Circularly polarized OLED light-emitting layer composition

Abstract

The present invention relates to an active light-emitting layer composition comprising a TADF molecule with TADF properties as a host material and a light-emitting molecule with CP properties as a dopant. The present invention also relates to a light-emitting device comprising an active light-emitting layer made from this composition.

Description

[Technical field]

[0001] The present disclosure relates to the technical field of compositions for organic light-emitting diodes (OLEDs) capable of emitting circularly polarized light, and also to light-emitting devices incorporating such compositions. More particularly, the present disclosure relates to the technical field of compositions for OLED light-emitting or active layers. [Background technology]

[0002] Flat panel displays are ubiquitous in modern life. They are widely used in small and large devices, such as mobile phones, TV sets, tablet computers, e-readers, VR (virtual reality) headsets, wearable smart devices, and other electronic products. Such flat panel displays have been primarily powered by LCDs, such as twisted nematic LCDs (TN-LCDs) and super twisted nematic LCDs (STN-LCDs). However, such devices have low inherent brightness and require powerful backlights, resulting in higher power consumption.

[0003] The development of organic light-emitting diodes (OLEDs) brings the possibility of brighter and more power-saving devices. In fact, OLEDs have the advantages of low operating power and low power consumption, fast response, wide viewing angle, high brightness, and high contrast ratio. Therefore, they are seen as the most promising next-generation display technology.

[0004] An OLED panel usually comprises a first electrode, a second electrode, and then a functional structure layer between the first electrode and the second electrode. The functional structure layer comprises a hole injection layer, a first hole transport layer, a second hole transport layer, an organic light emitting layer, an electron transport layer, and an electron injection layer, sequentially stacked on the first electrode. OLED technology can be classified into two main families of OLEDs, depending on the nature of the light emitting material that constitutes the organic light emitting layer: small molecule based materials and polymeric materials.

[0005] Research into OLED materials and devices has made significant progress. In recent years, researchers have explored the production of circularly polarized OLEDs (CP-OLEDs). CP-OLEDs provide superior contrast compared to non-polarized OLEDs, allowing for a reduction in overall brightness required to obtain the same contrast level as in non-polarized OLEDs. The reduction in overall brightness, in turn, results in lower power consumption.

[0006] To date, the most effective strategy is to use molecules capable of self-assembly on a supramolecular scale in order to obtain an amplification of the light polarization at the output. For this purpose, a chiral liquid crystal passive filter can be used in front of a light source generated by another molecule. This makes it possible to have a polarization ratio of about several tens of percent. Another possibility is to use luminescent polymers of the liquid crystal type, either intrinsically chiral polymers or achiral polymers doped with chiral molecules. This makes it possible to reach a high polarization ratio.

[0007] For example, EP 1 523 533 (B1) describes a composition comprising a chiral helical liquid crystal phase with a substantially fixed, temperature-independent helical pitch, consisting of calamitic (rod-like) liquid crystal molecules having luminescent moieties, which exists in a mesophase, i.e. intermediate between a liquid phase and a crystallized solid phase.

[0008] Another example is EP 2877552 (B2), which describes a composition consisting of an electroluminescent polymer, such as a poly(arylenevinylene) derivative, and a scalemic chiral non-emissive dopant, such as a helicene, blended together.

[0009] The principle of both documents is that they rely on the use of pure fluorescent emitters. Although the solutions realized by these two documents can exhibit very high levels of circular polarization, the maximum internal quantum yield that these systems can reach is theoretically limited to 25%. Thus, CP-OLEDs fabricated by these methods have limited performance efficiency, which hinders their use in large-scale applications.

[0010] The second approach is to use chiral luminescent materials inside a conductive matrix to generate circularly polarized light directly. This strategy is easy to implement and its performance depends entirely on the intrinsic properties of the luminescent material. It has proven difficult to find molecules that combine both high luminescent properties and high polarization efficiency. For example, lanthanide complexes have been used that have strong circular polarization efficiency up to 75%, but they suffer from poor chemical stability and very limited luminescence efficiency.

[0011] Other purely organic molecules are currently being explored. These organic molecules are interesting because they show high internal actuation yields of about 100%. Such molecules have thermally activated delayed fluorescence (TADF) properties (hereafter referred to as TADF molecules). TADF is a process in which, upon electrical or optical excitation of a TADF molecule, its excited state reaches a certain degree of equilibrium between singlet and triplet spin configurations, which leads to a large energy gap (ΔE ST ), during which the equilibrium shifts towards the singlet state, since the quenching of the singlet state by fluorescence occurs much faster than the phosphorescence from the triplet state (ns vs. μs, respectively). Finally, there are two fluorescence processes, one that occurs directly from the singlet state (prompt fluorescence, ns time scale) and one that is time-delayed due to the formation of a singlet-triplet excited state equilibrium (delayed fluorescence, μs time scale). This equilibrium is very important, for example, in OLEDs, since it can lead to a theoretical internal quantum efficiency of 100%, compared to a maximum of 25% for the purely fluorescent emitters.

[0012] Therefore, the current approach for such molecules is to combine both TADF and CP properties in a single molecule, which would facilitate the manufacturing process of CP-OLEDs. Designing such compounds for CP-OLEDs is a very challenging task, since such chiral TADF molecular emitters should have the chemical and photophysical properties to simultaneously reach both the TADF process and exhibit strong chiroptical properties (and high racemization barrier in the case of vacuum deposition). Even if recent examples show impressively that synergy between TADF and chiroptical properties can be easily obtained, adjusting either one of the chemical / photophysical properties and the chiroptical properties without hindering the other is a difficult task and only a compromise can be reached.

