Organic molecules having two non-conjugated bridges between a donor and an acceptor for effective thermally activated delayed fluorescence for use in optoelectronic devices

Abstract

The invention relates to purely organic emitter molecules of a new type according to formula I and to the use thereof in optoelectronic devices, in particular in organic light-emitting diodes (OLEDs), comprising donor D: an aromatic or heteraromatic chemical group on which the HOMO is located and which optionally has at least one substitution; acceptor A: an aromatic or heteromatic chemical group on which the LUMO is located and which optionally has at least one substitution; bridge B1, bridge B2: organic groups that link the donor D and the acceptor A in a non-conjugated manner; wherein in particular the energy difference ΔE(S.sub.1−T.sub.1) between the lowest excited singlet (S1) state of the organic emitter molecule and the triplet (T1) state of the organic emitter molecule lying thereunder is less than 2000 cm.sup.−1.

Claims

1. An organic molecule for luminescence, comprising the structure according to Formula XVIII or Formula XIX, ##STR00037## wherein Q3, Q4, Q5, and Q6 are each independently selected from the group consisting of H, CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7, C.sub.4H.sub.9, C.sub.5H.sub.11, C.sub.6H.sub.13, phenyl, tolyl, xylyl, benzyl, thienyl, pyrazolyl, diazolyl, triazolyl, tetrazolyl, oxazolyl, oxadiazolyl, furyl, and carbazolyl; Q1 and Q2 are each independently selected from the group consisting of H, CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7, C.sub.4H.sub.9, C.sub.5H.sub.11, C.sub.6H.sub.13, tolyl, xylyl, benzyl, thienyl, pyrazolyl, diazolyl, triazolyl, tetrazolyl, oxazolyl, oxadiazolyl, furyl, and carbazolyl; Q1 and Q2, Q3 and Q4, and Q5 and Q6 are optionally linked, thereby forming a cycloalkyl system or an aromatic spirocyclic system; and Alk2, Alk3, Alk4, Alk5, Alk7, Alk8, Alk9, and Alk10 are, independently of each other, H or an unbranched or branched aliphatic group or a cycloalkyl group Wherein at least one of Q3-Q6 is not hydrogen.

2. An organic molecule for luminescence, comprising the structure of Formula I, ##STR00038## where each of the electron acceptor A and the electron donor D independently is an aromatic or heteroaromatic group that optionally has at least one substitution, the bridge B1 and the bridge B2 connect organic groups of the electron donor D and the electron acceptor A in a non-conjugated manner, the bridge B1 and the bridge B2 are each independently represented by the structure of Formula V,
#A2-A3 #  Formula V where # represents a linking site of the bridge B2 for connecting to the electron donor D or the electron acceptor A; A2 is selected from the groun consisting of ##STR00039## A3 is selected from the group consisting of ##STR00040## each of R8 to R17 is independently selected from the group consisting of —H, substituted or unsubstituted alkyl, cycloalkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, alkoxy (—OR′), thioalkyl (—SR′), sulfonyl (—SO2R′), acyl (—COR′), formyl (—CHO), carboxyl (—CO.sub.2R′), boryl (—BR′R″), sulfinyl (—SOR′), amine (—NR′R″), phosphino (—PR′R″), phosphinyl (—POR′R″), amido (—NR′COR″), silyl (—SiR′R″R″), cyano (—CN), nitro (—NO.sub.2), nitroso (—NO), isocyanato (—NCO), thiocyano (—NCS), and halogen, where R′, R″, and R′″ each have the same definition as R8 to R17; at least one of R8, R9, R13, and R14 is the substituted or unsubstituted alkyl, the cycloalkyl, the substituted or unsubstituted alkenyl, the substituted or unsubstituted alkynyl, the substituted or unsubstituted aryl, the substituted or unsubstituted heteroaryl, the alkoxy, the thioalkyl, the sulfonyl, the acyl, the formyl, the carboxyl, the boryl, the sulfinyl, the amine, the phosphino, the phosphinyl, the amido, the silyl, cyano (—CN), nitro (—NO.sub.2), nitroso (—NO), isocyanato (—NCO), thiocyano (—NCS), or halogen; each of R18 to R22 is independently selected from the group consisting of —H, substituted or unsubstituted alkyl, cycloalkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, alkoxy (—OR′), thioalkyl (—SR′), sulfonyl (—SO.sub.2R′), acyl (—COR′), formyl (—CHO), carboxyl (—CO.sub.2R), boryl (—BR′R″), sulfinyl (—SOR′), amine (—NR′R″), phosphino (—PR′R″), phosphinyl (—POR′R″), amido (—NR′COR″), silyl (—SiR′R″R″), cyano (—CN), nitro (—NO.sub.2), nitroso (—NO), isocyanato (—NCO), thiocyano (—NCS), and halogen, where R′, R″, and R′″ each have the same definition as R8; the halogen is selected from the group consisting of —F, —Cl, —Br, and —I, the electron donor D and the electron acceptor A each independently include an aromatic or heteroaromatic group represented by Formula II or Formula III, ##STR00041## wherein the electron donor D and the electron acceptor A are different from each other, Formula II and Formula III are optionally part of a fused ring system, and Formula II and Formula III have # positions, the electron donor D and the electron acceptor A are linked to the bridge B1 and bridge B2 via the # positions, Y1, Y2, Y3, and Y4 are independently selected from the group consisting of C and N, each of X4 to X7 is independently selected from the group consisting of N, CH, NH, and C-R1, and at least one of X4 to X7 is C-R1, each of X1 to X3 is independently selected from the group consisting of N, O, S, Se, CH, NH, and C-R1, and at least one of X1 to X3 is C-R1, wherein R1 is independently selected from the group consisting of —H, substituted or unsubstituted alkyl, cycloalkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, alkoxy (—OR′), thioalkyl (—SR′), sulfonyl (—SO.sub.2R′), acyl (—COR′), formyl (—CHO), carboxyl (—CO.sub.2R′), boryl (—BR′R″), sulfinyl (—SOR′), amine (—NR′R″), phosphino (—PR′R″), phosphinyl (—POR′R″), amido (—NR′COR″), silyl (—SiR′R″R″), cyano (—CN), nitro (—NO.sub.2), nitroso (—NO), isocyanato (—NCO), and thiocyano (—NCS), wherein R′, R″, and R′″ each have the same definition as R1, and R′, R″, and R′″ are optionally linked to each other to form an additional aliphatic, aromatic or heteroaromatic ring system, the alkyl is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, and adamantyl, the cycloalkyl is selected from the group consisting of cyclopropyl, cyclopentyl, cyclohexyl, the alkenyl is vinyl or allyl, the alkynyl is ethynyl, and the heteroaryl is selected from the group consisting of furyl, thienyl, and pyrrolyl, and the energy difference ΔE(S1-T1) between the lowest excited singlet (S1) state of the organic molecule and the triplet (T1) state of the organic molecule is less than 2000 cm.sup.−1.

