CIRCULARLY POLARIZED OLED EMITTING LAYER COMPOSITION

Abstract

An active light-emitting layer composition including a thermally activated delayed fluorescence (TADF) molecule with TADF properties as a host material and a luminescent molecule with circularly polarized (CP) properties as a dopant. Also, a light-emitting device, such as an organic light-emitting diodes (OLED), including the active light-emitting layer made of this composition.

Claims

1-13. (canceled)

14. An active light-emitting layer composition comprising a TADF molecule with TADF properties as a host material and a luminescent molecule with CP properties as a dopant.

15. The active light-emitting layer composition of claim 14, wherein the TADF molecule exhibits a singlet state energy level and a triplet state energy level and the luminescent molecule exhibits a singlet state energy level lower than the singlet state and triplet state energy levels of the TADF molecule.

16. The active light-emitting layer composition of claim 14, wherein the luminescent molecule has an absorption spectrum and the TADF molecule has a luminescence spectrum overlapping the absorption spectrum of the luminescent molecule.

17. The active light-emitting layer composition of claim 14, wherein the composition exhibits at least one of the following properties: a TADF quantum yield of 0.01 or higher; a luminescence quantum yield of 0.10 or higher; and a luminescence polarization measured through the g.sub.lum value which is different from 0.

18. The active light-emitting layer composition of claim 14, wherein the luminescent molecule is a chiral molecule, such as a helicene derivative, a helicenoid compound, a biarylic system, a molecule with planar chirality (e.g. paracyclophane derivatives).

19. The active light-emitting layer composition of claim 18, wherein the luminescent molecule is carbo[6]helicene derivate (hereafter H6) with the general formula, in the M or P configuration: ##STR00018##

20. The active light-emitting layer composition of claim 19, wherein B is a linker with one of the following formulae: ##STR00019## or a combination thereof.

21. The active light-emitting layer composition of claim 19, wherein R is one of the following formulae: ##STR00020##

22. The active light-emitting layer composition of claim 19, wherein the luminescent molecule is one of: ##STR00021## ##STR00022## in their P or M isomeric configuration.

23. The active light-emitting layer composition of claim 14, wherein the TADF molecule is an achiral molecule, such as one of the following: ##STR00023##

24. The active light-emitting layer composition of claim 14, wherein with one of the following combination of TADF molecule and luminescent molecule: dt-BuCbzSulfone and H6(CN).sub.2; Cbz-TRZ2 and H6(NPh).sub.2; and 4-CbzIPN and H6(DPP).sub.2.

25. A light-emitting device having the active light-emitting layer of claim 14.

26. The light-emitting device of claim 25, wherein the light-emitting device is an OLED.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0055] Other features, details and advantages will be shown in the following detailed description and on the figures, on which:

[0056] FIG. 1 is an illustration showing the principle behind the present invention, notably the transfer of energy from the singlet energy level of the TADF molecule to the singlet energy level of the CP molecule.

[0057] FIG. 2 is a graph showing the absorption spectrum (dotted line) and the emission spectrum (solid line) of H6(CN).sub.2 between 250 nm and 600 nm recorded in dichloromethane solvent at room temperature, the values being normalized so that the highest peak has a value of 1.

[0058] FIG. 3 is a graph showing the intensity difference ΔI between left-handed emitted light and right-handed emitted light of M-H6(CN).sub.2 (dotted line) and P—H6(CN).sub.2 (solid line) approximately between 400 nm and 600 nm recorded in dichloromethane solvent at room temperature. The values are normalized so that the highest peak I.sub.max of the total emission spectrum has a value of 2. In such a situation, the value of ΔI at the wavelength of I.sub.max is the g.sub.lum value at that wavelength.

[0059] FIG. 4 is a graph showing the emission spectra between 370 nm and 370 nm of H6(CN).sub.2 alone, dt-BuCbzSulfone alone, and a composition consisting of dt-BuCbzSulfone and H6(CN).sub.2 at 1, 5, 10 and 20 mol. % of the amount of dt-BuCbzSulfone, recorded on films at room temperature.

[0060] FIG. 5 is a graph showing the intensity difference ΔI between left-handed emitted light and right-handed emitted light of BuCbzSulfone alone, and a composition consisting of dt-BuCbzSulfone and M-H6(CN).sub.2 or P—H6(CN).sub.2 at 10 mol. % of the amount of dt-BuCbzSulfone, approximately between 400 nm and 650 nm, recorded on films at room temperature. The values correspond to the normalized value of emission intensity in FIG. 5. In such situation, the value of ΔI at the wavelength of the highest peak in the emission spectrum is the g.sub.lum value at that wavelength.

[0061] FIG. 6 is a graph showing the intensity difference ΔI between left-handed emitted light and right-handed emitted light of M-H6(NPh).sub.2 (dotted line) and P—H6(NPh).sub.2 (solid line) approximately between 400 nm and 650 nm recorded in dichloromethane solvent at room temperature. The values are normalized so that the highest peak value I.sub.max of the total emission (I.sub.R+I.sub.L) is normalized to 2. In such situation, the value of ΔI at the wavelength of I.sub.max is the g.sub.lum value at that wavelength.