[0013] However, to date, the performance of such molecules has proven to be insufficient in terms of emission polarization rate. Indeed, to date, the best molecules possessing both TADF and CP properties have a polarization rate of about 5×10 -3 The polarization intensity glum was reached (Chen et al., Chem. Commun., 2020, 56, 9380-9383). [Prior art documents] [Patent documents]

[0014] [Patent Document 1] EP1523533(B1) [Patent Document 2] EP2877552(B2) [Non-patent literature]

[0015] [Non-Patent Document 1] Chen et al., Chem. Commun., 2020, 56, 9380-9383 Summary of the Invention [Problem to be solved by the invention]

[0016] Thus, there remains a need in the OLED art for improved light-emitting layer compositions. [Means for solving the problem]

[0017] To this end, the present invention provides an active type light-emitting layer composition comprising TADF molecules with TADF properties as a host material and light-emitting molecules with CP properties as a dopant.

[0018] That is, the approach of the present invention is a bimolecular strategy in an active light-emitting layer that combines a first TADF molecule with a high conversion rate of electrical excitation to light energy, which can transfer this energy to a second light-emitting molecule (hereafter CP molecule) with CP properties as a dopant and as an emitter capable of emitting circularly polarized light with a high polarization rate.

[0019] The present invention differs from the prior art in that it uses TADF molecules as host molecules that do not have any CP properties, and CP molecules as dopants that do not have any TADF properties.

[0020] This novel approach makes it possible to reach higher levels of polarization of the light emitted by the present compositions than were reached by the prior art.

[0021] Other optional and non-limiting features are as follows:

[0022] TADF molecules can exhibit singlet and triplet state energy levels, and CP molecules can exhibit singlet state energy levels that are lower than the singlet and triplet state energy levels of TADF molecules.

[0023] The CP molecule can have an absorption spectrum and the TADF molecule can have an emission spectrum that overlaps with the absorption spectrum of the CP molecule.

[0024] The composition has a non-zero g lum The absolute value |g lum | is 5×10 -4 Higher, preferably 1×10 -3 Higher than or 1×10 -2 This value is measured at the wavelength where the maximum of the emission intensity is measured.

[0025] The composition can exhibit a TADF quantum yield of 1% or greater. Preferably, the TADF quantum yield is greater than 5%. Preferably, the TADF quantum yield is less than 50%. For example, any of the following figures can serve as lower or higher ranges of values: 10%, 20%, 30% and 40%.

[0026] The composition can exhibit a luminescence quantum yield of 0.10 or more. Preferably, the luminescence quantum yield is higher than 5%. Preferably, the quantum yield is lower than 100%. For example, any of the following figures can serve as lower range values ​​or higher range values: 10%, 15%, 20%, 30%, 50%, 75% and 95%.

[0027] The CP molecule may be a chiral molecule, such as a helicene derivative, a helicenoid compound, a biaryl system, or a molecule with planar chirality (eg, a paracyclophane derivative).

[0028] The CP molecule may, for example, be of the general formula:

[0029] [ka]

[0030] The compound may be a carbo[6]helicene derivative (hereinafter H6) having the formula:

[0031] In formula 1, B, the linker, is the following chemical group represented in formula 2:

[0032] [ka]

[0033] It may be one of the following.

[0034] In formula (1), B may also be a combination of two of the chemical groups of formula (2), such as chemical group A and any one of the other chemical groups of formula (2), preferably in such a case chemical group A is bonded to the helicene group of formula (1). In particular, B may be chemical group A of formula (2) bonded to chemical group F of formula (2).

[0035] In formula 1, R is the following chemical group as illustrated in formula 3:

[0036] [ka]

[0037] It may be one of the following.

[0038] Also preferably, H6 has any one of the following formulae:

[0039] [ka]

[0040] 4,4'-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))dibenzonitrile (hereafter H6(CN)2).

[0041] [ka]

[0042] 4,4'-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))dipyridine (hereafter H6(Py)2).

[0043] [ka]

[0044] 4,4'-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))dianiline (hereafter H6(NH2)2).

[0045] [ka]

[0046] 4,4'-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))di(N,N-dimethylaniline) (hereafter H6(NMe2)2).

[0047] [ka]

[0048] 4,4'-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))di(trimethylsilane) (hereafter H6(TMS)2).

[0049] [ka]

[0050] 4,4'-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))di(N-hexyl-1,8-naphthalimide) (hereafter H6(NPh)2).

[0051] [ka]

[0052] 4,4'-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))di(2,5-N-octyl-3,6-di-2-thienyl-pyrrolo[3,4-c]pyrrole-1,4-dione) (hereafter H6(DPP)2).

[0053] H6 can exhibit the P or M configuration.

[0054] The TADF molecule may be an achiral molecule. In particular, the TADF molecule may have any one of the following structures:

[0055] [ka]

[0056] 9,9'-(sulfonylbis(4,1-phenylene))bis(3,6-di-tert-butyl-9H-carbazo) (hereafter dt-BuCbz sulfone).

[0057] [ka]

[0058] 9-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-1,3,6,8-tetramethyl-9H-carbazole (hereafter Cbz-TRZ2).

