Search

JP-2026076041-A - Organic electroluminescent elements and their design methods, methods for improving multi-resonance light-emitting materials, multi-resonance light-emitting materials and compounds

JP2026076041AJP 2026076041 AJP2026076041 AJP 2026076041AJP-2026076041-A

Abstract

[Problem] To provide an organic electroluminescent element that is highly stable and has suppressed roll-off, while using a combination of a delayed fluorescence material and a multi-resonance type light-emitting material in the light-emitting layer. [Solution] The organic electroluminescent element of the present invention is characterized in that the light-emitting layer includes at least a delayed fluorescence material and a multi-resonance type light-emitting material, substituents are introduced into the multi-resonance type condensed ring skeleton constituting the multi-resonance type light-emitting material, and the difference in HOMO energy levels between the multi-resonance type light-emitting material and the delayed fluorescence material is 0.4 eV or less. [Selection Diagram] None

Inventors

  • 湯 洵
  • 安達 千波矢
  • 范 孝春
  • 王 凱
  • 張 ▲暁▼宏
  • 畠山 琢次

Assignees

  • 国立大学法人九州大学
  • 蘇州大学
  • 国立大学法人京都大学

Dates

Publication Date
20260511
Application Date
20241023

Claims (20)

  1. The light-emitting layer includes at least a delayed fluorescence material and a multi-resonance light-emitting material. An organic electroluminescent element characterized in that a substituent with a σm of 0.2 or more is introduced into the multiple resonance condensed ring skeleton constituting the multiple resonance light-emitting material, and the difference in HOMO energy levels between the multiple resonance light-emitting material and the delayed fluorescence material is 0.4 eV or less.
  2. The organic electroluminescent element according to claim 1, wherein the substituent is a substituent bonded to an atom with a large electron density distribution in the HOMO.
  3. The organic electroluminescent element according to claim 1, wherein the substituent is bonded to an atom in which both the electron density distribution of the HOMO and the electron density distribution of the LUMO are large.
  4. The organic electroluminescent element according to claim 1, wherein the energy level of the HOMO of the multi-resonance type light-emitting material is -5.6 eV or lower.
  5. The organic electroluminescent element according to claim 1, wherein the HOMO energy level of the delayed fluorescence material is -5.9 eV or lower.
  6. The organic electroluminescent element according to claim 1, wherein the multi-resonance type light-emitting material contains a benzene ring bonded to a boron atom, and the substituent is bonded to the benzene ring at the meta position of the boron atom.
  7. The organic electroluminescent element according to claim 1, wherein the multi-resonance type light-emitting material contains a benzene ring bonded to a boron atom, and the substituent is bonded to the benzene ring at the para position of the boron atom.
  8. The organic electroluminescent element according to any one of claims 1 to 6, wherein the substituent is a fluorine atom, a cyano group, a trifluoromethyl group, a pyridyl group, a pyrimidyl group, a pyrazinyl group, a pyridadinyl group, or a triazyl group.
  9. A method for designing an organic electroluminescent element comprising a host material, a delayed fluorescence material, and a multi-resonance type light-emitting material in a light-emitting layer, A method for designing an organic electroluminescent element, characterized by selecting substituents present in a multi-resonance type light-emitting material to determine a structure in which the difference in HOMO energy levels between the multi-resonance type light-emitting material and the delayed fluorescence material is 0.4 eV or less, and designing an organic electroluminescent element comprising a multi-resonance type light-emitting material having that structure, the host material, and the delayed fluorescence material.
  10. The method for designing an organic electroluminescent element according to claim 9, wherein the substituent is a substituent bonded to an atom with a large electron density distribution of the HOMO.
  11. The method for designing an organic electroluminescent element according to claim 9, wherein the substituent is bonded to an atom in which both the electron density distribution of the HOMO and the electron density distribution of the LUMO are large.
  12. A method for designing an organic electroluminescent element according to claim 9, wherein the energy level of the HOMO of the structure to be determined is -5.6 eV or lower.
  13. The method for designing an organic electroluminescent element according to claim 9, wherein the energy level of the HOMO of the delayed fluorescence material is -5.9 eV or lower.
  14. The method for designing an organic electroluminescent element according to claim 9, wherein the multi-resonance type light-emitting material contains a benzene ring bonded to a boron atom, and the substituent is bonded to the benzene ring at the meta position of the boron atom.
  15. The method for designing an organic electroluminescent element according to claim 9, wherein the multi-resonance type light-emitting material contains a benzene ring bonded to a boron atom, and the substituent is bonded to the benzene ring at the para position of the boron atom.
  16. The method for designing an organic electroluminescent element according to claim 9, wherein the distance between the bonding atom of the substituent and the atom furthest from that bonding atom is 7 angstroms or less.
  17. The method for designing an organic electroluminescent element according to claim 16, wherein the substituent is a fluorine atom, a cyano group, a trifluoromethyl group, a methoxy group, a pyridyl group, a pyrimidyl group, a pyrazinyl group, a pyridadinyl group, or a triazyl group.
  18. An organic electroluminescent element manufactured using the design method described in any one of claims 9 to 17.
  19. A method for improving a multi-resonance luminescent material used in an organic electroluminescent element that includes a host material, a delayed fluorescence material, and a multi-resonance luminescent material in its light-emitting layer, A method characterized by finding a multi-resonance luminescent material having a structure in which the difference between the energy level of the HOMO of the delayed fluorescence material and the energy level of the delayed fluorescence material is 0.4 eV or less, by performing at least one step of calculating the difference between the structure and the energy level of the HOMO of the delayed fluorescence material, assuming a structure in which hydrogen atoms or groups present in the pre-improvement multi-resonance luminescent material are substituted.
  20. The improved method according to claim 19, wherein the hydrogen atom or group is a hydrogen atom or group bonded to an atom with a large electron density distribution in the HOMO.

