Organic modulation element and modulation device

Abstract

To provide an organic modulation element and modulation device which can modulate input light in accordance with purposes.SOLUTION: An organic modulation element 2A comprises an organic modulation layer 20 that includes a plurality of organic semiconductor molecules 20a, a first electrode 21, and a second electrode 22. Each of the plurality of organic semiconductor molecules 20a is a molecule in which an excitation state where reverse intersystem crossing from a lowest excited triplet state to a lowest excited singlet state is possible is formed by irradiation of input light L1, in each of the plurality of organic semiconductor molecules 20a. In each of the plurality of organic semiconductor molecules 20a, the velocity constant of intersystem crossing from the lowest excited singlet state to the lowest excited triplet state is larger than the velocity constant of reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state. In each of the plurality of organic semiconductor molecules 20a, the velocity constant of reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state is larger than the velocity constant of non-radiative decay from the lowest excited triplet state to a ground state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an organic modulation element and a modulation device.

Background Art

[0002] Patent Document 1 describes a solar cell including a wavelength conversion film and a photoelectric conversion element. An organic phosphor that converts light in a short wavelength region into light in a long wavelength region is used for the wavelength conversion film described in Patent Document 1.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The wavelength conversion film described in Patent Document 1 only has a certain function of converting light in a short wavelength region into light in a long wavelength region, and cannot modulate input light according to the purpose.

[0005] An object of the present invention is to provide an organic modulation element capable of modulating input light according to the purpose, and a modulation device including such an organic modulation element.

Means for Solving the Problems

[0006] The organic modulation element of the present invention includes an organic modulation layer containing a plurality of organic semiconductor molecules, a first electrode that is optically transparent to the input light to the organic modulation layer and is disposed on one side of the organic modulation layer, and a second electrode disposed on the other side of the organic modulation layer. Each of the plurality of organic semiconductor molecules is a molecule in which an excited state enabling reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state is formed in each of the plurality of organic semiconductor molecules by irradiation with input light. In each of the plurality of organic semiconductor molecules, the intersystem crossing rate constant from the lowest excited singlet state to the lowest excited triplet state is greater than the reverse intersystem crossing rate constant from the lowest excited triplet state to the lowest excited singlet state. In each of the plurality of organic semiconductor molecules, the reverse intersystem crossing rate constant from the lowest excited triplet state to the lowest excited singlet state is greater than the non-radiative deactivation rate constant from the lowest excited triplet state to the ground state.

[0007] In this organic modulation element, upon irradiation with input light that has passed through the first electrode, an excited state capable of reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state is formed in each of the plurality of organic semiconductor molecules. As a result, for each of the plurality of organic semiconductor molecules, in addition to the high-speed charge separation observed until the lowest excited singlet state relaxes, charge separation from the lowest excited triplet state, which has a longer lifetime than the lowest excited singlet state (hereinafter referred to as "direct charge separation from the lowest excited triplet state"), and / or charge separation from the lowest excited singlet state using the lowest excited triplet state, which has a longer lifetime than the lowest excited singlet state, as a temporary retreat location from deactivation (hereinafter referred to as "charge separation from the lowest excited singlet state via the lowest excited triplet state") becomes possible. Here, in each of the plurality of organic semiconductor molecules, the intersystem crossing rate constant from the lowest excited singlet state to the lowest excited triplet state is larger than the reverse intersystem crossing rate constant from the lowest excited triplet state to the lowest excited singlet state, so the lifetime of the lowest excited triplet state becomes longer and sufficient charge separation is easily obtained. Therefore, for example, by applying a voltage between the first electrode and the second electrode under irradiation with input light to generate an electric field in the organic modulation layer in the direction that causes charge separation, the excited state that should be deactivated (spontaneously emitted) with light emission is converted into a charge separation state, and dimming can be achieved. On the other hand, in each of the plurality of organic semiconductor molecules, since the reverse intersystem crossing rate constant from the lowest excited triplet state to the lowest excited singlet state is larger than the non-radiative deactivation rate constant from the lowest excited triplet state to the ground state, deactivation by heat is less likely to occur and light emission is easily obtained. Therefore, for example, by not applying a voltage between the first electrode and the second electrode and not generating an electric field in the organic modulation layer in the direction that causes charge separation, light emission by spontaneous emission can be promoted. As described above, according to the above organic modulation element, the input light can be modulated according to the purpose.

[0008] In the organic modulation device of the present invention, in each of a plurality of organic semiconductor molecules, the difference between the energy of the lowest excited singlet state and the energy of the lowest excited triplet state at an absolute temperature of 77 K may be less than 0.3 eV. Thereby, each organic semiconductor molecule can function as a molecule in which an excited state enabling reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state is formed by irradiation with input light.

[0009] In the organic modulation device of the present invention, in each of a plurality of organic semiconductor molecules, the intersystem crossing rate constant from the lowest excited singlet state to the lowest excited triplet state may be larger than the fluorescence rate constant from the lowest excited singlet state to the ground state. Thereby, while suppressing deactivation from the lowest excited singlet state by light emission, direct charge separation from the lowest excited triplet state and / or charge separation from the lowest excited singlet state via the lowest excited triplet state becomes possible.

[0010] In the organic modulation device of the present invention, in each of a plurality of organic semiconductor molecules, the intersystem crossing rate constant from the lowest excited singlet state to the lowest excited triplet state may be two times or more the reverse intersystem crossing rate constant from the lowest excited triplet state to the lowest excited singlet state. Thereby, the lifetime of the lowest excited triplet state can be prolonged and the photoelectric conversion efficiency can be improved.

[0011] In the organic modulation device of the present invention, in each of a plurality of organic semiconductor molecules, the reverse intersystem crossing rate constant from the lowest excited triplet state to the lowest excited singlet state is 1×10 7 (sec -1 ) or less. Thereby, the lifetime of the lowest excited triplet state can be prolonged and the photoelectric conversion efficiency can be improved.

[0012] In the organic modulation device of the present invention, the dipole moment of each of a plurality of organic semiconductor molecules may be larger than 0 D. Thereby, the energy for charge separation can be reduced.

[0013] In the organic modulation device of the present invention, the organic modulation layer further includes a plurality of host molecules, and the energy of the lowest excited triplet state at an absolute temperature of 77K in each of the plurality of host molecules may be higher than the energy of the lowest excited triplet state at an absolute temperature of 77K in each of the plurality of organic semiconductor molecules. Thereby, it is possible to suppress a decrease in the photoelectric conversion efficiency due to the influence of the plurality of host molecules.

[0014] In the organic modulation device of the present invention, the second electrode may have light transmissivity with respect to the output light from the organic modulation layer. Thereby, the modulated output light can be emitted to the side opposite to the incident side of the input light.

[0015] In the organic modulation device of the present invention, the first electrode may have light transmissivity with respect to the output light from the organic modulation layer. Thereby, the modulated output light can be emitted to the incident side of the input light.