3. An organic molecule for luminescence, comprising the structure of Formula I, ##STR00042## where each of the electron acceptor A and the electron donor D independently is an aromatic or heteroaromatic group that optionally has at least one substitution, the bridge B1 and the bridge B2 connect organic groups of the electron donor D and the electron acceptor A in a non-conjugated manner, structures of the bridge B1 and the bridge B2 are each independently selected from the group consisting of Formula IV and Formula V: ##STR00043## where # represents a linking site of the bridge B1 and the bridge B2 for connecting to the electron donor D or the electron acceptor A; A1 is selected from the group consisting of ##STR00044## O, S and ##STR00045## A2 is selected from the group consisting of ##STR00046## O, S, ##STR00047## ##STR00048## A3 is selected from the group consisting of ##STR00049## O, S ##STR00050## ##STR00051## each of R3 to R17 is independently selected from the group consisting of —H, substituted or unsubstituted alkyl, cycloalkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, alkoxy (—OR′), thioalkyl (—SR′), sulfonyl (—SO.sub.2R′), acyl (—COR′), formyl (—CHO), carboxyl (—CO.sub.2R′), boryl (—BR′R″), sulfinyl (—SOR′), amine (—NR′R″), phosphino (—PR′R″), phosphinyl (—POR′R″), amido (—NR′COR″), silyl (—SiR′R″R″), cyano (—CN), nitro (—NO.sub.2), nitroso (—NO), isocyanato (—NCO), thiocyano (—NCS), and halogen, where R′, R″, and R′″ each have the same definition as R3 to R17; at least one of R8, R9, R13, and R14 is the substituted or unsubstituted alkyl, the cycloalkyl, the substituted or unsubstituted alkenyl, the substituted or unsubstituted alkynyl, the substituted or unsubstituted aryl, the substituted or unsubstituted heteroaryl, the alkoxy, the thioalkyl, the sulfonyl, the acyl, the formyl, the carboxyl, the boryl, the sulfinyl, the amine, the phosphino, the phosphinyl, the amido, the silyl, cyano (—CN), nitro (—NO.sub.2), nitroso (—NO), isocyanato (—NCO), thiocyano (—NCS), or halogen; each of R18 to R22 is independently selected from the group consisting of -H, substituted or unsubstituted alkyl, cycloalkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, alkoxy (—OR′), thioalkyl (—SR′), sulfonyl (—SO.sub.2R′), acyl (—COR′), formyl (—CHO), carboxyl (—CO.sub.2R′), boryl (—BR′R″), sulfinyl (—SOR′), amine (—NR′R″), phosphino (—PR′R″), phosphinyl (—POR′R″), amido (—NR′COR″), silyl (—SiR′R″R″), cyano (—CN), nitro (—NO.sub.2), nitroso (—NO), isocyanato (—NCO), thiocyano (—NCS), and halogen, where R′, R″, and R′″ each have the same definition as R3; the halogen is selected from the group consisting of —F, —Cl, —Br, and —I, the electron donor D and the electron acceptor A each independently include an aromatic or heteroaromatic group represented by Formula II or Formula III, ##STR00052## wherein the electron donor D and the electron acceptor A are different from each other, Formula II and Formula III are optionally part of a fused ring system, and Formula II and Formula III have # positions, the electron donor D and the electron acceptor A are linked to the bridge B1 and bridge B2 via the # positions, Y1, Y2, Y3, and Y4 are independently selected from the group consisting of C and N, each of X4 to X7 is independently selected from the group consisting of N, CH, NH, and C-R1 and at least one of X4 to X7 is C-R1, each of X1 to X3 is independently selected from the group consisting of N, O, S, Se, CH, NH, and C-R1, and at least one of X1 to X3 is C-R1, wherein R1 is independently selected from the group consisting of cycloalkyl, thioalkyl (—SR′), sulfonyl (—SO.sub.2R′), acyl (—COR′), formyl (—CHO), carboxyl (—CO.sub.2R′), boryl (—BR′R″), sulfinyl (—SOR′), amine (—NR′R″), phosphino (—PR′R″), phosphinyl (—POR′R″), amido (—NR′COR″), nitro (—NO.sub.2), nitroso (—NO), isocyanato (—NCO), and thiocyano (—NCS), wherein R′, R″, and R′″ each have the same definition as R1, and R′, R″, and R′″ are optionally linked to each other to form an additional aliphatic, aromatic, or heteroaromatic ring system, and the cycloalkyl is selected from the group consisting of cyclopropyl, cyclopentyl, cyclohexyl, and the energy difference ΔE(S1-T1) between the lowest excited singlet (S1) state of the organic molecule and the triplet (T1) state of the organic molecule is less than 2000 cm.sup.−1.

4. An organic molecule for luminescence, wherein the organic molecule is selected from the group consisting of compounds 13-21 and 25-64, ##STR00053## ##STR00054## ##STR00055## ##STR00056## ##STR00057## ##STR00058## ##STR00059## ##STR00060## ##STR00061## ##STR00062##

Description

DETAILED DESCRIPTIONS OF EMBODIMENTS

(1) ##STR00011##

(2) The molecular structure of the emitter material having the formula I according to the invention is further explained by means of the structural formulas VI to XVII. These structural formulas represent examples of emitter materials according to the invention. Y1′-Y4′ and X1′-X7′ are defined as Y1-Y4 and XI-X7 (formulas II and III). A1′, A2′, A3′ groups are defined as A1 to A3. The bridge fragments A1 and A1′, A2 and A2′, A3 and A3′, respectively, may be the same or different.

(3) Additional bridging groups Z are, for example, —CH.sub.2—, —C(CH.sub.3).sub.2, —O—, —C.sub.6H.sub.4-(phenylene), —C.sub.5H.sub.8-(cyclopentylene), —CO-(carbonyl), —SO.sub.2—, —N(CH.sub.3)—. They represent the mutual connection of fragments A1 to A3 and A1′ to A3′ of bridges B1 and B2.