[0059] [ka]

[0060] 2,4,5,6-Tetra(9H-carbazol-9-yl)isophthalonitrile (hereafter 4-CbzIPN).

[0061] The active type light emitting layer composition is a mixture of TADF molecules and CP molecules, as follows: - dt-BuCbz sulfone and H6(CN)2; - Cbz-TRZ2 and H6(NPh)2; and - 4-CbzIPN and H6(DPP)2 The combination may include one of the following:

[0062] However, the present invention is not limited to these combinations: - dt-BuCbz sulfone with H6(NPh)2 or H6(DPP)2; - Cbz-TRZ2 with H6(CN)2 or H6(DPP)2; - 4-CbzIPN and H6(CN)2 or H6(NPh)2 Any other combination is possible.

[0063] The CP molecules can be present in an amount of 1-30 mol %, preferably 1-20 mol %, 1-10 mol %, or 1-5 mol % of the TADF molecules.

[0064] The composition may further comprise a conductive matrix for conducting charge from the light-emitting layer, in which case the amount of TADF molecules is preferably 1-30 mol %, preferably 1-20 mol %, 1-10 mol % or 1-5 mol % of the conductive matrix.

[0065] The total amount of both TADF molecules and CP molecules is preferably 1%-40%, 5%-30% of the total weight of the composition.

[0066] The present invention also provides a light emitting device having an active light emitting layer made from the above active light emitting layer composition, which may be an OLED display device.

[0067] Other features, details and advantages are set forth in the following detailed description and drawings. [Brief description of the drawings]

[0068] [Figure 1]FIG. 1 is an illustrative diagram showing the principles behind the present invention, in particular the transfer of energy from the singlet energy level of a TADF molecule to the singlet energy level of a CP molecule. [Diagram 2] FIG. 1 shows the absorption spectrum (dotted line) and emission spectrum (solid line) of H(CN) between 250 nm and 600 nm recorded in dichloromethane solvent at room temperature; values ​​are normalized so that the highest peak has a value of 1. [Diagram 3] 1 is a graph showing the intensity difference ΔI between left-handed and right-handed emission of M-H6(CN)2 (dotted line) and P-H6(CN)2 (solid line) recorded in dichloromethane solvent at room temperature between approximately 400 nm and 600 nm. The values ​​are normalized, so that the highest peak Imax of the entire emission spectrum has a value of 2. In this situation, the value of ΔI at the wavelength of Imax is the glum value at that wavelength. [Figure 4] FIG. 1 is a graph showing the emission spectra between 370 nm and 370 nm of H6(CN)2 alone, dt-BuCbz sulfone alone, and a composition consisting of dt-BuCbz sulfone and H6(CN)2 (with dt-BuCbz sulfone amounts of 1, 5, 10, and 20 mol %) recorded on film at room temperature. [Diagram 5] 1 is a graph showing the intensity difference ΔI between the left and right circular emission of BuCbz sulfone alone and compositions consisting of dt-BuCbz sulfone and M-H6(CN)2 or P-H6(CN)2 (the amount of dt-BuCbz sulfone is 10 mol %) recorded on a film at room temperature between approximately 400 nm and 650 nm. The values ​​correspond to the normalized values ​​of the emission intensities in FIG. 5. In this situation, the value of ΔI at the wavelength of the highest peak in the emission spectrum is the glum value at that wavelength. [Figure 6]1 is a graph showing the intensity difference ΔI between the left and right circular emission of M-H6(NPh)2 (dotted line) and P-H6(NPh)2 (solid line) recorded in dichloromethane solvent at room temperature between approximately 400 nm and 650 nm. The values ​​are normalized, so that the highest peak value Imax of the total emission (IR+IL) is normalized to 2. In this situation, the value of ΔI at the wavelength of Imax is the glum value at that wavelength. [Figure 7] 1 is a graph showing the intensity difference ΔI between the left and right circular emission of M-H6(DPP)2 (dotted line) and P-H6(DPP)2 (solid line) recorded in dichloromethane solvent at room temperature between approximately 550 nm and 725 nm. Values ​​are normalized, so that the highest peak value Imax of the total emission (IR+IL) is normalized to 2. In this situation, the value of ΔI at the wavelength of Imax is the glum value at that wavelength. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] The present invention will now be further described with reference to the accompanying Figures 1 to 7. Throughout this disclosure, in the event of a discrepancy between the name of a chemical compound and its developed structure, the developed structure shall prevail (without regard to its configuration, unless otherwise specified).

[0070] The principle of the present invention is based on the energy transfer that occurs from the TADF molecules to the CP molecules; the TADF molecules are the hosts and the CP molecules are the emitters, which ultimately emit circularly polarized luminescence.

[0071] More precisely, as shown in Fig. 1, upon electrical or photoexcitation of a TADF molecule, its excited state is in a certain equilibrium state (undergoing intersystem crossing and reverse intersystem crossing processes) between the singlet S1 spin configuration and the triplet T1 spin configuration, which is due to the energy gap ΔE STDuring that time, the equilibrium shifts towards the singlet state S1, since the deactivation of the singlet state S1 by fluorescence occurs much faster than the phosphorescence emission from the triplet state T1 (rates are of the order of ns and μs, respectively). Finally, there are two fluorescence processes, one that occurs directly from the singlet state S1 (prompt fluorescence, ns time scale) and the other that is time-delayed due to the formation of a singlet-triplet excited state equilibrium (delayed fluorescence, μs time scale). This equilibrium is very important, for example, in OLEDs, since it can lead to a theoretical internal quantum efficiency of 100%, compared to a maximum theoretical internal quantum efficiency of 25% for pure fluorescent emitters.