Description

This invention relates to an organic electroluminescent element containing a delayed fluorescence material and a multi-resonance luminescent material in its light-emitting layer, and to a method for designing the same. Furthermore, this invention also relates to a multi-resonance luminescent material and a method for improving it, as well as compounds useful as multi-resonance luminescent materials. Research is actively underway to improve the luminescence efficiency of organic electroluminescent devices (organic EL devices). In particular, various methods are being employed to improve luminescence efficiency and color purity by developing new material compositions for the light-emitting layer of organic electroluminescent devices. For example, Patent Document 1 proposes an organic electroluminescent element having a light-emitting layer containing a host material, a delayed fluorescence material, and a multi-resonance light-emitting material. Here, the delayed fluorescence material is an organic compound with a small difference between the excited singlet energy and the excited triplet energy, and has the function of converting the excited triplet state to the excited singlet state and supplying the excited singlet energy to the multi-resonance light-emitting material. The multi-resonance light-emitting material is a condensed polycyclic compound whose molecules are designed so that HOMO and LUMO are localized on different carbon atoms due to the multi-resonance effect of boron and nitrogen, and exhibits high color purity because it does not involve molecular stretching vibrations during radiative deactivation from the excited singlet S1 to the ground singlet S0 . In an organic electroluminescent element using a combination of these materials, the energy of the excited triplet state, which would normally be deactivated without radiation in ordinary organic compounds, is effectively utilized for the emission of light by the multi-resonance light-emitting material, resulting in high luminescence efficiency and high color purity. Adv. Mater. 2016, 28(14), 2777-2781Adv. Mater. 2022, 34(32), 2201778 This graph shows the electron density-driving voltage characteristics of element E1 with a mixed film of compound 1:HDT-1:mCBP, element E2 with a mixed film of compound 2:HDT-1:mCBP, comparative element E1 with a mixed film of comparative compound 1:HDT-1:mCBP, comparative element E2 with a mixed film of HDT-1:mCBP, and comparative element E3 with a single mCBP film.This graph shows the hole density-driving voltage characteristics of element H1 with a mixed film of compound 1:HDT-1:mCBP, element H2 with a mixed film of compound 2:HDT-1:mCBP, comparative element H1 with a mixed film of comparative compound 1:HDT-1:mCBP, comparative element H2 with a mixed film of HDT-1:mCBP, and comparative element E4 with a single mCBP film.These are the emission spectra of EL element 1 with a light-emitting layer of compound 1:HDT-1:mCBP, EL element 2 with a light-emitting layer of compound 2:HDT-1:mCBP, and comparative EL element 1 with a light-emitting layer of comparative compound 1:HDT-1:mCBP.This graph shows the current density-driving voltage-luminance characteristics of EL element 1, EL element 2, and comparative compound 1.This graph shows the external quantum efficiency (EQE)-luminance characteristics of EL element 1, EL element 2, and comparative compound 1.This graph shows the change in brightness over time when EL element 1, EL element 2, and comparative compound 1 are continuously driven.This graph shows the change in emission intensity over time when excitation light is continuously irradiated onto EL element 1, EL element 2, comparative EL element 1, and PL element 1, PL element 2, and comparative PL element 1, each having the same light-emitting layer.This graph shows the time evolution of EL intensity when pulsed EL excitation (pulse width: 100 μs) is performed on EL element 1, EL element 2, and comparison EL element 1, and then a reverse bias voltage is applied.These are the transient decay curves of the electroluminescent (EL) intensity of EL element 1, which has an EL light-emitting layer of compound 1:HDT-1:mCBP, and comparative EL element 2, which also has an EL light-emitting layer of compound 1:mCBP.These are the transient decay curves of the electroluminescent (EL) intensity of EL element 2, which has an EL light-emitting layer of compound 2:HDT-1:mCBP, and comparative EL element 3, which has an EL light-emitting layer of compound 1:mCBP.These are the transient decay curves of the electroluminescent (EL) intensity of EL element 1, which has an EL-emitting layer of comparative compound 1:HDT-1:mCBP, and comparative EL element 4, which has an EL-emitting layer of comparative compound 1:mCBP. The contents of the present invention will be described in detail below. The following descriptions of constituent elements may be based on representative embodiments and specific examples of the present invention, but th