(4) In a particular embodiment, the organic molecules according to the invention have a structure of Formula XVIII.

(5) ##STR00012##

(6) In the donor region, the emitter molecule has an aromatic amine group. The acceptor moiety is a dicyanophenyl group in which two CN-substituents may be ortho, meta or para to each other and may be adjacent to a bridged aliphatic group.

(7) Q1 to Q6 are each independently selected from the group consisting of H, CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7, C.sub.4H.sub.9, C.sub.5H.sub.11, C.sub.6H.sub.13, phenyl, tolyl, xylyl, benzyl, thienyl, oxazolyl, oxadiazolyl, triazolyl, tetrazolyl, oxazolyl, oxadiazolyl, furyl, and carbazolyl.

(8) Q1 and Q2, Q3 and Q4, and Q5 and Q6 may be linked together to form a cycloalkyl- or aromatic spiro system (e.g., to stabilize the molecular structure).

(9) Alk1 to Alk10 are H or a straight-chain or branched-chain (C.sub.nH.sub.2n+1; n=1, 2, 3, 4, 5, or 6) aliphatic group or a cycloalkyl group (C.sub.nH.sub.2n+1; n=5 or 6), independently of one another.

(10) In addition, Alk1 and Alk6 can be omitted and the two benzene rings of the donor system are covalently bonded together to form a carbazole unit, as shown in Formula XIX.

(11) ##STR00013##

(12) The formula XVIII illustrates the substituent.

EMBODIMENTS

(13) The molecules in the following examples of the present invention may have at least one substitutions of Cl, Br and/or I to increase spin-orbit coupling (SBK). The appropriate position for substitutions can be determined by quantum mechanical calculations, and a computational program including SBK (eg, ADF, ORCA program) is used herein. To know the trend, DFT or CC2 calculation can be conducted, so as to identify the substitution position of halogen, i.e. the halogen atom orbitals with a significant proportion in HOMO, HOMO-1, HOMO-2 and/or LUMO, LUMO+1, LUMO+2. For the substitution pattern identified by this way, it should be noted that, for example, when calculated by TDDFT or CC2, the energy difference ΔE (S.sub.1−T.sub.1) of organic molecules between the lowest excited singlet state (S.sub.1) and it below triplet state (T.sub.1) is less than 2,000 cm-.sup.1, in particular less than 1500 cm-.sup.1, preferably less than 800 cm-.sup.1, more preferably less than 400 cm-.sup.1 and most preferably less than 200 cm-.sup.1.

(14) The materials in the present invention can be synthesized using catalytic coupling reactions (e.g. Suzuki coupling reactions, Buchwald-Hartwig cross-coupling reactions) or various condensation reactions that are known to those skilled in the art.

Embodiment 1

(15) ##STR00014##

(16) Example Molecule 1

(17) The molecules according to the invention shown in Example 1 would be detailed below. As shown from the frontier orbital in FIG. 3, the HOMO and LUMO were located in distinctly different spatial regions of the molecule. It was expected that the gap between the lowest triplet state and the singlet state above it was small enough that the molecule exhibited a significant TADF effect. The calculation of the example molecule 1 within the range of TD-DFT calculation (function B3LYP, basis set 6-31G (d, p)) showed that the energy level difference of the optimized triplet-state geometrical structure was ΔE(S.sub.1−T.sub.1)=75 cm-.sup.1. Therefore, the example molecule 1 was a good TADF emitter. The following reaction scheme illustrated the chemical synthesis of example molecule 1:

(18) ##STR00015##

(19) Reactants and reaction conditions:

(20) (1) (t-C.sub.4H.sub.9—C.sub.6H.sub.5).sub.2NH, Pd(CH.sub.3COO).sub.2, P[(C(CH.sub.3).sub.3].sub.3, (CH.sub.3).sub.3CONa, 90° C., 19 hours.

(21) (2) K.sub.4[Fe(CN).sub.6], Pd(CH.sub.3COO).sub.2, P[(C(CH.sub.3).sub.3].sub.3, Na.sub.2CO.sub.3, (CH.sub.3).sub.2NCHO, 140° C., 12 hours.

(22) Synthesis can be performed according to the following detailed reaction scheme:

(23) ##STR00016##

(24) Reactants and reaction conditions:

(25) (1) CH.sub.3CO.sub.2Na, 230° C., 3 hours

(26) (2) HPO.sub.2, I.sub.2, red phosphorus, CH.sub.3COOH, 80° C., 24 hours

(27) (3) (H.sub.3PO.sub.4)n, 175° C., 5 hours

(28) (4) Al[OCH(CH.sub.3).sub.2].sub.3, 275° C., 3 hours

(29) (5) (t-C.sub.4H.sub.9—C.sub.6H.sub.5).sub.2NH, Pd(CH.sub.3COO).sub.2, P[(C(CH.sub.3).sub.3].sub.3, (CH.sub.3).sub.3CONa, 90° C., 19 hours

(30) (6) K.sub.4[Fe(CN).sub.6], Pd(CH.sub.3COO).sub.2, P[(C(CH.sub.3).sub.3].sub.3, Na.sub.2CO.sub.3, (CH.sub.3).sub.2NCHO, 140° C., 12 hours

(31) Chemical Analysis:

(32) R.sub.f(cyclohexane/ethyl acetate 10:1): 0.52. .sup.1H NMR (CDCl.sub.3, 300 MHz, δ ppm): 1.31 (s, 18H), 3.13 (m, 4H), 4.05 (s, 2H), 6.84 (dd, J=3.6 Hz, J=12.0 Hz, 1H), 6.90 (s, 1H), 6.95 (s, 1H), 6.95 (d, J=9 Hz, 5H), 7.22 (d, J=9 Hz, 4H), 7.55 (s, 2H). 13C-NMR (300 MHz CDCl.sub.3, δ ppm): 30.72 (CH2), 31.46 (CH3), 32.80 (CH2), 34.31 (CH2), 40.56 (Cquat), 113.16 (Cquat), 113.73 (Cquat), 115.59 (Cquat), 122.35 (Cquat), 123.48 (CH), 123.78 (CqUat), 126.03 (CH), 130.57 (CqUat), 130.94 (CH), 133.86 (CH), 134.48 (CH), 136.63 (Cquat), 144.91 (CqUat), 145.40 (Cquat), 145.69 (Cquat), 146.31 (Cquat).