[0016] The organic modulation device of the present invention includes an organic modulation layer containing a plurality of organic semiconductor molecules, a first electrode that has light transmissivity with respect to the input light to the organic modulation layer and is disposed on one side of the organic modulation layer, a second electrode that has light transmissivity with respect to the output light from the organic modulation layer and is disposed on the other side of the organic modulation layer, and a light receiving layer that is disposed on the other side of the second electrode and receives the output light. Each of the plurality of organic semiconductor molecules is a molecule in which an excited state capable of reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state is formed in each of the plurality of organic semiconductor molecules by irradiation with the input light.

[0017] According to this organic modulation device, the input light can be modulated according to the purpose, and the modulated output light can be detected according to the purpose.

[0018] The organic modulation element of the present invention includes an organic modulation layer containing a plurality of organic semiconductor molecules, a first electrode that is optically transparent to the input light to the organic modulation layer and is disposed on one side of the organic modulation layer, and a second electrode that is optically transparent to the output light from the organic modulation layer and is disposed on the other side of the organic modulation layer, and a light-emitting layer that is disposed on one side of the first electrode and emits input light. Each of the plurality of organic semiconductor molecules is a molecule in which an excited state enabling reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state is formed in each of the plurality of organic semiconductor molecules by irradiation with input light.

[0019] According to this organic modulation element, it is possible to modulate input light according to the purpose and emit output light modulated according to the purpose.

[0020] The modulation device of the present invention includes an organic modulation layer containing a plurality of organic semiconductor molecules, a first electrode that is optically transparent to the input light to the organic modulation layer and is disposed on one side of the organic modulation layer, a second electrode that is disposed on the other side of the organic modulation layer, and a control unit that modulates the voltage applied between the first electrode and the second electrode. Each of the plurality of organic semiconductor molecules is a molecule in which an excited state enabling reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state is formed in each of the plurality of organic semiconductor molecules by irradiation with input light.

[0021] According to this modulation device, it is possible to modulate input light according to the purpose.

Advantages of the Invention

[0022] According to the present invention, it is possible to provide an organic modulation element capable of modulating input light according to the purpose, and a modulation device including such an organic modulation element.

Brief Description of the Drawings

[0023]

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Embodiments for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and duplicate explanations are omitted. [First Embodiment]

[0025] As shown in FIG. 1, the modulation device 1A of the first embodiment includes an organic modulation element 2A. The organic modulation element 2A of the first embodiment has an organic modulation layer 20, a first electrode 21, and a second electrode 22. The first electrode 21 is disposed on one side of the organic modulation layer 20 (one side in the thickness direction of the organic modulation layer 20). The second electrode 22 is disposed on the other side of the organic modulation layer 20 (the side opposite to one side in the thickness direction of the organic modulation layer 20). As an example, the second electrode 22, the organic modulation layer 20, and the first electrode 21 are laminated in this order on a light-transmissive support substrate (not shown).

[0026] The first electrode 21 is light-transmissive to the input light L1 to the organic modulation layer 20. The second electrode 22 is light-transmissive to the output light L2 from the organic modulation layer 20. As materials for the electrode that functions as the anode among the first electrode 21 and the second electrode 22, for example, indium tin oxide, indium oxide, tin oxide, zinc oxide, etc. can be used. As materials for the electrode that functions as the cathode among the first electrode 21 and the second electrode 22, for example, aluminum, vanadium, gold, silver, platinum, iron, cobalt, carbon, nickel, tungsten, palladium, magnesium, calcium, tin, lead, titanium, yttrium, lithium, ruthenium, manganese, alloys containing these metals, etc. can be used. As an example, the thickness of each of the first electrode 21 and the second electrode 22 is, for example, about 100 nm in the case of an oxide system because it has high transparency but high resistance, and about 10 nm in the case of a metal system because it has low resistance but low transparency.

[0027] Note that a buffer layer (not shown) for adjusting the work function of the electrode and / or the charge injection barrier may be formed on at least one of the surfaces of the first electrode 21 on the organic modulation layer 20 side and the surface of the second electrode 22 on the organic modulation layer 20 side. The buffer layer on the first electrode 21 side needs to have light transmissibility with respect to the input light L1. The buffer layer on the second electrode 22 side needs to have light transmissibility with respect to the output light L2. As the material of the buffer layer on the electrode side that functions as the anode among the first electrode 21 and the second electrode 22, for example, metal oxides such as molybdenum oxide, tungsten oxide, nickel oxide, vanadium oxide, and conductive polymers represented by PEDOT:PSS can be used. As the material of the buffer layer on the electrode side that functions as the cathode among the first electrode 21 and the second electrode 22, for example, metals such as magnesium, silver, calcium, titanium, zinc, cesium, lithium, alloys containing these metals, metal oxides such as titanium oxide, zinc oxide, alkali metal compounds such as lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, and alkaline earth metal compounds such as magnesium fluoride, calcium fluoride can be used. Since the buffer layer needs to have light transmissibility with respect to the input light L1 or the output light L2, the thickness of the buffer layer is preferably, for example, 50 nm or less.

[0028] Also, a hole transport layer or an electron blocking layer may be disposed between the electrode that functions as an anode among the first electrode 21 and the second electrode 22 and the organic modulation layer 20. An electron transport layer or a hole blocking layer may be disposed between the electrode that functions as a cathode among the first electrode 21 and the second electrode 22 and the organic modulation layer 20. Among these layers, the layer on the first electrode 21 side needs to have light transmissivity with respect to the input light L1. Among these layers, the layer on the second electrode 22 side needs to have light transmissivity with respect to the output light L2. As the material of the hole transport layer or the electron blocking layer, for example, metal oxides, porphyrin derivatives, phthalocyanine derivatives, oxazole derivatives, oxadiazole derivatives, triazole derivatives, imidazole derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, hydrazone derivatives, stilbene derivatives, polyarylalkane derivatives, triarylamine derivatives, carbazole derivatives, indolocarbazole derivatives, isoindole derivatives, acene-based derivatives, fluorene derivatives, fluorenone derivatives, polyvinylcarbazole, polymer materials with aromatic amines introduced into the main chain or side chain, oligomers, polysilane, conductive polymers, etc. can be used. As the material of the electron transport layer or the hole blocking layer, for example, nitrogen-containing aromatic heterocyclic derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, silole derivatives, aromatic hydrocarbon ring derivatives, etc. can be used.

[0029] The organic modulation layer 20 contains a plurality of organic semiconductor molecules 20a and a plurality of host molecules 20b. The plurality of organic semiconductor molecules 20a are composed of the same type of organic semiconductor molecules, and the plurality of host molecules 20b are composed of the same type of host molecules. That is, the organic modulation layer 20 contains one type of organic semiconductor molecule 20a and one type of host molecule 20b. In the organic modulation layer 20, charge separation occurs by irradiation with the input light L1 (details will be described later). As an example, the organic modulation layer 20 is formed on the second electrode 22 formed on the support substrate by vacuum deposition of TPA-DCPP (a plurality of organic semiconductor molecules 20a) and CBP (a plurality of host molecules 20b) from different evaporation sources. The thickness of the organic modulation layer 20 is, for example, about 100 nm. The mass ratio of CBP to TPA-DCPP in the organic modulation layer 20 is, for example, 50:50.

