Composition, organic light-emitting device, light-emitting method, and method for designing a light-emitting composition.

Abstract

To provide stimulable light emission from a pure organic blend film constituted of an electron donor, a receiver, and a trap / light-emitting molecule, because although stimulable light emission has been gathering a large interest in a field of biomedical and in an information technology, because it makes it possible to store or release energy or data by using an electromagnetic wave for both of input and output, this phenomenon is almost limited to a solid state inorganic material.SOLUTION: An organic blend film, in which electric charges are stored as radical ions by ultraviolet light irradiation, are then extracted by near infrared light irradiation to generate visible light, is capable of a plurality of cycles (>10 times) of organic stimulable emission, and this emission can be observed from the film placed in a dark place at a room temperature for a week after excitation. by changing the trap / light emitter molecules, an emission color can be changed. These findings have wide impact on existing applications and provide new perspectives for innovative flexible devices.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to organic exhaustion luminescence. More specifically, this invention relates to compositions, the use of said compositions, organic exhaustion luminescence apparatuses, the use of said apparatuses, methods for designing exhaustion luminescence compositions, and programs for designing compositions. [Background technology]

[0002] Organic semiconductors 1~4 and certain types of soft crystals 5 (For example, photochromic compounds) 6 Porous coordination polymers / metal-organic frameworks 7 , and metal halide perovskite 8、9 These materials are promising for future technologies such as wearable optoelectronic devices and ultra-high-density data storage due to their structural diversity, mechanical elasticity, low cost, and ease of processing. In addition, the optical and electronic properties of these materials can be adapted through molecular design to obtain efficient light emission or power conversion through tunable bandgap energy.

[0003] In recent years, long-persistent luminescence (LPL) systems composed of two or more organic compounds have been demonstrated to maintain a long-lasting charge separation state for up to one hour at room temperature in blended films. 10、11 These novel systems do not contain rare metals and can be fabricated at relatively low temperatures by a simple melt-casting method. Following these pioneering studies, various organic LPL materials have been developed by combining different electron donor / acceptor pairs. 12~15 On the other hand, conventional rare metal LPL systems are known to exhibit strong photocatalytic emission (PSL) phenomena. In this case, excess charge accumulated in defects or dopant sites during pre-irradiation (e.g., X-rays) cannot be thermally activated at room temperature, but is released by a second irradiation (e.g., visible light), emitting photons. 16~19。Therefore, inorganic PSL materials are used for optical storage (e.g., BaFBr:Eu 2+ imaging plates) 20、21 and luminescent probes 22、23 in a variety of applications. If PSL were realized with organic materials, new fields of flexible optoelectronic devices and biomedical applications would be opened up.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

[0005] The objective of this invention is to realize PSL using organic materials. [Means for solving the problem]

[0006] This invention encompasses the following inventions. [1] A composition comprising an electron donor, an electron acceptor, and a third component, The combination of the electron donor and the electron acceptor is selected from combinations that exhibit phosphorescent emission upon excitation, and The third component is selected from materials that have the ability to accept electrons and then release electrons upon photostimulation, and materials that have the ability to accept holes and then release holes upon photostimulation.

[0007] The combination of electron donor and electron acceptor used in the composition of the present invention is a phosphorescent composition. After light irradiation of the phosphorescent composition is stopped, luminescence is observed at 10K (preferably also at 300K). The mechanism of phosphorescent luminescence can be distinguished from the luminescence mechanisms of phosphorescence and delayed fluorescence.

[0008] In this invention, "electron donor" refers to a molecule that releases electrons when the composition of this invention is irradiated with light and is converted to an oxidized state such as a neutral radical state or a radical cation state (in this invention, the neutral radical state is preferred). In this invention, "electron acceptor" refers to a molecule that accepts electrons released from the electron donor and is converted to a reduced state such as a radical anion state or a neutral radical state. The presence of radicals can be confirmed by ESR (electron spin resonance) measurement, absorbance measurement, etc.

[0009] The emission from the combination of electron donor and electron acceptor used in the composition of the present invention is preferably exciplex emission or emission from a charge-transfer excited state. In the present invention, "exciplex emission" or "emission from a charge-transfer excited state" means emission from an excited state (exciplex) generated when an electron donor associates with an electron acceptor. The emission spectral pattern of exciplex emission is different from the emission spectral patterns of emission observed from only an electron donor and emission observed from only an electron acceptor. "Exciplex emission" or "emission from a charge-transfer excited state" exhibits an emission spectral pattern different from the emission spectral patterns of emission observed from only an electron donor and emission observed from only an electron acceptor during light irradiation. Here, the emission spectral pattern of the phosphorescent composition of the present invention has an emission spectral shape different from the emission spectral shape of emission spectra observed from only an electron donor and emission spectra observed from only an electron acceptor. This means that the wavelength of maximum emission may differ, the halfwidth or rise slope of the emission peak may differ, or the number of emission peaks may differ.

[0010] The oxidation state of the electron donor and the reduction state of the electron acceptor are stable. Due to these characteristics, it is presumed that the electron donor in the oxidation state and the electron acceptor in the reduction state accumulate in the phosphorescent composition during light irradiation, and that luminescence continues even after light irradiation stops due to molecular recombination. Therefore, the phosphorescent composition can continue to emit light for a long period of time.

[0011] A phosphorescent composition refers to a phosphorescent composition that exhibits a sustained luminescence duration of 0.1 seconds or more. The luminescence duration of the phosphorescent composition of the present invention is preferably 1 second or more, more preferably 5 seconds or more, even more preferably 5 minutes or more, and still more preferably 20 minutes or more. Preferably, the phosphorescent composition of the present invention not only achieves such a long-lasting luminescence duration at 10K, but also achieves such a long-lasting luminescence duration at 20°C.

[0012] The luminescence intensity can be measured, for example, using a spectrometer. (0.01 cd / m²) 2 Luminescence intensities below a certain level can be considered undetectable. In the embodiments shown below, the detection limit is 1 / 1000 of the initial luminescence intensity.

[0013] If a log-log graph (luminescence intensity on a logarithmic scale on the y-axis and time on a logarithmic scale on the x-axis) showing the change in luminescence intensity over time after, for example, 3 minutes of light exposure to a phosphorescent composition and then stopping the light irradiation is non-exponential, then long-term sustained luminescence can be confirmed. In the case of general phosphorescence caused by the photoluminescence of organic compounds, it has been confirmed that the luminescence intensity decays exponentially. A semi-log graph of luminescence intensity on a logarithmic scale on the y-axis and time on the x-axis (time is on a linear scale, not a logarithmic scale) shows exponential decay (first-order decay). On the other hand, the semi-log graph of luminescence from the phosphorescent composition of the present invention shows non-exponential decay, and the luminescence mechanism is clearly different from that of general phosphorescence.

[0014] In some embodiments of the present invention, the phosphorescent composition (i.e., a combination of electron donors and electron acceptors) contains, based on the total molar amount of electron donors and electron acceptors, at least 70 mol% of electron donors and less than 30 mol% of electron acceptors, preferably at least 90 mol% of electron donors and less than 10 mol% of electron acceptors, for example, at least 95 mol% of electron donors and less than 5 mol% of electron acceptors, or at least 99 mol% of electron donors and less than 1 mol% of electron acceptors. The proportion of electron donors is greater than the proportion of electron acceptors. Therefore, holes can easily move from HOMO to HOMO of electron donors, and recombination of holes and electrons can be triggered with a high probability.

