DIRECT SINGLET CAPTURE ORGANIC MOLECULES WITH SHORT EMISSION DECAY TIME AND APPLICATION THEREOF IN OPTOELECTRONIC DEVICES

Abstract

The invention relates to novel pure organic emitter molecules and optoelectronic devices containing these organic emitter molecules. According to the invention, in the optoelectronic device, after the excitation of an organic molecule, relaxation and intersystem crossing processes also result from the almost isoenergetic charge transfer triplet state (.sup.3CT) for the direct rapid occupation and emission of the charge transfer singlet state (.sup.1CT), so that a .sup.1CT.fwdarw.S.sub.0 fluorescence occurs without a thermal activation.

Claims

1. An optoelectronic device in which upon excitation of an organic molecule direct and fast relaxation and intersystem crossing processes for filling the charge transfer singlet state (.sup.1CT) from the substantially isoenergetic charge transfer triplet state (.sup.1CT) of the organic molecule, so that a .sup.1CT.fwdarw.S.sub.0 fluorescence occurs, without the need for thermal activation, where S.sub.0 stands for the electronic ground state.

2. An optoelectronic device of claim 1, wherein the direct rapid occupation of the CT singlet state, compared to molecules which show thermally activated delayed fluorescence (TADF), in addition, results in 5 to 10 time faster emission decay from this CT-singlet state.

3. An optoelectronic device of claim 1 or 2, wherein the emission decay time of the organic molecule is less than 2 microseconds, particularly less than 1 microseconds or less than 500 ns.

4. An opto-electronic device of claims 1 to 3, wherein the emission is not a TADF emission.

5. An optoelectronic device of claims 1 to 4, wherein the .sup.1CT-fluorescence with a substantially iso-energetic charge transfer triplet (.sup.3CT) equilibrated state fluorescence from the .sup.1CT is singlet.

6. An optoelectronic device of claims 1 to 5, wherein the organic molecule has a structure of formula Ia or Ib, or of a structure according to formula Ia or Ib. ##STR00025## With an aromatic or hetero-aromatic donor segment D, D1, D2 and a two or four non-conjugated bridges B1, B2, B3 and B4 bound aromatic or hetero-aromatic acceptor segment A, wherein the aromatic or hetero-aromatic moieties (donor or acceptor) are substituted with electron-donating or -withdrawing substituents, wherein the bridges B1, B2, B3, B4 are chosen such that they prevent pronounced overlaps donor-HOMO to the LUMO acceptor.