(33) MS (ES-MS=electrospray ionization mass spectrometry) m/z: 523 (M.sup.+). MS (HR-ES-MS=high resolution electrospray ionization mass spectrometer) m/z: C.sub.37H.sub.37N.sub.3 Calculation: 523.2979, Measurement: 523.2980 (M+). C.sub.37H.sub.37N.sub.3 Calculation: C 84.86, H 7.12, N 8.02%, Measurement: C 84.54, H 7.36, N 7.90%.

(34) The example molecule 1 could be dissolved in many organic solvents such as methylene chloride (CH.sub.2Cl.sub.2), toluene, hexane, n-octane, tetrahydrofuran (THF), acetone, dimethylformamide (DMF), acetonitrile, ethyl alcohol, methanol, xylene or benzene. The excellent solubility in methylene chloride made polymethylmethacrylate (PMMA) or polystyrene (PS) doping possible.

(35) The emitter material according to Embodiment 1 could be sublimated (temperature 170° C., pressure 10-.sup.3 mbar).

(36) Photophysical measurements of example molecule 1 in PMMA or PS (doping concentration c≈1 wt %) demonstrated the occurrence of TADF and the favorable emission properties. At very low temperatures, for example when T=2K, thermal activation was not possible. Thus, the emission showed two very different decay times, namely, a very short component, which corresponded to an S.sub.1.fwdarw.S.sub.0-fluorescence transition, about 4 ns in PMMA, 25 ns in PS, and a very long component, which was classified as phosphorescence of T.sub.1.fwdarw.S.sub.0 transitions, τ(phos)≈550 ms in PMMA and τ(phos)≈450 ms in PS. (Note: nitrogen purging of samples)

(37) FIG. 4 showed the corresponding time-resolved emission spectra in PS, i.e. no delay time (t=0 ns), detection time window Δt=100 ns, corresponding to short-term spectra of fluorescence, and corresponding to the long-term spectra of phosphorescence (t=500 and Δt=900 ms).

(38) When the temperature rose to T=300K, drastic changes in spectra and decay behavior may occur, which would support the occurrence of TADF. FIG. 5 showed the short time domain (spontaneous fluorescence) and long time domain time-resolved emission spectra of example molecule 1 dissolved in PS. Since both spectra had approximately the same peak positions, long-lived components could also be interpreted as fluorescence-TADF emission in this case. The fluorescence decay time in PMMA was about 4 ns, and the fluorescence decay time in PS was about 25 ns. However, in PMMA, its long-lived component was greatly shortened to about 10 μs, and the long-lived component in PS was also shortened to about 10 μs.

(39) It was of significance to compare the emission quantum efficiency at T=300K with the value obtained in ambient air under nitrogen purging (PMMA-doped samples). pL (nitrogen)=40%, pL (air)=25%. The result showed that the triplet state was involved in the emission process, because oxygen in the air usually only caused quenching of long-lived triplet states (A. M. Prokhorov et al, J. Am. Chem. Soc. 2014, 136, 9637). Since triplet state occupation was a prerequisite for generating TADF, this behavior again showed that example molecule 1 had the desired TADF properties. Notes: The emission maximum in PMMA at T=300K within the blue-white range was λ(max)=486 nm (CIE x: 0.198, y: 0.287), and the emission maximum in PS at T=300K within the blue range was λ(max)=450 nm (CIE x: 0.174; y: 0.154).

(40) When studying substances dissolved in toluene, other photophysical properties of the emitter molecule according to Embodiment 1 can be identified. This further demonstrated that, for a simple measurement of the emitted quantum efficiency, as mentioned above, it was expected that the molecules dissolved in the toluene produced TADF because the emission quantum efficiency in air was significantly reduced. The corresponding measured values: Ø.sub.PL(nitrogen)=30% and Ø.sub.PL(air)=5%.

(41) FIGS. 6a and 6b showed the emission attenuation behavior at T=300K in the ns region (FIG. 6a) and the μs region (FIG. 6b). Spontaneous fluorescence decayed with τ(fluorine)=60 ns. (FIG. 6a) In addition, there were two attenuation components of τ(TADF 1)=270 ns and τ(TADF 2)=9 μs. Both components were classified as TADF emissions.

(42) FIG. 7 showed the time resolved emission spectra of example molecule 1 dissolved in toluene in three time domains, namely, the short time domain (spontaneous fluorescence) and two long time domains. These spectra were given of the attenuation components as shown in FIG. 6. Since all three spectra had the same peak position and the same spectral shape within the measurement accuracy range, the long-lived component could also be interpreted as fluorescence, i.e. two TADF emissions.

(43) If the study was carried out in the non-phase-change temperature range of toluene and the sample that was remained liquid, the attenuation behaviors of the long-lived components emitted from example molecule 1 (concentration c≈10-.sup.5 mol/l) dissolved in toluene could be obtained. A temperature range of about 200K to 300K was very suitable. The measured values of the corresponding attenuation components were shown as Arrhenius diagrams (Boltzmann diagrams) in FIG. 8. Using Equation 2, Equation 3 could be approximated as the experimentally derived emission decay time τ.sub.exp (see C. Baleizao, M. N. Berberan-Santos, J. Chem. Phys, 2007, 126, 204510):

(44) $\begin{array}{cc}\ln \left(\frac{1}{{\tau }_{\exp }}\right)=A-\frac{\Delta E_1\left(S_1-T_i\right)}{k_{B}T}& \left(3\right)\end{array}$

(45) Where, A was a constant, i represented the TADF process 1 with ΔE1 activation energy in triplet state T.sub.1 or TADF process 2 with activation energy ΔE2 in triplet state T.sub.2.

(46) The linear fitting of two time domain measurement points, ie two TADF emissions, was performed using Equation 3 according to FIG. 6. From the slope of the straight line, the activation energy could be obtained (ΔE[(S.sub.1−T.sub.1), TADF1]=310 cm-.sup.1 and ΔE [(S.sub.1-T.sub.2), TADF2]=85 cm-.sup.1).

(47) When cooled to T=77K, the long-lived unstructured emissions was frozen. There was only one structured phosphorescence, the decay time was very long, τ(phos)=450 ms (not shown in the figure). However, for long-lived components, the structure of the spectrum could also be observed in FIG. 4. This spectral structure could be attributed to the emission of donor or acceptor fragments. No charge transfer (CT) transition was involved in this case. If it is assumed that the correlation 0-0 transition at the intersection of the energetic (extrapolated) sides of the emission curve is reflected by the abscissa, these spectra could be used to roughly estimate the energy difference associated with the occurrence of TADF. The result was that the ΔE was about (300±100) cm-.sup.1, which also showed that the embodiment 1 was a TADF substance.