[0015] In some embodiments of the present invention, the phosphorescent composition contains, based on the total molar amount of electron donors and electron acceptors, at least 70 mol% electron acceptors and less than 30 mol% electron donors, preferably at least 90 mol% electron acceptors and less than 10 mol% electron donors, for example, at least 95 mol% electron acceptors and less than 5 mol% electron donors, or at least 99 mol% electron acceptors and less than 1 mol% electron donors. The proportion of electron acceptors is greater than the proportion of electron donors. Therefore, electrons can easily move from LUMO to LUMO of electron acceptors, and recombination of holes and electrons can be triggered with a high probability.

[0016] The electron donor-electron acceptor combinations disclosed in Non-Patent Documents Nos. 10-15, International Publication No. 2018 / 105633 (US Patent No. 2018-0346807A1), International Publication No. 2019 / 031524 (US Patent No. 2020-0165516A), and International Publication No. 2019 / 189045 can be used in this application. These six Non-Patent Documents and five Patent Documents are explicitly incorporated into this application in their entirety by reference.

[0017] The third component (trap / luminescent material) may be an organic semiconductor, a cationic material, an anionic material, or a metallic material. Preferably, the third component (trap / luminescent material) is an organic material. In a preferred embodiment, when the third component (trap / luminescent material) is in a radical anionic state and is subjected to photostimulation, the third component emits unpaired electrons.

[0018] In one embodiment of the present invention, the electron acceptor and the third component satisfy one of the following equations. LUMO(Acpt)>LUMO(Trap / Em)+0.4eV LUMO(Acpt)>LUMO(Trap / Em)+0.5eV LUMO(Acpt)≧LUMO(Trap / Em)+0.6eV In the formula, LUMO(Acpt) represents the lowest excited singlet energy level of the electron acceptor, and LUMO(Trap / Em) represents the lowest excited singlet energy level of the third component.

[0019] The electron donor, electron acceptor, and third component may consist of three or more atoms selected from the group consisting of C, H, N, O, S, P, B, and halogen atoms. In some embodiments of the present invention, the electron donor, electron acceptor, and third component consist of three or more atoms selected from the group consisting of C, H, N, O, S, and P. In some embodiments of the present invention, the electron donor, electron acceptor, and third component consist of three or more atoms selected from the group consisting of C, H, N, O, B, and F.

[0020] [2] The composition according to [1], wherein the light stimulation is near-infrared light irradiation.

[0021] The composition of the present invention may be in the form of a film (layer), coating, plate, particles, dispersion, solution, etc.

[0022] [3] The composition according to [1] or [2], which exhibits light emission mainly from the third component when excited.

[0023] [4] The composition according to [1] or [2], which exhibits light emission mainly from an exciplex formed by the electron donor and the electron acceptor when excited.

[0024] An organic luminescence device comprising the composition described in any one of items [5][1] to [4].

[0025] The term "exhausted light emission device" refers to a device that releases stored energy by generating a light emission signal in response to a light stimulus. In a preferred embodiment of the present invention, the exhausted light emission device emits visible light in response to a light stimulus. Examples of light stimuli include infrared light irradiation, including near-infrared irradiation (780 nm to 2500 nm), and visible light irradiation, including red light irradiation (640 nm to 770 nm), orange light irradiation (590 nm to 640 nm), yellow light irradiation (550 nm to 590 nm), green light irradiation (490 nm to 550 nm), and blue light irradiation (380 nm to 490 nm). In a preferred embodiment of the present invention, the light stimulus is near-infrared light irradiation.

[0026] Energy for exhaustion is stored before photostimulation. This energy may be stored by photostimulation such as ultraviolet light (100nm–400nm; typically UV-A (315nm–400nm)), blue light (380–490nm), and green light (490nm–550nm). The photostimulation for energy storage generally has a shorter wavelength than the photostimulation for photostimulation. Energy for exhaustion may also be stored by electric current injection.

[0027] The term "organic exhausted light-emitting device" refers to a exhausted light-emitting device in which the electron donor, electron acceptor, and third component are all organic materials that do not contain rare metal elements, preferably organic materials that do not contain metallic elements. In a preferred embodiment of the present invention, the organic material consists of C and at least one element selected from H, B, N, O, F, Si, P, S, Cl, Se, Br, and I. In a more preferred embodiment of the present invention, the organic material consists of C and at least one element selected from H, B, N, O, Si, P, and S.

[0028] In a preferred embodiment of the present invention, the organic exhaustion luminescence apparatus has a layer containing the composition. When the energy for exhaustion luminescence is stored by electric current injection, the apparatus generally has a pair of electrodes flanking the layer containing the composition.

[0029] According to the present invention, a flexible organic light emission device can be provided.

[0030] In a preferred embodiment of the present invention, the third component (trap / luminescent element) emits visible light. In one embodiment, the exciplex between the electron donor and electron acceptor also emits light. In another embodiment, the exciplex between the electron donor and electron acceptor emits light, but the third component does not.

[0031] [6] A method of light emission by light stimulation, Exciting the composition described in any one of items [1] to [4], and To cause the aforementioned composition to emit light by light stimulation, Methods that include...

[0032] [7] A light-induced luminescence method as described in [6], satisfying either (1) or (2) below: (1) The excitation causes electrons to be transferred from the electron donor to the electron acceptor, generating an electron donor in a radical cation state and an electron acceptor in a radical anion state. The electrons of the electron acceptor in the radical anion state are trapped by the third component, The electrons trapped on the third component are detrapped by photostimulation and transferred to the electron acceptor, generating an electron acceptor in a radical anion state, and The detrapped electrons of the electron acceptor in the radical anion state recombine with the holes of the electron donor in the radical cation state, thereby generating an exciplex between the electron donor and the electron acceptor and producing light emission, or (2) The excitation causes electrons to be transferred from the electron donor to the electron acceptor, generating an electron donor in a radical cation state and an electron acceptor in a radical anion state. The holes in the electron donor in the radical cation state are trapped by the third component. The trapped holes on the third component are detrapped by photostimulation and transferred to an electron donor, generating an electron donor in a radical cation state, and The detrapped holes in the electron donor in the radical cation state recombine with electrons in the electron acceptor in the radical anion state, thereby generating an exciplex between the electron donor and the electron acceptor and producing light emission.

[0033] In a preferred embodiment of the present invention, a third component that receives energy from the exciplex emits light. In some embodiments of the present invention, energy is further transferred from the third component to a light-emitting material, and the light-emitting material emits light.

[0034] In a preferred embodiment of the present invention, when a light stimulus is applied to a device from which no light emission has been observed, the device emits exhausted light.

[0035] [8] The method for light emission by light stimulation according to [6] or [7], further comprising applying a magnetic field to the composition to control the intensity of light emission during the light stimulation.