7. Opto-electronic device of claim 6, wherein the organic molecule has a structure to one of the following displayed formulas or consists of such a structure ##STR00026## Wherein the 2,3:6,7-dibenzosuberane backbone is substituted so the electronic properties of the aromatic ring systems are modified. The R1 to R4 are substituted with the donor D, or the R1 to R4 and R1 to R4 be substituted by donor D1 and D2, described by the formulas Ia and Ib. And R5 through R8 moiety is substituted with the acceptor A, wherein Q1 to Q6 on the bridges B1 of 2,3:6,7-Dibenzosuberans was substituted with methylene and ethylene groups. B2 of the formula Ia and Q1 to Q6 and Q1 to Q6 of the 2,3:6,7-dibenzosuberane are substituted by the methylene and ethylene groups, Which represent the bridges B1 or B2 and B3 or B4 of the formulas Ib, with Bridges Q1, Q2, and Q1 Q2 are independently selected from the group consisting of alkyl, alkenyl, alkynyl, cycloalkyl and aryl; Q3 to Q6 and Q3 to Q6 are independently selected from the group consisting of H, alkyl, alkenyl, alkynyl, cycloalkyl and aryl; where: Alkyl is a straight-chain (unbranched) or branched (C.sub.1-C.sub.10) alkyl having 1 to 10 carbon atoms in the main hydrocarbon chain, Alkenyl is a straight or branched (C.sub.1-C.sub.10) alkenyl having 1 to 10 carbon atoms in the main hydrocarbon chain, Alkynyl is a straight or branched (C.sub.1-C.sub.10) alkynyl, having 1 to 10 carbon atoms in the main hydrocarbon chain, Cycloalkyl is a (C.sub.3-C.sub.7) -cycloalkyl having 3 to 7 ring carbon atoms, and Aryl is a 5-ring or 6-membered aromatic or heteroaromatic group, main hydrocarbon chain used herein is the longest chain of the branched or non-linear alkyl, alkenyl or alkynyl; Wherein Each group Q1 to Q6 and Q1 to Q6 independently may be substituted or unsubstituted with one or more F, Cl, Br, alkoxyl, thioalkoxyl, amine, silane, phosphine, borane, or aryl; the groups Q1 and Q2, Q3 and Q4 groups, the groups Q5 and Q6, the groups Q1 and Q2, the groups Q3 and Q4, as well as the groups Q5 Q6 and are optionally chemically linked together to form other ring systems. Donor member: R1 to R4 and R1 to R4 are independently selected from the group consisting of H, alkyl, alkenyl, alkynyl, cycloalkyl, alkoxyl, thioalkoxyl, amine, phosphine, silane, borane, fluorine, chlorine, bromine. Below at least one position of R1 to R4 in the formulas IIb and Akr to IIe is at least one position of R1 to R4 Akr and at least one position of R1 to R4 Akr with reference to formula III defined group Akr wherein, in formula IIa. Wherein: Alkyl is a straight or branched C.sub.1-C.sub.10) alkyl having 1 to 10 carbon atoms in the main hydrocarbon chain, Alkenyl is a straight or branched C.sub.1-C.sub.10) alkenyl having 1 to 10 carbon atoms in the main hydrocarbon chain, Alkynyl is a straight or branched C.sub.1-C.sub.10) alkynyl, having 1 to 10 carbon atoms in the main hydrocarbon chain, Cycloalkyl is a (C.sub.3-C.sub.7)-cycloalkyl having 3 to 7 ring carbon atoms, and Aryl is a 5-ring or 6-ring aromatic or heteroaromatic group, wherein the substitutions alkoxyl, thioalkoxyl, amine, phosphine, silane and borane is in each case an alkoxyl OR, SR thioalkoxyl, amine NRR, phosphine PRR, silane SiRRR and borane BRR. Wherein R, R and R independently a straight or branched C.sub.1-C.sub.10) alkyl, (C.sub.1-C.sub.10)-alkene, (C.sub.1C.sub.10) alkyne, (C.sub.3-C.sub.7) cycloalkyl or a 5-ring or 6-ring which aromatic or heteroaromatic group; wherein the group Akr has a structure of the formula IIIa and IIIb or consists of Formula IIIa Formula IIIb ##STR00027## Wherein: # marks the point through which the Akr group is connected to the rest of the molecule, R9 to R16 and R9 to R16 are independently selected from H, (C.sub.1-C.sub.10) alkyl, (C.sub.1-C.sub.10)-alkenyl, (C.sub.1-C.sub.10)-alkynyl, (C.sub.3-C.sub.7) cycloalkyl, alkoxyl oR; amine NRR, phosphine PRR, silane SiRRR, borane BRR, fluorine, chlorine, bromine, or aryl, wherein the R, R and R is a straight or branched (C.sub.1-C.sub.10) alkyl, (C.sub.1-C.sub.10) alkene, (C.sub.1-C.sub.10) alkyne, (C.sub.3-C.sub.7) cycloalkyl or a 5 mean-Ring- or 6-membered aromatic or heteroaromatic group; Q7, Q8, and Q7 Q8 are defined as Q1 to Q6 and Q1 to Q6 and may be linked together to form a further ring system; Acceptor: R5 to R8 are independently selected from H, CH.sub.3, CN, COR, CO (OR), CO (NRR), SO.sub.2R; SO.sub.2 (OR), SOR, CF.sub.3, CF.sub.2R, wherein R and R are straight or branched (C1-C10) alkyl, (C.sub.1-C.sub.10) alkene, (C.sub.1-C.sub.10) alkyne, (C.sub.3-C.sub.7) cycloalkyl or a 5-membered ring- or 6-membered aromatic or heteroaromatic group, and at least one group is not H or CH.sub.3; wherein in the formula IIa, at least two substituents selected from R5, R6, R7 and R8 are not H or CH.sub.3; This would mean that R5 to R8 right akr can be actually required and optional two adjacent groups selected from R5, R6, R7 and R8 are linked with each other chemically

8. An opto-electronic device of claim 7, wherein the organic molecule has or consists of a structure according to the formulas IVa to IVd ##STR00028## ##STR00029## wherein the substituents R1 to R8, R1 to R8, Q3 are explained by Q6 and Q3 to Q6 from the formulas IIa to IIe and the substituents R9 to R16 and Q7 to Q8 from the formulas IIIa and IIIb, wherein R16 to R23 and R16 are defined by R23 as while as R9 to R16 and R9 to R16.