[0072] The present inventors have found that when a solid film of TADF molecules is doped with an emissive molecule having an excited state S'1 with lower energy than the singlet and triplet states of the TADF molecules, its deactivation can occur via a route different from immediate and delayed fluorescence, i.e., energy transfer from the singlet state S1 of the TADF molecule to the excited state S'1 of the emissive molecule with the lowest energy. The emissive molecule eventually emits light when it returns to its ground state S'0. In this case, for example, when the emissive molecule is a chiral molecule, the emissive molecule exhibits circular polarization properties, and the emissive molecule emits circularly polarized light upon optical and / or electrical excitation of the TADF molecule.

[0073] "Doping ratio" refers to the proportion (in moles) of dopant present in the composition when referring to a TADF host. This bimolecular system can also be placed in an organic matrix to form a ternary active layer (where "doping ratio" again refers to the proportion (in moles) of chiral emitter to TADF host) when referring to a TADF host.

[0074] To ensure more efficient energy transfer, the emission spectrum of TADF molecules should overlap with the absorption spectrum of CP molecules. Furthermore, in the emitting layer of an OLED device, the ratio of CP molecules to TADF molecules should be as low as possible to avoid direct carrier capture, since CP molecules are used as dopants and not as the main components of the composition. However, there should not be too few CP molecules to ensure sufficient energy transfer and no residual TADF emission. Therefore, the optimal ratio of CP molecules to TADF molecules may vary, and those skilled in the art would be able to optimize the ratio for various combinations of TADF molecules and CP molecules.

[0075] method NMR spectrum measurement. 1 H and 13 C NMR spectra were recorded at room temperature on an AVANCE III 400 BRUKER or an AVANCE I 500 BRUKER. Chemical shifts δ are given in ppm and coupling constants J in Hz. 1 Chemical shifts in 1 H NMR spectra are referenced to residual protons in deuterated solvents (δ=7.26 ppm, CDCl3). 13 C shifts are referenced to the CDCl3 peak at δ=77.16 ppm.

[0076] Mass spectrometry. High resolution mass (HR-MS) determinations were carried out on a Bruker MaXis 4G, CRMPO, by ASAP (+ or -) or ESI and MALDI using CH2Cl2 as solvent technique. Experimental and calculated masses are given taking into account the electron mass.

[0077] UV spectrum measurement. UV-visible (UV-vis, M -1 cm -1 ) Absorption spectra were recorded on a UV-2401PC Shimadzu spectrophotometer.

[0078] Fluorescence Spectra Measurements. Fluorescence spectra were recorded on an FL920 Edinburgh fluorometer.

[0079] Fluorescence quantum yield measurements. Fluorescence quantum yield in dilute solution (dichloromethane) is measured using the following formula 1: where the subscripts "ST" and "X" stand for "standard" and "sample", respectively, Φ is the fluorescence quantum yield, Grad is the slope from a plot of integrated fluorescence intensity versus absorbance, and η is the refractive index of the solvent. The fluorescence quantum yield standards used herein are quinine sulfate in 0.5 M sulfuric acid and rhodamine 6G (excitation of the reference and sample compounds was performed at the same wavelength):

[0080]

number

[0081] The solid-state fluorescence quantum yield was measured using the following equation 2, where "R" and "X" represent the reference and sample, respectively. A(λ) is the absorbance at the excitation wavelength λ, n is the refractive index, and D is the integrated intensity. The luminescence quantum yield was measured for rhodamine 6G in ethanol (Φ R = 0.91). The reference and sample compounds were excited at the same wavelength.

[0082]

number

[0083] TADF quantum yield measurement. The TADF quantum yield is measured in the presence of oxygen (Φ Ox ) and in the absence (Φ Ar ) using the fluorescence quantum yield determined in Eq. (3); delayed fluorescence is assumed to be negligible in the presence of oxygen (see Eq. 3). [Formula 3] Φ X= Φ TADF +Φ CP= Φ Ar Φ CP= ΦOx Φ TADF= Φ Ar -Φ Ox

[0084] Φ Ox and Φ Ar is determined by using the total photoluminescence quantum efficiency, measured using a Hamamatsu C9920-03 integrating sphere.

[0085] Luminescence anisotropy factor measurement. Luminescence anisotropy factor g lum is representative of circularly polarized light. It is measured by Equation 4, I L and I R refer to the left-handed and right-handed circular polarization intensities, respectively.

[0086]

number

[0087] g lum The value of ranges from -2 to +2, with negative values ​​meaning right circular CP and positive values ​​meaning left circular CP. A value of 0 means there is no CP, while an absolute value of 2 means perfect circular polarization.

[0088] These measurements were performed using a CPL spectrometer (JASCO). Samples were dissolved in dichloromethane and excited using a 90° geometry with a Xenon ozone-free lamp 150W LS. The following parameters were used: emission slit width approximately 2mm, integration time = 4 seconds, scan speed = 50nm / min, accumulation = 5. Sample excitation was performed at 350nm. Further details can be found in Abbate et al., 2016[1]. EXAMPLES

[0089] (Examples 1 and 2: 2,15-bisethynylhexahelicene H6(H)2 and 4,4'-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))di(trimethylsylane)H6(TMS)2) P-H6(H)2 and H6(TMS)2 of formula 14 were prepared according to the strategy previously reported by Crassous, J. et al. (2018)[2].

