organic component as a triplet quencher, the difference between the excited triplet energy level E _T1 excited triplet energy level E _T and organic component of the inorganic component (E T _-E _T1) is not particularly limited However, for example, it can be 0.05 eV or more, 0.10 eV or more, 0.20 eV or more, 0.30 eV or more, 0.35 eV or more. The upper limit of the energy difference _(E T _{-E T1),} for example 1.00eV or less, 0.75 eV or less, may be either the following 0.50EV.

Emission excited singlet energy level of the inorganic component constituting the quasi-two-dimensional perovskites of the present invention (E _S) and excited triplet energy level (E _T), the light-emitting excited singlet of the organic components constituting the quasi-two-dimensional perovskite energy level _{(E S1)} and excited triplet energy level _{(E T1),} the energy level difference between the excited triplet _(E T _{-E T1)} is measured as follows. Here, the measurement target compound in the case of measuring E _S, the E _T is the inorganic component constituting the quasi-two-dimensional perovskite, measurement target compound in the case of measuring E _S1, E _T1 is a quasi-two-dimensional perovskite It is a constituent organic cation.
(1) emitting an excitation singlet energy level of the inorganic component (E _S) and emission excited singlet energy level of the organic component (E _S1)
A solution containing the compound to be measured is applied onto a Si substrate and dried to prepare a sample of a film having a thickness of 70 to 110 nm. The fluorescence spectrum of this sample with 337 nm excitation light is measured at 30 K. Here, by integrating the light emission from immediately after the excitation light is incident to 1 microsecond after the incident, a fluorescence spectrum having the vertical axis as the emission intensity and the horizontal axis as the wavelength is obtained. A tangent line is drawn with respect to the rising edge of the fluorescence spectrum on the short wavelength side, and the wavelength value λedge [nm] at the intersection of the tangent line and the horizontal axis is obtained. The value converted to the energy value conversion equation shown below the wavelength value and emitting excitation singlet energy level E _S or E _S1.
Conversion formula: Emission-excited singlet energy level [eV] = 1239.85 / λedge
The fluorescence spectrum can be measured, for example, by using a nitrogen laser (Lasertechnik Berlin, MNL200) as an excitation light source and a streak camera (Hamamatsu Photonics, C4334) as a detector.
(2) excited triplet energy level of the inorganic component _{(E T)} and excited triplet energy level of the organic component _{(E T1)}
A sample similar to that used for the measurement of the luminescence excitation singlet energy level is cooled to 30K, this sample is irradiated with 337 nm excitation light, and the phosphorescence intensity is measured using a streak camera. By integrating the emission from 1 microsecond after the excitation light is incident to several tens of microseconds after the incident, a phosphorescence spectrum having the emission intensity on the vertical axis and the wavelength on the horizontal axis can be obtained. A tangent line is drawn with respect to the rising edge of the phosphorescence spectrum on the short wavelength side, and the wavelength value λedge [nm] at the intersection of the tangent line and the horizontal axis is obtained. The value converted to the energy value conversion equation shown below the wavelength value and excited triplet energy level E _T or E _T1.
Conversion formula: Excited triplet energy level [eV] = 1239.85 / λedge
The tangent to the rising edge of the phosphorescence spectrum on the short wavelength side is drawn as follows. When moving on the spectrum curve from the short wavelength side of the phosphorescent spectrum to the maximum value on the shortest wavelength side of the maximum values of the spectrum, consider the tangents at each point on the curve toward the long wavelength side. This tangent increases in slope as the curve rises (ie, as the vertical axis increases). The tangent line drawn at the point where the value of the slope reaches the maximum value is defined as the tangent line to the rising edge of the phosphorescence spectrum on the short wavelength side.
The maximum point having a peak intensity of 10% or less of the maximum peak intensity of the spectrum is not included in the maximum value on the shortest wavelength side described above, and the slope value closest to the maximum value on the shortest wavelength side is the maximum. The tangent line drawn at the point where the value is taken is taken as the tangent line to the rising edge of the phosphorescent spectrum on the short wavelength side.
(3) the difference between the excited triplet energy level of the inorganic component excited triplet energy level of the _{(E T)} and the organic component _{_{_{(E T1) (E T -E}}} T1)
_(E T _{-E T1)} is the measured value from the measurement values of the excited triplet energy level according to the method of (2) _{(E T),} excited triplet energy level according to the method of _{(2) (E T1)} Obtain by pulling.

The organic component used as the triplet quencher is not particularly limited and may be appropriately selected depending on the inorganic component to be combined with the organic component. For example, an organic cation having a naphthalene ring is preferable, and ammonium having a naphthalene ring is used. It is more preferably present, and even more preferably substituted or unsubstituted naphthylalkylammonium. Here, the number of carbon atoms in the alkyl moiety of the substituted or unsubstituted naphthylalkylammonium is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 6. It is even more preferably 3. The bond position to the alkyl moiety in the naphthalene ring is not particularly limited, but is preferably 1-position. For the description and preferable range of the substituent that can be introduced into the naphthalene ring, the description and the preferable range of the substituent of the aromatic ring represented by Ar in the following general formula (11) can be referred to.
In the following, specific examples of organic components that can be used as triplet quenchers will be illustrated. However, the triplet quencher that can be used in the present invention should not be construed as limiting by this embodiment.

When using an organic component as a triplet quencher, may be composed of any organic components quasi-two-dimensional perovskite contains a triplet quencher (organic component satisfying E _T> E _T1), a portion of the organic components May be constructed as a triplet citrate, and the remaining organic components may be those that do not function as a triplet citrate. Further, the number of organic machine components constituting the triplet quencher may be one or more.