[0036] Use of the compositions described in [9][6] or [7] in imaging, marking, optical data storage, optical sensing, optical energy conversion, and security seals.

[0037] More specifically, the composition may be used in solar cells, photocatalysts, bioimaging, biomarkers, medical imaging plates (X-ray imaging plates), optical sensors, bioimaging probes, optical energy sensors, security stickers, security labels, security tapes, etc. If the security label of the present invention is attached inside a security or confidential document that is set to be exposed to excitation light upon opening, it is possible to check whether the document has been opened by irradiating the seal with NIR light.

[0038]

[10] A method for designing a composition for exhaustion and luminescence, 1) Evaluate the exhaustion luminescence of the composition described in any one of items [1] to [4], 2) Designing a novel composition to improve exhaust luminescence by adjusting at least one of the electron donor, the electron acceptor, and the third component, and 3) Optionally, repeat step 2) at least once. Methods that include...

[0039] A biocompatible composition can be designed by selecting the three components from biocompatible materials. A soluble composition can be designed by selecting the three components from materials soluble in the solvent used. The excitation wavelength can be adjusted by selecting an electron donor from a material excited by a desired wavelength. The stimulation wavelength can be adjusted by selecting a donor from a material in which unpaired electrons in a radical anion state are excited by a desired wavelength. The wavelength of exhausted emission can be adjusted by selecting a donor from a light-emitting material having a desired emission wavelength. [Brief explanation of the drawing]

[0040] [Figure 1]Schematic diagram of the organic PSL system. a) Molecular structures of m-MTDATA, PPT, and Rb, used as electron donor, acceptor, and trap / luminescent molecules, respectively. b) Energy diagram of the organic PSL system. During UV excitation, electrons are transferred from the excited state of the donor (D) to the acceptor (A), forming a CT excited state or exciplex (Dδ+Aδ-). Electrons in the film diffuse between A molecules and are partially captured by trap / luminescent (T) molecules, forming their radical anions (T·-). The excited state of T·- (T·-*) formed by NIR stimulation triggers electron transfer to A and subsequent re-encounter of A·- with D·+. Subsequently, the excited state of T (T*) is formed from the regenerated CT state via FRET, resulting in visible PSL in addition to LPL. The emission from T* is also regulated by an external magnetic field through long-range spin entanglement between the singlet and triplet states of the D·+···T·- pair. [Figure 2] Organic PSL from m-MTDATA / PPT / Rb blend film. a) Writing and reading processes. b) Photographs of the m-MTDATA / PPT / Rb film. Part of the sample was masked during UV irradiation. Scale bar is 10 mm. c) Photographs of the sample with and without NIR irradiation after UV irradiation has stopped. d) Emission decay profiles obtained for the m-MTDATA / PPT / Rb film with and without NIR irradiation (red and black lines, respectively). The inset shows a logarithmic plot of the decay profiles. The wavelengths of UV and NIR light were 365 nm and 800 nm, respectively. e) Differential absorption spectra obtained for m-MTDATA / PPT / Rb (0, 1 mol%) film before and after 365 nm light irradiation. [Figure 3]Color adjustment of PSL using different trap / luminescent molecules. The molecular structure of the trap / luminescent molecules and corresponding photographs of blend films containing different trap / luminescent molecules (1 mol%) with and without NIR irradiation are shown. The wavelengths of UV and NIR light were 365 nm and 800 nm, respectively. The actual size of the film in the images is 5 mm x 5 mm. The difference in LUMO energy (ΔELUMO) was calculated from ELUMO(trap / luminescent)-ELUMO(PPT) based on the reduction potential of the material (Figure 5). The average intensity (I-mean) of PSL was calculated from the red, green, and blue components of the color images captured with a digital camera. The exposure time was 10 seconds. Image brightness and contrast differed for each sample. [Figure 4] Magnetic field effects. a) Response of LPL intensity to an external magnetic field observed for m-MTDATA / PPT / Rb film. The inset shows a magnified view of the region contained within the dotted line and the applied magnetic field. b) Plot of XLPL(B) as a function of the external magnetic field(B). The solid line shows the least-squares fit of the data to the Lorentz function. The inset shows the dependence of saturated XLPL(B) and B1 / 2 values ​​on Rb concentration. c) Simplified model of magnetic field-induced population changes (circles in the dotted line) for singlet (green) and triplet (blue) charge-separated states (CSS). [Figure 5] HOMO and LUMO energy levels. The HOMO level of m-MTDATA and the LUMO levels of PPT and trap / luminescent molecules were calculated from the redox peaks of the cyclic voltammogram. The energy gap between the HOMO and LUMO levels was calculated from the rise times (onsets) of the absorption spectra observed for the solution sample. [Figure 6]Fluorescence microscopy measurements. a) Preparation of the experiment based on an inverted fluorescence microscope. NIR light and magnetic field were applied from above the sample. b) Fluorescence image observed on m-MTDATA / PPT / Rb film under 365 nm light irradiation. c) LPL image observed on m-MTDATA / PPT / Rb film 10 seconds after stopping 365 nm light irradiation. Scale bar is 10 μm. Regions that emitted uniformly without showing obvious structural disorder were selected for analysis. [Figure 7] Luminescence properties of the film. a) Normalized emission spectra of m-MTDATA / PPT film containing 1 mol% trap / luminescent molecule (Rb, TBPe, TTPA, TBRb, or DCM2) with and without NIR irradiation (black line) and with NIR irradiation (red line). Prior to measurement using a fluorescence microscope, the sample was excited with UV light to accumulate charge. The wavelengths of the UV and NIR light were 365 nm and 810 nm, respectively. The blue (approx. 500 nm) and red (approx. 700 nm) edges of the spectrum were removed using a short-pass filter and a dichroic mirror, respectively. b) Time tracking of emission intensity (left) and the change in PSL intensity integrated over 20 minutes (right) obtained from 10 repeated experiments. The inset in the left panel shows the initial time profile of PSL. First, the sample was exposed to 365 nm light for 60 seconds. After being held in the dark for 2 minutes, the sample was exposed to 800 nm light for 20 minutes, and then cooled in the dark for 10 minutes. This cycle was repeated 10 times. [Figure 8] Electrochemical measurements. a) Cyclic voltammograms of the organic compounds used in the study. b) Absorption spectra of m-MTDATA radical cations, PPT radical anions, Rb radical anions, and TBPe radical anions obtained by differential absorption spectroscopy of electro-oxidation or reduction. [Figure 9]Observation of long-lived radicals. a) Time profile of differential absorbance observed at 1100 nm for m-MTDATA / PPT / Rb film. b) Time profile of differential absorbance observed at 1100 nm for m-MTDATA / PPT film. c) Time profile of differential absorbance observed at 740 nm for m-MTDATA / PPT / Rb film. The excitation wavelength was 365 nm. d) Changes in emission intensity at each excitation wavelength observed 100 seconds after stopping 365 nm light irradiation for m-MTDATA / PPT (black) and m-MTDATA / PPT / Rb (red) films. Error bars indicate the bandwidth (FWHM) of the bandpass filter (Thorlabs) used for monochromatic excitation by the same number of emitter photons. [Figure 10] ESR measurement. a) ESR spectra of m-MTDATA / PPT / Rb film under dark conditions (black line), UV irradiation (red line), and UV and NIR irradiation (blue line). The wavelengths of UV and NIR light were 365 nm and 810 nm, respectively. b) Difference ESR spectrum obtained by subtracting the blue line from the red line in panel a. [Figure 11] PSL at 77K. a) Photographs showing LPL and PSL taken at 298K (left) and 77K (right) for m-MTDATA / PPT / Rb amorphous solid. The LPL photograph was obtained after a 60-second cessation of UV light irradiation. The PSL photograph was obtained under NIR light irradiation 100 seconds after a 60-second cessation of UV light irradiation. The acquisition time was 10 seconds. b) Emission attenuation profiles obtained at 298K (black) and 77K (red) for m-MTDATA / PPT / Rb amorphous solid with and without NIR irradiation (see arrows). The wavelengths of UV and NIR light were 365nm and 850nm, respectively. The sample was placed directly above the objective lens (Figure 6a) and exposed to UV or NIR light. The wavelengths of UV and NIR light were 365nm and 850nm, respectively. [Figure 12]MFE for LPL. a) MFE for LPL attenuation profiles of m-MTDATA / PPT / Rb(1mol%) film with and without NIR irradiation. The magnetic field was adjusted between 0.6 and 30 mT. The wavelengths of UV and NIR light were 365 nm and 800 nm, respectively. Values ​​of XLPL(B) obtained with and without NIR irradiation (upper right) and with (lower right). b) Response of LPL intensity to an external magnetic field after stopping UV irradiation, obtained for the film with and without Rb(1mol%) (red line) (black line). Gray indicates the application of a magnetic field. c) Plot of XLPL(B) as a function of magnetic field obtained for m-MTDATA(1mol%) / PPT / Rb(0.1, 1, and 5mol%) film. Solid lines show data fitted by the Lorentz function. [Figure 13] MFE for fluorescence. a) Fluorescence intensity response of m-MTDATA / PPT / Rb film to an external magnetic field under UV irradiation. The excitation wavelength was 365 nm. b) Plot of XFL(B) values ​​as a function of magnetic field observed for m-MTDATA / PPT / Rb (0, 0.1, 1, 5, and 10 mol%) films. c) Dependence of XFL and B1 / 2 values ​​on Rb concentration. [Figure 14] Chemical structures of TPP+, TPBi, and TCTA. [Figure 15] a) Emission decay profiles of TPP+ / TPBi / TCTA films with and without 850nm light stimulation. Mixed films were photostimulated 10 seconds and 32 seconds after initial photoexcitation. Emission intensity from 500nm to 700nm was integrated. b) Emission spectra of TPP+ / TPBi / TCTA films with and without light stimulation. [Figure 16] Top: Delta absorption spectra of TPP+ / TPBi, TPP+ / TPBi / TCTA, and TPBi / TCTA films before and after photoexcitation (300K, N2). Bottom: Absorption spectra of TCTA in 0.1M TBAPF6-containing DCM with and without electro-oxidation (300K, N2). Absorbance data in the 1650-1700 nm range were excluded due to absorption by the quartz substrate. [Modes for carrying out the invention]