(48) Therefore, the experiment demonstrated that the example molecule 1 produced TADF according to invention. The corresponding results of TADF behaviors for example molecule 1 doped in PMMA were also available.

(49) It should be emphasized that this also showed that the energy difference 75 cm-.sup.1 calculated for the CT transitions (see the description of FIG. 3) was very consistent with the activation energy of TADF 2 process determined in the experiments.

(50) FIG. 9 schematically summarized the measurement results in a formal energy level diagram. The emission behavior of example molecule 1 was described by three excitation energy states. There was another triplet state T1 (Lok) that could be assigned to local emission under two CT states 5.sub.1 (CT) and T.sub.2 (CT) with an experimentally determined energy difference of 85 cm.sup.−1. The S.sub.1 (CT) state showed transient spontaneous fluorescence and two emissions of long decay time but different time-lasting at room temperature, which were generated from the thermal activation of T.sub.2 (CT) and T.sub.1 (lok), respectively, thus representing different TADF emissions. The formal model described here was based on long-lived TADF components longer than 9 μs for the relaxation process between triplet states.

(51) Here also illustrated one aspect for the naming of triplet state. It was based on the numbering by energy order, rather than by the type of electron excitation. Therefore, in the case of example molecule 1, the energy gap ΔE (S.sub.1−T.sub.1) between the CT states used was referred to as ΔE [S.sub.1(CT)−T.sub.2(CT)] due to the generation of the state T.sub.1(Iok) of low energy.

Embodiment 2

(52) ##STR00017##

(53) Example Molecule 2

(54) The example molecule 2 according to the invention would be detailed below. As shown from the frontier orbital in FIG. 10, the HOMO and LUMO were located in distinctly different spatial regions of the molecule. It was expected that the gap between the lowest triplet state and the singlet state above it was small enough that the molecule exhibited a significant TADF effect. The calculation of the example molecule 2 within the range of TD-DFT calculation (function B3LYP, basis set 6-31G (d, p)) showed that the energy level difference of the optimized triplet-state geometrical structure was ΔE(S.sub.1−T.sub.1)=85 cm-.sup.1. Therefore, the example molecule 2 was a good TADF emitter. The following reaction scheme illustrated the chemical synthesis of example molecule 2.

(55) ##STR00018##

(56) Reactants and reaction conditions:

(57) (1) CH.sub.3CO.sub.2Na, 230° C., 3 hours

(58) (2) HPO.sub.2, 1.sub.2, red phosphorus, CH.sub.3COOH, 80° C., 24 hours

(59) (3) (H.sub.3PO.sub.4)n, 175° C., 5 hours

(60) (4) Al[OCH(CH.sub.3).sub.2].sub.3, 275° C., 3 hours

(61) (5) (t-C.sub.4H.sub.9—C.sub.6H.sub.5).sub.2NH, Pd(CH.sub.3COO).sub.2, P[(C(CH.sub.3).sub.3].sub.3, (CH.sub.3).sub.3CONa, 90° C., 19 hours

(62) (6) K.sub.4[Fe(CN).sub.6], Pd(CH.sub.3COO).sub.2, P[(C(CH.sub.3).sub.3].sub.3, Na.sub.2CO.sub.3, (CH.sub.3).sub.2NCHO, 140° C., 12 hours

Embodiment 3

(63) ##STR00019##

(64) Example Molecule 3

(65) The molecules according to the invention shown in Embodiment 3 would be detailed below. As shown from the frontier orbital in FIG. 11, the HOMO and LUMO were located in distinctly different spatial regions of the molecule. It was expected that the gap between the lowest triplet state and the singlet state above it was small enough that the molecule exhibited a significant TADF effect. The calculation of the example molecule 3 within the range of TD-DFT calculation (function B3LYP, basis set 6-31G (d, p)) showed that the energy level difference of the optimized triplet-state geometrical structure was ΔE (S.sub.1−T.sub.1)=55 cm-.sup.1. Therefore, the example molecule 3 was a good TADF emitter.

(66) The following reaction scheme illustrated the chemical synthesis of example molecule 3.

(67) ##STR00020## ##STR00021##

(68) Reactants and reaction conditions:

(69) (1) CH.sub.3CO.sub.2Na, 230° C., 3 hours.

(70) (2) HPO.sub.2, I.sub.2, red phosphorus, CH.sub.3COOH, 80° C., 24 hours

(71) (3) (H.sub.3PO.sub.4)n, 175° C., 5 hours

(72) (4) (C.sub.2H.sub.5).sub.2O, 30° C., 24 hours NH.sub.4Cl, H.sub.2O; F.sub.3CCO.sub.2H, 3 hours, 50° C.

(73) (5) Carbazole, Pd(CH.sub.3COO).sub.2, P[(C(CH.sub.3).sub.3].sub.3, (CH.sub.3).sub.3CONa, 90° C., 19 hours

(74) (6) K.sub.4 [Fe(CN).sub.6], Pd(CH.sub.3COO).sub.2, P[(C(CH3).sub.3].sub.3, Na.sub.2CO.sub.3, (CH.sub.3).sub.2NCHO, 140° C., 12 hours

Embodiment 4

(75) ##STR00022##

(76) Example Molecule 4

(77) The example molecule 4 according to the invention would be detailed below. As shown from the frontier orbital in FIG. 12, the HOMO and LUMO were located in distinctly different spatial regions of the molecule. It was expected that the gap between the lowest triplet state and the singlet state above it was small enough that the molecule exhibited a significant TADF effect. The calculation of the example molecule 4 within the range of TD-DFT calculation (function B3LYP, basis set 6-31G (d, p)) showed that the energy level difference of the optimized triplet-state geometrical structure was ΔE(S.sub.1−T.sub.1)=88 cm-.sup.1. Therefore, the example molecule 4 was a good TADF emitter.

(78) The following reaction scheme illustrated the chemical synthesis of example molecule 4.