[0090] [ka]

[0091] (Example 2: 4,4'-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))dibenzonitrile H6(CN)2) P-H6(CN)2 was synthesized according to formula (15) as exemplified below. First, P-H6(H)2 (50 mg, 0.13 mmol) and 4-bromobenzonitrile (71 mg, 0.39 mmol) were placed in a 25 mL oven-dried flask under argon. Then, 4 mL of dry toluene and 1 mL of dry triethylamine (Et3N) were added, and the resulting solution was made oxygen-free by bubbling argon through it for 1 h. Tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) (15 mg, 0.013 mmol) and copper(I) iodide (CuI) (4.9 mg, 0.026 mmol) were added, and the solution was refluxed for 3 h. After cooling to room temperature, the solution was passed through a short silica plug (dichloromethane, CHCl2). The crude mixture was further purified by column chromatography on silica (8 / 2 heptane / CH2Cl2 eluent system) to give P-H6(CN)2 (63.9 mg, 85%) as a yellow solid.

[0092] [ka]

[0093] 1H NMR (300 MHz, methylene chloride-d2) δ 8.19 - 8.07 (m, 6H), 8.04 - 7.99 (d, J = 8.6 Hz, 2H), 7.90 - 7.88 (s, 1H), 7.87 - 7.83 (dd, J = 3.1, 2.0 Hz, 3H), 7.69 - 7.67 (d, J = 1.3 Hz, 2H), 7.67 - 7.63 (d, J = 1.3 Hz, 2H), 7.47 - 7.44 (d, J = 1.2 Hz, 2H), 7.44 - 7.42 (d, J = 1.6 Hz, 3H), 7.41 - 7.39 (d, J = 1.5 Hz, 1H). 13 C NMR (75 MHz, methylene chloride-d2) δ 133.6, 133.2, 132.2, 132.1, 132.11, 132.1 - 132.0, 132.0 - 131.9, 131.8 - 131.7, 129.2 - 128.9, 128.2 - 128.0, 127.9 - 127.8, 127.9 - 127.8, 127.8 - 127.7, 127.7 - 127.6, 127.5 - 127.4, 127.4 - 127.3, 127.0 - 126.9, 124.0 - 123.6, 118.5 - 118.4, 118.4 - 118.3, 111.5 - 111.2, 94.3 - 93.1, 88.2 - 86.0. HR-MS Ultraflex III, MALDI, 370 °C; ion [M] + , C 44 H 22 N2, m / z calculated 578.17775, m / z experimental 578.182 (Δ=7 ppm).

[0094] (Example 3: 4,4'-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))dipyridine H6(Py)2) P-H6(Py)2 was synthesized according to formula (16) as exemplified below. A mixture of P-H6(H)2 (50 mg, 0.13 mmol) and 4-bromopyridine hydrochloride (75.8 mg, 0.39 mmol) was placed in a 25 mL oven-dried flask under argon. 5 mL of dry propylamine was then added and the resulting solution was made oxygen-free by bubbling argon through it for 1 h. Pd(PPh3)4 (15 mg, 0.013 mmol) and CuI (4.9 mg, 0.026 mmol) were added and the solution was refluxed for 3 h. After cooling to room temperature, the solution was passed through a short silica plug (CH2Cl2). The crude mixture was further purified by column chromatography on silica (5 / 5 heptane / CH2Cl2 eluent system) to give P-H6(Py)2 (44.8 mg, 65%) as a yellow solid.

[0095] [ka]

[0096] 1 H NMR (400 MHz, methylene chloride-d2) δ 8.61 - 8.59 (d, J = 1.7 Hz, 2H), 8.59 - 8.56 (d, J = 1.7 Hz, 2H), 8.16 - 8.12 (d, J = 8.2 Hz, 2H), 8.12 - 8.10 (d, J = 1.6 Hz, 2H), 8.10 - 8.06 (d, J = 2.0 Hz, 2H), 8.05 - 8.02 (s, 1H), 8.02 - 8.00 (s, 1H), 7.91 - 7.89 (s, 1H), 7.88 - 7.87 (s, 1H), 7.87 - 7.83 (m, 2H), 7.44 - 7.43 (d, J = 1.6 Hz, 1H), 7.42 - 7.41 (d, J = 1.6 Hz, 1H), 7.24 - 7.22 (d, J = 1.7 Hz, 2H), 7.22 - 7.20 (d, J = 1.6 Hz, 2H). 13C NMR (101 MHz, methylene chloride-d2) δ 149.9, 149.6, 133.6, 133.3, 132.4, 132.2, 132.2, 132.1, 132.0, 131.8, 131.6, 131.0, 129.1, 129.0, 127.9, 127.9, 127.9, 127.9, 127.9, 127.8, 127.7, 127.6, 127.5, 127. 5, 127.4, 127.4, 127.1, 126.8, 125.5, 124.9, 124.0, 123.4, 118.4, 118.0, 94.3, 92.0, 87.1, 84.2. HR-MS Ultraflex III, MALDI, 370°C; ions [M+H] + , C 40 H 23 N2, m / z calculated 531.18557, m / z experimental 531.182 (Δ=7 ppm).