[0041] In this paper, we demonstrate purely organic phototextrous emission (PSL) across a wide range of colors using ultraviolet (UV) and near-infrared (NIR) light for multiple write and read cycles, respectively, by adding molecules with dual roles as electron traps and photoluminescent elements to an organic LPL system. As a model system, we first explore a ternary blend film containing an electron donor (4,4',4”-tris[(3-methylphenyl)phenylamino]triphenylamine; m-MTDATA) (1 mol%), an electron acceptor (2,8-bis(diphenylphosphoryl)dibenzo[b,d]thiophene; PPT), and an electron trap / luminescent element (5,6,11,12-tetraphenyltetracene; Rb) (1 mol%) (Figure 1a).

[0042] UV light excitation of the film induces the formation of a charge-separated state between m-MTDATA and PPT, resulting in a green-emitting charge-transfer (CT) excited state or exciplex (Figure 1b). 20 The excitation energy of the CT excited state is transferred to Rb via Forster resonance energy transfer (FRET), resulting in persistent orange luminescence. These processes are similar to the previously reported organic LPL phenomenon. 15 It is similar to that.

[0043] Simultaneously, some of the electrons are captured by a neutral Rb molecule with the lowest unoccupied molecular orbital (LUMO), which is approximately 0.8 eV lower than the LUMO of PPT, resulting in the long-lived radical anion of Rb (Rb ·- ) forms Rb ·- Because it has a strong absorption band in the NIR region, NIR excitation causes doublet excitation of Rb ·-Electron transfer can be induced from one PPT molecule to an adjacent PPT molecule, thereby generating mobile electrons in the PPT film for the formation of a CT state and subsequent FRET to Rb. In this way, the trap / emissive material enables optical writing and reading of PSL and data in the organic film.

[0044] Organic PSL characteristics Figure 2a schematically illustrates the optical writing and reading process based on organic PSL. First, the organic film is exposed to UV light for approximately 1 minute to write information. After the irradiated film is held in the dark for a predetermined time, it is exposed to NIR light to read out the stored information as visible PSL. Figure 2b shows a photograph of an m-MTDATA / PPT / Rb film prepared according to the reported procedure in an argon-filled glove box. 15 After stopping the 1-minute UV irradiation, an orange LPL was clearly visible from the film, excluding the masked area, and gradually weakened over time. Surprisingly, NIR irradiation of the film dramatically increased this orange emission to a point where it was visible to the naked eye and, one week after UV irradiation, to a point visible with a commercially available digital camera (Figure 2c). Although emission was observed in cracks within the masked area, likely due to light scattering or waveguide properties within the film, the irradiated triangular area was preserved, ensuring long-term storage capability. Such a remarkable improvement was not observed in the absence of Rb.

[0045] The luminescence properties of the film were tested using an inverted fluorescence microscope (Figure 6a). To avoid the influence of structural inhomogeneities such as cracks, homogeneous regions were carefully selected for measurement (extended data Figures 2b and c). A typical time profile of LPL after UV irradiation cessation is shown in Figure 2d. The LPL intensity suddenly increased by more than 15 times upon NIR irradiation (see arrow), and there was no clear change in the spectral shape (Figure 7a). This observation suggested PSL, and this PSL could be repeated for 10 write / read cycles with a loss of approximately 10% of the initial intensity for the same sample (Figure 7b).

[0046] Rb ·- To confirm the presence of Rb, the optical absorption spectra of m-MTDATA / PPT / Rb (Rb concentration of 0 or 1 mol%) films were measured before and after UV irradiation, and the difference spectra were derived. As shown in Figures 2e and 8, only for films containing Rb, Rb was present at approximately 800 and 1,000 nm. ·- Characteristic absorption zones 21 Although this was observed, both films exhibited a broad band of 900-1,400 nm, which is m-MTDATA radical cation (m-MTDATA ·+ The absorption spectrum is similar to that of ) 22 The absorption slowly decayed over time after UV irradiation ceased (extended data Figures 5a-c), indicating the gradual depletion of radical species accumulated in the film. Rb ·- The presence of was further supported by electron spin resonance (ESR) spectroscopy measurements (Figure 10).

