SUPERFLUORESCENT CERIUM (III)-CONTAINING CHELATE APPLICABLE TO PHOTOELECTRIC DEVICES AND HAVING A DUAL CAPTURE MECHANISM AND ULTRA-SHORT DECAY TIME

Abstract

The present invention relates to a composition of a superfluorescent cerium (III)-containing chelate having ultra-short decay time, especially a molecular composition for OLED applications, having a neutral donor in the form of a Ce(III) chelate and a neutral fluorescent receptor molecule. The composition of the present invention can be used to produce pure color luminescence with very short emission decay time, especially for a dark blue luminous region. The composition utilizes an excited state dual capture mechanism, and such kind of novel exciton capture mechanism can be classified into a fifth-generation organic light-emitting diode (OLED) and other photoelectric devices.

Claims

1. A molecule, having the following structural formula I or II, or consisting of the following structural formula I or II: ##STR00047## ##STR00048## wherein: R.sup.1 is selected from pyrazolyl, triazolyl, heteroaryl, alkyl, aryl, alkoxy, phenol group, amido and acylamino; these groups are substituted or unsubstituted; R.sup.5 is R.sup.1 or H; and R.sup.2, R.sup.3, R.sup.4, R.sup.6, R.sup.7 are independently selected from H, halogen, hydrocarbonyl or hydrocarbonyl containing a heteroatom, especially alkyl, aryl and heteroaryl; preferably, R .sup.2—R .sup.7 are each independently fluorated, namely, particularly having at least one F.

2. The molecule according to claim 1, having the following structure, or consisting of the following structure: ##STR00049## wherein Cz is carbazolyl and pz is pyrazolyl, wherein optionally, Cz is each independently substituted by one or two tert-butyl in any position.

3. The molecule according to claim 2, having or consisting of the following structure: ##STR00050## ##STR00051## wherein t-Bu is tert-butyl.

4. The molecule according to claim 1, having the following structural formula III or IV, or consisting of the following structural formula III or IV: ##STR00052## ##STR00053## being a tetra(cis)pyrazolyl borate ligand or a tetra(cis)triazolyl borate ligand herein.

5. The molecule according to claim 4, wherein R.sup.2, R.sup.3, R.sup.4, R.sup.6 and R.sup.7 are each independently selected from hydrogen and halogen, or one optional hydrocarbonyl containing a heteroatom and/or substituted or unsubstituted hydrocarbonyl, wherein the heteroatom is particularly selected from O, S, N, P, Si, Se, F, Cl, Br and/or I.

6. The molecule according to claim 5, wherein R.sup.2, R.sup.3, R.sup.4, R.sup.6 and R.sup.7 are hydrogen and halogen.

7. A molecule, having the following structural formula V or VI, or consisting of the following structural formula V or VI: ##STR00054## ##STR00055## wherein R is CH.sub.3CH.sub.2, CH.sub.3CH.sub.2CH.sub.2 or CH.sub.3-CH-CH.sub.3.

8. The molecule according to any one of claims 1-7, optionally, having at least one deuterium.

9. An application of the molecule according to any one of claims 1-7 as a neutral donor molecule in a composition consisting of a fluorescent receptor molecule therewith.

10. A composition, consisting of: a neutral donor molecule with the molecule according to any one of claims 1-8 as a Ce(III) chelate form, and a fluorescent receptor molecule, particularly being the compound according to formulas VII-IX, ##STR00056## ##STR00057## ##STR00058##

11. The composition according to claim 10, wherein the neutral donor molecule has a Ce(III) central ion, which is eight to twelve-coordinated, and particularly coordinated with an organic ligand.

12. The composition according to claim 11, wherein the organic ligand is a two-coordinated or preferably, three-coordinated chelating ligand and/or the lowest triplet energy of the organic ligand is higher than an excited state energy of the Ce(III) chelate with the lowest energy.

13. The composition according to claims 10-12, wherein the organic ligand has one or two aromatic or heteromatic ring systems, used for capturing singlet excitons and triplet excitons such that the lowest ligand excited singlet state S.sub.1(L) and the lowest ligand excited triplet state T.sub.1(L) are occupied, and perform rapid intersystem crossing from S.sub.1(L) to T.sub.1(L), and rapidly transfer to the center of the Ce(III) therewith via intramolecular energy.

