Triazolotriazine-based excimer donor materials and applications

Abstract

The application belongs to the field of organic electroluminescent materials, and relates to a kind of blue fluorescent material, and specifically relates to a kind of excimer donor material based on tri(triazole)triazine and application. With triazolotriazine and its derivatives as electron acceptor, acridine as electron donor, a kind of new excimer donor material is synthesized. Because the tri(triazole)triazine core is planar, the material has good electron transport capacity, and is conducive to better realization of intermolecular charge transfer with acceptor material molecules, and then higher efficiency excimer is obtained. The application discusses the relationship between molecular structure and performance in detail, and has important significance for constructing new excimer donor material.

Description

Technical Field

[0001] This invention belongs to the field of organic electroluminescent materials, and relates to a class of blue fluorescent materials, specifically to a class of excitopolymer donor materials based on tris(triazol)triazine and their applications. Background Technology

[0002] Currently, organic light-emitting diodes (OLEDs) have been developed into three generations. The third-generation TADF material can break the spin statistics limitation by utilizing antisystem crossing, enabling exciton utilization to reach 100%. Although single-molecule TADF materials have advantages such as high color purity, high performance, and low price, they also have problems such as excessively high turn-on voltage, low power efficiency, and severe efficiency roll-off at high brightness.

[0003] To address these issues, another type of intermolecular charge transfer material system has gradually emerged—the excitocomplex system. This type of molecular system is formed through charge transfer between donor and acceptor molecules, and it exhibits TADF (Charge-Off-Demand) properties. Compared to single-molecule TADF materials, the lowest unoccupied molecular orbital (LUMO) level of the excitocomplex is located on the acceptor molecule, while the highest occupied molecular orbital (HOMO) level is located on the donor molecule. The complete separation of the HOMO and LUMO energy levels results in a significant difference in energy density (ΔE). ST Values ​​are often less than 0.05 eV, which is more conducive to anti-system cross-linking (RISC). Furthermore, the synthesis of donor-acceptor molecules in exciton complexes is less difficult than that of single-molecule TADF materials, and the controllable HOMO and LUMO are more conducive to regulating the turn-on voltage of electroluminescent devices. In addition, since the donors or acceptors commonly found in exciton complexes can act as hole transport layers or electron transport layers, respectively, there are no additional potential barriers to overcome during carrier transport. Devices based on exciton complex systems can achieve high power efficiency at lower turn-on voltages. Moreover, by adjusting the ratio of donors to acceptors, a relative balance between electrons and holes can be achieved, which is beneficial for expanding the exciton recombination region and thus improving device efficiency.

[0004] Due to the unique formation of excitocomplexes, the system can be controlled by modulating the properties of the donor and acceptor molecules. Furthermore, the delayed fluorescence lifetime of this system's films is in the microsecond range. Such a short delay lifetime helps reduce the quenching probability of excited states, thereby improving exciton utilization, device efficiency, and reducing roll-off at high current densities. Compared to single-molecule TADF materials, excitocomplexes have the potential to be excellent host materials. For ordinary host materials, excitocomplexes, as host materials, can have better carrier balancing capabilities, which is beneficial for charge transport and widening the exciton recombination region. Simultaneously, because the HOMO and LUMO of excitocomplexes can be tuned, a lower injection barrier can be obtained, resulting in devices with very low start-up voltage but low roll-off at high brightness. However, because excitocomplexes are formed through intermolecular charge transfer, the weak CT interaction leads to the inherent instability of the excitocomplex itself. Summary of the Invention

[0005] To enhance the CT interaction between donors and acceptors and obtain a more stable excitocomplex material system, this invention, for the first time, uses tris(triazol)triazine derivatives in the design and synthesis of two molecules for excitocomplexes. Tris(triazol)triazine is used as the electron acceptor unit, and acridine or diphenylamine is used as the electron donor to synthesize a class of excitocomplex donor materials.

[0006] To achieve the above objectives, the present invention provides a class of excitokinin complex donor materials using acridine or diphenylamine as donors and tris(triazol)triazine as acceptors, the structure of which is as follows:

[0007]

[0008] The synthesized tris(triazol)triazine derivative was used as the donor material for the exciton complex. The acceptor material was selected from commercially available material PO-T2T (2,4,6-tris[3-(diphenylphosphino)phenyl]-1,3,5-triazine) blend as the luminescent layer material, or the tris(triazol)triazine-based exciton complex donor material TTT-1-Me was blended with PO-T2T as the host material for the luminescent guest BN5, or the tris(triazol)triazine-based fluorescent material TTT-TPA-F was used as the dopant for the host material CBP of the luminescent layer. Electroluminescent devices were prepared by solution processing and a maximum external quantum efficiency of >19% was obtained.