(Triplet quencher, which is a substance different from pseudo-two-dimensional perovskite)
The quencher, which is another substance, may be in either a gas phase, a liquid phase, or a solid phase at room temperature, but is preferably a substance that can be brought into contact with the inorganic component of the pseudo-two-dimensional perovskite. .. For the triplet quencher, which is another substance, for example, a composition containing a molecule having a basal triplet state or a molecule having a basal triplet state can be used, and as a specific example, oxygen in contact with an inorganic component or The atmosphere (air) containing oxygen can be mentioned. Oxygen is a molecule that takes a basal triplet state, and is a triplet quencher that reduces or eliminates the excited triplet of the inorganic component by receiving the energy of the excited triplet of the inorganic component and transitioning itself to singlet oxygen. Functions as. When oxygen or the atmosphere is used as a triplet quencher, the oxygen concentration is preferably 0.1% to 99.9%.
Examples of other triplet quenchers include xenon, radon, oganeson and the like.
The triplet quencher, which is a substance different from the pseudo-two-dimensional perovskite, may be used alone or in combination of two or more. When oxygen, air, etc. are used as the triplet quencher, the excited triplet energy level of the organic component constituting the pseudo two-dimensional perovskite is higher than the excited triplet energy level of the inorganic component constituting the pseudo two-dimensional perovskite. May be high or low. That is, by using a triplet quencher such as oxygen or air, the range of selection of organic components can be widened.

[Pseudo 2D perovskite]
The pseudo two-dimensional perovskite contained in the laser device of the present invention preferably comprises a compound represented by the following general formula (10).
R ₂ A _n-1 B _n X _{3n + 1} (10)
In the general formula (10), R represents a monovalent organic cation, A represents a monovalent cation, B represents a divalent metal ion, and X represents a halogen ion. n is an integer of 2 or more. The two Rs, the plurality of Bs, and the plurality of Xs may be the same or different from each other. When there are a plurality of A's, the A's may be the same or different from each other.
In the compound represented by the general formula (10), _{components having a composition represented by An-1} B _n X _{3n + 1} constitute a perovskite layer, and the unit cell BX ₆ shares a vertex and is arranged two-dimensionally. BX ₄ constitutes an inorganic component (inorganic layer), and a monovalent organic cation represented by R constitutes an organic component. n corresponds to the number of layers of the two-dimensional array structure in the perovskite layer, and is preferably an integer of 2 to 100.

The monovalent organic cation represented by R preferably has an aromatic ring, more preferably has an alkylene group and an aromatic ring, and further preferably has a structure in which an alkylene group and an aromatic ring are linked, and an alkylene group. It is even more preferable that the ammonium has a structure in which the aromatic ring and the aromatic ring are linked, and it is particularly preferable that the ammonium is represented by the following general formula (11).
Ar (CH ₂ ) _n1 NH ₃ ⁺ (11)
In the general formula (11), Ar represents an aromatic ring. n1 is an integer from 1 to 20.
The aromatic ring contained in the organic cation may be an aromatic hydrocarbon or an aromatic heterocycle, but is preferably an aromatic hydrocarbon. Examples of the hetero atom of the aromatic hetero ring include a nitrogen atom, an oxygen atom, a sulfur atom and the like. The aromatic hydrocarbon is preferably a condensed polycyclic hydrocarbon having a structure in which a benzene ring and a plurality of benzene rings are condensed, and is preferably a benzene ring, a naphthalene ring, a phenanthrene ring, an anthracene ring, a chrysen ring, a tetracene ring, and the like. It is preferably a perylene ring, more preferably a benzene ring or a naphthalene ring, and even more preferably a naphthalene ring. Since Ar is a naphthalene ring, the excited triplet energy level of the organic cation can be easily lowered as compared with that of the inorganic component, and the organic cation can be easily formed as a triplet quencher. When Ar is a naphthalene ring, _{the bonding position to the alkylene group (CH 2} ) _n1 in the naphthalene ring is not particularly limited, but it is preferable to bond to the alkylene group at the 1-position. The aromatic heterocycle is preferably a pyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, a pyrrol ring, a thiophene ring, a furan ring, a carbazole ring, or a triazine ring, preferably a pyridine ring, a pyrazine ring, a pyrimidine ring, or a pyridazine ring. Is more preferable, and a pyridine ring is further preferable. The aromatic ring of the organic cation may have a substituent such as an alkyl group, an aryl group, or a halogen atom (preferably a fluorine atom), and is present in the aromatic ring or the substituent bonded to the aromatic ring. The hydrogen atom may be a heavy hydrogen atom.
n1 is more preferably 1 to 10, further preferably 1 to 6, and even more preferably 1 to 3.

The monovalent cation represented by A may be an organic cation or an inorganic cation. Examples of the monovalent cation include formamidium, ammonium, cesium and the like, and formamidium is preferable.

Examples of the divalent metal ion represented by B include Cu ²⁺ , Ni ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Pd ²⁺ , Ge ²⁺ , Sn ²⁺ , Pb ²⁺ , Eu ²⁺ , and Sn. It is preferably ²⁺ and Pb ²⁺ , and more preferably ^{Pb 2+.}
Examples of the halogen ion represented by X include fluorine, chlorine, bromine, and iodine ions. The halogen ions represented by the plurality of Xs may all be the same, or may be a combination of two or three types of halogen ions. It is preferable that the plurality of Xs are all the same halogen ion, and it is more preferable that the plurality of Xs are all bromine ions.

As a preferable specific example of the compound represented by the general formula (10), a compound represented by any of the following formulas (A) to (D) can be mentioned. However, the pseudo-two-dimensional perovskite that can be used in the present invention is not limitedly interpreted by this specific example.
PEA ₂ FA _n-1 Pb _n Br _{3n + 1} equation (A)
PEA ₂ MA _n-1 Pb _n Br _{3n + 1} equation (B)
NMA ₂ FA _n-1 Pb _n Br _{3n + 1} equation (C)
NMA ₂ MA _n-1 Pb _n Br _{3n + 1} equation (D)
In formulas (A) and (B), PEA represents phenylethylammonium. In formulas (C) and (D), NMA represents 1-naphthylmethylammonium. In formulas (A) to (D), FA represents formamidium and MA represents methylammonium. n is an integer of 2 or more.
In the compound represented by any of the formulas (A) to (D), the _{structure PbX 4} _{in which the unit cell PbX 6} shares a vertex and is arranged two-dimensionally constitutes an inorganic component (inorganic layer), and is PEA or A monovalent organic cation represented by NMA constitutes an organic component. Among these, the compound represented by the formula (C) or the formula (D) is preferable, and the compound represented by the formula (C) is more preferable because the NMA can function as a triplet quencher.