9. An opto-electronic device of claim 7, wherein the organic molecule has or consists of a structure according to formula V; ##STR00030## wherein the substituents R1 to R23 and Q3 to Q8 are described under the formulas IIa to IIe, III, IIIb and IVa to IVd and Q9 and Q10 are defined as Q1 to Q8 and Q1 to Q8 and are optionally linked to one another so that a further ring system is formed

10. An optoelectronic device of claim 7, wherein the organic molecule has or consists of a structure according to formula VI ##STR00031## wherein the substituents R1 to R23, R1 to R23, Q3 to Q10 and Q3 to Q8 are explained under the formulas IIa to IIe, III, IIIb, IVa to IVd and V, and wherein Q9 and Q10 are defined as Q1 to Q10 and Q1 to Q8 and are optionally linked to one another to further form a ring system.

11. An optoelectronic device of claim 7, wherein the organic molecule has or consists of a structure according to the formulas VII to XVI ##STR00032## ##STR00033## ##STR00034## wherein the substituents are as defined above

12. Optoelectronic device of claim 6, wherein the hydrogen atoms in one, several or in all positions of the organic molecule are replaced by deuterium

13. An organic molecule comprising a structure or consisting of a structure according to a formula selected from the group consisting of formula Ia, formula Ib, formula IIa, formula IIb, formula IIc, formula IId, formula IIe, formula IIIa, formula IIIb, Formula VIII, Formula VIII, Formula IVa, Formula IVa, Formula IVa, Formula IVa, Formula V, Formula VI, Formula VII, Formula VIII, Formula IX, Formula X, Formula XI, Formula XII Formula XIII Formula XIV Formula XV and Formula XVI. The hydrogen atoms in one, several or in all positions of the organic molecule of the abovementioned formulas are replaced by deuterium.

14. Use of an organic molecule of claim 13 for the emission of light, in particular in an emitter layer of an optoelectronic device.

15. A process for preparing an optoelectronic device, wherein an organic molecule of claim 13 is used.

16. Optoelectronic device of claims 1 to 12, organic molecule of claim 13, use according to claim 14, method of claim 15, wherein the optoelectronic device is selected from the group consisting of organic light emitting diodes (OLEDs), light emitting electrochemical cells (LEECs or LECs), OLED sensors, in particular non-hermetically shielded gas and vapor sensors, optical temperature sensors, organic Solar cells (OSCs), organic field effect transistors, organic lasers, organic diodes, organic photodiodes and down conversion systems

Description

EXAMPLES

[0062] The organic molecules presented in the invention, which may be part of a composition or combination with a matrix material, can be synthesized through known catalytic coupling reactions (eg, Suzuki coupling reaction, Buchwald-Hartwig cross-coupling reaction).

[0063] The organic molecules (emitter molecules) have an energy gap between the charge-transfer conditions E (.sup.1CT-.sup.3CT), which is less than 20 cm.sup.1 (2.5 meV), preferably less than 10 cm.sup.1 (1.2 meV). In contrast to the previous technology, this small difference in energy is achieved by an bridge(s), in which existing Hyper-Conjugation is significantly reduced by substitution(s) at the C.sub.1-bridge B2 and B3. The structure motif is illustrated here:

##STR00011##

[0064] in which

[0065] # marks the position in which the carbon atom or the spiro carbon atom of the bridge B2 or B3 is connected to the donor or acceptor fragment in the molecule of the formula Ia or Ib. Furthermore: Q1, Q2, Q1 and Q2 H.

[0066] The emitter molecules are in a solid matrix (e.g. in OLEDs) and thus represent the emission layer. The polarity of the matrix is selected so that the localized .sup.3LE states are energetically above the .sup.1,3CT states, for example, less than 1500 cm.sup.1 (190 meV) or preferably less 500 cm.sup.1 (63 meV), more preferably less than 100 cm.sup.1 (12 meV). On the other hand, the .sup.3LE state may be 50 cm.sup.1 (6 meV) below the .sup.13CT states. The matrix polarity can be selected, for example, in terms of the dielectric constant , in the range of 2.25.0.