[0097] (Example 4: 4,4'-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))dianiline H6(NH2)2) P-H6(NH2)2 was synthesized according to formula (17) as exemplified below. P-H6(H)2 (50 mg, 0.13 mmol) and 4-iodoaniline (126 mg, 0.575 mmol) were placed in a 25 mL oven-dried flask under argon. 5 mL of dry propylamine was then added and the resulting solution was made oxygen-free by bubbling argon through it for 1 h. Pd(PPh3)4 (15 mg, 0.013 mmol) and CuI (4.9 mg, 0.026 mmol) were added and the solution was refluxed for 3 h. After cooling to room temperature, the solution was passed through a short silica plug (CH2Cl2). The crude mixture was further purified by column chromatography on silica (5 / 5 heptane / CH2Cl2 eluent system) to give P-H6(NH2)2 (47.2 mg, 65%) as a yellow solid.

[0098] 1H NMR (400 MHz, methylene chloride-d2) δ 8.10 - 7.94 (m, 8H), 7.85 - 7.78 (d, J = 8.3 Hz, 2H), 7.75 - 7.72 (m, 2H), 7.37 - 7.35 (d, J = 1.6 Hz, 1H), 7.34 - 7.33 (d, J = 1.6 Hz, 1H), 7.14 - 7.13 (d, J = 2.0 Hz, 2H), 7.12 - 7.11 (d, J = 2.0 Hz, 2H), 6.64 - 6.62 (d, J = 2.0 Hz, 2H), 6.62 - 6.59 (d, J = 2.0 Hz, 2H), 3.93 - 3.85 (s, 4H). 13 C NMR (101 MHz, methylene chloride-d2) δ 148.1, 146.2, 133.6, 133.3, 132.9, 132.7, 132.2, 131.8, 131.6, 131.4, 131.3, 131.1, 129.6, 129.3, 128.2, 127.9, 127.8, 127.7, 127.7,127.6, 127.5, 127.4, 127.3, 127.2, 127.1, 126.9, 124.5, 123.6, 120.7, 119.9, 115.3 ,114.3, 112.9, 111.9, 90.4, 88.7, 88.1, 86.7. HR-MS Ultraflex III, MALDI, 370 °C; ion [M] + , C 42 H 26 N2, m / z calculated 558.20905, m / z experimental 558.207 (Δ=4 ppm).

[0099] (Example 5: 4,4'-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))di(N,N-dimethylaniline)H6(NMe2)2) P-H6(NMe2)2 was synthesized from H6(NH2)2 of Example 4 as illustrated below by formula 17. To a solution of P-H6(NH2)2 (30 mg, 0.054 mmol) dissolved in 5 mL of tetrahydrofuran (THF) in a round-bottom flask, formaldehyde (0.04 mL, 0.13 mmol) was added dropwise. The mixture was stirred at room temperature for 15 minutes under argon. Sodium cyanoborohydride (NaBH3CN) (34 mg, 0.54 mmol) was then directly introduced into the solution. The mixture was stirred a second time at room temperature for 15 minutes. Acetic acid (1 mL) was added to quench the reaction, and the solution was stirred at room temperature for 2 hours. After adding water and dichloromethane (25 mL each), the organic layer was separated and the aqueous layer was extracted with dichloromethane. All the organic layers were collected, dried over MgSO4, and the solvent was evaporated. The crude product was purified by a plug of silica and washed with dichloromethane to give the desired product P-H6(NMe2)2 as a yellow solid (14.9 mg, 45%).

[0100] [ka]

[0101] 1 H NMR (400 MHz, methylene chloride-d2) δ 8.16-7.97 (m, 8H), 7.91-7.81 (d, J = 8.3 Hz, 2H), 7.81 - 7.74 (d, J = 1.5 Hz, 2H), 7.43 - 7.34 (dd, J = 8.2, 1.6 Hz, 2H), 7.26 - 7.24 (d, J = 2.1 Hz, 2H), 7.23 - 7.21 (d, J = 2.0 Hz, 2H), 6.73 - 6.69 (d, J = 2.1 Hz, 2H), 6.69 - 6.66 (s, 2H), 3.20 - 2.52 (s, 12H). 13C NMR (126 MHz, methylene chloride-d2) δ 150.6, 149.5, 133.4, 133.1, 132.5, 132.3, 131.9, 131.7, 131.3, 131.2, 131.0, 130.7, 129.5, 129.3, 127.9, 127.8, 127.6, 127.6, 127.5, 127.4, 127.3 - 127.2 (d, J = 3.7 Hz), 127.2, 127.1, 126.8, 126.7, 124.1, 123.8, 120.6, 120.3, 112.7, 110.6, 110.5, 109.4, 90.4, 89.1, 88.2, 86.4, 40.5, 39.2. HR-MS Ultraflex III, ESI, 370°C; ions [M+H] + , C 46 H 35 N2, m / z calculated 615.27947, m / z experimental 615.2796 (Δ=0 ppm).

[0102] Example 6 The measurement results of the luminescence quantum yield and the luminescence anisotropy factor in dichloromethane at 298 K for the above Examples 1 to 5 are summarized in the following Table 1 (in the table, "yEx" stands for "y×10 x ").

[0103] [Table 1]

[0104] Example 7 An example of the present invention is presented here. In this example, the active-type emissive layer composition includes dt-BuCbz sulfone as the TADF molecule and H6(CN)2 as the CP molecule. The TADF molecule dt-BuCbz sulfone was developed by Adachi et al. in 2012 [3], while H6(CN)2 was synthesized and developed for the first time by the present applicant, to the best of the inventors' knowledge.