(79) ##STR00023## ##STR00024##

(80) Reactants and reaction conditions

(81) (1) CH.sub.3CO.sub.2Na, 230° C., 3 hours

(82) (2) HPO.sub.2, I.sub.2, red phosphorus, CH.sub.3COOH, 80° C., 24 hours

(83) (3) (H.sub.3PO.sub.4).sub.n, 175° C., 5 hours

(84) (4) Al[OCH(CH.sub.3).sub.2].sub.3, 275° C., 3 hours

(85) (5) (t-C.sub.4H.sub.9—C.sub.6H.sub.5).sub.2NH, Pd(CH.sub.3COO).sub.2, P[(C(CH3).sub.3].sub.3, (CH.sub.3).sub.3CONa, 90° C., 19 hours

(86) (6) K.sub.4[Fe(CN).sub.6], Pd(CH.sub.3COO).sub.2, P[(C(CH3).sub.3].sub.3, Na.sub.2CO.sub.3, (CH.sub.3).sub.2NCHO, 140° C., 12 hours

Embodiment 5

(87) ##STR00025##

(88) Example Molecule 5

(89) The example molecule 5 according to the invention would be detailed below. As shown from the frontier orbital in FIG. 13, the HOMO and LUMO were located in distinctly different spatial regions of the molecule. It was expected that the gap between the lowest triplet state and the singlet state above it was small enough that the molecule exhibited a significant TADF effect. The calculation of the example molecule 5 within the range of TD-DFT calculation (function B3LYP, basis set 6-31G (d, p)) showed that the energy level difference of the optimized triplet-state geometrical structure was ΔE(S.sub.1−T.sub.1)=150 cm-.sup.1. Therefore, the example molecule 5 was a good TADF emitter. The following reaction scheme illustrated the chemical synthesis of example molecule 5.

(90) ##STR00026## ##STR00027##

(91) Reactants and reaction conditions:

(92) (1) CH.sub.3CO.sub.2Na, 230° C., 3 hours

(93) (2) HPO.sub.2, I.sub.2, red phosphorus, CH.sub.3COOH, 80° C., 24 hours

(94) (3) (H.sub.3PO.sub.4).sub.n, 175° C., 5 hours

(95) (4) Al[OCH(CH.sub.3).sub.2].sub.3, 275° C., 3 hours

(96) (5) (t-C.sub.4H.sub.9—C.sub.6H.sub.5).sub.2NH, Pd(CH.sub.3COO).sub.2, P[(C(CH3).sub.3].sub.3, (CH.sub.3).sub.3CONa, 90° C., 19 hours

(97) (6) K.sub.4[Fe(CN).sub.6], Pd(CH.sub.3COO).sub.2, P[(C(CH3).sub.3].sub.3, Na.sub.2CO.sub.3, (CH.sub.3).sub.2NCHO, 140° C., 12 hours

Embodiment 6

(98) ##STR00028##

(99) Example Molecule 6

(100) The example molecule 6 according to the invention would be detailed below. As shown from the frontier orbital in FIG. 14, the HOMO and LUMO were located in distinctly different spatial regions of the molecule. It was expected that the gap between the lowest triplet state and the singlet state above it was small enough that the molecule exhibited a significant TADF effect. The calculation of the example molecule 6 within the range of TD-DFT calculation (function B3LYP, basis set 6-31G (d, p)) showed that the energy level difference of the optimized triplet-state geometrical structure was ΔE(S.sub.1−T.sub.1)=30 cm-.sup.1. Therefore, the example molecule 6 was a good TADF emitter.

Embodiment 7

(101) ##STR00029##

(102) Example Molecule 7

(103) FIG. 15 showed the frontier orbitals HOMO and LUMO of example molecule 7. Since these orbitals were located in distinctly different spatial regions of the molecule, it could be expected that the gap between the lowest triplet state and the singlet state above it was small enough that the molecule exhibited a significant TADF effect. The calculation of the example molecule 7 within the range of TD-DFT calculation (function B3LYP, basis set 6-31G (d, p)) showed that the energy level difference of the optimized triplet-state geometrical structure was ΔE(S.sub.1−T.sub.1)=550 cm-.sup.1. Therefore, the example molecule 7 was a good TADF emitter.

(104) The following reaction scheme illustrated the chemical synthesis of example molecule 7.

(105) ##STR00030##

(106) Reactants and reaction conditions:

(107) (1) CH.sub.3CO.sub.2Na, 230° C., 3 hours

(108) (2) HI (57% aqueous solution), red phosphorus, 80° C., 24 hours

(109) (3) (H.sub.3PO.sub.4).sub.n, 175° C., 5 hours

(110) (4) Al[OCH(CH.sub.3).sub.2].sub.3, 275° C., 3 hours

(111) (5) (CH.sub.3).sub.2NH, Pd (CH.sub.3COO).sub.2, P[(C(CH.sub.3).sub.3].sub.3, (CH.sub.3).sub.3CONa, 90° C., 19 hours

Embodiment 8

(112) ##STR00031##

(113) Example Molecule 8

(114) As shown from the frontier orbitals in FIG. 16, the HOMO and LUMO were located in distinctly different spatial regions of the molecule. It was expected that the gap between the lowest triplet state and the singlet state above it was small enough that the molecule exhibited a significant TADF effect. The calculation of the example molecule 8 within the range of TD-DFT calculation (function B3LYP, basis set 6-31G (d, p)) showed that the energy level difference of the optimized triplet-state geometrical structure was ΔE(S.sub.1−T.sub.1)=540 cm-.sup.1. Therefore, the example molecule 8 was a good TADF emitter.

(115) The following reaction scheme illustrated the chemical synthesis of example molecule 8.

(116) ##STR00032##

(117) Reactants and reaction conditions:

(118) (1) CH.sub.3CO.sub.2Na, 230° C., 3 hours

(119) (2) HI (57% aqueous solution), red phosphorus, 80° C., 24 hours

(120) (3) CH.sub.2N.sub.2, SO.sub.2Cl.sub.2, 80° C., 2 hours; (CH.sub.3).sub.3COH, C.sub.6H.sub.5COOAg, Et.sub.3N, 90° C., 2 hours

(121) (4) (H.sub.3PO.sub.4).sub.n, 175° C., 5 hours

(122) (5) Al[OCH(CH.sub.3).sub.2].sub.3, 275° C., 3 hours

(123) (6) (CH.sub.3).sub.2NH, Pd(CH.sub.3COO).sub.2, P[(C(CH3).sub.3].sub.3, (CH.sub.3).sub.3CONa, 90° C., 19 hours

(124) (7) K.sub.4[Fe(CN).sub.6], Pd(CH.sub.3COO).sub.2, P[(C(CH3).sub.3].sub.3, Na.sub.2CO.sub.3, (CH.sub.3).sub.2NCHO, 140° C., 12 hours

Embodiment 9

(125) ##STR00033##

(126) Example Molecule 9

(127) FIG. 17 showed the frontier orbitals HOMO and LUMO of example molecule 9. Since these orbitals were located in distinctly different spatial regions of the molecule, it could be expected that the gap between the lowest triplet state and the singlet state above it was small enough that the molecule exhibited a significant TADF effect. The calculation of the example molecule 9 within the range of TD-DFT calculation (function B3LYP, basis set 6-31G (d, p)) showed that the energy level difference of the optimized triplet-state geometrical structure was ΔE(S.sub.1−T.sub.1)=550 cm-.sup.1. Therefore, the example molecule 9 was a good TADF emitter.