Example 1

[0067] ##STR00012##

Example Molecule 1

[0068] Hereinafter, the molecule shown in example 1 according to the invention is discussed in more detail.

[0069] The frontier orbitals shown in FIG. 3 show that HOMO and LUMO are located in distinctly different regions of the molecule. This suggests that the energy splitting between the lowest triplet and the above singlet state is small. Calculation for the example molecule 1 in a TD-DFT calculation (Functional B3LYP and also Functional MO6) shows that the energy difference for the optimized triplet geometry E (.sup.1CT-.sup.3CT)=7 cm.sup.1 (0.87 meV). Thus, example 1 represents an emitter molecule according to the invention, which is suitable for use in optoelectronic devices, such as OLEDs.

[0070] The chemical synthesis of the molecule example 1 started from commercially available materials is shown in the following scheme.

##STR00013##

[0071] Chemical Analysis:

[0072] .sup.1H NMR (300 MHz, CDCl.sub.3, ): 7.71 (d, J=7.5 Hz, 2H), 7.66 (s, 1H), 7:34 (q, J=7.5 Hz, 6H), 7.22 (d, J=7.5 Hz, 1H), 7.11 (d, J=7.5 Hz, 2H), 6.92 (d, J=7.5 Hz, 1H), 6.80 (t, J=9 Hz, 3H), 6.71 (t, J=7.5 Hz, 2H), 6.32 (d, J=3 Hz, 1H), 5.72 (d, J=7.5 Hz, 2H), 3.48 (d, J=3.6 Hz, 4H), 1.53 (s, 6H). .sup.13C NMR (75 MHz, CDCl.sub.3, ): 156.35, 148.69, 148.36, 140.53, 130.07, 129.22, 128.59, 126.07, 124.79, 124.67, 121.51, 120.43, 113.66, 66.47, 38.13, 36.73, 35.82, 30.49. MS (HR-ES-MS=high resolution electrospray mass spectrometry) m/z: C.sub.44H.sub.31N.sub.3 gives: 601.2518; found 601.3514. C.sub.44H.sub.31N.sub.3 results: C, 87.82; H, 5.19; N, 6.98, found: C, 87.48; H, 5.41; N, 6.60.

[0073] Crystal Structure:

[0074] FIG. 4 shows the molecular structure which results from an X-ray structure determination. Further structural data are summarized in Tables 1 and 2.

TABLE-US-00001 TABLE 1 X-ray diffraction data for the molecule of Example 1. Formula C.sub.44H.sub.31N.sub.3 D .sub.calc/G cm .sup.3 1.237 /mm.sup.1 0.556 Molar mass 601.72 Colour yellow Shape irregular Size/mm .sup.3 0.21 0.20 0.14 T/K 123.00 (10) crystal system monoclinic space group P2.sub.1/c a/ 10.68690 (10) b/ 12.46700 (10) c/ 24.3981 (3) a/ 90 b/ 96.2130 (10) g/ 90 V/ .sup.3 3231.55 (6) Z 4 Z 1 Wavelength/ 1.54184 Radiation CuK .sub.a .sub.min/ 3.645 .sub.max/ 73.424 Measured 35409 reflections Independent 6430 reflections Used reflections 5714 R.sub.int 0.0284 Parameter 426 Restrictions 0 the biggest Peak 0.229 the deepest hole 0.238 GoF 1.024 wR .sub.2 (all data) 0.1037 wR .sub.2 0.0988 R .sub.1 (all data) 0.0438 R .sub.1 0.0388