[Pseudo-two-dimensional perovskite film formation method]
The pseudo two-dimensional perovskite included in the laser element of the present invention can be formed, for example, in the form of a film to form an active layer of the laser element.
The method for forming the film is not particularly limited, and may be a dry process such as a vacuum vapor deposition method or a wet process such as a solution coating method. Here, if the solution coating method is used, the film can be formed in a short time with a simple device, so that there is an advantage that the cost can be suppressed and mass production is easy. Further, the vacuum vapor deposition method has an advantage that a film having a better surface condition can be formed.

For example, lead _{bromide (PbBr 2} ) and 1-naphthylmethylammonium are used to form a film containing pseudo-two-dimensional perovskite represented by _{NMA 2} FA _n-1 _{Pb n} Br _{3n + 1} using the vacuum deposition method. A co-deposited method of co-depositing bromide (NMABr) and formamidium bromide (FABr) from different deposition sources can be used. In addition, other films containing pseudo-two-dimensional perovskite also apply this method to a metal halide, a compound composed of a monovalent organic cation and a halogen ion, and another monovalent cation and a halogen ion. It can be formed by co-depositing a compound.

In addition, lead _{bromide (PbBr 2} ) and 1-naphthylmethylammonium are used to form a film containing a pseudo-two-dimensional perovskite represented by _{NMA 2} FA _n-1 _{Pb n} Br _{3n + 1} by using a solution coating method. Bromide (NMABr) and formamidium bromide (FABr) are reacted in a solvent to prepare a pseudo two-dimensional perovskite or precursor, and a coating solution containing this pseudo two-dimensional perovskite is applied to the surface of the support and dried. A film is formed by doing so. For other films containing pseudo-two-dimensional perovskite, this method is applied to synthesize pseudo-two-dimensional perovskite in a solvent, and a coating liquid containing this pseudo-two-dimensional perovskite is applied to the surface of the support and dried. Can be formed. Further, if necessary, a baking treatment may be performed after applying the coating liquid.

The coating method of the coating liquid is not particularly limited, and conventionally known coating methods such as a gravure coating method, a bar coating method, a printing method, a spray method, a spin coating method, a dip method, and a die coating method can be used. It is preferable to use the spin coating method because a coating film having a relatively thin thickness can be uniformly formed.

The solvent of the coating liquid is not particularly limited as long as it can dissolve the perovskite type compound. Specifically, ethers (methylformate, ethylformate, propylformate, pentalformate, methylacetate, ethylacetate, pentylacetate, etc.), ketones (γ-butyrolactone, N-methyl-2-pyrrolidone, acetone) , Dimethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, etc.), ethers (diethyl ether, methyl-tert-butyl ether, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane) , 4-Methyldioxolane, tetrahydrofuran, methyl tetrahydrofuran, anisole, phenetol, etc.), alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2 -Methyl-2-butanol, methoxypropanol, diacetone alcohol, cyclohexanol, 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol, etc.), glycol Ethers (cellosolves) (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, triethylene glycol dimethyl ether, etc.), amide-based solvents (N, N-dimethylformamide, acetamide, N , N-Dimethylacetamide, etc.), nitrile-based solvents (acetoyl, isobutyronitrile, propionitrile, methoxynitrile, etc.), carboat-based agents (ethylene carbonate, propylene carbonate, etc.), halogenated hydrocarbons (methylene chloride, dichloromethane, etc.) (Hyrochloroene, etc.), hydrocarbons (n-pentane, cyclohexane, n-hexane, benzene, toluene, xylene, etc.), dimethylsulfoxide, etc. can be mentioned. In addition, it may have two or more functional groups of esters, ketones, ethers and alcohols (that is, -O-, -CO-, -COO-, -OH). , The hydrogen atom in the hydrocarbon moiety of esters, ketones, ethers and alcohols may be substituted with a halogen atom (particularly, a fluorine atom).
The content of the perovskite-type compound in the coating liquid is preferably 1 to 50% by mass, more preferably 2 to 30% by mass, and 5 to 20% by mass with respect to the total amount of the coating liquid. Is even more preferable. The content of the organic material in the coating liquid is preferably 0.001% by mass or more and less than 50% by mass with respect to the total amount of the perovskite compound and the organic material.
Further, the coating liquid applied to the surface of the support is preferably dried by natural drying or heat drying in an atmosphere substituted with an inert gas such as nitrogen.

[Implementation of Laser Element]
The laser element of the present invention includes a pseudo two-dimensional perovskite and has a quencher (triplet quencher) for quenching the excited triplet of the inorganic component constituting the pseudo two-dimensional perovskite, and as an embodiment thereof, Examples thereof include a configuration in which a membrane containing a pseudo-two-dimensional perovskite is used as the active layer. Here, quasi-two-dimensional perovskite that constitutes the active layer may comprise an organic component is a triplet quencher (organic component satisfying E _T> E _T1), may be free. When the pseudo-two-dimensional perovskite does not contain an organic component which is a triplet quencher, the laser element is configured so that oxygen or the atmosphere, which is a triplet quencher, comes into contact with the inorganic layer of the pseudo-two-dimensional perovskite. Specific configurations include a configuration in which the active layer is covered with a protective cover and the protective cover is filled with oxygen and air, a configuration in which an opening is provided in the protective cover and air is allowed to enter the cover through the opening, and an active layer. There is a configuration in which the air is exposed to the outside air without being covered with a protective cover. The configuration in which oxygen or the like is brought into contact with the active layer can also be adopted when the pseudo-two-dimensional perovskite contains an organic component which is a triplet quencher. The laser element may have only one layer of the film containing the pseudo two-dimensional perovskite as described above, or may have two or more layers. When the laser element has two or more layers of films containing pseudo-two-dimensional perovskite, the organic-inorganic perovskite contained in those films may be the same or different.