[0030] The modulation device 1A further includes a control unit 3. The control unit 3 is electrically connected to the organic modulation element 2A. The control unit 3 applies a voltage between the first electrode 21 and the second electrode 22 so that an electric field in the direction causing charge separation is generated in the organic modulation layer 20, and modulates the voltage. As an example, when the first electrode 21 functions as an anode and the second electrode 22 functions as a cathode, the control unit 3 may apply a voltage between the first electrode 21 and the second electrode 22 so that the potential of the first electrode 21 becomes negative with reference to the potential of the second electrode 22, or may apply a voltage between the first electrode 21 and the second electrode 22 so that the potential of the second electrode 22 becomes positive with reference to the potential of the first electrode 21. Further, when the first electrode 21 functions as a cathode and the second electrode 22 functions as an anode, the control unit 3 may apply a voltage between the first electrode 21 and the second electrode 22 so that the potential of the first electrode 21 becomes positive with reference to the potential of the second electrode 22, or may apply a voltage between the first electrode 21 and the second electrode 22 so that the potential of the second electrode 22 becomes negative with reference to the potential of the first electrode 21. The control unit 3 is composed of, for example, a voltage application circuit, a current reading circuit, and the like.

[0031] Figure 2 is an energy diagram of the organic modulation layer 20 shown in Figure 1. More specifically, Figure 2 is an energy diagram of the organic modulation layer 20 in which an excited state is formed by irradiation with the input light L1. In Figure 2, S0 represents the ground state, S1 represents the lowest excited singlet state, and T1 represents the lowest excited triplet state. k S r is the fluorescence rate constant from the lowest excited singlet state S1 to the ground state S0, and k S nr is the non-radiative deactivation rate constant from the lowest excited singlet state S1 to the ground state S0. k T r is the phosphorescence rate constant from the lowest excited triplet state T1 to the ground state S0, and k T nr is the non-radiative deactivation rate constant from the lowest excited triplet state T1 to the ground state S0. k ISC is the intersystem crossing rate constant from the lowest excited singlet state S1 to the lowest excited triplet state T1, and k RISC is the reverse intersystem crossing rate constant from the lowest excited triplet state T1 to the lowest excited singlet state S1.

[0032] As shown in Figure 2, each of the plurality of organic semiconductor molecules 20a is a molecule in which an excited state enabling reverse intersystem crossing from the lowest excited triplet state T1 to the lowest excited singlet state S1 is formed in each of the plurality of organic semiconductor molecules 20a by irradiation with the input light L1. In this case, intersystem crossing from the lowest excited singlet state S1 to the lowest excited triplet state T1 is also possible in each of the plurality of organic semiconductor molecules 20a. Each of the plurality of organic semiconductor molecules 20a preferably contains a donor functional group and an acceptor functional group.

[0033] Note that the "reverse intersystem crossing from the lowest excited triplet state T1 to the lowest excited singlet state S1" includes not only the "reverse intersystem crossing in which an excited molecule moves from the lowest excited triplet state T1 to the lowest excited singlet state S1 without passing through another energy level" but also the "reverse intersystem crossing in which an excited molecule moves from the lowest excited triplet state T1 to the lowest excited singlet state S1 through another energy level (for example, a higher energy level, etc.). Similarly, the "intersystem crossing from the lowest excited singlet state S1 to the lowest excited triplet state T1" includes not only the "intersystem crossing in which an excited molecule moves from the lowest excited singlet state S1 to the lowest excited triplet state T1 without passing through another energy level" but also the "intersystem crossing in which an excited molecule moves from the lowest excited singlet state S1 to the lowest excited triplet state T1 through another energy level (for example, a higher energy level, etc.).

[0034] In each of the plurality of organic semiconductor molecules 20a, the difference between the energy of the lowest excited singlet state S1 and the energy of the lowest excited triplet state T1 at an absolute temperature of 77K is less than 0.3 eV. Although not shown in FIG. 2, the energy of the lowest excited triplet state at an absolute temperature of 77K in each of the plurality of host molecules 20b is higher than the energy of the lowest excited triplet state T1 at an absolute temperature of 77K in each of the plurality of organic semiconductor molecules 20a.

[0035] The energy level E which is the energy of the lowest excited singlet state S1 S1 is obtained as follows. First, a film composed of a plurality of organic semiconductor molecules 20a is formed on a Si wafer. When the film is formed by vapor deposition, the film thickness is preferably 50 nm or more and 100 nm or less. When the film is formed by spin coating, the film thickness may be about 30 nm. Subsequently, the fluorescence spectrum of the film composed of the plurality of organic semiconductor molecules 20a is measured at room temperature (absolute temperature 300K). In the measurement of the fluorescence spectrum, an LED, a tungsten lamp, or a deuterium lamp is used as an excitation light source, and a multichannel spectroscope (C10027 manufactured by Hamamatsu Photonics) is used as a detector. Subsequently, a tangent is drawn to the rise on the short-wavelength side of the emission spectrum whose vertical axis is the light intensity and whose horizontal axis is the wavelength, and the wavelength value λ of the intersection of the tangent and the horizontal axisedge Determine (nm), and obtain the energy level E from the following formula (1). S1 Obtain it. E S1 (eV) = 1239.85 / λ edge …(1)

[0036] Note that the tangent line drawn with respect to the rising edge on the short-wavelength side of the fluorescence spectrum is the tangent line with the maximum slope among the tangent lines drawn at each point of the fluorescence spectrum in the range from the short-wavelength side of the fluorescence spectrum to the maximum value of the fluorescence spectrum that appears on the shortest-wavelength side. The maximum value having a peak intensity of 10% or less of the maximum peak intensity of the fluorescence spectrum is not regarded as the "maximum value of the fluorescence spectrum that appears on the shortest-wavelength side" described above.

[0037] The energy level E, which is the energy of the lowest excited triplet state T1 at an absolute temperature of 77K, is obtained as follows. First, cool the Si wafer (the one described above) on which a film composed of a plurality of organic semiconductor molecules 20a is formed to an absolute temperature of 77K using a cryostat (OptistatDN manufactured by Oxford Instruments). Subsequently, in the measurement of the phosphorescence spectrum, measure the phosphorescence spectrum of the film composed of a plurality of organic semiconductor molecules 20a using the same excitation light source and detector as those used in the measurement of the fluorescence spectrum described above. Subsequently, draw a tangent line with respect to the rising edge on the short-wavelength side of the phosphorescence spectrum where the vertical axis is the light intensity and the horizontal axis is the wavelength, and obtain the wavelength value λ T1 (nm) of the intersection point of the tangent line and the horizontal axis, and obtain the energy level E from the following formula (2). edge Determine (nm), and obtain the energy level E from the following formula (1). T1 Obtain it. E T1 (eV) = 1239.85 / λ edge …(2)

[0038] Note that the tangent line drawn with respect to the rise on the short wavelength side of the phosphorescence spectrum is the tangent line with the maximum slope among the tangent lines drawn at each point of the phosphorescence spectrum in the range from the short wavelength side of the phosphorescence spectrum to the maximum value of the phosphorescence spectrum that appears on the shortest wavelength side. A maximum value having a peak intensity of 10% or less of the maximum peak intensity of the phosphorescence spectrum is not the "maximum value of the phosphorescence spectrum that appears on the shortest wavelength side" described above.