[0105] H6(CN)2 exhibits singlet energy levels of 2.99 eV at 415 nm and 2.92 eV at 425 nm. The photophysical and chiroptical properties of H6(CN)2 are shown in Figures 2 and 3.

[0106] Table 2 below shows the normalized absorption values ​​and Table 3 shows the normalized emission values ​​between 250 nm and 600 nm, corresponding to Figure 2. In Figure 2, the normalized absorption is represented by a dotted line, while the normalized emission is represented as a solid line. The highest peak is normalized to a value of 1 and the others are proportional to it.

[0107] [Table 2]

[0108] [Table 3]

[0109] Table 4 below shows the intensity difference ΔI between the normalized left circle emission value and the normalized right circle emission value between 250 nm and 600 nm for P-H6(CN)2 (solid line) and M-H6(CN)2 (dotted line), which corresponds to FIG. 3 (in the table, “yEx” stands for “y×10 x It can be observed that the difference between the normalized left circle emission and the normalized right circle emission for the P and M configurations of H6(CN)2 is almost symmetrical from the line of coordinate 0. Furthermore, since the normalization is based on the highest peak of the total emission spectrum normalized by a value of 2 (different from Figure 2), the value of ΔI at the wavelength of the highest total intensity peak is g lum G of H6(CN)2 lum The value is approximately 3 x 10 -2 However, it does not have TADF properties.

[0110] [Table 4]

[0111] To test the combination of dt-BuCbz sulfone doped with H6(CN)2, five doping ratios (total amount of dt-BuCbz sulfone: 1, 5, 10, and 20 mol.%) were prepared and spin-coated into solid films on substrates. Emission measurements are presented in FIG. 4 from 370 nm to 650 nm, and values ​​are further shown in Table 5 below (where "yEx" stands for "y×10 x "CP" stands for "H6(CN)2 alone", "TADF" stands for "dt-BuCbz sulfone alone", and "x%" stands for "dt-BuCbz sulfone doped with x mol.% of H6(CN)2".

[0112] [Table 5A]

[0113] [Table 5B]

[0114] Table 6 below shows the intensity difference ΔI between the normalized left and right circular emission values ​​between approximately 400 nm and 650 nm for dt-BuCbz sulfone alone (TADF), and compositions of dt-BuCbz sulfone with P-H6(CN)2 (P-CP; dotted line) and M-H6(CN)2 (M-CP; solid line) constituting 10 mol.% of the total amount of dt-BuCbz sulfone (in the table, "yEx" stands for "y×10 x "). Table 6 corresponds to FIG. 5. It can be observed that the difference between the normalized left circle emission and the normalized right circle emission for the P and M configurations of H6(CN)2 is almost symmetrical from the line of coordinate 0. Furthermore, since the normalization is based on the highest peak of the total emission spectrum normalized by a value of 2, the value of ΔI at the wavelength of the highest total emission peak is g lumFrom Table 5, it can be observed that the maximum intensity for dt-BuCbz sulfone containing 10 mol.% H6(CN)2 corresponds to a wavelength of 430 nm. From Table 6, at 430 nm, the value of ΔI (i.e., g lum The values ​​of M-H6(CN)2 and P-H6(CN)2 were 1.59 × 10 -2 and 1.44 x 10 -2 It can be observed that

[0115] [Table 6]

[0116] Dt-BuCbz sulfone has singlet and triplet states at higher energy levels than the singlet of H6(CN)2, 2.99 eV at 415 nm and 2.92 eV at 425 nm. Furthermore, the emission spectrum of dt-BuCbz sulfone overlaps with the absorption spectrum of H6(CN)2.

[0117] These results show that the emission transfer from TADF molecules to CP molecules is quantitative even with only 1% dopant, providing evidence of the transfer of unpolarized emission from TADF molecules to CP molecules resulting in circularly polarized emission. The overall emission intensity decreases as the ratio of H6(CN)2 in dt-BuCbz sulfone decreases from 1 mol.% to 10 mol.%. However, the overall emission intensity instead increases from 10 mol.% to 20 mol.%. The composition of Example 1 results in a cyan blue color.

[0118] Example 8 The CP molecule of Example 7 can be replaced by H6(NPh)2 or H6(DPP)2.

[0119] FIG. 6 shows that the intensity difference ΔI between the left and right circular luminescence light of P-H6(NPh)2 (solid line) and M-H6(NPh)2 (dotted line) is shown. It can be observed that P-H6(NPh)2 emits more left circular light than right circular light, so that it can be stated that P-H6-(NPh)2 emits left circularly polarized light to some extent. Similarly, M-H6(NPh)2 emits more right circular light than left circular light, so that it can be stated that M-H6-(NPh)2 emits right circularly polarized light to some extent. The maximum value of ΔI for both molecules was observed near 495 nm. H6(NPh)2 has a luminescence quantum yield of 70% and a wavelength of 3×10 -3 H6(NPh)2 gives a green color.