[0062] FIG. 7 is a graph showing the intensity difference ΔI between left-handed emitted light and right-handed emitted light of M-H6(DPP).sub.2 (dotted line) and P—H6(DPP).sub.2 (solid line) approximately between 550 nm and 725 nm recorded in dichloromethane solvent at room temperature. The values are normalized so that the highest peak value I.sub.max of the total emission (I.sub.R+I.sub.L) is normalized to 2. In such situation, the value of ΔI at the wavelength of I.sub.max is the g.sub.lum value at that wavelength.

DETAILED DESCRIPTION

[0063] The present invention is now further described with reference to the accompanying FIGS. 1 to 7. Throughout this disclosure, when there is a discrepancy between the name of a chemical compound and its developed structure, precedence should be given to the developed structure (without consideration of its configuration unless stated otherwise).

[0064] The principle of the present invention is based on the energy transfer occurring from the TADF molecule to the CP molecule; the TADF molecule being the host and the CP molecule being an emitter, which ultimately emits circularly polarized emission.

[0065] More precisely, as shown in FIG. 1, upon electrical or optical excitation of the TADF molecule, its excited-state will be in equilibrium between the singlet S.sub.1 and triplet T.sub.1 spin configurations to some extent (through intersystem crossing and reverse intersystem crossing processes), which is governed by the energy gap between these two states ΔE.sub.ST. During that period of time, the equilibrium is shifted toward the singlet state S.sub.1 since its deactivation through fluorescence emission occurs much faster than phosphorescence emission from the triplet state T.sub.1 (rates being of the order of ns and μs, respectively). Finally, there are two fluorescence emission processes, one occurring directly from the singlet state S.sub.1 (prompt fluorescence, in ns timescale) and another one that delayed in time (delayed fluorescence, in μs timescale) due to the formation of the singlet-triplet excited states equilibrium. This equilibrium is very important for instance in OLEDs since it can yield a theoretical internal quantum efficiency of 100%, in comparison to the maximum theoretical internal quantum efficiency of 25% for pure fluorescence emitters.

[0066] The present authors found out that doping a solid film of a TADF molecule with a luminescence molecule with an excited state S′.sub.1 lower in energy than the singlet and triplet states of the TADF molecule, its deactivation may occur through a different pathway than the prompt and delayed fluorescences; that is an energy transfer from the singlet state S.sub.1 of the TADF molecule to the excited state S′.sub.1 of the luminescence molecule with lowest energy. The luminescence molecule eventually emits light when it goes back to its ground state S′.sub.0. In the present case, the luminescent molecule exhibits circular polarization properties, for example when it is a chiral molecule, and it emits a circularly polarized light upon optical and/or electrical excitation of the TADF molecule.

[0067] The ‘doping ratio’ is the proportion of dopant present in a composition, by moles, with reference to the TADF host. This bimolecular system can be also placed in an organic matrix to form a ternary active layer (here again the ‘doping ratio’ will be based on the proportion of the chiral emitter and the TADF host, by moles, regarding the TADF host).

[0068] In order to ensure a more efficient energy transfer, the luminescence spectrum of the TADF molecule should overlap with the absorption spectrum of the CP molecule. Moreover, within the emitting layer of an OLED device, the ratio of the CP molecule with regard to the TADF molecule should be as low as possible to avoid direct carrier trapping. This is why it is used as a dopant and not as a main component of the composition. However, it should not be too low to ensure sufficient energy transfer and no residual TADF emission. Accordingly, the optimum ratio of CP molecule to TADF molecule may change and the person skilled in the art would be able to optimize the ratio for different combinations of TADF molecule and CP molecule.

Methods

[0069] NMR spectrum measurements. .sup.1H and .sup.13C NMR spectra were recorded at room temperature on an A VANCE III 400 BRUKER or an AVANCE 1500 BRUKER. Chemical shifts δ are given in ppm and coupling constants J in Hz. Chemical shifts for .sup.1H NMR spectra are referenced relative to residual protium in the deuterated solvent (δ=7.26 ppm, CDCl.sub.3). .sup.13C shifts are referenced to CDCl.sub.3 peaks at δ=77.16 ppm.

[0070] Mass-spectrometry measurements. High-resolution mass (HR-MS) determinations were performed at CRMPO on a Bruker MaXis 4G by ASAP (+or −) or ESI and MALDI with CH.sub.2Cl.sub.2 as solvent techniques. Experimental and calculated masses are given with consideration of the mass of the electron.

[0071] UV spectrum measurements. UV-Visible (UV-vis, in M−1 cm−1) absorption spectra were recorded on a UV-2401PC Shimadzu spectrophotometer.

[0072] Fluorescence spectrum measurements. Fluorescence spectra were recorded on a FL 920 Edinburgh fluorimeter.