TABLE-US-00002 TABLE 2 Atomic coordinates x, y, z (x 10 .sup.4 ) and displacement parameters U (eq) (.sup.2 10.sup.3) for the example molecule 1. C(16) 7402.8(10) 2049.8(9) 5585.6(4) 23.7(2) C(21) 8030.3(11) 3858.2(9) 3240.5(5) 24.8(2) C(19) 7645.4(10) 3096.7(8) 4145.6(4) 21.4(2) C(22) 8573(1) 3936.8(9) 2753.4(5) 25.2(2) C(1) 6884.5(11) 2918.2(9) 6429.5(5) 24.9(2) C(5) 5332.2(11) 1756.1(9) 5912.3(5) 24.3(2) C(40) 7533.0(11) 4274.0(9) 4318.0(4) 25.7(2) N(2) 10626.8(11) 3462.3(12) 1766.7(5) 47.8(3) C(25) 9216.8(11) 2264.9(9) 3493.5(5) 26.1(2) C(33) 6256.0(11) 2827.1(10) 3965.1(4) 25.5(2) C(30) 8434.4(11) 1387(1) 5703.9(5) 28.7(3) C(32) 8222.1(11) 4777.5(10) 2362.9(5) 30.4(3) C(23) 9493.8(11) 3196(1) 2638.9(5) 26.9(2) C(28) 9138.5(11) 1837.9(9) 4812.4(5) 25.5(2) C(29) 9292.5(12) 1309.6(10) 5322.5(5) 30.6(3) C(4) 4527.6(11) 1832.9(9) 6326.9(5) 28.0(2) C(6) 4920.9(12) 1231.6(9) 5415.4(5) 29.5(3) C(24) 9783.3(12) 2364.2(10) 3005.9(5) 29.4(3) C(39) 6273.3(12) 4601.8(10) 4262.2(5) 31.6(3) C(34) 5755.3(12) 1848.6(11) 3783.0(5) 33.3(3) C(2) 6125.4(12) 3020(1) 6861.2(5) 29.6(3) C(3) 4907.4(12) 2390.2(10) 6877.4(5) 30.8(3) C(15) 7982.5(12) 3530.6(10) 6432.3(5) 31.8(3) C(7) 3735.3(12) 784.4(10) 5331.2(6) 35.6(3) C(38) 5484.3(12) 3714.1(11) 4032.5(5) 32.2(3) C(27) 10145.3(12) 1681.8(11) 4433.3(5) 31.4(3) C(26) 9615.5(13) 1326.1(10) 3858.0(5) 31.9(3) C(41) 8492.1(14) 4958.6(10) 4511.5(5) 34.9(3) C(31) 10125.5(11) 3318.4(11) 2151.1(5) 32.9(3) C(9) 3345.8(12) 1353.5(11) 6230.5(6) 38.1(3) C(8) 2943.3(12) 838.5(11) 5740.3(7) 40.8(3) C(44) 5964.0(16) 5627.9(11) 4426.3(6) 43.9(4) C(11) 5092.0(14) 1528.7(12) 7334.7(6) 42.4(3) C(14) 8339.7(14) 4229.3(11) 6862.5(6) 41.2(3) C(10) 3850.2(14) 3162.4(13) 7009.6(6) 42.7(3) C(12) 6530.2(14) 3722.4(12) 7290.8(6) 41.8(3) C(35) 4458.2(14) 1764.8(14) 3659.6(6) 46.5(4) C(42) 8171.6(17) 5992.8(11) 4664.7(6) 48.4(4) C(37) 4182.6(13) 3620.1(15) 3900.4(6) 47.3(4) C(13) 7613.4(15) 4322.9(13) 7297.2(6) 47.4(4) C(43) 6920.2(18) 6310.2(11) 4629.1(6) 52.0(4) C(36) 3693.7(14) 2642.2(17) 3713.7(6) 54.3(4)

[0075] The example molecule 1 can be vacuum-sublimed (Temperature 250 C., Pressure 610.sup.5 mbar) and can also dissolve in many organic solvents, such as in Dichloromethane (CH.sub.2Cl.sub.2), Toluene, Tetrahydrofuran (THF), Acetone, Dimethylformamide (DMF), Acetonitrile, Ethanol, Methanol, Xylene or Benzene. The good solubility in Chloroform also allows doping, for example, in Polymethylmethacrylate (PMMA) or polystyrene.

[0076] Photophysical Measurements

[0077] Example molecule 1 dissolved in toluene with a value of dielectric constant =2.4 (T=300 K) shows an emission (T=300 K) with a maximum in blue at 468 nm (FIG. 5). The emission quantum yield .sub.PL is high (.sub.PL=65% for a nitrogen-purged solution). The decay time for example 1 is only 420 ns (FIG. 6). A short decay time is very important for OLED applications, because short decay time have less roll-off effects and increases the device stability, which is well-known to the person skilled in the art. Emitter has a shorter decay time, compared with the reported TADF decay time (about 5 s).

[0078] DFT calculations (FIG. 3) show the Charge-Transfer (CT) transitions of sample molecule 1. Such transitions are influenced by the immediate vicinity of the emitter (Matrix/Solvent). FIG. 2 illustrates this behavior. With increasing polarity of the matrix, the emitting of .sup.1CT-singlet state has a red shift. Corresponding statements also result from TD-DFT calculations, in which dielectric constant is considered mathematically as a parameter.