[0047] To investigate the origin of PSL, the action spectrum was measured, plotting the intensity change during NIR stimulation as a function of the excitation wavelength. As shown in Figure 9d, the intensity change is strongly dependent on the excitation wavelength. For example, the intensity change at 850 nm is almost seven times larger than the intensity change at 1,000 nm, which corresponds to a photon energy (approximately 1.24 eV) larger than the energy difference between the LUMO levels of PPT and Rb (approximately 0.8 eV) (Figure 5). The obtained spectral shape is Rb ·- The near-match between the absorption spectra suggests the importance of spectral matching between the stimulating light and the electron absorption of the radical anion of the trap / luminescent molecule. Electron transfer from excited radical anions (e.g., perylenediimide radical anions) has been characterized by time-resolved spectroscopy and, despite their short lifetimes on the pico-nanosecond scale, is utilized in photoredox reactions such as the reductive dehalogenation of aryl halides. 23~26 Rb ·- High extinction coefficient (ε ≈ 2 × 10 at approximately 800 nm) 4 M -1 cm-1 ) 21 Therefore, it is preferable for NIR stimulation. The increase in intensity of the film without trap / luminescent molecules is very small, which is shown in Figure 2e, PPT ·- This is consistent with the fact that negligible absorption was observed, which may be due to a small ε. We can conclude that trap / luminescent molecules in the film capture some of the electrons and, upon NIR excitation of their radical anion states, release them as visible PSL (Figure 1b).

[0048] Multicolor organic PSL The proposed scheme is applicable to color tuning using different trap / luminescent molecules (2,5,8,11-tetra-t-butylperylene (TBPe), 9,10-bis[N,N-di-(p-tolyl)-amino]anthracene (TTPA), 2,8-di-t-butyl-5, 11-bis(4-t-butylphenyl)-6, 12-diphenyltetracene (TBRb), and 4-(dicyanomethylene)-2-methyl-6-juloridyl-9-enyl-4H-pyran (DCM2)), whose LUMO levels are lower than those of PPT (-2.2 eV). As shown in Figures 3 and 7a, all samples exhibited detectable PSLs with different colors and spectra similar to their LPLs without NIR irradiation. The m-MTDATA / PPT / TBRb film exhibited similar properties to the Rb sample, due to the similar structure of the trap / luminescent molecules. DCM2 also showed a strong red PSL (Photon Scheme Line).

[0049] On the other hand, relatively weak NIR responses were observed for TBPe and TTPA. Since these molecules have lower LUMO energies than others, the possibility that PSL simply originates from thermal emission of electrons from the trapping site due to NIR irradiation can be ruled out. In fact, significant PSL was observed even at 77K for the m-MTDATA / PPT / Rb film (Figure 11). ·- Because it has a very weak absorption band in the NIR region, in the case of TBPe, weak PSL may be due to inefficient excitation of radical anions.27 These results also suggest that for strong PSL, electron trapping at a depth greater than 0.5 eV from the LUMO level of PPT may be necessary. Unfortunately, the absorption spectra of the radical anions of TTPA and DCM2 could not be obtained by spectroelectrochemistry due to simultaneous oxidation on the counter electrode and irreversibility in solution, respectively (Figure 8a). Thus, further research is needed to establish the design principles of organic PSL systems.

[0050] Magnetic field effect To investigate the dynamics of long-lived radical species in the aforementioned blend film, an external magnetic field (B) was applied to the sample using an electron magnet under an inverted fluorescence microscope. 28 The magnetic field effects (MFE) on LPL and PSL were investigated. As demonstrated in previous studies... 29~31 In organic light-emitting diodes (OLEDs), MFE provides a fundamental model for the interconversion between singlet and triplet states, which is highly correlated with device performance. Interestingly, as shown in Figures 4a and 12, a significant negative MFE was observed for LPL and PSL, while no MFE was observed for Rb-less films, suggesting that trap / luminescent molecules play an important role.

[0051] In the LPL process, the MFE is expressed by the following formula.

number

[0052] Curve shapes of positive and negative MFE and their B 1 / 2 The fact that the values ​​are almost exactly the same (Figure 4b and extended data Figures 8 and 9) suggests that similar interactions governing spin conversion may be involved. However, the populations of spin states are thought to be different from one another. In the fluorescence process, electron transfer from excited donor molecules generated by UV irradiation is involved in radioactive singlet CT ( 1 CT) is the main pathway for the formation of excited states (Figure 4c). Under continuous excitation, a singlet charge-separated state ( 1 CSS) is in a triplet state ( 3 CSS 0、± Because a state with more than ) is maintained, Zeeman splitting of triplet sublevels due to a magnetic field is 1 From CSS 3 CSS ± This inhibits intersystem crossing (ISC) and can lead to increased fluorescence intensity. Such positive MFE has been observed in the so-called magneto-photoluminescence behavior in OLEDs and can be interpreted by hyperfine interactions and / or Δg mechanisms. 29、30 On the other hand, negative MFE in LPL and PSL processes cannot be explained by the inhibition of positive (forward) ISC.

[0053] In organic LPL materials, a large amount of CSS is stored in the film under pre-excitation conditions and after pre-excitation (extended data Figures 5a-c). If spin mixing occurs effectively within the lifetime of spin-correlated CSS, the spin distribution progresses to a 1:3 equilibrium based on spin statistics (Figure 4c). In the presence of an external magnetic field of approximately 10 mT, Zeeman splitting occurs via spin mixing. 3 CSS ± from 1Population flow to CSS is suppressed, leading to a decrease in LPL intensity. Triplets accumulated inside OLED devices maintain their spin state and have a long lifetime, resulting in negative MFE. 32 This is very similar to our case. As shown in Figures 4b and 13c, the increase in Rb concentration is X LPL / FL This results in an increase in the absolute value of (B). This suggests that the trap / luminescent molecule effectively traps electrons to form long-range CSSs, and exchange interactions can be ignored (Figure 1b). 33、34 The density of PPT is (1.34 ± 0.1 g / cm³). -3 ) and molecular weight (584.6 molg -1 From this, the average distance between m-MTDATA and 1 mol% of trap / luminescent molecules can be roughly estimated to be approximately 3 nm, which is consistent with the range (>1 nm) expected from MFE results that take its distribution into account. In addition to the trap / luminescent molecules, the long lifetime of CSS may be partly due to the inherent trapping sites in the m-MTDATA / PPT film (which include structural disorder and impurities that are difficult to remove).

[0054] Experiment Section material m-MTDATA was obtained from Sigma-Aldrich. The PPT was synthesized according to the literature. 37 The predicted density of PPT using Advanced Chemistry Development (ACD / Labs) software was obtained from SciFinder for molecular distance calculations. Rb, TBPe, TTPA, TBRb, and DCM2 were obtained from Luminescence Technology Corp. All compounds were purified by sublimation and stored in argon-filled glove boxes.