[0039] In each of the plurality of organic semiconductor molecules 20a, the intersystem crossing rate constant k from the lowest excited singlet state S1 to the lowest excited triplet state T1 ISC is larger than the fluorescence rate constant k from the lowest excited singlet state S1 to the ground state S0. S r In each of the plurality of organic semiconductor molecules 20a, the intersystem crossing rate constant k from the lowest excited singlet state S1 to the lowest excited triplet state T1 ISC is larger than the reverse intersystem crossing rate constant k from the lowest excited triplet state T1 to the lowest excited singlet state S1. RISC In each of the plurality of organic semiconductor molecules 20a, the intersystem crossing rate constant k from the lowest excited singlet state S1 to the lowest excited triplet state T1 ISC is larger than the reverse intersystem crossing rate constant k from the lowest excited triplet state T1 to the lowest excited singlet state S1. RISC is at least twice that of the reverse intersystem crossing rate constant k from the lowest excited triplet state T1 to the lowest excited singlet state S1. In each of the plurality of organic semiconductor molecules 20a, the reverse intersystem crossing rate constant k from the lowest excited triplet state T1 to the lowest excited singlet state S1 RISC is 1 × 10 7 (sec -1 ) or less. In each of the plurality of organic semiconductor molecules 20a, the reverse intersystem crossing rate constant k from the lowest excited triplet state T1 to the lowest excited singlet state S1 RISC is larger than the non-radiative deactivation rate constant k from the lowest excited triplet state T1 to the ground state S0. T nr

[0040] The fluorescence rate constant k from the lowest excited singlet state S1 to the ground state S0 S r and the intersystem crossing rate constant k from the lowest excited singlet state S1 to the lowest excited triplet state T1​ISC and the reverse intersystem crossing rate constant k from the lowest excited triplet state T1 to the lowest excited singlet state S1 RISC are determined as follows. First, a film composed of a plurality of organic semiconductor molecules 20a is formed on a quartz substrate. When film formation is carried out by a vapor deposition method, the film thickness is preferably 50 nm or more and 100 nm or less. When film formation is carried out by a spin coating method, the film thickness may be about 30 nm. Subsequently, using an absolute PL quantum yield measurement device (C11347 manufactured by Hamamatsu Photonics), the luminescence quantum yield (number of emitted photons / number of absorbed photons) of the film composed of a plurality of organic semiconductor molecules 20a is measured at room temperature (300 K). In this measurement, excitation is performed with light in the absorption wavelength band of the film composed of a plurality of organic semiconductor molecules 20a, and the luminescence quantum yield is calculated from the luminescence spectrum detected under the condition that the absorbance (“Abs” in the measurement device) is 0.1 or more and 0.9 or less, and the average value of three measurements is taken as Φ.

[0041] Subsequently, using a small fluorescence lifetime measurement device (C11367 manufactured by Hamamatsu Photonics), the fluorescence lifetime of the film composed of a plurality of organic semiconductor molecules 20a is measured. In this measurement, excitation is performed with light in the absorption wavelength band of the film composed of a plurality of organic semiconductor molecules 20a, and the peak wavelength of the luminescence spectrum obtained at the time of measuring the luminescence quantum yield is used as the detection wavelength. Note that all measurements are carried out with an integration count such that the peak count is 10,000 or more. In the film composed of a plurality of organic semiconductor molecules 20a, a prompt luminescence decay component (τ p ) that emits light from the lowest excited singlet state S1 without passing through the lowest excited triplet state T1, and the intersystem crossing rate from the lowest excited singlet state S1 to the lowest excited triplet state T1, and a delayed luminescence decay component (τ d ) that emits light after passing through the reverse intersystem crossing from the lowest excited triplet state T1 to the lowest excited singlet state S1 are observed, but since it is necessary to measure in a time range corresponding to each time scale, the measurement is carried out in the following procedure.

[0042] First, the fluorescence lifetime is measured in a time range where τ d (sec) observable in the film composed of a plurality of organic semiconductor molecules 20a is measurable. A reasonable τ dWhen calculating [τ], since it is necessary to observe the time-resolved emission waveform of the excitation light, the Spectralon (standard diffusive reflection plate) is used as the measurement target, and the apparatus response function (IRF) is measured under the same measurement conditions (excitation wavelength, repetition frequency, time range) as the above-described fluorescence lifetime measurement. Subsequently, for the emission decay curve of the previously measured molecule, perform a 1st Order "Tail fit" (single-component exponential function fitting) on the measuring apparatus to calculate τ d (sec). Regarding the calculation range when performing the Tail fit, after performing the measurement in a time range sufficiently wider than the excitation pulse width obtained in the IRF measurement, either the time when the emission decay curve of the prompt component has sufficiently decayed or the time when the excitation pulse light has decayed to the dark level, perform the calculation in a time region where the S / N of the emission intensity can be ensured (a region where the average value of the emission intensity of 21 points including 10 points before and after the time of interest is 5 counts or more greater than the dark level).

[0043] Subsequently, in order to calculate τ p , measure a film composed of a plurality of organic semiconductor molecules 20a in a time range (for example, 1 microsecond) that can sufficiently ensure the time resolution of the emission decay curve of the prompt component and also includes the emission decay curve of the delay component. Subsequently, measure the IRF under the same conditions with the Spectralon as the measurement target, and perform a multi-component exponential function fitting with the previously obtained τ d as a fixed parameter to calculate τ p (sec) and the prompt and delay component ratios. Regarding the prompt component, since the emission decay process of two or more components may be included due to intermolecular interactions, etc., in that case, perform fitting with three or more components including the prompt and delay components, but define and calculate any emission decay that does not pass through the cross-term as the prompt component. Regarding the fitting method, follow the method described in the manual of C11367.

[0044] By the above measurements, the prompt component Φ p and the delay component Φ d of the emission quantum yield (Φ = Φ p + Φd ) and the prompt component τ of the fluorescence lifetime p and the delay component τ d are obtained. Therefore, according to the following formulas (3) to (8), various rate constants (k S r , k ISC , k RISC , k T nr ) are calculated (however, non-radiative deactivation from the lowest excited singlet state S1 is ignored). τ p = 1 / k p …(3) τ d = 1 / k d …(4) k S r = Φ p k p …(5) k ISC = (1 - Φ p )k p …(6) k RISC = (k p k d Φ d ) / (k ISC Φ p )…(7) k T nr = k d - Φ p k RISC …(8)

[0045] In addition, when an ideal molecular design is realized as the modulation material, k S r is expected to be significantly lower than k ISC . As a result, the emission intensity of the prompt component decreases and the T1 generation efficiency increases. Under this condition, k RISC is small, and when the non-radiative deactivation rate constant k T nr from T1 is significantly smaller than k RISC , a very long fluorescence lifetime is observed. In such a case, sufficient S / N for rate constant calculation may not be obtained in fluorescence lifetime measurement, but that is the convergence to the ideal condition (k RISCThis is a phenomenon that can be regarded as →0). Furthermore, in polar organic semiconductor molecules having a dipole moment of 0D or more, a phenomenon may occur in which excited molecules formed by photoexcitation in the film spontaneously dissociate into charges without contributing to luminescence. Therefore, its component may not be observed as luminescence, and there is a possibility that sufficient S / N for calculating the rate constant cannot be obtained in fluorescence lifetime measurement.