The laser device of the present invention may be a photoexcited laser device that emits laser light by irradiating the active layer with excitation light, or holes and electrons are injected into the active layer and they are recombined. It may be a current excitation type laser element (semiconductor laser element) that emits a laser beam by the energy generated by the above. The photoexcited laser device has a structure in which at least an active layer is formed on a substrate. Further, the current-excited laser device has a structure in which at least an anode, a cathode, and a perovskite layer are formed between the anode and the cathode. The perovskite layer has at least an active layer and may be composed of only an active layer, or may have one or more other organic layers or a perovskite layer in addition to the active layer. .. Examples of such other organic layers or perovskite layers include hole transport layers, hole injection layers, electron blocking layers, hole blocking layers, electron injection layers, electron transport layers, exciton blocking layers and the like. The hole transport layer may be a hole injection transport layer having a hole injection function, and the electron transport layer may be an electron injection transport layer having an electron injection function. A specific structural example of the current excitation type laser element is shown in FIG. In FIG. 3, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 is an active layer, 6 is an electron transport layer, and 7 is a cathode. In the current-excited current-excited laser element, the laser light generated in the active layer may pass through the anode and be taken out to the outside, or may pass through the cathode and be taken out to the outside, and pass through the anode and the cathode. And may be taken out to the outside. Further, the laser light generated in the active layer may be taken out from the end face of the perovskite layer.
Hereinafter, each member and each layer of the current excitation type laser element will be described. The description of the substrate and the active layer also applies to the photoexcited laser device and the active layer.

(substrate)
The current-excited laser device of the present invention is preferably supported by a substrate. When the current-excited laser element has a configuration in which laser light is extracted from the substrate side, a substrate having translucency to the laser light is used as the substrate, and a transparent substrate made of glass, transparent plastic, quartz, or the like is used. Is preferably used. On the other hand, when the current excitation type laser element has a configuration in which laser light is extracted from the side opposite to the substrate, the substrate is not particularly limited, and a substrate made of silicon, paper, or cloth may be used in addition to the above transparent substrate. it can.

(anode)
As the anode in the current excitation type laser element, a metal having a large work function (4 eV or more), an alloy, an electrically conductive compound, or a mixture thereof as an electrode material is preferably used. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as _{CuI, indium zinc oxide (ITO), SnO 2, ZnO, and TiN.} Further, a material capable of producing an amorphous and transparent conductive film such as IDIXO (In ₂ O _{3-ZnO) may be used.} The anode can be formed by forming a film of these electrode materials by a method such as vapor deposition or sputtering. Further, a pattern having a desired shape may be formed on the formed thin film by a photolithography method to serve as an anode, or when pattern accuracy is not required so much (about 100 μm or more), it is desired at the time of vapor deposition or sputtering of the electrode material. The pattern may be formed through a mask having the shape of. Alternatively, when a coatable material such as an organic conductive compound is used, a wet film forming method such as a printing method or a coating method can also be used.
However, when the current excitation type laser element is configured to transmit the laser light through the anode, the anode needs to have translucency with respect to the laser light, and the transmittance of the laser light is 1. It is preferably configured to be greater than%, and more preferably configured to be greater than 10%. Specifically, it is preferable to use the above-mentioned conductive transparent material for the anode, or to use a thin film formed of a metal or alloy having a thickness of 10 to 100 nm for the anode.
The sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, the film thickness depends on the material, but is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

(cathode)
On the other hand, as the cathode, a metal having a smaller work function than the material used for the anode (referred to as an electron-injectable metal), an alloy, an electrically conductive compound, or a mixture thereof is used as an electrode material. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O). ₃ ) Examples thereof include a mixture, an indium, a lithium / aluminum mixture, and a rare earth metal. Among these, from the viewpoint of electron injectability and durability against oxidation and the like, a mixture of an electron injectable metal and a second metal which is a stable metal having a larger work function value than this, for example, a magnesium / silver mixture. Magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, lithium / aluminum mixture, aluminum and the like are suitable. The cathode can be formed by forming a film of these electrode materials by a method such as vapor deposition or sputtering.
However, when the current excitation type laser element is configured to transmit the laser light through the cathode, the cathode needs to have translucency with respect to the laser light, and the transmittance of the laser light is 1. It is preferably configured to be greater than%, and more preferably configured to be greater than 10%. Specifically, it is preferable to use a thin film formed by forming the above electrode material with a thickness of 10 to 100 nm as the cathode.
The sheet resistance as a cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.

(Active layer)
The active layer is a layer that emits laser light after holes and electrons injected from the anode and the cathode are recombined to generate excitons and a population inversion is formed. In the laser device of the present invention, the active layer is composed of a film containing a pseudo-two-dimensional perovskite.
The thickness of the active layer is preferably 0 to 500 nm, more preferably 50 to 300 nm.

(Injection layer)
The injection layer is a layer provided between the electrode and the perovskite layer in order to reduce the driving voltage and improve the emission brightness. There are a hole injection layer and an electron injection layer, and between the anode and the active layer or the hole transport layer, And may be present between the cathode and the active layer or electron transport layer. The injection layer can be provided as needed.

(Blocking layer)
The blocking layer is a layer capable of blocking the diffusion of charges (electrons or holes) and / or excitons existing in the active layer to the outside of the active layer. The electron blocking layer can be placed between the active layer and the hole transporting layer to prevent electrons from passing through the active layer towards the hole transporting layer. Similarly, the hole blocking layer can be placed between the active layer and the electron transporting layer, blocking holes from passing through the active layer towards the electron transporting layer. The blocking layer can also be used to prevent excitons from diffusing outside the active layer. That is, the electron blocking layer and the hole blocking layer can also function as exciton blocking layers, respectively. The electron blocking layer or exciton blocking layer referred to in the present specification is used in the sense that one layer includes a layer having the functions of an electron blocking layer and an exciton blocking layer.

(Hole blocking layer)
The hole blocking layer has a function of an electron transporting layer in a broad sense. The hole blocking layer has a role of blocking the holes from reaching the electron transporting layer while transporting electrons, which can improve the recombination probability of electrons and holes in the active layer. As the material of the hole blocking layer, a material of the electron transport layer described later can be used as needed.

(Electronic blocking layer)
The electron blocking layer has a function of transporting holes in a broad sense. The electron blocking layer has a role of blocking electrons from reaching the hole transporting layer while transporting holes, which can improve the probability that electrons and holes are recombined in the active layer. ..