[0055] Sample preparation. A ternary blend film was prepared according to the reported procedure. 15In short, m-MTDATA (1 mol%), PPT (98 mol%), and trap / luminescent molecules (1 mol%) (unless otherwise specified) were dissolved in dichloromethane. The solvent was then removed under reduced pressure in the dark. The mixture was dried using a 3-cycle freeze pump method. The dried mixture was placed on a glass plate in a glove box filled with argon and heated to 250°C for 10 seconds. After melting, the substrate was rapidly cooled to room temperature and sealed with a coverslip and UV-curable epoxy resin (Figure 2b). For low-temperature experiments, a quartz glass tube containing a mixture of m-MTDATA (1 mol%), PPT (98 mol%), and Rb (1 mol%) was evacuated under vacuum at room temperature and then heated to 250°C to melt the mixture. After cooling to room temperature, the sample tube was inserted into a clear glass Dewar flask. For emission measurements at 77K, the flask was filled with liquid nitrogen.

[0056] Characterization To observe PSL, UV light irradiation (365 nm, 35 mW / cm² at the sample) was performed using an LED light source (Thorlabs, M365LP1). -2 After stopping the Xe lamp (Asahi Spectra, MAX-303), use a bandpass filter to expose the sample to monochromatic NIR light (e.g., 800 nm, 12 mW / cm² at the sample) emitted from the Xe lamp. -2The sample was excited by a 355 nm pulsed laser (PL2210, Ekspla) at 10 Hz. Before the repeat experiment, the sample was exposed to strong NIR light (750-1050 nm) from a Xe lamp for 10 minutes to remove as many long-lived trapped electrons as possible. Optical absorption spectra were obtained using a UV-Vis-Near-Infrared spectrophotometer (JASCO, V-770). Transient emission decay profiles were obtained using a streak camera system (C10910). The sample was excited by a 355 nm pulsed laser (PL2210, Ekspla) at 10 Hz. Cyclic voltammetry (CV) was performed using an electrochemical analyzer (BAS, model 610E). Measurements were taken in dry, oxygen-free dichloromethane (CH2Cl2) or N,N-dimethylformamide (DMF) with 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) as the supporting electrolyte. Platinum fiber as the working electrode, glassy carbon as the counter electrode, and Ag / Ag as the reference electrode. + The following was used. The redox potential was ferrocene / ferrocenium (Fc / Fc + ) was used as a comparison. E HOMO又はLUMO =-E 酸化還元(対Fc / Fc+) The highest occupied molecular orbital (HOMO) and LUMO energy levels were calculated according to the formula for -4.8eV. 38 Absorption spectra of radical anions or radical cations of the material were obtained using a UV-Vis-Near-Infrared spectrophotometer (Shimadzu, UV-3600Plus). Using an electrochemical analyzer (BAS, model 610E), samples in dry, oxygen-free CH2Cl2 or DMF containing 0.1 M TBAPF6 were oxidized or reduced using a platinum mesh electrode.

[0057] Fluorescence microscopy measurement Fluorescence microscopy measurements were performed using an inverted fluorescence microscope (Nikon, Ti-E). A 365nm LED (Thorlabs, M365LP1; 0.85Wcm² at the sample) was used. -2The sample was excited using an objective lens (CFI Plan Apo λ100×H, Nikon; NA (numerical aperture) = 1.45) with NIR stimulation. An 810nm LED light source (Thorlabs, M810L3; 810nm, 12mWcm² at the sample) was used for NIR stimulation. -2 A Xe lamp (Asahi Spectra, MAX-303) and a bandpass filter were used to obtain the action spectrum for NIR excitation with the same number of synchrotron photons. NIR light was irradiated from above the sample. The emission from the sample was collected with the same objective lens and then magnified with a 1.5× built-in magnification converter. Undesirable scattered light was then removed by passing the light through a dichroic mirror (Semrock, FF697-SDI01 or Di02-R405) and a short-pass filter (Semrock, FF02-694 / SP-25) or a long-pass filter (Semrock, BLP01-405R). An electron-multiplier charge-coupled device camera (Roper Scientific, Evolve512) was used to record emission images using Micro-Manager (https: / / www.micro-manager.org / ). For spectroscopic analysis, only the light emitted through a long-pass filter (Semrock, BLP01-405R) and slit was fed into an imaging spectrograph (SOL Instruments, MS3504i) equipped with a CCD camera (Andor, DU416A-LDC-DD). A magnetic field was applied using a custom-made electromagnet and calibrated using a Gauss meter. All experimental data were acquired at room temperature unless otherwise noted.

[0058] Supplementary results Fluorescence and LPL measurement. Figure 6 shows some of the experimental preparations and typical fluorescence and LPL images observed for the m-MTDATA / PPT / Rb film. The interface between the bright and dark regions indicates the boundary in the film.

[0059] Figure 7a shows the normalized emission spectra of films containing m-MTDATA, PPT, and trap / emissive molecules (1 mol%) with and without NIR irradiation (λ=810 nm) after cessation of 365 nm light irradiation (black line) and with NIR irradiation (red line). No significant spectral changes were observed, indicating that emission originates from the trap / emissive molecules in both the LPL and PSL processes.

[0060] The repeatability of the PSL phenomenon was tested using m-MTDATA / PPT / Rb film. As shown in Figure 7b, after experiencing 10 write / write cycles, the initial PSL intensity at 120 seconds (left panel) and the intensity integrated over a 20-minute period (right panel) decreased by approximately 10% and 17%, respectively. Since the LPL intensity observed immediately before NIR stimulation also decreased, this decrease is likely due to the photodegradation of the sample under prolonged light irradiation.

[0061] The NIR-induced increase in LPL is strongly dependent on the excitation wavelength. Therefore, the intensity change was plotted as a function of the excitation wavelength. In this case, the number of photons incident on the sample is the same for each wavelength. As shown in Figure 9d, the obtained action spectrum is Rb ·- The absorption spectrum roughly matched (Figure 2e, Figure 8b, and references). 1 (See reference). PSL in m-MTDATA / PPT films may be due to shallowly trapped electrons in the PPT or impurities.

[0062] As shown in Figure 11, for the m-MTDATA / PPT / Rb film, strong PSL was observed at 77K rather than at room temperature. This result may be due to a higher concentration of trapped electrons.

[0063] Time tracking of long-lived radicals. The absorption spectra of the radicals were measured by spectroelectrochemistry at different applied potentials determined from cyclic voltammetry experiments (Figure 8).

[0064] Even after stopping UV irradiation, m-MTDATA ·+ To confirm whether or not it remains present for a long period of time, the change in absorbance over time was observed. As shown in Figure 9a, an increase in absorbance was observed during UV irradiation (20-250 seconds), and after UV irradiation was stopped (250-1,000 seconds), the absorbance gradually decreased. In the absence of Rb (i.e., m-MTDATA (1 mol%) / PPT (99 mol%) film), the m-MTDATA after UV irradiation was stopped was observed. ·+ The lifespan of the Rb molecule is clearly reduced, and the Rb molecule is PPT ·- It was shown that trapping electrons suppresses charge recombination (Figure 9b). m-MTDATA ·+ The half-lives were determined to be 88 seconds and 36 seconds, respectively, with and without Rb (1 mol%).