[0079] The effect of the polarity of the matrix is also investigated with example molecule 1 dissolved in diethyl ether. This matrix has a higher value on =4.3 than toluene. The emission (T=300 K) shows a red-shifted maximum at 515 nm (FIG. 7a), and the emission quantum yield .sub.PL is 70% in a nitrogen-purged solution. The decay time of =960 ns is determined (FIG. 7b). The corresponding radiative rate to kr=.sub.PL/=7.3 10.sup.5 s.sup.1 can be determined from the given values. This emission is a fluorescence equilibrated with the nearly iso-energetic .sup.3CT state. Further details are given below. This interpretation is confirmed by quantum-mechanical calculations. For electronic transition S.sub.0.fwdarw..sup.1CT, the TD-DFT calculation results (for the .sup.1CT-geometry) give an oscillator strength f=0.00115. The radiative rate for the transition can be estimated based on the literature [N. Turro, Modern Molecular Photochemistry, The Benjamin/Cummings Publ., Menlo Park, Calif. 1978, page 87], using specified approximation and the energetic position of the emission (FIG. 7a). The assessment gives a radiative rate for the prompt fluorescence of kr=6.510.sup.5 s.sup.1, which is relatively close to the experimentally determined rate, based on the simple approximation. The alternative interpretation, in which emission process from the triplet state is phosphorescence can be excluded for a liquid solution emitter due to the short decay time of less than 1 s and the high emission quantum yield. This value of the decay time of 980 ns is also shorter than the shortest TADF decay time measured so far. However, the described emission process is not a TADF emission. It is, rather, fluorescence from the .sup.1CT singlet state equilibrated with the nearly iso-energetic .sup.3CT-state. When used in an OLED, all triplet and singlet excitons are collected. This important feature will be discussed in detail below.

[0080] FIG. 8 shows the emission characteristics of the sample substance 1 doped in a polar matrix (with a formal value of 4.4), the higher-energy .sup.1,3CT states of sample molecule 1 and a small singlet-triplet energy gap. This matrix is a TADF-emitter, but emission characteristics are not relevant here. The structural formula of the matrix substance is:

##STR00014##

[0081] The emission spectrum of this emitter-matrix combination/composition) is shown in FIG. 8. This emission decay time of 530 ns is also fluorescence from the .sup.1CT-singlet state, which is equilibrated with the iso-energetic .sup.3CT-state

[0082] In FIG. 9, emission spectra of the sample molecule 1 for various temperatures (T=300 K, 150 K and 10 K) were compared. Except for a slight spectral shift, there are no changes over the entire temperature range, as expected, in contrast to TADF-emitter (freezing of TADF emissions). The radiative rate of emission does not change significantly either. These measurement results show that the emission mechanism remains unchanged over the entire temperature range, expected as fluorescence from the 1CT-singlet state equilibrated with iso-energetic .sup.3CT-state.

[0083] In FIG. 10, the emission behavior of the sample molecule 1 in a polar environment such as diethyl ether or the discussed solid TADF matrix, is displayed with an energy level diagram. Low temperature measurements show that the localized .sup.3LE-state energy is above the .sup.1,3CT states.

[0084] Quantum mechanical mixtures of this .sup.3LE state via the mechanisms of SOC (spin-orbit coupling=spin-orbit interaction) and the configuration interaction (CI) are possible with the CT-states. Furthermore, since the singlet and triplet CT states have similar potential areas, the Franck-Condon factors responsible for the ISC rate are large. (This term is known to a person skilled in the art) Because of these properties, it is expected that rapid ISC occurs between the .sup.1CT state and the .sup.3CT state. Fast means that the ISC processes take place faster than the prompt fluorescence in this context. In fact, even at low temperature (e.g. T=10 K), no .sup.3CT phosphorescence was observed for molecule 1 in the TADF matrix.