(Exciton blocking layer)
The exciton blocking layer is a layer for blocking excitons generated by the recombination of holes and electrons in the active layer from diffusing into the charge transport layer, and the excitons are inserted by inserting this layer. It is possible to efficiently confine it in the active layer, and it is possible to improve the light emission efficiency of the element. The exciton blocking layer can be inserted on either the anode side or the cathode side adjacent to the active layer, and both can be inserted at the same time. That is, when the exciton blocking layer is provided on the anode side, the layer can be inserted between the hole transport layer and the active layer adjacent to the active layer, and when inserted on the cathode side, the active layer and the cathode can be inserted. The layer can be inserted adjacent to the active layer between and. Further, a hole injection layer, an electron blocking layer, or the like can be provided between the anode and the exciton blocking layer adjacent to the anode side of the active layer, and the cathode and the excitation adjacent to the cathode side of the active layer can be provided. An electron injection layer, an electron transport layer, a hole blocking layer, and the like can be provided between the child blocking layer and the electron blocking layer. When the blocking layer is arranged, it is preferable that at least one of the excited singlet energy and the excited triplet energy of the material used as the blocking layer is higher than the excited singlet energy and the excited triplet energy of the light emitting material.

(Hole transport layer)
The hole transport layer is made of a hole transport material having a function of transporting holes, and the hole transport layer may be provided with a single layer or a plurality of layers.
The hole transporting material has either injection or transport of holes or an electron barrier property, and may be either an organic substance or an inorganic substance. Known hole transporting materials that can be used include, for example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, carbazole derivatives, indolocarbazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, etc. Amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilben derivatives, silazane derivatives, aniline copolymers, conductive polymer oligomers, especially thiophene oligomers, etc. It is preferable to use a group tertiary amine compound and a styrylamine compound, and it is more preferable to use an aromatic tertiary amine compound.

(Electronic transport layer)
The electron transport layer is made of a material having a function of transporting electrons, and the electron transport layer may be provided with a single layer or a plurality of layers.
The electron transporting material (which may also serve as a hole blocking material) may have a function of transferring electrons injected from the cathode to the active layer. Examples of the electron transporting layer that can be used include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyrandioxide derivatives, carbodiimides, freolenidenemethane derivatives, anthracinodimethane and anthrone derivatives, and oxadiazole derivatives. Further, among the above-mentioned oxadiazole derivatives, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is replaced with a sulfur atom, and a quinoxalin derivative having a quinoxalin ring known as an electron-withdrawing group can also be used as an electron transport material. Further, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

The film forming method of each layer constituting these laser elements is not particularly limited, and may be produced by either a dry process or a wet process.

(Resonator structure)
The laser device of the present invention may further have a resonator structure. The "resonator structure" is a structure for reciprocating the light emitted by the light emitting material in the active layer. As a result, the light repeatedly travels in the active layer to cause stimulated emission, so that a higher intensity laser beam can be obtained. The resonator structure is specifically composed of a pair of reflectors, one of which preferably has a reflectance of 100% and the other of which has a reflectance of 50-95%. preferable. By setting the reflectance of the other reflector to be relatively low, it is possible to allow the laser beam to pass through the reflector and take out the laser beam to the outside. Hereinafter, the reflecting mirror on the side that extracts the laser beam is referred to as an "output mirror". The reflector and the output mirror may be provided separately from each layer and each part constituting the current excitation type laser element, or the anode and cathode may also have the function of the reflector or the output mirror.

For example, when the anode also functions as a reflector or an output mirror, the anode is made of a metal film having a small absorption of visible light, a high reflectance, and a relatively large work function (4.0 eV or more). It is preferable to configure it. Examples of such a metal film include a metal film such as Ag, Pt, and Au, or an alloy film containing these metals. The reflectance and transmittance of the anode can be adjusted to desired values by controlling the film thickness of the metal film, for example, in the range of several tens of nm or more.
When the cathode also functions as a reflector or an output mirror, the cathode is preferably formed of a metal film having a small absorption of visible light, a high reflectance, and a relatively small work function. Examples of such a metal film include a metal film such as Al and Mg, or an alloy film containing these metals. The reflectance and transmittance of the cathode can be adjusted to desired values by controlling the film thickness of the metal film, for example, in the range of several tens of nm or more.
When a reflector or an output mirror is provided separately from each of the above layers and parts, a reflective film is formed between the anode and the organic layer or between the substrate and the anode to form a reflector or an output mirror. It is preferable to make it work.
When a reflector or an output mirror is provided between the anode and the organic layer, as those materials, the absorption of visible light is small, high reflectance can be obtained, and the work function is large (work function 4.0 eV). Above) It is preferable to use a conductive material. Specifically, a metal film made of a metal such as Ag, Pt, Au, or an alloy containing these metals can be used as a reflector or an output mirror. The reflectance and transmittance of this reflector or output mirror can be adjusted to desired values by controlling the film thickness of the metal film, for example, in the range of several tens of nm or more. Here, when such a reflector or an output mirror is provided between the anode and the organic layer, the material of the anode does not need to have a large work function, and a known electrode material can be widely used.
When a reflector or an output mirror is provided between the substrate and the anode, it is preferable to use a material having a small absorption of visible light and a high reflectance. Specifically, a metal film made of a metal such as Al, Ag, Pt, or an alloy containing these metals, a laminated film in which a Ti film is laminated on an alloy film of Al and Si, silicon oxide and titanium oxide are alternately alternated. A dielectric multilayer film or the like formed on the above can be used as a reflecting mirror or an output mirror. Of these, the reflectance and transmittance of the metal film can be adjusted to desired values by controlling the film thickness in the range of, for example, several tens of nm or more. Further, the reflectance and transmittance of the dielectric multilayer film can be adjusted to desired values by controlling the film thickness and the number of layers of silicon oxide and titanium oxide.
The combination of the reflector and the output mirror is a combination in which the output mirror is the anode and the reflector is the cathode, and the output mirror is a reflective film arranged between the anode and the organic layer or between the substrate and the anode. , A combination in which the reflector is the cathode, a combination in which the reflector is the anode and the output mirror is the cathode, the reflector is a reflective film placed between the anode and the organic layer or between the substrate and the anode. A combination in which the output mirror is a cathode can be mentioned.
In such a cavity structure, the total optical thickness of the layers interposed between the reflector and the output mirror (the total of the values obtained by multiplying the thickness of each layer by the refractive index) is an integer of the half wavelength of the laser beam. It is preferable to design the layer structure of the element so as to be doubled. As a result, a standing wave is formed between the reflecting mirror and the output mirror, the light is amplified, and a higher intensity laser beam can be obtained.