[0065] Figure 9c shows Rb observed at 740 nm. ·- This shows the time tracking. The overall behavior appears to be similar to that observed at 1100 nm in Figure 9a, but sharp decreases and increases were observed immediately after the UV light was turned on and immediately after it was turned off, respectively. Rb ·- Because it can absorb light at 365nm 39 The sharp decrease is due to the residual Rb under steady-state conditions induced by UV light. ·- This is caused by excitation of and leads to detrapping. On the other hand, a sharp increase is due to PPT ·- From there, Rb is transferred by electron transfer to the neutral Rb molecule produced when UV light irradiation is stopped. ·- This is due to the formation of Rb. After 180 seconds of UV light irradiation, Rb accumulated in a film approximately 1 mm thick. ·- The concentration is estimated to be approximately 15 μM, which is much lower than the concentration of added Rb (approximately 23 mM).

[0066] ESR spectrum. We will test which magnetic interactions are affecting the magnetic field-sensitive LPL and Rb ·-To confirm whether the detrapping of is caused by NIR irradiation, the X-band ESR spectrum of the m-MTDATA / PPT / Rb film was measured using a Bruker EMX spectrometer. The black line in Fig. 10a is the ESR spectrum measured in the dark, indicating the presence of long-lived radical species. The asymmetric ESR line shape may be due to the overlap of species with the sharp ESR line shape shown in Fig. 10b as a minor contribution. The main broad ESR line shows a g-factor of g = 2.00358 from the central field with a linewidth of approximately 1.1 mT. The cause of this broad width is due to the hyperfine interaction commonly observed for long-lived nitrogen atom-containing aromatic radical species such as oxidized spiro-OMeTAD molecules under dark conditions 40、41 which is also inferred from B 1 / 2 obtained in the MFE measurement as described later. g = 2.00358 is slightly larger than the g-factor of aromatic hydrocarbon radicals. This is explained by the heavy atom effect of nitrogen. Therefore, the observed broad spectrum is attributed to m-MTDATA ·+ . The red line shows the spectrum under 365 nm light irradiation. The signal intensity increased significantly with the appearance of new sharp peaks. These results are due to the generation of additional radical species along with the increase in m-MTDATA ·+ by light. When the sample was irradiated with UV and NIR light simultaneously, a slight intensity decrease and shape change were obtained (blue line). The g-value (2.00245) of the difference spectrum (Fig. 10b) agrees well with the theoretical value (2.00235) for Rb ·- obtained by Gaussian 09. Therefore, these differences may be due to the neutralization by photoinduced detrapping of Rb ·- . The theoretical g-value of Rb ·- was obtained using density functional theory (DFT) calculations with a set of B3LYP functional and 6-31+G(d,p) basis functions. The calculated principal values of the g tensor are g xx = 2.00162, g yy = 2.00271, and g zzIt was 2.00273. The line width of the sharp peak in Fig. 10b was 0.3 mT. B in the hyperfine coupling (HFC) mechanism of MFE 1 / 2 is empirically calculated by the following formula 42 .

[0067] [Number]

[0068] In the formula, B Ra· and B Rb· represent the HFC constants of each radical. From the line widths of the sharp and broad ESR spectra in Fig. 10b, by applying B Ra· = 0.3 mT and B Rb· = 1.1 mT, B 1 / 2 = 1.9 mT was obtained. The magnetic field effects on the reaction yield (MARY) curves for LPL and fluorescence shown in Fig. 4b and Fig. 13b respectively indicate a B 1 / 2 value of approximately 3 mT, which is in good agreement with the B 1 / 2 value obtained from the ESR line width. This demonstrates that, as described in detail in the following section, the singlet-triplet spin conversion of the highly separated long-lived radical pairs of m-MTDATA<00.....···Rb ·- is involved in the existing LPL.<000.....​​​​​​​​​​Figure 12b shows the LPL decay profiles of m-MTDATA / PPT / Rb (0, 1 mol%) films measured while adjusting the magnetic field after stopping UV irradiation. Significant MFE was observed only for films containing Rb.

[0071] Figure 12c shows X in each magnetic field. LPL (B) shows the Rb concentration dependence of the MARY spectrum plotted for the value. X increases with increasing Rb concentration. LPL (B) The saturation absolute value increases, while B 1 / 2 The value (i.e., the magnetic field at which the change in luminescence intensity reached half of the saturation value) remained constant.

[0072] MFE for fluorescence. Figure 13a shows the change in fluorescence intensity observed for the m-MTDATA / PPT / Rb blend film at each magnetic field. Unlike the negative MFE in the LPL and PSL processes, a positive MFE was clearly observed. Figure 13b also shows the X at each magnetic field using the following equation. FL (B) shows the Rb concentration dependence of the MARY spectrum plotted from the values.

[0073]

number

[0074] Other examples of the present invention In a glove box filled with nitrogen, the TPP shown in Figure 14 + A mixture of TPBi and TCTA (1:99:1) with a surface area of ​​100 mm² 2 The material was placed on a 0.5 mm deep template glass substrate and heated at 300°C for 10 seconds. After melting, the substrate was rapidly cooled to room temperature.

[0075] LPL spectra and attenuation profiles were obtained using a measurement system in a glove box. The fabricated film was placed in a dark box and excited with a 365 nm LED at a power of 1 mW cm using a bandpass filter. -2 The sample was excited for 300 seconds. PL and LPL spectra were recorded using a multi-channel spectrometer (PMA-12, Hamamatsu Photonics). After the initial photoexcitation, the sample was photostimulated with an 850 nm LED.

[0076] Figure 15(a) shows TPP with and without light stimulation at 850 nm. + Figure 15(b) shows the emission decay profile of the / TPBi / TCTA film. This mixed film was photostimulated 10 seconds and 32 seconds after the initial photoexcitation. The emission intensity from 500 nm to 700 nm was integrated. + This shows the emission spectra of / TPBi / TCTA film with and without light stimulation.

[0077] Figure 16 (top) shows the TPP before and after photoexcitation (300K, N2 bottom). + / TPBi, TPP + The delta absorption spectra of TPBi / TCTA and TPBi / TCTA film are shown. Figure 16 (bottom) shows the absorption spectra of TCTA in a DCM containing 0.1 M TBAPF6, with and without electro-oxidation (300 K, N2). Absorbance data at 1650-1700 nm has been omitted due to absorption by the quartz substrate.

Claims

1. A luminescent composition for emitting light in response to a light stimulus, It comprises an electron donor, an electron acceptor, and a third component, The combination of the electron donor and the electron acceptor is selected from combinations that, when excited with light of a wavelength included in the absorption wavelength range of the composition, cause electrons to transfer from the electron donor to the electron acceptor, generating an electron donor in a radical cation state and an electron acceptor in a radical anion state, and exhibiting sustained luminescence for 0.1 seconds or more, and The third component is selected from materials that satisfy either (a) or (b) below. composition. (a) A material having a LUMO level lower than the LUMO level of the electron acceptor, and which, after accepting electrons from the electron acceptor in the radical anion state and becoming a radical state, has the ability to emit electrons when photostimulated by light of a wavelength included in the absorption wavelength range of the composition when the third component is in the radical state. (b) A material having a HOMO level higher than the HOMO level of the electron donor, which accepts a hole from the electron donor in a radical cation state and becomes a radical state, and which has the ability to emit a hole when photostimulated by light of a wavelength included in the absorption wavelength range of the composition when the third component is in a radical state.