[0009] When blended as a light-emitting layer material, the mass ratio of the excitopolymer donor material based on tri(triazol)triazine to PO-T2T is 83:17-89:11.

[0010] When BN5 is used as a luminescent guest material, its doping mass percentage is 1%-5% of the mass of the excitocomplex donor material TTT-1-Me and PO-T2T blend; when used as a dopant, the doping mass percentage of TTT-TPA-F is 10%-25% of the mass of CBP.

[0011] When the blend is used as the main material of BN5, the mass ratio of the excitocomplex donor material TTT-1-Me to PO-T2T is 85:15.

[0012] The beneficial effects of the technical solution of this invention are as follows:

[0013] 1. This invention introduces an acridine group into the tri(triazol)triazine unit to construct a rigid material with good electron transport properties. Furthermore, the rigid planar structure of the tri(triazol)triazine is beneficial for suppressing nonradiative transitions in the molecule, resulting in a material with high fluorescence.

[0014] 2. Although introducing a weak donor diphenylamine derivative did not yield a good excitogenes complex donor material, the introduction of heavy atoms made the entire molecule more blue-shifted, modulating the light color to deep blue. At the same time, it strengthened the local excited state of the molecule, making the entire molecule exhibit hybrid local charge transfer (HLCT) characteristics.

[0015] 3. The introduction of acridine has little effect on intramolecular charge transfer. Tris(triazol)triazine acts as a strong acceptor, and the HOMO and LUMO of this fluorescent material are relatively separated, which is conducive to the formation of excitosome complexes.

[0016] 4. When this TTT-1-Me material is used in an excimer composite system, the maximum efficiency can reach 16.9% as a self-luminescent layer and >19% as a host material. Attached image description:

[0017] Figure 1 The UV-Vis absorption spectra of compounds TTT-TPA-F and TTT-1-Me obtained in Example 1 are shown in the thin film.

[0018] Figure 2 The photoluminescence spectra of compounds TTT-TPA-F and TTT-1-Me obtained in Example 1 in thin films are shown.

[0019] Figure 3 The photoluminescence spectra of compound TTT-TPA-F obtained in Example 1 in hexane, toluene, chloroform, tetrahydrofuran, and dichloromethane are shown.

[0020] Figure 4 The photoluminescence spectra of compound TTT-1-Me obtained in Example 1 in hexane, toluene, chloroform, tetrahydrofuran, and dichloromethane are shown.

[0021] Figure 5 The image shows the absorption and CBP photoluminescence spectra of the compound TTT-TPA-F obtained in Example 1.

[0022] Figure 6 The photoluminescence spectra of compounds TTT-1-Me, ​​PO-T2T, and a blend of the two materials in a mass ratio of 85:15 prepared in Example 1 are shown in thin films.

[0023] Figure 7 The graph shows the instantaneous lifetime of the compound TTT-1-Me obtained in Example 1 in the thin film.

[0024] Figure 8 The graph shows the lifetime of the thin film in which the compound TTT-1-Me and PO-T2T were blended at a mass ratio of 85:15.

[0025] Figure 9 The electroluminescence spectra of the compound TTT-1-Me obtained in Example 1, the excitosome complex formed by PO-T2T, and the host-guest doping of TTT-TPA-F and CBP are shown.

[0026] Figure 10 The electroluminescence spectra and the original graph showing the relationship between brightness and external quantum efficiency of the compound TTT-1-Me obtained in Example 1, which forms an excitosome complex with PO-T2T, and the host-guest doped TTT-TPA-F with CBP.

[0027] Figure 11 The photoluminescence spectrum of the excitocomplex formed by the compound TTT-1-Me and PO-T2T in Example 1 at a mass ratio of 85:15, which serves as the host of BN5, is shown.

[0028] Figure 12 The electroluminescence spectrum of the excitocomplex formed by the compound TTT-1-Me and PO-T2T in Example 1 at a mass ratio of 85:15, with BN5 as the host, is shown.

[0029] Figure 13 The graph shows the relationship between the brightness and external quantum efficiency of the excitocomplex formed by the compound TTT-1-Me and PO-T2T prepared in Example 1 of this invention with a mass ratio of 85:15 as the BN5 host.