[0046] The dipole moment (μ) of each of the plurality of organic semiconductor molecules 20a is greater than 0D. The dipole moment is a value that can be calculated by quantum chemical calculation, and generally, it is a value calculated by a calculation method called the Hartree-Fock (HF) method or the density functional (DFT) method. Among them, the most frequently used conditions (combination of functional and basis function) are B3LYP / 6-31(d).

[0047] An example of the organic semiconductor molecule 20a that satisfies the above conditions is a TADF molecule such as TPA-DCPP, 4CzIPN, 4CzTPN, etc. TADF molecules are molecules known in the field of luminescence, but they can be used as the organic semiconductor molecule 20a that satisfies the above conditions. The organic semiconductor molecule 20a is designed by quantum chemical calculation or the like so as to satisfy the above conditions and is generated by organic synthesis. An example of the host molecule 20b that satisfies the above conditions is CBP, mCBP, T2T, mCP, PPT, DPEPO, etc.

[0048] In the organic modulation layer 20 configured as described above, upon irradiation with the input light L1, an excited state capable of reverse intersystem crossing from the lowest excited triplet state T1 to the lowest excited singlet state S1 is formed within each organic semiconductor molecule 20a. As a result, in each of the plurality of organic semiconductor molecules 20a, in addition to the fast charge separation observed until the lowest excited singlet state S1 relaxes, charge separation from the lowest excited triplet state T1, which has a longer lifetime than the lowest excited singlet state S1 (hereinafter referred to as "direct charge separation from the lowest excited triplet state T1"), and / or charge separation from the lowest excited singlet state S1 using the lowest excited triplet state T1, which has a longer lifetime than the lowest excited singlet state S1, as a temporary retreat location from deactivation (hereinafter referred to as "charge separation from the lowest excited singlet state S1 via the lowest excited triplet state T1") occurs.

[0049] In the modulation device 1A, the characteristics of such an organic modulation layer 20 are utilized to modulate the input light L1 as follows. As shown in Fig. 3(a), when the input light L1 is incident on the organic modulation layer 20 through the first electrode 21 in a state where no voltage is applied between the first electrode 21 and the second electrode 22 and no electric field in the direction of causing charge separation is generated in the organic modulation layer 20 by the control unit 3, the light La contained in the input light L1 is absorbed by the organic modulation layer 20, and the light Lb is emitted to the outside through the second electrode 22 by spontaneous emission. At this time, the light Lc contained in the input light L1 is not absorbed by the organic modulation layer 20 and is emitted to the outside through the second electrode 22. Therefore, in this case, the output light L2 containing the light Lb and the light Lc is obtained. Note that the light La, the light Lb, and the light Lc are lights in different wavelength bands from each other.

[0050] As shown in FIG. 3(b), with a voltage applied between the first electrode 21 and the second electrode 22 by the control unit 3 to generate an electric field in the organic modulation layer 20 in a direction that causes charge separation, when the input light L1 enters the organic modulation layer 20 through the first electrode 21, the light La contained in the input light L1 is absorbed by the organic modulation layer 20. However, since the molecules in the excited state are dimmed by charge separation, the light Lb (see FIG. 3(a)) is not generated. At this time, the light Lc contained in the input light L1 is not absorbed by the organic modulation layer 20 and is emitted to the outside through the second electrode 22. Therefore, in this case, the output light L2 containing the light Lc but not the light Lb can be obtained. Note that by increasing the value (absolute value) of the voltage that generates an electric field in the organic modulation layer 20 in a direction that causes charge separation, the ratio of the light Lb contained in the output light L2 can be decreased, and by decreasing the value of the voltage, the ratio of the light Lb contained in the output light L2 can be increased.

[0051] As described above, in the organic modulation element 2A, by irradiating the input light L1 transmitted through the first electrode 21, an excited state in which reverse intersystem crossing from the lowest excited triplet state T1 to the lowest excited singlet state S1 is possible is formed in each of the plurality of organic semiconductor molecules 20a. As a result, in addition to the high-speed charge separation observed until the lowest excited singlet state S1 relaxes in each of the plurality of organic semiconductor molecules 20a, direct charge separation from the lowest excited triplet state T1 and / or charge separation from the lowest excited singlet state S1 via the lowest excited triplet state T1 becomes possible. Here, in each of the plurality of organic semiconductor molecules 20a, the intersystem crossing rate constant k from the lowest excited singlet state S1 to the lowest excited triplet state T1 ISC is the reverse intersystem crossing rate constant k from the lowest excited triplet state T1 to the lowest excited singlet state S1 RISCSince it is larger than [the relevant value], the lifetime of the lowest excited triplet state T1 becomes longer, and sufficient charge separation is likely to be obtained. Therefore, for example, by applying a voltage between the first electrode 21 and the second electrode 22 under irradiation with the input light L1 to generate an electric field in the organic modulation layer 20 in the direction of causing charge separation, the excited state that should originally be deactivated (naturally emitted) with light emission is converted into a charge separation state, and dimming can be achieved. On the other hand, in each of the plurality of organic semiconductor molecules 20a, the reverse intersystem crossing rate constant k from the lowest excited triplet state T1 to the lowest excited singlet state S1 RISC is larger than the non-radiative deactivation rate constant k from the lowest excited triplet state T1 to the ground state S0 T nr Therefore, deactivation due to heat is unlikely to occur, and light emission is likely to be obtained. Therefore, for example, by not applying a voltage between the first electrode 21 and the second electrode 22 and not generating an electric field in the organic modulation layer 20 in the direction of causing charge separation, light emission due to natural emission can be promoted. As described above, according to the organic modulation element 2A, the input light L1 can be modulated according to the purpose.

[0052] In the organic modulation element 2A, in each of the plurality of organic semiconductor molecules 20a, the difference between the energy of the lowest excited singlet state S1 and the energy of the lowest excited triplet state T1 at an absolute temperature of 77K is smaller than 0.3 eV. Thereby, each organic semiconductor molecule 20a can function as a molecule in which an excited state enabling reverse intersystem crossing from the lowest excited triplet state T1 to the lowest excited singlet state S1 is formed by irradiation with the input light L1.

[0053] In the organic modulation element 2A, in each of the plurality of organic semiconductor molecules 20a, the intersystem crossing rate constant k from the lowest excited singlet state S1 to the lowest excited triplet state T1 ISC is larger than the fluorescence rate constant k from the lowest excited singlet state S1 to the ground state S0 S r As a result, while suppressing deactivation from the lowest excited singlet state S1 by light emission, direct charge separation from the lowest excited triplet state T1 and / or charge separation from the lowest excited singlet state S1 via the lowest excited triplet state T1 becomes possible.