Embodiment 10

(128) ##STR00034##

(129) Example Molecule 10

(130) FIG. 18 showed the frontier orbitals HOMO and LUMO of example molecule 10. Since these orbitals were located in distinctly different spatial regions of the molecule, it could be expected that the gap between the lowest triplet state and the singlet state above it was small enough that the molecule exhibited a significant TADF effect. The calculation of the example molecule 10 within the range of TD-DFT calculation (function B3LYP, basis set 6-31G (d, p)) showed that the energy level difference of the optimized triplet-state geometrical structure was ΔE(S.sub.1−T.sub.1)=140 cm-.sup.1. Therefore, the example molecule 10 was a good TADF emitter.

Embodiment 11

(131) ##STR00035##

(132) Example Molecule 11

(133) FIG. 19 showed the frontier orbitals HOMO and LUMO of example molecule 11. Since these orbitals were located in distinctly different spatial regions of the molecule, it could be expected that the gap between the lowest triplet state and the singlet state above it was small enough that the molecule exhibited a significant TADF effect. The calculation of the example molecule 11 within the range of TD-DFT calculation (function B3LYP, basis set 6-31G (d, p)) showed that the energy level difference of the optimized triplet-state geometrical structure was ΔE(S.sub.1−T.sub.1)=420 cm-.sup.1. Therefore, the example molecule 11 was a good TADF emitter.

Embodiment 12

(134) ##STR00036##

(135) Example Molecule 12

(136) FIG. 20 showed the frontier orbitals HOMO and LUMO of example molecule 12. Since these orbitals were located in distinctly different spatial regions of the molecule, it could be expected that the gap between the lowest triplet state and the singlet state above it was small enough that the molecule exhibited a significant TADF effect. The calculation of the example molecule 12 within the range of TD-DFT calculation (function B3LYP, basis set 6-31G (d, p)) showed that the energy level difference of the optimized triplet-state geometrical structure was ΔE(S.sub.1−T.sub.1)=1250 cm-.sup.1. Therefore, the example molecule 12 was a good TADF emitter.

(137) FIG. 21 showed other example molecules.

BRIEF DESCRIPTION OF THE DRAWINGS

(138) FIG. 1 shows a schematic diagram of the energy level of the thermally activated delayed fluorescence (TADF) process. k.sub.BT represents thermal energy with a Boltzmann constant k.sub.B and an absolute temperature T. This figure shows both the radiative and non-radiative (marked by wavy lines) attenuation processes of the radiation TADF process and the low-temperature observable T.sub.1 state. The figure does not mark the spontaneous S.sub.1.fwdarw.S.sub.0 fluorescence process.

(139) FIG. 2 shows a schematic diagram of orbital energies of molecules with donor fragments and receptor fragments (D-A molecules) according to the present invention. Due to non-conjugated bridges, the interaction between the donor and acceptor tracks is small. Thus, the electronic properties of the D and A fragments can be approximated separately, that is, the D orbital energy is approximately equal to the energy of the corresponding free (unlinked) donor molecule, and the A orbital energy is approximately equal to the energy of the corresponding free (unlinked) acceptor molecule. The HOMO energy of the isolated donor (electron-rich) is significantly higher than HOMO energy of the isolated acceptor (electron-deficient). The LUMO of an isolated donor is much higher than the LUMO energy of an acceptor. Therefore, the HOMO of the D-A molecule is mainly located on the D fragment, while the LUMO of the D-A molecule is mainly located on the A fragment.

(140) FIG. 3 shows an isosurface of the frontier orbital of the example molecule 1 (see Embodiment 1), HOMO: left, LUMO: right. The electronic ground state S.sub.0 geometry is optimized. Calculation method: DFT and TD-DFT, function: B3LYP, basis set: 6-31G (d, p), calculation software: Gaussian 09. The calculation result showed that the energy difference between the singlet state-CT state and the triplet state-CT state is 75 cm-.sup.1 (S.sub.0-geometry). This value indicates that the example molecule 1 is a good TADF emitter.

(141) FIG. 4 shows time-resolved emission spectra of example molecule 1 doped about 1% by weight in PS at T=2K. Record the short-term spectrum in case of no time delay (t=0 ns) and detection time window Δ1 t=100 ns and record the long-term spectrum in case of a time delay t=500 μs (time window Δt=900 ms). Excitation: short-time spectrum: 375 nm, pulse width 70 ps; long-time spectrum, excitation: 365 nm, pulse width: 10 ns.

(142) FIG. 5 shows time-resolved emission spectra and decay time τ of example molecule 1 doped about 1% by weight in PS at T=300K. Record the short-term spectrum in case of no time delay (t=0 ns) and detection time window Δt=100 ns and record the long-term spectrum in case of a time delay t=1 μs (time window Δt=100 μs). Excitation: short-time spectrum: 375 nm, pulse width 70 ps; long-time spectrum, excitation: 355 nm, pulse width: 2.9 ns.

(143) FIG. 6 shows the emission decay behaviors of example substance 1 dissolved in toluene, (a) short time domain (spontaneous fluorescence) and (b) long time domain, T=300K. Record the spontaneous fluorescence emission decay time τ(fluorescence)=60n and TADF decay time τ(TADF 1)=270 ns and τ(TADF 2)=9 μs of respective components. Introduce nitrogen for 120 min to degas the solution. Excitation wavelength: 355 nm, pulse duration: 2.9 ns, and concentration: about 10-.sup.5 mol/l.

(144) FIG. 7 shows the time-resolved emission spectra of example molecule 1 at a concentration of 10-.sup.5 M dissolved in toluene when T=300K. Record (a) short-time spectra (spontaneous fluorescence) of no time delay (t=0 ns) and test time window Δt=50 ns, (b) long-term spectrum (TADF1) with time delay t=300 μs (time window Δt=600 ns) and (c) long time spectrum (TADF2) with time delay t=5 μs (time window Δt=30 μs). Excitation: Short-time spectrum: 375 nm, pulse width 70 ps, long-time spectrum, excitation: 355 nm, pulse width: 2.9 ns.