Further, the above resonator structure reciprocates the laser beam in the direction perpendicular to the main surface of the substrate, but the resonator structure reciprocates the laser beam in the horizontal direction with respect to the main surface of the substrate. Good. In such a resonator structure, the end face of the perovskite layer can be configured as a reflector or an output mirror by utilizing the reflection due to the difference in refractive index between the perovskite layer and air. Further, a diffraction grating is provided near the active layer at a lattice spacing of λ / 2n (λ: wavelength of light, an integer of n: 1 or more), and the light generated in the active layer is periodically reflected by the lattice spacing of the diffraction grating. A DFB (distributed feedback) structure may be adopted. As a result, a single longitudinal mode can be realized, and a laser beam having good monochromaticity can be emitted from the end face of the perovskite layer.

The current excitation type laser element as described above emits laser light by passing a current equal to or higher than the threshold current density between the anode and the cathode. Further, the photoexcitation type laser element emits laser light by irradiating the active layer with excitation light of a threshold value or more. At this time, in the laser element of the present invention, the active layer contains the pseudo-two-dimensional perovskite and has a triplet quencher, so that the accumulation of the excited triplet in the perovskite layer of the pseudo-two-dimensional perobskite is suppressed and excited. The occurrence of singlet-triplet annihilation (STA) due to the accumulation of triplets and the phenomenon that the laser oscillation that follows STA stops in the middle (laser death phenomenon) is suppressed. Therefore, it is possible to continuously obtain laser oscillation characteristics that reflect the excellent characteristics of the pseudo two-dimensional perovskite. Therefore, the laser element of the present invention can also be suitably used as a continuous wave laser element.

<Laser oscillation method and method for improving laser oscillation characteristics>
Next, the laser oscillation method and the method for improving the laser oscillation characteristics of the present invention will be described.
The laser oscillation method of the present invention is a method of oscillating a laser from a pseudo two-dimensional perovskite by quenching an excited triplet of an inorganic component constituting the pseudo two-dimensional perovskite.
The method for improving the laser oscillation characteristic of the present invention is a method for improving the laser oscillation characteristic of the pseudo two-dimensional perovskite by quenching the excited triplet of the inorganic component constituting the pseudo two-dimensional perovskite.
For the description of the pseudo-two-dimensional perovskite, the inorganic component, and the excited triplet used in the laser oscillation method and the method for improving the laser oscillation characteristics of the present invention, the corresponding description in the <Laser element> column can be referred to.
The excitation triplet quenching performed by each method can be performed using a quencher for quenching the excited triplet. For the description, preferred range, and specific example of the quencher used here, the description, preferred range, and specific example of the quencher in the column of <laser> element can be referred to.
According to the laser oscillation method and the method for improving the laser oscillation characteristics of the present invention, the accumulation of excited triplets in the perovskite layer of the pseudo-two-dimensional perovskite is suppressed, and the singlet-triplet disappearance due to the accumulation of the excited triplets. (STA), the occurrence of a phenomenon (laser death phenomenon) in which laser oscillation that occurs following STA stops in the middle is suppressed. Therefore, the laser beam reflecting the excellent characteristics of the pseudo two-dimensional perovskite can be continuously oscillated, and the laser oscillation characteristics can be remarkably improved.

The features of the present invention will be described in more detail with reference to Examples below. The materials, treatment contents, treatment procedures, etc. shown below can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the specific examples shown below. The light absorption spectrum is measured using an ultraviolet-visible near-infrared spectrophotometer (Perkin Elmer: Lambda 950-PKA), and the emission spectrum is measured using a measuring device (Fluoromax-4, Horiba Jobin Yvon). The transient attenuation curve of light emission is measured using a streak camera (C4334, Hamamatsu Photonics), and X-ray diffraction analysis is performed using an X-ray diffractometer (RINT-2500, manufactured by Rigaku). The intensity is measured using a photonic multi-channel analyzer (Hamamatsu PMA 12), the laser intensity is measured using a spectroscope (Hamamatsu PMA-50), and the film thickness is measured using a profile meter (Bulker). : DektakXT) was used.
The pseudo two-dimensional perovskites used in Production Examples 1 to 4 below are PEA ₂ FA _n-1 Pb _n Br _{3n + 1} (n = 8) and NMA ₂ FA _n-1 Pb _n Br _{3n + 1} (n = 8). Here, PEA represents phenylethylammonium, NMA represents 1-naphthylmethylammonium, and FA represents formamidium. Emission excited singlet energy level E _S, and triplet energy level E _T inorganic components constituting each quasi-two-dimensional _perovskite, emission excited singlet organic component energy level E _S1 and the light-emitting triplet energy level E _T1 is shown in Table 1.

(Production Example 1) Fabrication of ASE element using N2F8 perovskite film In a glove box with a nitrogen atmosphere having a water concentration and an oxygen concentration of less than 1 ppm, NMA ₂ FA _n-1 Pb _n Br _{3n + 1} (n =) as follows. A film composed of 8) (hereinafter referred to as "N2F8 perovskite film") was formed. First, 1-naphthylmethylammonium bromide (C) was dissolved in an N, N-dimethylformamide solution in which formamidium bromide (HC (NH ₂ ) ₂ Br) and lead bromide (PbBr _{2) were dissolved in a molar ratio of 1: 1.} ₁₀ H ₇ CH ₂ NH ₃ Br) was added at 25 mol% to prepare a precursor solution having a concentration of N2F8 perovskite of 0.4 mM. 50 μL of this N2F8 perovskite precursor solution was dropped onto a quartz glass substrate and spin-coated at 3,000 rpm for 30 seconds to form an N2F8 perovskite precursor film. During this spin coating, 0.2 mL of toluene was added dropwise onto the membrane. Subsequently, the substrate on which the perovskite precursor film was formed was placed on a hot plate and baked at 70 ° C. for 10 minutes, and further baked at 100 ° C. for 10 minutes to obtain a thickness of 70 to 70 to An N2F8 perovskite film having a diameter of 110 nm was formed and used as an ASE element.