[0054] In the organic modulation element 2A, in each of a plurality of organic semiconductor molecules 20a, the intersystem crossing rate constant k from the lowest excited singlet state S1 to the lowest excited triplet state T1 ISC is more than twice the reverse intersystem crossing rate constant k from the lowest excited triplet state T1 to the lowest excited singlet state S1. Thereby, the lifetime of the lowest excited triplet state T1 can be lengthened and the photoelectric conversion efficiency can be improved. RISC

[0055] In the organic modulation element 2A, in each of a plurality of organic semiconductor molecules 20a, the reverse intersystem crossing rate constant k from the lowest excited triplet state T1 to the lowest excited singlet state S1 RISC is 1×10 7 (sec -1 ) or less. Thereby, the lifetime of the lowest excited triplet state T1 can be lengthened and the photoelectric conversion efficiency can be improved.

[0056] In the organic modulation element 2A, the dipole moment of each of a plurality of organic semiconductor molecules 20a is greater than 0 D. Thereby, the energy for charge separation can be reduced.

[0057] In the organic modulation element 2A, the energy of the lowest excited triplet state T1 at an absolute temperature of 77 K in each of a plurality of host molecules 20b is higher than the energy of the lowest excited triplet state T1 at an absolute temperature of 77 K in each of a plurality of organic semiconductor molecules 20a. Thereby, the transfer of an excited molecule from the lowest excited triplet state T1 of the organic semiconductor molecule 20a to the lowest excited triplet state T1 of the host molecule 20b, and the case where the host molecule 20b of the lowest excited triplet state T1 becomes a loss path when an excited state is reformed by the recombination of charges generated by charge separation are suppressed. That is, it is possible to suppress a decrease in the photoelectric conversion efficiency due to the influence of a plurality of host molecules 20b.

[0058] In the organic modulation element 2A, the second electrode 22 has light transmissivity with respect to the output light L2 from the organic modulation layer 20. Thereby, the modulated output light L2 can be emitted to the side opposite to the incident side of the input light L1.

[0059] In the modulation device 1A, the control unit 3 modulates the voltage applied between the first electrode 21 and the second electrode 22. Thereby, the input light L1 can be modulated according to the purpose.

[0060] FIG. 4 is an energy diagram of the organic modulation layer of the comparative example. The organic modulation layer of the comparative example shown in FIG. 4 includes a plurality of organic semiconductor molecules 20c. The organic semiconductor molecule 20c is a fluorescent molecule (for example, Alq3 or the like). In the organic modulation layer of the comparative example shown in FIG. 4, the difference between the energy of the lowest excited singlet state S1 and the energy of the lowest excited triplet state T1 at an absolute temperature of 77K is large, and even when irradiated with light, an intersystem crossing from the lowest excited singlet state S1 to the lowest excited triplet state T1 does not occur within each organic semiconductor molecule 20c. Therefore, neither direct charge separation from the lowest excited triplet state T1 nor charge separation from the lowest excited singlet state S1 via the lowest excited triplet state T1 occurs naturally. Therefore, in the organic modulation layer of the comparative example shown in FIG. 4, the dissociation efficiency into charges decreases, and the components that become losses as light and heat increase. As a result, the organic modulation layer of the comparative example shown in FIG. 4 does not function as an effective modulation layer.

[0061] FIG. 5 is a graph showing the voltage dependence of the quantum efficiency for the organic light-receiving layer of an example containing a plurality of TADF molecules and the organic light-receiving layer of a comparative example containing a plurality of fluorescent molecules. In FIG. 5, the “quantum efficiency” is the ratio of the “number of electrons detected from the organic light-receiving layer” to the “number of photons absorbed by the organic light-receiving layer”. Further, the “voltage” is the voltage applied to the organic light-receiving layer during light irradiation, and a negative value is a value that generates an electric field in the organic light-receiving layer in the direction that causes charge separation (the same applies hereinafter). As shown in FIG. 5, in the organic light-receiving layer of the example containing a plurality of TADF molecules, the quantum efficiency is higher and the rate of change of the quantum efficiency with respect to the voltage is also larger than that of the organic light-receiving layer of the comparative example containing a plurality of fluorescent molecules. This indicates that the organic light-receiving layer of the example functions as an effective modulation layer. [Second Embodiment]

[0062] As shown in FIGS. 6(a) and 6(b), the modulation device 1B of the second embodiment is different from the modulation device 1A of the first embodiment in that the organic modulation element 2B has a light-receiving layer 23. The organic modulation element 2B of the second embodiment includes an organic modulation layer 20, a first electrode 21 disposed on one side of the organic modulation layer 20, a second electrode 22 disposed on the other side of the organic modulation layer 20, and a light-receiving layer 23 disposed on the other side of the second electrode 22. The light-receiving layer 23 receives the output light L2. The light-receiving layer 23 constitutes, for example, a PD, and charges generated by receiving the output light L2 are detected as a current signal from an electrode (not shown) electrically connected to the light-receiving layer 23.

[0063] According to the organic modulation element 2B configured as described above, the input light L1 can be modulated according to the purpose, and the modulated output light L2 can be detected according to the purpose.

[0064] Specifically, as shown in Fig. 6(a), when the input light L1 is incident on the organic modulation layer 20 through the first electrode 21 in a state where no voltage is applied between the first electrode 21 and the second electrode 22 and no electric field in the direction of causing charge separation is generated in the organic modulation layer 20, the light La contained in the input light L1 is absorbed by the organic modulation layer 20, and light emission due to charge separation and spontaneous emission occurs in the organic modulation layer 20, and the light Lb is incident on the light receiving layer 23 through the second electrode 22. At this time, the light Lc contained in the input light L1 is not absorbed by the organic modulation layer 20 and is incident on the light receiving layer 23 through the second electrode 22. Therefore, in this case, the output light L2 including the light Lb and the light Lc is detected.

[0065] As shown in Fig. 6(b), when the input light L1 is incident on the organic modulation layer 20 through the first electrode 21 in a state where a voltage is applied between the first electrode 21 and the second electrode 22 and an electric field in the direction of causing charge separation is generated in the organic modulation layer 20, the light La contained in the input light L1 is absorbed by the organic modulation layer 20, and charge separation occurs in the organic modulation layer 20 but light emission due to spontaneous emission does not occur, and the light Lb (see Fig. 6(a)) is not generated. At this time, the light Lc contained in the input light L1 is not absorbed by the organic modulation layer 20 and is incident on the light receiving layer 23 through the second electrode 22. Therefore, in this case, the output light L2 including the light Lc but not including the light Lb is detected. Thus, in a state where a voltage is applied between the first electrode 21 and the second electrode 22, the light La contained in the input light L1 can be detected by the organic modulation layer 20, and the light Lc contained in the input light L1 can be detected by the light receiving layer 23. Note that by increasing the value (absolute value) of the voltage that generates an electric field in the direction of causing charge separation in the organic modulation layer 20, the ratio of the light Lb contained in the output light L2 can be decreased, and by decreasing the value of the voltage, the ratio of the light Lb contained in the output light L2 can be increased.