(145) FIG. 8 shows the Boltzmann diagram (Arrhenius diagram) of long-lived composition of the corresponding emission decay time of example molecule 1 dissolved in toluene according to equation 3. The activation energy ΔE(S.sub.1−T.sub.1)=(310±10)cm-.sup.1 and ΔE(S.sub.1−T.sub.2)=(85±5)cm.sup.−1 obtained by fitting. The T1 state is the local state, and the T2 is classified as the charge donor transfer state.

(146) FIG. 9 shows the formal energy level diagram, used to schematically describe the experimental emission decay time and activation energy. T.sub.1(lok) represents the local state, while T.sub.2(CT) and S.sub.1(CT) represent the charge transfer state. The heat returns from T.sub.1(lok) and T.sub.2(CT) to the S.sub.1(CT) state, resulting in two TADF processes.

(147) FIG. 10 shows an isosurface of the frontier orbital of the example molecule 2 (see Embodiment 2), HOMO: left, LUMO: right. Optimization of the lowest triplet state T.sub.1 geometry. Calculation method: DFT and TD-DFT, function: B3LYP, basis set: 6-31G (d, p), calculation software: Gaussian 09. The result: ΔE(S.sub.1−T.sub.1)=85 cm-.sup.1 Both values indicate that example molecule 2 is a good TADF emitter.

(148) FIG. 11 shows an isosurface of the frontier orbital of the example molecule 3 (see Embodiment 3), HOMO: left, LUMO: right. Optimization of the lowest triplet state T.sub.1 geometry. Calculation method: DFT and TD-DFT, function: B3LYP, basis set: 6-31G (d, p), calculation software: Gaussian 09. The result: ΔE(S.sub.1−T.sub.1)=55 cm-.sup.1 The result indicates that example molecule 3 is a good TADF emitter.

(149) FIG. 12 shows an isosurface of the frontier orbital of the example molecule 4 (see Embodiment 4), HOMO: left, LUMO: right. Optimization of the lowest triplet state T.sub.1 geometry. Calculation method: DFT and TD-DFT, function: B3LYP, basis set: 6-31G (d, p), calculation software: Gaussian 09. The result: ΔE(S.sub.1−T.sub.1)=88 cm-.sup.1 The result indicates that example molecule 4 is a good TADF emitter.

(150) FIG. 13 shows an isosurface of the frontier orbital of the example molecule 5 (see Embodiment 5), HOMO: left, LUMO: right. Optimization of the lowest triplet state T.sub.1 geometry. Calculation method: DFT and TD-DFT, function: B3LYP, basis set: 6-31G (d, p), calculation software: Gaussian 09. The result: ΔE(S.sub.1−T.sub.1)=150 cm-.sup.1 The result indicates that example molecule 5 is a good TADF emitter.

(151) FIG. 14 shows an isosurface of the frontier orbital of the example molecule 6 (see Embodiment 6), HOMO: left, LUMO: right. Optimization of the electron ground state S.sub.0 and the lowest triplet state T.sub.1 geometry. Calculation method: DFT and TD-DFT, function: B3LYP, basis set: 6-31G (d, p), calculation software: Gaussian 09. The result: ΔE(S.sub.1−T.sub.1)=35 cm-.sup.1 (S.sub.0-geometry) and 30 cm.sup.−1 (T.sub.1-geometry). Both values indicate that example molecule 2 is a good TADF emitter.

(152) FIG. 15 shows an isosurface of the frontier orbital of the example molecule 7 (see Embodiment 7), HOMO: left, LUMO: right. Optimization of the lowest triplet state T.sub.1 geometry. Calculation method: DFT and TD-DFT, function: B3LYP, basis set: 6-31G (d, p), calculation software: Gaussian 09. The result: ΔE(S.sub.1−T.sub.1)=550 cm-.sup.1 The result indicates that example molecule 7 is a good TADF emitter.

(153) FIG. 16 shows an isosurface of the frontier orbital of the example molecule 8 (see Embodiment 8), HOMO: left, LUMO: right. Optimization of the lowest triplet state T, geometry. Calculation method: DFT and TD-DFT, function: B3LYP, basis set: 6-31G (d, p), calculation software: Gaussian 09. The result: ΔE(S.sub.1−T.sub.1)=540 cm-.sup.1 (T, geometry) The result indicates that example molecule 8 is a good TADF emitter.

(154) FIG. 17 shows an isosurface of the frontier orbital of the example molecule 9 (see Embodiment 9), HOMO: left, LUMO: right. Optimization of the lowest triplet state T.sub.1 geometry. Calculation method: DFT and TD-DFT, function: B3LYP, basis set: 6-31G (d, p), calculation software: Gaussian 09. The result: ΔE(S.sub.1−T.sub.1)=550 cm.sup.−1 (T.sub.1-geometry) The result indicates that example molecule 9 is a good TADF emitter.

(155) FIG. 18 shows an isosurface of the frontier orbital of the example molecule 10 (see Embodiment 10), HOMO: left, LUMO: right. Optimization of the electron ground state geometry. Calculation method: DFT and TD-DFT, function: B3LYP, basis set: 6-31G (d, p), calculation software: Gaussian 09. The result: ΔE(S.sub.1−T.sub.1)=140 cm-.sup.1 The result indicates that example molecule 10 is a good TADF emitter.

(156) FIG. 19 shows an isosurface of the frontier orbital of the example molecule 11 (see Embodiment 11), HOMO: left, LUMO: right. Optimization of the electron T.sub.1 state geometry. Calculation method: DFT and TD-DFT, function: B3LYP, basis set: 6-31G (d, p), calculation software: Gaussian 09. The result: ΔE(S.sub.1−T.sub.1)=420 cm.sup.−1 The result indicates that example molecule 11 is a good TADF emitter.

(157) FIG. 20 shows an isosurface of the frontier orbital of the example molecule 12 (see Embodiment 12), HOMO: left, LUMO: right. Optimization of the lowest triplet state T.sub.1 geometry. Calculation method: DFT and TD-DFT, function: B3LYP, basis set: 6-31G (d, p), calculation software: Gaussian 09. The result: ΔE(S.sub.1−T.sub.1)=1250 cm-.sup.1 (T.sub.1 geometry) The result indicates that example molecule 12 is a good TADF emitter.

(158) FIG. 21 A and B show schematic representations of other molecules according to the invention.