[0120] FIG. 7 shows the intensity difference ΔI between the left and right circular luminescence light of P-H6(DPP)2 (solid line) and M-H6(DPP)2 (dotted line). It can be observed that P-H6(DPP)2 emits more left circular light than right circular light, so that it can be stated that P-H6(DPP)2 emits left circularly polarized light to some extent. Similarly, M-H6(DPP)2 emits more right circular light than left circular light, so that it can be stated that M-H6(DPP)2 emits right circularly polarized light to some extent. The maximum value of ΔI for both molecules was observed near 605 nm. H6(DPP)2 has a luminescence quantum yield of 40% and a wavelength of 7×10 -4 H6(DPP)2 gives rise to a red color.

[0121] The TADF molecule of Example 7 can be replaced by Cbz-TRZ2 or 4-CbzIPN, described in Adachi et al., 2017[4] and Adachi et al., 2012[5], respectively. Cbz-TRZ2 has a TADF quantum yield of 86%, while for 4-CbzIPN, the quantum yield is 94%.

[0122] The following combinations give particularly good results: Cbz-TRZ2 with H6(NPh)2 and 4-CbzIPN with H6(DPP)2.

[0123] In addition to the TADF and CP molecules described herein, numerous possible combinations of TADF and CP molecules can be contemplated to obtain the desired synergistic CP-TADF properties. For example, in the case of CP molecules, chiral molecules with planar chirality such as other helicene derivatives, helicenoid compounds (where the helical polycyclic compounds are not fully conjugated), biaryl systems, and paracyclophane derivatives can be considered.

[0124] References [1] Longhi, G.; Castiglioni, E.; Koshoubu, J.; Mazzeo, G.; Abbate, S., “Circularly Polarized Luminescence: A Review of Experimental and Theoretical Aspects”, Chirality 2016, 28 (10), 696-707 [2] Dhbaibi, K.; Favereau, L.; Srebro-Hooper, M.; Jean, M.; Vanthuyne, N.; Zinna, F.; Jamoussi, B.; Di Bari, L.; Autschbach, J.; Crassous, J., “Exciton coupling in diketopyrrolopyrrole-helicene derivatives leads to red and near-infrared circularly polarized luminescence”, Chem. Sci. 2018, 9, 735-742 [3] Zhang, Q.; Li, J.; Shizu, K.; Huang, S.; Hirata, S.; Miyazaki, H.; Adachi, C., “Design of Efficient Thermally Activated Delayed Fluorescence Materials for Pure Blue Organic Light Emitting Diodes”, J. Am. Chem. Soc., 134, 36, 14706-14709 (2012) [4] Cui, L.-S.; Nomura, H.; Geng, Y.; Kim, J. U.; Nakanotani, H.; Adachi, C., “Controlling Singlet-Triplet Energy Splitting for Deep-Blue Thermally Activated Delayed Fluorescence Emitters”, Angew. Chem. Int. Ed., 56, 1571 (2017) [5] Uoyama, H.; Goushi, K.; Shizu, K.; Nomura, H.; Adachi, C., “Highly efficient organic light-emitting diodes from delayed fluorescence”, Nature, 492, 234-238 (2012).

Claims

1. A light-emitting layer composition for an active-type light-emitting device, comprising a TADF molecule having TADF properties as a host material and a light-emitting molecule having circular polarization (CP) properties as a dopant, The luminescent molecule has the following general formula: 【Chemistry 1】 A carbo[6]helicene derivative (hereinafter referred to as H6) having the formula: B has the formula: 【Chemistry 2】 One or a combination of is a linker having the formula R has the formula: 【Chemistry 3】 One of these is a light-emitting layer composition for an active light-emitting device.

2. 2. The active light emitting device light emitting layer composition of claim 1, wherein the TADF molecules exhibit singlet and triplet state energy levels, and the light emitting molecules exhibit singlet state energy levels lower than the singlet and triplet state energy levels of the TADF molecules.

3. 3. The light-emitting layer composition for active light-emitting devices according to claim 1, wherein the light-emitting molecule has an absorption spectrum and the TADF molecule has an emission spectrum that overlaps with the absorption spectrum of the light-emitting molecule.

4. At least one of the following characteristics: - TADF quantum yield of 0.01 or higher - a luminescence quantum yield of 0.10 or more, and - g is not 0 lum Emission polarization measured by the value 4. The light-emitting layer composition for an active light-emitting device according to claim 1, wherein

5. The luminescent molecules are in the P or M isomeric configuration, 【Chemistry 4】 From now on, H6(CN) 2 ; 【Chemistry 5】 From now on, H6(Py) 2 ; 【Chemistry 6】 From now on, H6 (NH 2 ) 2 ; 【Chemistry 7】 From this point on, H6 (NMe 2 ) 2 and 【Chemistry 8】 From now on, H6 (TMS) 2 ; 5. The light-emitting layer composition for an active light-emitting device according to claim 1, wherein the light-emitting layer composition is one of the following:

6. The TADF molecule is: 【Chemistry 11】 Henceforth dt-BuCbz sulfone; 【Chemistry 12】 Hereafter, Cbz-TRZ2; and 【Chemistry 13】 From now on 4-CbzIPN 6. The light-emitting layer composition for an active light-emitting device according to claim 1, wherein the achiral molecule is one of the following:

7. TADF molecules and luminescent molecules: - dt-BuCbz sulfone and H6(CN) 2 5. The light emitting layer composition for an active light emitting device according to claim 1, comprising a combination of:

8. 8. A light emitting device having a light emitting layer formed from the light emitting layer composition for active light emitting devices defined in any one of claims 1 to 7.

9. 9. The light-emitting device of claim 8 which is an OLED.

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