2. A composition comprising an electron donor, an electron acceptor, and a third component, The combination of the electron donor and the electron acceptor is selected from combinations that, when excited with light of a wavelength included in the absorption wavelength range of the composition, cause electrons to transfer from the electron donor to the electron acceptor, generating an electron donor in a radical cation state and an electron acceptor in a radical anion state, and exhibiting sustained luminescence for 0.1 seconds or more, and The above third component is selected from materials that satisfy the following conditions: composition. The material has a HOMO level higher than the HOMO level of the electron donor, and after accepting a hole from the electron donor in a radical cation state and becoming a radical state, it has the ability to emit a hole when photostimulated by light of a wavelength included in the absorption wavelength range of the composition when the third component is in a radical state.

3. The composition according to claim 1 or 2, which exhibits light emission mainly from the third component when excited.

4. The composition according to claim 1 or 2, wherein, upon excitation, it mainly exhibits light emission from an exciplex formed by the electron donor and the electron acceptor.

5. An organic light-emitting device comprising a light-emitting composition, The aforementioned composition comprises an electron donor, an electron acceptor, and a third component. The apparatus emits light by photostimulating the composition with light of a wavelength included in the absorption wavelength range when the third component is in a radical state. The combination of the electron donor and the electron acceptor is selected from combinations that, when excited with light of a wavelength included in the absorption wavelength range of the composition, cause electrons to transfer from the electron donor to the electron acceptor, generating an electron donor in a radical cation state and an electron acceptor in a radical anion state to form an exciplex between the electron donor and the electron acceptor, and exhibiting luminescence with a duration of 0.1 seconds or more. The third component is a composition selected from materials satisfying either (a) or (b) below, wherein the organic luminescence device is an organic luminescence device. (a) A material having a LUMO level lower than the LUMO level of the electron acceptor, and which, after accepting electrons from the electron acceptor in the radical anion state and becoming a radical state, has the ability to emit electrons when photostimulated by light of a wavelength included in the absorption wavelength range of the composition when the third component is in the radical state. (b) A material having a HOMO level higher than the HOMO level of the electron donor, which accepts a hole from the electron donor in a radical cation state and becomes a radical state, and which has the ability to emit a hole when photostimulated by light of a wavelength included in the absorption wavelength range of the composition when the third component is in a radical state.

6. A method of luminescence induced by light stimulation, Exciting the composition, and To cause the aforementioned composition to emit light by light stimulation, Includes, The aforementioned composition comprises an electron donor, an electron acceptor, and a third component, The combination of the electron donor and the electron acceptor is selected from combinations that, when excited with light of a wavelength included in the absorption wavelength range of the composition, cause electrons to transfer from the electron donor to the electron acceptor, generating an electron donor in a radical cation state and an electron acceptor in a radical anion state to form an exciplex between the electron donor and the electron acceptor, and exhibiting luminescence with a duration of 0.1 seconds or more. A method for emitting light, wherein the third component is a composition selected from materials satisfying either (a) or (b) below. (a) A material having a LUMO level lower than the LUMO level of the electron acceptor, and which, after accepting electrons from the electron acceptor in the radical anion state and becoming a radical state, has the ability to emit electrons when photostimulated by light of a wavelength included in the absorption wavelength range of the composition when the third component is in the radical state. (b) A material having a HOMO level higher than the HOMO level of the electron donor, which accepts a hole from the electron donor in a radical cation state and becomes a radical state, and which has the ability to release a hole when photostimulated by light of a wavelength included in the absorption wavelength range of the composition when the third component is in a radical state.

7. A method of light emission by light stimulation according to claim 6, satisfying either [1] or [2] below: ［１］ The excitation causes electrons to be transferred from the electron donor to the electron acceptor, generating an electron donor in a radical cation state and an electron acceptor in a radical anion state. The electrons of the electron acceptor in the radical anion state are trapped by the third component. The trapped electrons on the third component are detrapped by photostimulation and transferred to electron acceptors, generating electron acceptors in a radical anion state, and The detrapped electrons of the electron acceptor in the radical anion state recombine with the holes of the electron donor in the radical cation state, thereby generating an exciplex between the electron donor and the electron acceptor and producing light emission, or ［２］ The excitation causes electrons to be transferred from the electron donor to the electron acceptor, generating an electron donor in a radical cation state and an electron acceptor in a radical anion state. The holes in the electron donor in the radical cation state are trapped by the third component. The trapped holes on the third component are detrapped by photostimulation and transferred to an electron donor, generating an electron donor in a radical cation state, and The detrapped holes in the electron donor in the radical cation state recombine with electrons in the electron acceptor in the radical anion state, thereby generating an exciplex between the electron donor and the electron acceptor and producing light emission.

8. The method for emitting light by light stimulation according to claim 6 or 7, further comprising applying a magnetic field to the composition to control the intensity of light emission during the light stimulation.

9. Use of the composition according to any one of claims 1 to 4 in imaging, marking, optical data storage, optical sensing, optical energy conversion, and security seals.

10. A method for designing a composition for complete emission, The aforementioned emission-enhanced composition is a composition comprising an electron donor, an electron acceptor, and a third component, The combination of the electron donor and the electron acceptor is selected from combinations that, when excited with light of a wavelength included in the absorption wavelength range of the composition, cause electrons to transfer from the electron donor to the electron acceptor, generating an electron donor in a radical cation state and an electron acceptor in a radical anion state to form an exciplex between the electron donor and the electron acceptor, and exhibiting luminescence with a duration of 0.1 seconds or more. The third component is a composition selected from materials satisfying (a) or (b) below, and the method comprises the steps 1) to 3) below. (a) A material having a LUMO level lower than the LUMO level of the electron acceptor, and after accepting electrons from the electron acceptor in the radical anion state and becoming a radical anion state, having the ability to emit electrons when photostimulated by light of a wavelength included in the absorption wavelength range of the composition when the third component is in the radical anion state. (b) A material having a HOMO level higher than the HOMO level of the electron donor, which accepts a hole from the electron donor in the radical cation state to become a radical anion state, and which has the ability to release a hole when photostimulated by light of a wavelength included in the absorption wavelength range of the composition when the third component is in the radical cation state. 1) Evaluate at least one of the excitation wavelength, stimulation wavelength, and exhaust emission wavelength of the specific composition in which the electron donor, electron acceptor, and third component have been identified. 2) By selecting and replacing at least one of the electron donor, electron acceptor, and third component of the specified composition with another material corresponding to the electron donor, electron acceptor, or third component, to adjust at least one of the excitation wavelength, stimulation wavelength, and exhaust emission wavelength, thereby designing a novel composition in which at least one of the excitation wavelength, stimulation wavelength, and exhaust emission wavelength is closer to a set value, and 3) Optionally, repeat step 2) at least once.

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