(Production Example 2) Preparation of ASE element using P2F8 perovskite film When forming a perovskite film, phenylethylammonium bromide (C ₆ H ₅ CH ₂ CH ₂ NH ₃ Br) is used instead of 1-naphthyl methyl ammonium bromide. An ASE element was produced in the same manner as in Production Example 1 except that a film composed of PEA ₂ FA _n-1 Pb _n Br _{3n + 1 (n = 8) (hereinafter referred to as “P2F8 perobskite film”) was formed.}

When the N2F8 perovskite film and the P2F8 perovskite film produced in each production example were subjected to X-ray diffraction analysis, it was confirmed that they were pseudo-two-dimensional perovskite including a perovskite layer composed of eight inorganic layers.
The ultraviolet-visible absorption spectrum of each perovskite film and the emission spectrum in a steady state by 337 nm excitation light are shown in FIG. In addition, for each perovskite film, the emission spectrum was measured by changing the irradiation intensity of pulsed excitation light stepwise at room temperature, and the results of investigating the excitation light intensity dependence of the peak intensity and full width at half maximum (FWHM) at the emission peak were obtained. It is shown in FIG. The excitation light used for this measurement is a pulse excitation light having a wavelength of 337 nm and a pulse width of 0.8 ns. In FIGS. 4 and 5 and FIG. 6 below, "N2F8" indicates "N2F8 perovskite film" and "P2F8" indicates "P2F8 perovskite film".
As shown in FIG. 5, in the range where the pulse excitation light intensity was low, the full width at half maximum of the emission peak was about 20 nm, and the pattern of the emission spectrum was similar to the emission spectrum in the steady state shown in FIG. On the other hand, when the pulse excitation light intensity exceeded a certain value, a strong emission peak appeared at the position of 550 nm in P2F8 and 555 nm in N2F8, and the full width at half maximum was reduced to 4 nm. This sudden change in the emission spectrum indicates that ASE radiation has started, and the pulse excitation light intensity (ASE threshold) at that time is 16.7 μJ / cm ^{2 for} the P2F8 perovskite film and 33.1 μJ / for the N2F8 perovskite film. It was cm ^2. From these results, it was confirmed that both the P2F8 perovskite membrane and the N2F8 perovskite membrane are active layers exhibiting ASE radiation.

Next, changes in ASE intensity were measured while irradiating continuous pulse excitation light at room temperature under various atmospheres. Specifically, the measurement was performed in an oxygen atmosphere for the first 750 seconds, the measurement was performed in the air for 750 to 1500 seconds, and the measurement was performed in a nitrogen atmosphere for 1500 to 3000 seconds. The excitation light used for the measurement was a continuous pulse excitation light having a wavelength of 337 nm and a pulse width of 3 ns, and was irradiated with an irradiation intensity of ^{70 μJ / cm 2.} The measurement result of the ASE intensity change is shown in FIG.
As shown in FIG. 6, both the P2F8 perovskite membrane and the N2F8 perovskite membrane showed constant ASE intensity in an oxygen atmosphere and in air. On the other hand, when the measurement was performed in a nitrogen atmosphere, the N2F8 perovskite membrane obtained almost the same ASE intensity as in an oxygen atmosphere or air, but the P2F8 perovskite membrane gradually decreased in ASE intensity. In this way, in the P2F8 perovskite film, the ASE intensity changes depending on the measurement atmosphere because the energy of the photoexcited triplet generated in the perovskite layer moves to the triplet oxygen in the atmosphere in the oxygen atmosphere and in the air. It is considered that the singlet-triplet annihilation is suppressed, but the quenching mechanism of such a photoexcited triplet does not work in a nitrogen atmosphere. On the other hand, in the N2F8 perovskite membrane, it is presumed that NMA having a low excited triplet energy level functions as a quencher of the excited triplet, so that stable ASE is obtained even in a nitrogen atmosphere in which oxygen does not exist. From this, it is possible to remarkably improve the ASE characteristics by introducing or contacting a pseudo-two-dimensional perovskite with a substance that functions as a quencher of the excited triplet, for example, oxygen or a compound having a low excited triplet energy level. all right.
Further, here, in an oxygen atmosphere and in the air, high ASE strength was obtained without covering the perovskite film with a protective cap or the like. It is considered that this is because the organic layer of the pseudo two-dimensional perovskite functioned as a protective layer of the perovskite layer. From this, it was also found that the pseudo two-dimensional perovskite is more advantageous as the active layer material of the laser device than the three-dimensional perovskite.

(Manufacturing Example 3) Fabrication of DFB Laser Element Using N2F8 Perovskite Film A hexamethyldisilazane layer and a resist layer are formed on the surface of a silicon substrate on which a silicon thermal oxide film having a thickness of 1 μm is formed, and then an electron beam is formed. A DFB (distributed feedback) lattice was formed using a lithography method. At this time, the lattice pitch was 250 nm, the lattice height was 60 nm, and the air trench width was 120 nm. Subsequently, an N2F8 perovskite film was formed on the surface of the silicon substrate on which the DFB lattice was formed in the same manner as in Production Example 1 to obtain a DFB laser element (N2F8 laser).

(Manufacturing Example 4) Fabrication of DFB Laser Element Using P2F8 Perobskite Film The same as in Production Example 3 except that the P2F8 perovskite film was formed on the surface of the silicon substrate on which the DFB lattice was formed in the same manner as in Production Example 2. DFB laser element (P2F8 laser) was manufactured.

FIG. 7 shows the results of measuring the emission spectrum of the produced N2F8 laser and P2F8 laser by changing the irradiation intensity of pulsed excitation light stepwise and examining the dependence of the emission peak intensity on the excitation light intensity. The excitation light used for the measurement is a pulse excitation light having a wavelength of 337 nm and a pulse width of 3 ns. In FIG. 7 and FIG. 8 below, "N2F8" indicates "N2F8 laser" and "P2F8" indicates "P2F8 laser".
As shown in FIG. 7, both the N2F8 laser and the P2F8 laser rapidly increased the emission intensity at a constant excitation light intensity, and at the same time, the full width at half maximum reached about 0.45 nm. At this time, the Q factor was 1000. From this, it was confirmed that each element exhibited good laser oscillation characteristics. Lasing threshold determined from FIG. 7, 4.7MyuJcm ^-2 at P2F8 laser is 32.8MyuJcm ^-2 in N2F8 laser oscillation wavelength determined from the emission spectrum was 552nm at 559 nm, P2F8 laser in N2F8 laser .. For the N2F8 laser, it is considered that the laser threshold can be lowered by optimizing the conditions of the DFB lattice.