[0073] Fluorescence quantum yield measurements. Fluorescence quantum yields in diluted solution (in dichloromethane) are measured using the following equation Math. 1; where the subscripts “ST” and “X” denote “standard” and “sample” respectively, Φ is the fluorescence quantum yield, Grad is the gradient from the plot of integrated fluorescence intensity vs. absorbance, and η is the refractive index of the solvent. Reference for fluorescence quantum yields used herein are quinine sulfate in 0.5 M sulfuric acid and rhodamine 6G (Excitation of reference and sample compounds was performed at the same wavelength):

[00001]$\begin{array}{cc}{\Phi }_X={\Phi }_{\mathrm{ST}}\left(\frac{{\mathrm{Grad}}_X}{{\mathrm{Grad}}_{\mathrm{ST}}}\right)\left(\frac{{\eta }_X^2}{{\eta }_{\mathrm{ST}}^2}\right)& \left[\mathrm{Math}.1\right]\end{array}$

[0074] Fluorescence quantum yields in solid state are measured using the following equation Math. 2; where “R” and “X” stand for 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 yields were measured relative to rhodamine 6G in ethanol (Φ.sub.R=0.91). Excitation of reference and sample compounds was performed at the same wavelength

[00002]$\begin{array}{cc}\frac{{\Phi }_X}{{\Phi }_{\mathrm{ST}}}=\left(\frac{A_R\left(\lambda \right)}{A_X\left(\lambda \right)}\right)\left(\frac{n_X^2}{n_R^2}\right)\left(\frac{D_X}{D_R}\right)& \left[\mathrm{Math}.2\right]\end{array}$

[0075] TADF quantum yield measurements. The TADF quantum yields are determined by using fluorescence quantum yields determined in the presence (Φ.sub.Ox) and absence (Φ.sub.Ar) of oxygen; assuming that delayed fluorescence is negligible in the presence of oxygen (see Math. 3).

Φ.sub.X=Φ.sub.TADF+Φ.sub.CP=Φ.sub.A1

Φ.sub.CP=Φ.sub.O1

Φ.sub.TADF=Φ.sub.A1 . . . Φ.sub.Ox   [Math. 3]

[0076] Φ.sub.Ox and Φ.sub.Ar are determined by using total photoluminescence quantum efficiency and are measured using a Hamamatsu C9920-03 integrating sphere.

[0077] Luminescence dissymmetry factor measurements. The luminescence dissymmetry factor g.sub.lum is representative of the circular polarization. It is measured by formula Math. 4, where I.sub.L and I.sub.R refer to the left-handed and right-handed polarized light intensities, respectively.

[00003]$\begin{array}{cc}{g}_{\mathrm{lum}}=\frac{I_L-I_R}{I_L+I_R}& \left[\mathrm{Math}.4\right]\end{array}$

[0078] Values of g.sub.lum range from −2 to +2 in which a negative value means a right-handed CP and a positive value a left-handed CP. The value of 0 means absence of CP, whereas an absolute value of 2 means completely circularly polarized light.

[0079] These measurements were performed using a CPL spectrometer (JASCO Company). The samples were dissolved in dichloromethane and excited using a 90° geometry with a Xenon ozone-free lamp 150 W LS. The following parameters were used: emission slit width≈2 mm, integration time=4 sec, scan speed=50 nm/min, accumulations=5. Excitation of the samples was performed at 350 nm. Further details can be found in Abbate et al., 2016 [1].

Examples 1 and 2: 2,15-bisethynylhexahelicene H6(H).SUB.2 .and 4,4′-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))di(trimethylsylane) H6(TMS).SUB.2

[0080] P—H6(H).sub.2 of formula Chem. 14 and H6(TMS).sub.2 were prepared following the strategy previously reported by Crassous, J et al. (2018) [2].

##STR00014##

Example 2: 4,4′-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))dibenzonitrile H6(CN).SUB.2

[0081] P—H6(CN).sub.2 was synthesized as illustrated below by Chem. 15. First P—H6(H).sub.2 (50 mg, 0.13 mmol) and 4-bromobenzonitrile (71 mg, 0.39 mmol) were placed in an oven-dried flask of 25 mL under argon. Then 4 mL of dry toluene and 1 mL of dry triethylamine (Et.sub.3N) were added and the resulting solution was freed from oxygen by bubbling argon for 1 hour. Tetrakis(triphenylphosphine)palladium(0) (Pd(PPh.sub.3).sub.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 hours. After cooling down to room temperature, the solution was passed through a short silica plug (dichloromethane, CH.sub.2Cl.sub.2). The crude mixture was further purified by column chromatography on silica (8/2 Heptane/CH.sub.2Cl.sub.2 eluent system) to yield P—H6(CN).sub.2 (63.9 mg, 85%) as a yellow solid.

##STR00015##

[0082] .sup.1H NMR (300 MHz, Methylene Chloride-d.sub.2) 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).

[0083] .sup.13C NMR (75 MHz, Methylene Chloride-d.sub.2) 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.

[0084] HR-MS Ultraflex III, MALDI, 370° C.; ion [M].sup.+, C.sub.44 H.sub.22 N.sub.2, m/z calculated 578.17775, m/z experimental 578.182 (Δ=7 ppm).

Example 3: 4,4′-(hexahelicene-2,15-diylbis(ethyne-2,1 -diyl))dipyridine H6(Py).SUB.2

[0085] P—H6(Py).sub.2 was synthesized as illustrated below by Chem. 16. A mixture of P—H6(H).sub.2 (50 mg, 0.13 mmol) and 4-bromopyridine hydrochloride (75.8 mg, 0.39 mmol) were placed in an oven-dried flask of 25 mL under argon. Then 5 mL of dry propylamine was added and the resulting solution was freed from oxygen by bubbling argon for 1 hour. Pd(PPh.sub.3).sub.4 (15 mg, 0.013 mmol) and CuI (4.9 mg, 0.026 mmol) were added and the solution was refluxed for 3 hours. After cooling down to room temperature, the solution was passed through a short silica plug (CH.sub.2Cl.sub.2). The crude mixture was further purified by column chromatography on silica (5/5 Heptane/CH.sub.2Cl.sub.2 eluent system) to yield P—H6(Py).sub.2 (44.8 mg, 65%) as a yellow solid.