[0085] When the composition (emitter molecules in a polar matrix) is used in an OLED, the singlet excitons occupy the CT-singlet and triplet excitons occupy the CT-triplet state according to the invention. Since the occupation of both CT states is in equilibrium with the rapid ISC processes and the prompt .sup.1CT.fwdarw.S.sub.0 fluorescence is much faster than the spin-forbidden .sup.3CT.fwdarw.S.sub.0 phosphorescence, fluorescence from the .sup.1CT-singlet states equilibrated with the nearly iso-energetic .sup.3CT state can be observed. This means that all excitation processes can lead to the direct occupation and emission from the CT singlet state. That is, there is a direct singlet harvesting. This invention thus provides organic emitter molecules for optoelectronic devices, as well as a method for adapting these, which lead to a significant shortening of the emission decay time (eg., by a factor of five to ten) compared to the prior art.

Example 2

[0086] ##STR00015##

Example Molecule 2

[0087] The frontier orbitals shown in FIG. 11 indicate that HOMO and LUMO are located in distinctly different spatial regions of the molecule. This suggests a very small splitting between the lowest triplet CT and the above singlet CT state. A calculation for the sample molecule 2 in a TD-DFT calculation (Functional B3LYP; basic set 6-31G (d, p)) shows that this energy difference for the optimized singlet geometry E (.sup.1CT-.sup.3CT)=5 cm.sup.1 is (0.6 meV). Thus, example molecule 2 represents an organic molecule of the invention.

[0088] The chemical synthesis of the molecule Example 2 started from commercially available starting materials is explained in the following scheme.

##STR00016##

Example 3

[0089] ##STR00017##

Example Molecule 3

[0090] The frontier orbitals shown in FIG. 12 indicate that HOMO and LUMO are located in distinctly different spatial regions of the molecule. This suggests that the splitting between the lowest triplet CT and the above singlet CT state is small. Calculation for the sample molecule 3 in a TD-DFT calculation (Functional B3LYP; basic set 6-31G (d, p)) shows that the energy gap E (.sup.1CT-.sup.3CT) for the optimized singlet geometry is 5 cm.sup.1 (0.6 meV). Thus, example molecule 3 represents an organic molecule of the invention.

[0091] The chemical synthesis of the molecule example 3 started from commercially available starting materials is explained in the following Scheme.

##STR00018##

Example 4

[0092] ##STR00019##

Example Molecule 4

[0093] Calculation for the sample molecule 4 in a TD-DFT calculation (Functional B3LYP; basic set, 6-31G (d, p) shows that the energy gap E (.sup.1CT-.sup.3CT) for the optimized triplet geometry is 8 cm .sup.1 (1 meV). Thus, example molecule 4 represents an organic molecule of the invention.

[0094] The chemical synthesis of the example molecule 4 started from commercially available starting materials is explained in the following Scheme.

##STR00020##

Example 5

[0095] ##STR00021##

Example Molecule 5

[0096] Calculation for the sample molecule 5 in a TD-DFT calculation (Functional B3LYP; basic set 6-31G (d, p)) shows that the energy gap E (.sup.1CT-.sup.3CT) for the optimized triplet geometry is 9 cm.sup.1 (1.1 meV). Thus, example molecule 5 represents an organic molecule of the invention.

[0097] The chemical synthesis of the molecule example 5 started from commercially available starting materials is explained in the following Scheme.

##STR00022##

Example 6

[0098] ##STR00023##

Example Molecule 6

[0099] Calculation for the sample molecule 6 in a TD-DFT calculation (Functional B3LYP; basic set, (6-31G (d, p) shows that the energy gap E (.sup.1CT-.sup.3CT) for the optimized triplet geometry is 12 cm.sup.1 (1.5 meV). Thus, example molecule 6 represents an organic molecule according to the invention.

[0100] The chemical synthesis of the molecule example 6 started from commercially available starting materials is explained in the following scheme.

##STR00024##

[0101] FIG. 13 shows another example molecule of the invention.

FIGURE

[0102] FIG. 1: Energy level diagram illustrates the process of thermally activated delayed (delayed) fluorescence (TADF). k.sub.B represents the thermal energy k.sub.B of the Boltzmann constant and T is the absolute temperature. The diagram shows the radiative TADF process, observed at low temperature and non-radiating (wavy) deactivation from the T.sub.1 state. The process of spontaneous S.sub.1.fwdarw.S.sub.0 fluorescence is not shown in the diagram.

[0103] FIG. 2: Influence of polarity of the solvent on the energy position of the .sup.1CT-emission for the dissolved sample molecule 1 at T=300 K. The figure shows the red shift of the emission spectra with increasing polarity of the solvent (quantified by the dielectric constant ).