Next, the P2F8 laser was irradiated with continuous excitation light, the laser intensity was measured in air, and then the laser intensity was measured in a nitrogen atmosphere. The cycle was repeated, and the change in laser intensity during that period was investigated. The excitation light used for the measurement was continuous excitation light having a wavelength of 448 nm, and was irradiated with an irradiation intensity of ^{1.7 kW / cm 2.} The measurement result of the laser intensity change is shown in FIG.
As shown in FIG. 8, laser oscillation is observed in the air, and when nitrogen is injected into the sample chamber to create a nitrogen atmosphere in the chamber, the laser intensity immediately decreases, and then the injection of nitrogen is stopped and the air is stopped. Was introduced into the sample chamber, and the laser oscillation was completely restored. From this result, it was found that the laser oscillation characteristics are effectively improved by bringing a triplet quencher such as oxygen into contact with the laser element. Further, the response speed (the speed at which the laser intensity changes) according to the change in the atmosphere of the laser oscillation was much faster than the response speed in the ASE operation. This suggests that the singlet-triplet annihilation induced by the long-lived photoexcited triplet is the essential cause of the laser death phenomenon during continuous-wave laser oscillation.

The laser element of the present invention has excellent laser oscillation characteristics, and since it uses a pseudo two-dimensional perovskite, it has high stability and is advantageous in reducing the manufacturing cost of the laser element. Therefore, according to the present invention, it is possible to inexpensively provide a laser element having excellent laser oscillation characteristics and practicality. Therefore, the present invention has high industrial applicability.

1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Active layer 6 Electron transport layer 7 Cathode

Claims

A laser device containing a pseudo two-dimensional perovskite, which has a quencher for quenching an excited triplet of an inorganic component constituting a pseudo two-dimensional perovskite.
The quencher is an organic component constituting the pseudo two-dimensional perovskite, and the excited triplet energy level of the organic component is lower than the excited triplet energy level of the inorganic component constituting the pseudo two-dimensional perovskite. , The laser element according to claim 1.
The laser element according to claim 2, wherein the excited triplet energy level of the organic component is 0.10 eV or more lower than the excited triplet energy level of the inorganic component constituting the pseudo two-dimensional perovskite.
The laser device according to claim 2, wherein the organic component of the quencher is a substituted or unsubstituted naphthylalkylammonium.
The laser device according to claim 1, wherein the quencher is a molecule having a basal triplet state or a composition containing a molecule having a basal triplet state.
The laser element according to claim 1, wherein the quencher is oxygen that comes into contact with an inorganic component constituting a pseudo two-dimensional perovskite.
The laser element according to claim 1, wherein the quencher is an atmosphere in contact with an inorganic component constituting a pseudo two-dimensional perovskite.
Any one of claims 5 to 7, wherein the excited triplet energy level of the organic component constituting the pseudo two-dimensional perovskite is higher than the excited triplet energy level of the inorganic component constituting the pseudo two-dimensional perovskite. The laser element described in.
The pseudo two-dimensional perovskite comprises a compound represented by the following general formula (10).
R 2 A n-1 B n X 3n + 1 (10)
[In the general formula (10), R represents a monovalent organic cation, A represents a monovalent cation, B represents a divalent metal ion, and X represents a halogen ion. n is an integer of 2 or more. ]
The laser device according to claim 1, wherein an inorganic layer having a composition represented by BX 4 of the general formula (10) constitutes the inorganic component.
The quencher is an organic component composed of an organic cation represented by R in the general formula (10), and the excitation triplet energy level of the organic component excites the inorganic component constituting the pseudo-two-dimensional perovskite. The laser element according to claim 9, which is lower than the triplet energy level.
The organic-inorganic perovskite according to claim 9, wherein R of the general formula (10) is ammonium represented by the following general formula (11).
Ar (CH 2 ) n1 NH 3 + (11)
[In the general formula (11), Ar represents an aromatic ring. n1 is an integer from 1 to 20. ]
The laser device according to claim 11, wherein Ar in the general formula (11) is a benzene ring or a naphthalene ring.
The laser device according to any one of claims 9 to 12, wherein A of the general formula (10) is formamidium or methylammonium.
The laser device according to any one of claims 9 to 13, wherein B of the general formula (10) is Pb 2+.
The laser device according to any one of claims 9 to 14, wherein X in the general formula (10) is Br −.
The compound represented by the general formula (10) is a compound represented by the following formula (A) or the following formula (B).
PEA 2 FA n-1 Pb n Br 3n + 1 equation (A)
PEA 2 MA n-1 Pb n Br 3n + 1 equation (B)
[In formulas (A) and (B), PEA represents phenylethylammonium, FA represents formamidium, and MA represents methylammonium. n is an integer of 2 or more. ]
The laser device according to claim 9, wherein an inorganic layer having a composition represented by PbBr 4 of the formula (A) or the formula (B) constitutes the inorganic component.
The compound represented by the general formula (10) is a compound represented by the following formula (C) or the following formula (D).
NMA 2 FA n-1 Pb n Br 3n + 1 equation (C)
NMA 2 MA n-1 Pb n Br 3n + 1 equation (D)
[In formulas (C) and (D), NMA represents 1-naphthylmethylammonium, FA represents formamidium, and MA represents methylammonium. n is an integer of 2 or more. ]
The laser device according to claim 9, wherein an inorganic layer having a composition represented by PbBr 4 of the formula (C) or the formula (D) constitutes the inorganic component.
The laser element according to any one of claims 1 to 17, which oscillates a laser at a temperature of 20 ° C. or higher.
The laser element according to any one of claims 1 to 18, which has a resonator.
The laser element according to claim 19, which is a distributed feedback type laser element.
A laser oscillation method in which a laser is oscillated from the pseudo two-dimensional perovskite by quenching the excited triplet of the inorganic component constituting the pseudo two-dimensional perovskite.
A method for improving the laser oscillation characteristics, which improves the laser oscillation characteristics of the pseudo-two-dimensional perovskite by quenching the excited triplet of the inorganic component constituting the pseudotwo-dimensional perovskite.