##STR00016##

[0086] .sup.1H NMR (400 MHz, Methylene Chloride-d.sub.2) 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).

[0087] .sup.13C NMR (101 MHz, Methylene Chloride-d.sub.2) 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.

[0088] HR-MS Ultraflex III, MALDI, 370° C.; ion [M+H].sup.+, C.sub.40 H.sub.23 N.sub.2, m/z calculated 531.18557, m/z experimental 531.182 (Δ=7 ppm).

Example 4: 4,4′-(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))dianiline H6(NH.SUB.2.).SUB.2

[0089] P—H6(NH.sub.2).sub.2 was synthesized as illustrated below by Chem. 17. P—H6(H).sub.2 (50 mg, 0.13 mmol) and 4-iodoaniline (126 mg, 0.575 mmol) were placed in an oven-dried flask of 25 mL under argon. Then 5 mL of dry propylamine was added and the resulting solution was freed from oxygen by bubbling argon for 1 hour. 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 hours. After cooling down to room temperature, the solution was passed through a short silica plug (CH.sub.2Cl.sub.2). The crude mixture was further purified by column chromatography on silica (5/5Heptane/CH.sub.2Cl.sub.2 eluent system) to yield P—H6(NH.sub.2).sub.2 (47.2 mg, 65%) as a yellow solid.

[0090] .sup.1H NMR (400 MHz, Methylene Chloride-d.sub.2) 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).

[0091] .sup.13C NMR (101 MHz, Methylene Chloride-d.sub.2) 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.

[0092] HR-MS Ultraflex III, MALDI, 370° C.; ion [M].sup.+, C.sub.42 H.sub.26 N.sub.2, m/z calculated 558.20905, m/z experimental 558.207 (Δ=4 ppm).

Example 5: 4,4′ -(hexahelicene-2,15-diylbis(ethyne-2,1-diyl))di(N,N-dimethylaniline) H6(NMe.SUB.2.).SUB.2

[0093] P—H6(NMe.sub.2).sub.2 was synthesized as illustrated below by Chem. 17 from H6(NH.sub.2).sub.2 of Example 4. To a solution of P—H6(NH.sub.2).sub.2 (30 mg, 0.054 mmol) dissolved in 5 mL of tetrahydrofurane (THF) in a round-bottomed flask, formaldehyde (0.04 mL, 0.13 mmol) was added dropwise to the flask. The mixture was stirred for 15 min at room temperature under argon. Then, sodium cyanoborohydride (NaBH.sub.3CN) (34 mg, 0.54 mmol) was introduced directly into the solution. The mixture was stirred for 15 min at room temperature a second time. Acetic acid (1 mL) was added to stop the reaction and the solution was stirred for 2 h at room temperature. After addition of water and dichloromethane (25 mL each), the organic layer was separated and the aqueous layer was extracted with dichloromethane. All organic layers were gathered, dried over mgSO.sub.4 and the solvent was evaporated. The crude product was purified by a plug of silica and washed by dichloromethane and the desired product P—H6(NMe.sub.2).sub.2 was obtained as a yellow solid (14.9 mg, 45%).

##STR00017##

[0094] .sup.1H NMR (400 MHz, Methylene Chloride-d.sub.2) 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).

[0095] .sup.13C NMR (126 MHz, Methylene Chloride-d.sub.2) 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.

[0096] HR-MS Ultraflex III, ESI, 370° C.; ion [M+H].sup.+, C.sub.46 H.sub.35 N.sub.2, m/z calculated 615.27947, m/z experimental 615.2796 (Δ=0 ppm).

Example 6

[0097] Results of measurements of luminescence quantum yield in dichloromethane at 298 K and luminescence dissymmetry factor for Examples 1 to 5 above are summed up in the following Table 1 (in the table “yEx” stands for “y×10.sup.x”).

TABLE-US-00001 TABLE 1 Φ.sub.X |g.sub.lum| Compounds (%) λ(nm) H6(TMS).sub.2 6 1.1E−2 421 H6(CN).sub.2 9 2.7E−2 426 H6(Py).sub.2 6 2.5E−2 429 H6(NH.sub.2).sub.2 16 2.5E−2 430 H6(NMe.sub.2).sub.2 41 5.2E−3 500

Example 7

[0098] An illustration of the present invention is provided here. In this example, the active light-emitting layer composition comprises as a TADF molecule dt-BuCbzSulfone and as a CP molecule H6(CN).sub.2. TADF molecule dt-BuCbzSulfone was developed in 2012 by Adachi et al. [3] whereas H6(CN).sub.2 has been first synthetized and developed by the applicant to their knowledge.

[0099] H6(CN).sub.2 presents a singlet energy level at 2.99 eV at 415 nm and 2.92 eV at 425 nm. Photophysical and chiroptical properties of H6(CN).sub.2 are shown in FIGS. 2 and 3.

[0100] Table 2 below shows normalized absorption values and Table 3 normalized emission values between 250 nm and 600 nm and correspond to FIG. 2. In FIG. 2, the normalized absorption is represented in dotted line whereas the normalized emission is represented as a solid line. The highest peak is normalized to a value of 1 and the other are proportional thereto.