14. The composition according to claim 13, wherein the fluorescent receptor molecule has: wherein the receptor has a decimal molar extinction coefficient greater than 20,000 Lmol.sup.-1cm.sup.-1; a full width at half maximum (FWHM) less than 0.25 eV, particularly less than 0.2 eV; an emission quantum efficiency φ.sub.PL greater than 70%, particularly greater than 90%; emission decay time τ less than 10 ns, particularly less than 2 ns; and/or a maximum emission peak within a range of 420 nm-480 nm, in particular to a dark blue spectrum region.

15. An application of the composition according to claims 10-14 for the preparation of a photoelectric device, particularly selected from an organic light emitting diode (OLED), light emitting electrochemical cell (LEEC), an OLED sensor and an organic light emitting transistor and organic laser.

16. A photoelectric device, having the molecule according to claims 1-9 or the composition of claims 10-14.

17. The photoelectric device according to claim 16, comprising a substrate; an anode and a cathode, wherein the anode or the cathode is applied on the substrate; and at least one light emitting layer which is disposed between the anode and the cathode, and has the molecule of claims 1-9 or the composition of claims 10-14.

18. The photoelectric device according to claim 17, wherein a doping mass ratio of the Ce(III) chelate donor molecule in the light emitting layer accounts for 99%-10% in the light emitting layer, in particular being 18%-12%.

19. The photoelectric device according to claim 18, wherein a doping mass ratio of the fluorescent receptor molecule accounts for 0.5%-5% in the emitting layer, in particular being 1%.

20. A method for preparing the photoelectric device according to claims 16-19, wherein the molecule according to claims 1-9 or the composition of claims 10-14 is used.

21. A method for completely capturing all singlet and triplet excitons in a photoelectric device, wherein the molecule of claims 1-9, as a Ce(III) chelate donor, is used for non-radiative energy transfer to a fluorescent receptor.

22. The method according to claim 21, wherein a fluorescent receptor molecule emitting a green or red light is used to produce a superfluorescence which has a short service life, in particular being less than 10 ns or greater than 2 ns and has a high color purity to the corresponding spectral regions.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0048] FIG. 1 shows a photophysical process of, for example, dark blue superfluorescence emission achieved by a dual capture mechanism.

[0049] The singlet and triplet excitons produced in an OLED light emitting layer are captured by the states S.sub.1(L) and T.sub.1(L) of a Ce(III) chelate ligand. Rapid intramolecular energy transfer causes that the lowest excited state is occupied by the state .sup.2D.sub.3/2 in the Ce(III) chelate. The decay time of the fluorescent radiative jump (no receptor) to the states .sup.2F.sub.5/2 and .sup.2F.sub.7/2 is 50-100 ns. Such kind of Ce(III) chelate is used as a donor to transfer energy to for example, the state S.sub.1 of an organic receptor molecule of dark blue fluorescence through a Förster-energy transfer mechanism (FRET) of rapid fluorescence resonance, thus producing fluorescence emission finally. The selected organic receptor molecule has a narrow FWHM (for example, <0.2 eV) and higher photoluminescent quantum efficiency φ.sub.PL (for example, 90%) and very short emission decay time (for example, 2 ns). The short range non-radiative energy transfer from the state .sup.2D.sub.3/2 to the state T.sub.1 of a receptor based on a Dexter mechanism may be greatly inhibited. The method may be also used to produce green or red superfluorescence.

DETAILED DESCRIPTION OF EMBODIMENTS

[0050] The present invention will be further described in detail with reference to the examples.

Example 1

[0051] Structure of the OLED light emitting layer: layer thickness: 20 nm; host: 2,8-bis(diphenylphosphineoxy)dibenzofuran (DBFPO) doped with 15% Ce[B(pz).sub.4].sub.3, pz=pyrazolyl and 1% BPPyA (formula VIII).

Example 2

[0052] Structure of the OLED light emitting layer: layer thickness: 20 nm; host: 2,8-bis(diphenylphosphineoxy) dibenzofuran (DBFPO) doped with 15% Ce[B(pz).sub.4]3, pz=pyrazolyl and 1% compound of formula IX.

Example 3

[0053] Structure of the OLED light emitting layer: layer thickness: 20 nm; host: 2,8-bis(diphenylphosphineoxy) dibenzofuran (DBFPO) doped with 15% Ce[B(pz).sub.3(Cz-tert-Butyl).sub.3], pz=pyrazolyl and Cz-tert-Butyl=carbazolyl substituted by tert-butyl; and 1% compound of formula VIII.

Example 4

[0054] Structure of the OLED light emitting layer: layer thickness: 20 nm; host: 2,8-bis(diphenylphosphineoxy) dibenzofuran (DBFPO) doped with 18% compound of formula VI and 1% compound of formula VII.