[0104] FIG. 3: Isosurfaces of the frontier orbitals for the sample molecule 1 (see example 1), HOMO: left, LUMO: right. Geometry optimizations were carried out for the electronic ground state S.sub.0. Calculation methods: DFT and TD-DFT, Functional: B3LYP, basic set: 6-31G (d, p), calculation software: Gaussian 09. The calculations show the energy gap between the singlet CT state and the triplet-CT state is 7 cm.sup.1 (T.sub.1 geometry). This value indicates that example 1 is a good emitter for use in optoelectronic devices.

[0105] FIG. 4: Perspective view of example molecule 1, resulted from an X-ray structure determination. The single crystal used for structure analysis was performed by slow diffusion of hexane into a saturated dichloromethane solution of 1.

[0106] FIG. 5: Emission and excitation spectrum of example substance 1 dissolved in toluene (c10.sup.5 M). The residual oxygen was removed from the solution by passing nitrogen over 120 minutes. The emission quantum yield was .sub.PL=65%. Excitation: 310 nm, detection: 468 nm.

[0107] FIG. 6: TADF decay time of the sample molecule 1 dissolved in toluene and nitrogen-purged (T=300K, c10.sup.5 M). Excitation: 310 nm, pulse duration: 10 ns. The measured value of =420 ns represents the shortest decay time, which is significantly shorter than the previously measured TADF shortest decay time.

[0108] FIG. 7: (a) Emission spectrum of example molecule 1 in diethyl ether (c10 .sup.5 M). The emission represents the .sup.1CT-fluorescence equilibrated with the .sup.3CT state with a decay time of =960 ns (b). The sample was purged with nitrogen for 120 minutes. Excitation: Spectrum (a): 310 nm (cw-LED); Decay curve (b): 310 nm (LED pulsed). Temperature (T)=300 K.

[0109] FIG. 8: Emission spectrum of example molecule 1 in a fixed TADF matrix (see text) (c10 wt. %). The emission represented a fluorescence equilibrated with .sup.3CT-state with a decay time of 530 ns. The sample was carefully degassed. Excitation: 310 nm (cw-LED). Temperature (T)=300 K.

[0110] FIG. 9: Emission spectra of example molecule 1 in a fixed TADF matrix (see text) (c10 wt. %) at various temperatures (spectra normalized). The emission spectra vary only slightly with cooling. The decay times are extended from 530 ns (300 K) to 1 us (10 K). The radiative rate changes only slightly with cooling.

[0111] FIG. 10: Energy level diagram for explaining the emission behavior of the example molecule 1 in a polar matrix, such as diethyl ether or the above-described TADF matrix. The localized .sup.3LE state is energetically above the .sup.1,3CT states. The states can comprise quantum mechanical mixtures, namely the .sup.3LE-state and the .sup.1CT-state can be mixed by spin-orbit coupling (SOC), while the two triplet states can interact through configuration interaction (CI). This result is in a rapid intersystem crossing (ISC) between the .sup.1CT and the .sup.3CT state. As a result, even at low temperature, only .sup.1CT-fluorescence equilibrated with the .sup.3CT state can be observed, neither a .sup.3CT phosphorescence, nor a TADF.

[0112] FIG. 11: Isosurfaces of the frontier orbitals for the sample molecule 2 (see example 2.), HOMO: left, LUMO: right. Geometry optimizations were carried out for the electronic ground state S.sub.0. Calculation methods: DFT and TD-DFT, Functional: B3LYP, basic rate: 6-31G (d, p), Calculation software: Gaussian 09. The calculations predict 5 cm.sup.1 (0.6 meV) (S.sub.0 geometry) for the energy difference between the singlet CT state and the triplet-CT state.

[0113] FIG. 12: Isosurfaces of the frontier orbitals for the sample molecule 3 (see example 3.), HOMO: left, LUMO: right. It made geometry optimizations for the electronic ground state S.sub.0. Accounting methods: DFT and TD-DFT, Functional: B3LYP, basic rate: 6-31G (d, p), invoice Software: Gaussian 09. The calculations predict for the energy gap between the singlet state and the triplet CT-CT state 5 cm .sup.1 (S.sub.0 (0.6 MeV) geometry).

[0114] FIG. 13: Further examples of the invention organic emitter molecules that are suitable for the usage in opto-electronic devices.