TABLE-US-00002 TABLE 2 λ (nm) I (a.u.) 250 0.553 255 0.556 260 0.599 265 0.678 270 0.733 275 0.697 280 0.672 285 0.687 290 0.727 295 0.784 300 0.890 305 1.000 310 0.955 315 0.846 320 0.716 325 0.637 330 0.567 335 0.510 340 0.475 345 0.452 350 0.423 355 0.392 360 0.355 365 0.316 370 0.267 375 0.239 380 0.223 385 0.186 390 0.127 395 0.072 400 0.046 405 0.026 410 0.011 415 0.009 420 0.011 425 0.012 430 0.005 435 0.001 440 0.001 445 0.003 450 0.004 455 0.005 460 0.004 465 0.003 470 0.001 475 0.000 480 0.000 485 0.000 490 0.000 495 0.000 500 0.000 505 0.001 510 0.001 515 0.000 520 0.001 525 0.001 530 0.000 535 0.000 540 0.000 545 0.000 550 0.000 555 0.000 560 0.000 565 0.000 570 0.000 575 0.000 580 0.000 585 0.000 590 0.000 595 0.000 600 0.000

TABLE-US-00003 TABLE 3 λ (nm) I (a.u.) 402 0.008 404 0.011 406 0.013 408 0.018 410 0.024 412 0.038 414 0.065 416 0.117 418 0.223 420 0.413 422 0.663 424 0.895 426 1.000 428 0.994 430 0.916 432 0.803 434 0.699 436 0.604 438 0.528 440 0.478 442 0.460 444 0.479 446 0.534 448 0.586 450 0.656 452 0.710 454 0.739 456 0.734 458 0.687 460 0.620 462 0.549 464 0.485 466 0.428 468 0.389 470 0.355 472 0.334 474 0.317 476 0.305 478 0.300 480 0.294 482 0.290 484 0.282 486 0.271 488 0.252 490 0.232 492 0.212 494 0.189 496 0.172 498 0.155 500 0.140 502 0.127 504 0.116 506 0.108 508 0.101 510 0.093 512 0.088 514 0.082 516 0.078 518 0.073 520 0.068 522 0.064 524 0.059 526 0.054 528 0.050 530 0.045 532 0.040 534 0.037 536 0.033 538 0.031 540 0.028 542 0.025 544 0.023 546 0.021 548 0.020 550 0.018 552 0.017 554 0.016 556 0.015 558 0.013 560 0.012 562 0.012 564 0.011 566 0.010 568 0.009 570 0.009 572 0.008 574 0.007 576 0.006 578 0.006 580 0.005 582 0.005 584 0.005 586 0.004 588 0.004 590 0.004 592 0.004 594 0.003 596 0.003 598 0.003 600 0.003

[0101] Table 4 below shows the intensity difference ΔI between normalized left-handed emission and normalized right-handed emission values between 250 nm and 600 nm of P—H6(CN).sub.2 (solid line) and M-H6(CN).sub.2 (dotted line) and corresponds to FIG. 3 (in the table “yEx” stands for “y×10.sup.x”). It can be seen that the difference between normalized left-handed emission and normalized right-handed emission for the P and M configurations of H6(CN).sub.2 are mostly symmetrical through a line of coordinate 0. Further, since the normalization is based on the highest peak of the total emission spectrum normalized at a value of 2 (unlike in FIG. 2), the value of ΔI at the wavelength of the highest total intensity peak gives the g.sub.lum. The g.sub.lum value of H6(CN).sub.2 was found to be about 3×10.sup.−2. It has, however, no TADF property.

TABLE-US-00004 TABLE 4 ΔI (a.u.) P- M- λ (nm) H6(CN).sub.2 H6(CN).sub.2 380 −2.27E−04 — 385 −2.23E−04 −5.90E−04 390 −1.93E−04 −5.82E−04 395 −1.37E−04 −6.20E−04 400 −9.41E−05 −8.07E−04 405   2.23E−04 −9.93E−04 410   1.41E−03 −2.39E−03 415   5.72E−03 −6.58E−03 420   1.44E−02 −1.47E−02 425   2.29E−02 −2.36E−02 430   2.74E−02 −2.77E−02 435   2.41E−02 −2.40E−02 440   1.85E−02 −1.92E−02 445   1.56E−02 −1.56E−02 450   1.62E−02 −1.69E−02 455   1.69E−02 −1.82E−02 460   1.56E−02 −1.68E−02 465   1.32E−02 −1.30E−02 470   9.60E−03 −1.02E−02 475   7.36E−03 −8.28E−03 480   6.33E−03 −6.73E−03 485   5.25E−03 −5.95E−03 490   4.34E−03 −4.96E−03 495   3.55E−03 −3.65E−03 500   2.57E−03 −2.96E−03 505   1.67E−03 −2.35E−03 510   1.40E−03 −1.99E−03 515   8.96E−04 −1.69E−03 520   7.12E−04 −1.65E−03 525   5.63E−04 −1.08E−03 530   2.85E−04 −1.26E−03 535   2.34E−04 −8.30E−04 540   1.16E−04 −8.40E−04 545   7.35E−05 −8.60E−04 550 −6.46E−05 −8.11E−04 555 −8.35E−05 −7.51E−04 560 −1.22E−04 −6.27E−04 565 −1.73E−04 −7.16E−04 570 −1.59E−04 −6.41E−04 575 −1.49E−04 −5.58E−04 580 −2.15E−04 −6.59E−04 585 −1.74E−04 −5.70E−04 590 −2.01E−04 −5.80E−04 595 −2.19E−04 −5.89E−04 600 −1.96E−04 −5.59E−04