[0066] FIG. 7 is a configuration diagram of a system S1 for verifying the function of the modulation device 1B according to the second embodiment. In the system S1, an organic modulation element 2B is used, which sandwiches an organic modulation layer 20 containing TPA-DCPP (a plurality of organic semiconductor molecules 20a) and CBP (a plurality of host molecules 20b) in a mass ratio of 50:50 between a first electrode 21 and a second electrode 22. As the material for the first electrode 21, a material having light transmissivity with respect to the input light L1 and the output light L2 was used. As the material for the second electrode 22, a material that reflects the input light L1 and the output light L2 was used. In the system S1, the input light L1 emitted from the LED 4 was made to enter the organic modulation layer 20 through the first electrode 21. Then, the output light L2 emitted from the organic modulation layer 20 to the outside through the first electrode 21 was made to enter the SiPD 6 through the optical fiber 5.

[0067] As a result of the verification in the system S1, the following results were obtained. As shown in FIG. 8(a), the current value detected by the SiPD 6 in a state where no voltage is applied between the first electrode 21 and the second electrode 22 was larger than the current value detected by the SiPD 6 in a state where a voltage is applied between the first electrode 21 and the second electrode 22. Conversely, as shown in FIG. 8(b), the current value detected by the organic modulation layer 20 in a state where a voltage is applied between the first electrode 21 and the second electrode 22 was larger than the current value detected by the organic modulation layer 20 in a state where no voltage is applied between the first electrode 21 and the second electrode 22. This indicates that the modulation device 1B of the second embodiment functions properly. [Third Embodiment]

[0068] As shown in FIGS. 9(a) and 9(b), the modulation device 1C according to the third embodiment is different from the modulation device 1A according to the first embodiment in that the organic modulation element 2C has a light emitting layer 24. The organic modulation element 2C according to the third embodiment includes an organic modulation layer 20, a first electrode 21 disposed on one side of the organic modulation layer 20, a second electrode 22 disposed on the other side of the organic modulation layer 20, and a light emitting layer 24 disposed on one side of the first electrode 21. The light emitting layer 24 emits the input light L1. The light emitting layer 24 constitutes, for example, an LED.

[0069] According to the organic modulation element 2C configured as described above, the input light L1 can be modulated according to the purpose, and the output light L2 modulated according to the purpose can be emitted.

[0070] Specifically, as shown in FIG. 9(a), when no voltage is applied between the first electrode 21 and the second electrode 22 by the control unit 3 and no electric field in the direction of causing charge separation is generated in the organic modulation layer 20, and the input light L1 is emitted from the light-emitting layer 24 and the input light L1 is incident on the organic modulation layer 20 through the first electrode 21, a part of the light L11 of the input light L1 is absorbed by the organic modulation layer 20, and charge separation and light emission due to spontaneous emission occur in the organic modulation layer 20, and the light Lb is emitted to the outside through the second electrode 22. At this time, the remaining light L12 of the input light L1 is not absorbed by the organic modulation layer 20 and is emitted to the outside through the second electrode 22. Therefore, in this case, the output light L2 including the light Lb and the light L12 is emitted to the outside.

[0071] As shown in FIG. 9(b), when a voltage is applied between the first electrode 21 and the second electrode 22 by the control unit 3 and an electric field in the direction of causing charge separation is generated in the organic modulation layer 20, and the input light L1 is emitted from the light-emitting layer 24 and the input light L1 is incident on the organic modulation layer 20 through the first electrode 21, a part of the light L11 of the input light L1 is absorbed by the organic modulation layer 20, and charge separation occurs in the organic modulation layer 20 but light emission due to spontaneous emission does not occur, and the light Lb (see FIG. 9(a)) is not generated. At this time, the remaining light L12 of the input light L1 is not absorbed by the organic modulation layer 20 and is emitted to the outside through the second electrode 22. Therefore, in this case, the output light L2 including the light L12 but not including the light Lb is emitted to the outside. Note that by increasing the value (absolute value) of the voltage that generates an electric field in the direction of causing charge separation in the organic modulation layer 20, the ratio of the light Lb included in the output light L2 can be decreased, and by decreasing the value of the voltage, the ratio of the light Lb included in the output light L2 can be increased.

[0072] FIG. 10 is a configuration diagram of a system S2 for verifying the function of the modulation device 1C according to the third embodiment. In the system S2, an organic modulation element 2C is used, which sandwiches an organic modulation layer 20 containing TPA-DCPP (a plurality of organic semiconductor molecules 20a) and CBP (a plurality of host molecules 20b) in a mass ratio of 50:50 between a first electrode 21 and a second electrode 22. As the material for the first electrode 21, a material having light transmissivity with respect to the input light L1 and the output light L2 is used. As the material for the second electrode 22, a material that reflects the input light L1 and the output light L2 is used. In the system S2, the input light L1 emitted from the LED 4 is made incident on the organic modulation layer 20 through the first electrode 21. Then, the output light L2 emitted from the organic modulation layer 20 to the outside through the first electrode 21 is made incident on the spectroscope 7 through the optical fiber 5.

[0073] As a result of verification in the system S2, the following results were obtained. FIG. 11(a) is a graph showing the spectrum of the output light L2 detected by the spectroscope 7 when blue input light L1 is emitted from the LED 4. As shown in FIG. 11(a), when the value (absolute value) of the voltage that generates an electric field in the organic modulation layer 20 in the direction of causing charge separation is increased, the ratio of red light contained in the output light L2 decreases. FIG. 11(b) is a graph showing the spectrum of the output light L2 detected by the spectroscope 7 when green input light L1 is emitted from the LED 4. As shown in FIG. 11(b), when the value (absolute value) of the voltage that generates an electric field in the organic modulation layer 20 in the direction of causing charge separation is increased, the ratio of red light contained in the output light L2 decreases. This indicates that the modulation device 1C according to the third embodiment functions properly. [Fourth Embodiment]

[0074] As shown in FIG. 12, the modulation device 1D according to the fourth embodiment is different from the modulation device 1A according to the first embodiment in that the second electrode 22 in the organic modulation element 2D does not have light transmissivity with respect to the input light L1 and the output light L2. In the organic modulation element 2D according to the fourth embodiment, the first electrode 21 has light transmissivity with respect to the input light L1 and the output light L2. Thereby, the modulated output light L2 can be emitted to the incident side of the input light L1.

[0075] In the modulation device 1D, the control unit 3 applies an arbitrary pulse voltage between the first electrode 21 and the second electrode 22. When the input light L1, which is CW light, is incident on the organic modulation layer 20 from the outside through the first electrode 21 in a state where a pulse voltage is applied between the first electrode 21 and the second electrode 22, the output light L2, which is pulse light having a pulse waveform corresponding to the pulse voltage, is emitted from the organic modulation layer 20 to the outside through the first electrode 21.