[0102] In order to test the combination consisting of dt-BuCbzSulfone doped with H6(CN).sub.2, five doping ratios (1, 5, 10 and 20 mol. % of the total amount of dt-BuCbzSulfone) were made and spin-coated onto a substrate into a solid film. Luminescence measurements are provided in FIG. 4 from 370 nm to 650 nm, with values further shown in Table 5 below (in the table “yEx” stands for “y×10.sup.x”; “CP” stands for “H6(CN).sub.2 alone”, “TADF” for “dt-BuCbzSulfone alone” and “x %” for “dt-BuCbzSulfone doped with x mol. % of H6(CN).sub.2”).

TABLE-US-00005 TABLE 5 λ (nm) CP TADF 1% 5% 10% 20% 370 2.07E+05 7.44E+05 4.98E+05 5.41E+05 3.55E+05 6.20E+05 375 1.02E+05 1.13E+06 3.26E+05 3.01E+05 2.27E+05 2.97E+05 380 7.21E+04 2.43E+06 3.77E+05 2.97E+05 2.00E+05 1.73E+05 385 5.11E+04 4.92E+06 5.14E+05 3.84E+05 1.97E+05 1.33E+05 390 4.45E+04 8.99E+06 7.63E+05 5.36E+05 2.33E+05 1.15E+05 395 3.83E+04 1.47E+07 1.07E+06 6.65E+05 2.51E+05 1.21E+05 400 3.88E+04 2.09E+07 1.36E+06 8.70E+05 2.72E+05 1.43E+05 405 3.70E+04 2.66E+07 1.70E+06 1.10E+06 2.88E+05 2.02E+05 410 3.71E+04 2.99E+07 2.04E+06 1.36E+06 2.98E+05 2.81E+05 415 5.50E+04 3.12E+07 2.75E+06 1.97E+06 4.08E+05 5.82E+05 420 1.15E+05 3.12E+07 5.73E+06 4.80E+06 8.06E+05 1.96E+06 425 2.34E+05 3.00E+07 1.27E+07 1.18E+07 1.98E+06 6.06E+06 430 3.59E+05 2.84E+07 1.51E+07 1.46E+07 2.73E+06 9.18E+06 435 4.33E+05 2.63E+07 1.25E+07 1.23E+07 2.36E+06 8.70E+06 440 3.84E+05 2.39E+07 9.25E+06 9.10E+06 1.72E+06 6.97E+06 445 3.13E+05 2.13E+07 7.82E+06 7.64E+06 1.35E+06 5.60E+06 450 2.91E+05 1.88E+07 8.89E+06 8.75E+06 1.50E+06 5.97E+06 455 3.10E+05 1.65E+07 1.01E+07 1.01E+07 1.74E+06 7.14E+06 460 3.42E+05 1.41E+07 9.11E+06 9.24E+06 1.63E+06 7.18E+06 465 3.31E+05 1.21E+07 6.97E+06 7.18E+06 1.25E+06 5.89E+06 470 3.07E+05 1.04E+07 5.41E+06 5.51E+06 9.81E+05 4.61E+06 475 2.80E+05 8.93E+06 4.49E+06 4.56E+06 7.81E+05 3.76E+06 480 2.39E+05 7.64E+06 4.07E+06 4.00E+06 6.89E+05 3.31E+06 485 2.30E+05 6.46E+06 3.77E+06 3.74E+06 6.54E+05 3.03E+06 490 2.14E+05 5.61E+06 3.24E+06 3.31E+06 5.86E+05 2.72E+06 495 1.92E+05 4.66E+06 2.68E+06 2.70E+06 4.85E+05 2.30E+06 500 1.77E+05 3.99E+06 2.11E+06 2.16E+06 4.16E+05 1.88E+06 505 1.75E+05 3.38E+06 1.70E+06 1.74E+06 3.23E+05 1.53E+06 510 1.58E+05 2.92E+06 1.40E+06 1.42E+06 2.81E+05 1.25E+06 515 1.47E+05 2.44E+06 1.19E+06 1.19E+06 2.38E+05 1.04E+06 520 1.36E+05 2.11E+06 9.93E+05 9.87E+05 2.10E+05 8.98E+05 525 1.22E+05 1.76E+06 8.67E+05 8.71E+05 1.82E+05 7.53E+05 530 1.08E+05 1.54E+06 7.17E+05 7.17E+05 1.48E+05 6.53E+05 535 9.97E+04 1.36E+06 6.40E+05 6.29E+05 1.41E+05 5.54E+05 540 9.67E+04 1.19E+06 5.06E+05 5.07E+05 1.19E+05 4.57E+05 545 9.13E+04 1.00E+06 4.48E+05 4.22E+05 1.03E+05 3.99E+05 550 8.34E+04 9.05E+05 3.71E+05 3.76E+05 7.38E+04 3.58E+05 555 7.60E+04 7.68E+05 3.33E+05 3.14E+05 7.96E+04 3.02E+05 560 7.38E+04 6.80E+05 2.61E+05 2.87E+05 8.17E+04 2.59E+05 565 6.10E+04 6.00E+05 2.56E+05 2.46E+05 6.65E+04 2.27E+05 570 6.02E+04 5.28E+05 2.01E+05 1.99E+05 5.40E+04 1.93E+05 575 6.05E+04 4.57E+05 1.84E+05 1.76E+05 6.63E+04 1.75E+05 580 5.53E+04 4.03E+05 1.77E+05 1.69E+05 5.30E+04 1.69E+05 585 5.16E+04 3.47E+05 1.47E+05 1.27E+05 4.78E+04 1.46E+05 590 5.15E+04 3.03E+05 1.29E+05 1.23E+05 5.30E+04 1.30E+05 595 4.80E+04 3.01E+05 1.01E+05 1.10E+05 4.26E+04 1.19E+05 600 5.19E+04 2.50E+05 1.06E+05 9.26E+04 4.93E+04 1.13E+05 605 4.56E+04 2.30E+05 9.89E+04 9.77E+04 3.83E+04 1.04E+05 610 4.92E+04 2.12E+05 1.07E+05 9.95E+04 4.38E+04 1.01E+05 615 4.30E+04 2.19E+05 9.00E+04 8.39E+04 4.17E+04 9.02E+04 620 4.60E+04 1.77E+05 9.22E+04 9.38E+04 4.35E+04 8.87E+04 625 4.96E+04 1.57E+05 8.06E+04 7.88E+04 4.10E+04 8.53E+04 630 4.40E+04 1.56E+05 7.82E+04 9.24E+04 6.06E+04 8.60E+04 635 5.96E+04 1.42E+05 7.17E+04 7.53E+04 4.18E+04 8.82E+04 640 7.43E+04 1.68E+05 7.53E+04 8.48E+04 6.31E+04 1.07E+05 645 5.70E+04 1.68E+05 8.56E+04 8.31E+04 4.79E+04 1.07E+05 650 7.65E+04 1.39E+05 9.07E+04 9.07E+04 5.42E+04 1.11E+05

[0103] Table 6 below shows the intensity difference ΔI between normalized left-handed emission and normalized right-handed emission values between approximately 400 nm and 650 nm of dt-BuCbzSulfone alone (TADF) and compositions constituting of dt-BuCbzSulfone with P—H6(CN).sub.2 (P-CP; dotted line) and M-H6(CN).sub.2 (M-CP; solid line) at 10 mol. % of the total amount of dt-BuCbzSulfone (in the table “yEx” stands for “y×10.sup.x”). Table 6 corresponds to FIG. 5. It can be seen that the difference between normalized left-handed emission and normalized right-handed emission for the P and M configurations of H6(CN).sub.2 are mostly symmetrical through a line of coordinate 0. Further, since the normalization is based on the highest peak of the total emission spectrum normalized at a value of 2, the value of ΔI at the wavelength of the highest total emission peak gives the g.sub.lum. From Table 5, it can be seen that the maximum intensity for dt-BuCbzSulfone with 10 mol. % H6(CN).sub.2 corresponds to a wavelength of 430 nm. From Table 6, it can be seen that at 430 nm, the values of ΔI (thus the value of g.sub.lum) are 1.59×10.sup.−2 and 1.44×10.sup.−2 for the composition with M-H6(CN).sub.2 and P—H6(CN).sub.2, respectively.

TABLE-US-00006 TABLE 6 λ (nm) TADF M-CP P-CP 380 7.19E−03  1.70E−03 2.77E−03 385 4.83E−03  8.68E−04 2.00E−03 390 3.96E−03 −6.87E−05 1.42E−03 395 3.10E−03 −9.80E−04 8.39E−04 400 2.33E−03 −7.21E−04 8.30E−04 405 1.55E−03  2.29E−05 1.21E−03 410 1.07E−03  1.93E−05 1.55E−03 415 6.44E−04 −1.47E−03 2.64E−03 420 1.21E−04 −6.03E−03 5.97E−03 425 3.16E−04 −1.14E−02 1.07E−02 430 4.81E−04 −1.59E−02 1.44E−02 435 2.83E−04 −1.61E−02 1.56E−02 440 5.28E−04 −1.37E−02 1.33E−02 445 3.48E−04 −1.14E−02 1.13E−02 450 −2.57E−05  −1.09E−02 1.03E−02 455 −3.14E−04  −1.13E−02 1.07E−02 460 −2.30E−04  −1.14E−02 1.06E−02 465 −1.32E−04  −1.01E−02 9.55E−03 470 −8.78E−05  −8.29E−03 7.54E−03 475 3.71E−04 −6.53E−03 6.01E−03 480 1.81E−04 −5.13E−03 5.03E−03 485 2.74E−05 −4.63E−03 4.01E−03 490 2.70E−04 −3.92E−03 3.71E−03 495 2.55E−04 −3.39E−03 2.92E−03 500 2.94E−04 −2.81E−03 2.45E−03 505 5.47E−04 −2.26E−03 1.85E−03 510 4.70E−04 −1.62E−03 1.33E−03 515 3.59E−04 −1.48E−03 1.25E−03 520 4.40E−04 −1.21E−03 1.11E−03 525 4.90E−04 −9.76E−04 7.24E−04 530 3.94E−04 −7.41E−04 8.32E−04 535 4.83E−04 −6.93E−04 6.93E−04 540 4.65E−04 −5.88E−04 5.58E−04 545 4.25E−04 −4.67E−04 5.51E−04 550 4.93E−04 −4.37E−04 4.12E−04 555 4.70E−04 −3.45E−04 4.36E−04 560 4.60E−04 −9.08E−05 3.19E−04 565 4.42E−04 −1.89E−04 3.48E−04 570 4.30E−04 −7.53E−05 3.59E−04 575 3.92E−04 −1.39E−04 2.12E−04 580 3.50E−04 −7.02E−05 2.94E−04 585 4.05E−04 −2.22E−05 2.43E−04 590 3.75E−04 −2.97E−05 2.99E−04 595 4.16E−04 −5.76E−05 2.20E−04 600 3.36E−04  3.00E−05 1.59E−04 605 3.44E−04 −1.60E−06 1.35E−04 610 3.20E−04 −7.47E−05 9.78E−05 615 3.84E−04 −6.42E−06 1.81E−04 620 3.72E−04  6.25E−05 2.25E−04 625 3.69E−04  1.02E−04 1.90E−04 630 3.18E−04  2.50E−04 2.96E−04 635 3.53E−04  9.92E−05 2.75E−04 640 3.02E−04  1.02E−04 2.03E−04 645 2.67E−04  1.29E−04 1.87E−04 650 2.60E−04  1.50E−04 1.96E−04