[0076] FIG. 13 is a graph showing the verification results regarding the function of the modulation device 1D of the fourth embodiment. As shown in FIG. 13, when a normal OLED is electrically excited (electrically driven), the waveform of the output light is distorted when trying to modulate at high speed. On the other hand, in the modulation device 1D (organic modulation layer 20 of the example), since the organic semiconductor molecules 20a in the excited state are forcibly dissociated into charges and the afterglow component is suppressed, the output light L2 having a rectangular-wave emission intensity can be obtained. In order to suppress the afterglow component, it is preferable to dispose a hole transport layer having a HOMO level shallower than the HOMO level of the organic modulation layer 20 between the electrode functioning as the anode among the first electrode 21 and the second electrode 22 and the organic modulation layer 20. Also, in order to suppress the afterglow component, it is preferable to dispose an electron transport layer having an LUMO level shallower than the LUMO level of the organic modulation layer 20 between the electrode functioning as the cathode among the first electrode 21 and the second electrode 22 and the organic modulation layer 20. Regarding the above-described disposition of the hole transport layer and the disposition of the electron transport layer, either one may be implemented or both may be implemented. Further, the light-emitting layer may contain either one or both of the molecules used for the above-described hole transport layer and electron transport layer, or the light-emitting layer may have a structure in which a layer containing the molecules used for the hole transport layer and a layer containing the molecules used for the electron transport layer are laminated. [Modification Example]

[0077] The present invention is not limited to the above-described embodiments. In each of the above-described embodiments, the plurality of organic semiconductor molecules 20a included in the organic modulation layer 20 may be composed of a plurality of types of organic semiconductor molecules. In each of the above-described embodiments, the plurality of host molecules 20b included in the organic modulation layer 20 may be composed of a plurality of types of host molecules. In each of the above-described embodiments, the organic modulation layer 20 may not include a plurality of host molecules 20b.

[0078] In each of the above-described embodiments, each of the plurality of organic semiconductor molecules 20a may not satisfy all of the above-described various conditions as long as it is a molecule in which an excited state enabling reverse intersystem crossing from the lowest excited triplet state T1 to the lowest excited singlet state S1 is formed in each of the plurality of organic semiconductor molecules 20a by irradiation with the input light L1.

[0079] In the first embodiment, the first electrode 21 may have light transmissivity with respect to the input light L1 and the output light L2, and the second electrode 22 may not have light transmissivity with respect to the input light L1 and the output light L2. In the fourth embodiment, the first electrode 21 may have light transmissivity with respect to the input light L1, and the second electrode 22 may have light transmissivity with respect to the output light L2. In each of the above-described embodiments, the plurality of organic modulation layers 20 may be arranged one-dimensionally or two-dimensionally.

Explanation of Reference Numerals

[0080] 1A, 1B, 1C, 1D... modulation device, 2A, 2B, 2C, 2D... organic modulation element, 3... control unit, 20... organic modulation layer, 20a... organic semiconductor molecule, 20b... host molecule, 21... first electrode, 22... second electrode, 23... light receiving layer, 24... light emitting layer, L1... input light, L2... output light.

Claims

1. An organic modulation layer containing a plurality of organic semiconductor molecules, A first electrode that is optically transparent to the input light to the organic modulation layer and is disposed on one side of the organic modulation layer, A second electrode disposed on the other side of the organic modulation layer, and comprising: Each of the plurality of organic semiconductor molecules is a molecule in which an excited state enabling reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state is formed in each of the plurality of organic semiconductor molecules by irradiation with the input light, In each of the plurality of organic semiconductor molecules, the intersystem crossing rate constant from the lowest excited singlet state to the lowest excited triplet state is greater than the reverse intersystem crossing rate constant from the lowest excited triplet state to the lowest excited singlet state, In each of the plurality of organic semiconductor molecules, the reverse intersystem crossing rate constant from the lowest excited triplet state to the lowest excited singlet state is greater than the non-radiative deactivation rate constant from the lowest excited triplet state to the ground state. An organic modulation element.

2. In each of the plurality of organic semiconductor molecules, the difference between the energy of the lowest excited singlet state and the energy of the lowest excited triplet state at an absolute temperature of 77 K is less than 0.3 eV. The organic modulation element according to claim 1.

3. In each of the plurality of organic semiconductor molecules, the intersystem crossing rate constant from the lowest excited singlet state to the lowest excited triplet state is greater than the fluorescence rate constant from the lowest excited singlet state to the ground state. The organic modulation element according to claim 1 or 2.

4. In each of the plurality of organic semiconductor molecules, the intersystem crossing rate constant from the lowest excited singlet state to the lowest excited triplet state is at least twice the reverse intersystem crossing rate constant from the lowest excited triplet state to the lowest excited singlet state. The organic modulation element according to any one of claims 1 to 3.

5. In each of the plurality of organic semiconductor molecules, the reverse intersystem crossing rate constant from the lowest excited triplet state to the lowest excited singlet state is 1×10 ７ (sec －１ ) or less. The organic modulation device according to claim 4.

6. The dipole moment of each of the plurality of organic semiconductor molecules is greater than 0 D. The organic modulation device according to any one of claims 1 to 5.

7. The organic modulation layer further includes a plurality of host molecules, The energy of the lowest excited triplet state at an absolute temperature of 77 K in each of the plurality of host molecules is higher than the energy of the lowest excited triplet state at an absolute temperature of 77 K in each of the plurality of organic semiconductor molecules. The organic modulation device according to any one of claims 1 to 6.

8. The second electrode is optically transparent to the output light from the organic modulation layer. The organic modulation device according to any one of claims 1 to 7.

9. The first electrode is optically transparent to the output light from the organic modulation layer. The organic modulation device according to any one of claims 1 to 7.

10. An organic modulation layer including a plurality of organic semiconductor molecules, A first electrode that is optically transparent to the input light to the organic modulation layer and is disposed on one side of the organic modulation layer, A second electrode that is optically transparent to the output light from the organic modulation layer and is disposed on the other side of the organic modulation layer, A light receiving layer disposed on the other side of the second electrode and receiving the output light. The organic modulation device includes: Each of the plurality of organic semiconductor molecules is a molecule in which an excited state capable of reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state is formed in each of the plurality of organic semiconductor molecules by irradiation with the input light. Organic modulation device.

11. An organic modulation layer including a plurality of organic semiconductor molecules, A first electrode having light transmissivity with respect to input light to the organic modulation layer and disposed on one side of the organic modulation layer, A second electrode having light transmissivity with respect to output light from the organic modulation layer and disposed on the other side of the organic modulation layer, A light emitting layer disposed on the one side of the first electrode and emitting the input light, and An organic modulation element, wherein each of the plurality of organic semiconductor molecules is a molecule in which an excited state enabling reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state is formed in each of the plurality of organic semiconductor molecules by irradiation with the input light.

12. An organic modulation layer including a plurality of organic semiconductor molecules, A first electrode having light transmissivity with respect to input light to the organic modulation layer and disposed on one side of the organic modulation layer, A second electrode disposed on the other side of the organic modulation layer, A control unit that modulates a voltage applied between the first electrode and the second electrode, and each of the plurality of organic semiconductor molecules is a molecule in which an excited state enabling reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state is formed in each of the plurality of organic semiconductor molecules by irradiation with the input light, and the modulation device, wherein when the control unit reduces light emission due to spontaneous emission from the organic modulation layer under irradiation with the input light, a voltage is applied between the first electrode and the second electrode so that an electric field in a direction causing charge separation is generated in the organic modulation layer.

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