[0104] Dt-BuCbzSulfone has singlet and triplet states at a higher energy level than the singlet of H6(CN).sub.2 which is at 2.99 eV at 415 nm and 2.92 eV at 425 nm. Moreover, the luminescence spectrum of dt-BuCbzSulfone overlaps the absorption spectrum of H6(CN).sub.2.

[0105] These results show that even at only 1% of dopant, luminescence transfer from the TADF molecule to the CP molecule is quantitative, which provide evidence of transfer of unpolarized luminescence from the TADF molecule to the CP molecule providing circularly polarized luminescence. The intensity of the overall luminescence decreases as the ratio of H6(CN).sub.2 in dt-BuCbzSulfone decreases from 1 mol. % to 10 mol. %. However, from 10 mol. % to 20 mol. % it increases instead. The composition of example 1 provides a cyan blue colour.

Example 8

[0106] The CP molecule of Example 7 can be replaced by H6(NPh).sub.2 or H6(DPP).sub.2.

[0107] FIG. 6 shows the intensity difference ΔI between left-handed luminescence light and right-handed luminescence light of P—H6(NPh).sub.2 (solid line) and M-H6(NPh).sub.2 (dotted line) are shown. It can be observed that P—H6(NPh).sub.2 emits more left-handed light than right-handed light so that it can be said that P—H6-(NPh).sub.2 emits a left-handed circular polarized light to some extent. Similarly, M-H6(NPh).sub.2 emits more right-handed light than left-handed light so that it can be said that M-H6-(NPh).sub.2 emits a right-handed circular polarized light to some extent. The maximum value of ΔI for both molecules was observed close to 495 nm. H6(NPh).sub.2 has a luminescence quantum yield of 70% and a luminescence dissymmetry factor of 3×10.sup.−3. H6(NPh).sub.2 provides a green colour.

[0108] FIG. 7 shows the intensity difference ΔI between left-handed luminescence light and right-handed luminescence light of P—H6(DPP).sub.2 (solid line) and M-H6(DPP).sub.2 (dotted line). It can be observed that P—H6(DPP).sub.2 emits more left-handed light than right-handed light so that it can be said that P—H6-(DPP).sub.2 emits a left-handed circular polarized light to some extent. Similarly, M-H6(DPP).sub.2 emits more right-handed light than left-handed light so that it can be said that M-H6-(DPP).sub.2 emits a right-handed circular polarized light to some extent. The maximum value of ΔI for both molecules was observed close to 605 nm. H6(DPP).sub.2 has a luminescence quantum yield of 40% and a luminescence dissymmetry factor of 7×10.sup.−4. H6(DPP).sub.2 provides a red colour.

[0109] The TADF molecule of Example 7 can be replaced by Cbz-TRZ2 or 4-CbzIPN which are described in Adachi et al., 2017 [4] and Adachi et al., 2012 [5] respectively. Cbz-TRZ2 has a TADF quantum yield of 86%, whereas it is 94% for 4-CbzIPN.

[0110] The following combinations provide particularly good results: Cbz-TRZ2 with H6(NPh).sub.2 and 4-CbzIPN with H6(DPP).sub.2.

[0111] In addition to the TADF molecules and CP molecules described herein, many possible associations of TADF molecules and CP molecules can be contemplated in order to obtain the desired synergetic CP-TADF property. For instance, one can think about other helicene derivatives, helicenoid compounds (where the helical polycyclic compound is not fully conjugated), biarylic systems, and chiral molecules with planar chirality such as paracyclophane derivatives for the CP molecule.

BIBLIOGRAPHY

[0112] [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 [0113] [2] Dhbaibi, K.; Favereau, L.; Srebro-Hooper, M.; Jean, M.; Vanthuyne, N.; Zinna, F.; Jamoussi, B.; Di Bari, L.; Autschbach, J.; Cras sous, J., “Exciton coupling in diketopyrrolopyrrole-helicene derivatives leads to red and near-infrared circularly polarized luminescence”, Chem. Sci. 2018, 9, 735-742 [0114] [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) [0115] [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) [0116] [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).