[0030] Figure 14 The current density-voltage-luminance (JVL) plot is shown for the excitocomplex formed by the compound TTT-1-Me and PO-T2T in Example 1 at a mass ratio of 85:15, which serves as the host of BN5.

[0031] Figure 15 In Example 1, compounds TTT-1-Me and PO-T2T were prepared into thin films at a mass ratio of 85:15. The films were then exposed to nitrogen atmosphere for 0h, 24h, and 48h, and their morphological changes were measured using atomic force microscopy.

[0032] Figure 16 The above are the hydrogen nuclear magnetic resonance spectra of compounds TTT-TPA-F and TTT-1-Me obtained in Example 1. Detailed Implementation

[0033] The following specific implementation examples are intended to further illustrate the present invention, but these specific implementation examples do not limit the scope of protection of the present invention in any way.

[0034] Example 1

[0035] The synthetic scheme for the exciton complex donor material based on tris(triazol)triazine is as follows:

[0036]

[0037] Synthesis of intermediate core TTT-CPh-Br

[0038] A mixture of 3.5 g (14.8 mmol) of 5-(5-bromo-2-methylbenzene)-2-hydro-tetrazole, 8.2 g (59.2 mmol) of potassium bicarbonate, 1.0 g (5.4 mmol) of cyanuric chloride, and 50 mL of 2-butanone was heated to 90 °C and stirred in air for 48 hours. After cooling to room temperature, the mixture was poured into water and extracted with dichloromethane. The organic layer was collected, washed with water, and dried over anhydrous MgSO4. The filter was evaporated to remove the solvent. CH2Cl2 was then used as the eluent to give a white solid, TTT-CPh-Br. 1 H NMR (400MHz, CDCl3) δ8.28(t,J=2.0Hz,3H),8.12–8.10(m,3H),7.79(m,3H),7.50(t,J=8.0Hz,3H),1.61(s,9H).

[0039] Synthesis of intermediate core TTT-Br

[0040] A mixture of 5-(4-bromobenzene)-2-hydro-tetrazole (3.3 g, 14.8 mmol), potassium bicarbonate (8.2 g, 59.2 mmol), cyanuric chloride (1.0 g, 5.4 mmol), and 50 mL of 2-butanone was heated to 90 °C and stirred in air for 48 hours. After cooling to room temperature, the mixture was poured into water and extracted with dichloromethane. The organic layer was collected, washed with water, and dried over anhydrous MgSO4. The filter was evaporated to remove the solvent. CH2Cl2 was then used as the eluent to give a white solid, TTT-Br.1 H NMR (400MHz, CD2Cl2) δ7.95 (d, J = 8.8 Hz, 6H), 7.71 (d, J = 8.8 Hz, 6H).

[0041] Synthesis of compound TTT-1-Me

[0042] Intermediate core TTT-CPh-Br (531 mg, 0.75 mmol), acridine (942 mg, 4.50 mmol), sodium tert-butoxide (288 mg, 3.00 mmol), tris(dibenzylacetone)dipalladium (41 mg, 0.05 mmol), tri-tert-butylphosphine tetrafluoroborate (26 mg, 0.09 mmol), and 40 mL of toluene were added to a 200 mL single-necked flask. The mixture was heated to 120 °C and stirred for 24 hours under a nitrogen atmosphere. After cooling to room temperature, the mixture was poured into water and extracted with dichloromethane. The synthesized organic layer was washed with water, dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure. The residue was separated by column chromatography using a petroleum ether:ethyl acetate (v:v = 5:1) as the eluent to give 516 mg of a white solid, in 35% yield. 1 H NMR(400MHz,DMSO)δ7.91(d,J=8.0Hz,3H),7.58–7.50(m,12H),7.08(t,J=7.6H z, 6H), 6.97 (t, J = 7.4Hz, 6H), 6.37 (d, J = 8.0Hz, 6H), 2.44 (s, 9H), 1.67 (s, 18H).

[0043] Synthesis of compound TTT-TPA-F

[0044] The intermediate core TTT-Br (500 mg, 0.75 mmol), 4,4'-difluorodiphenylamine (923 mg, 4.50 mmol), sodium tert-butoxide (288 mg, 3.00 mmol), tris(dibenzylacetone)dipalladium (41 mg, 0.05 mmol), tritert-butylphosphine tetrafluoroborate (26 mg, 0.09 mmol), and 40 mL of toluene were added to a 200 mL single-necked flask. The synthesis route for compound TTT-1-Me was followed. The residue was separated by column chromatography using a petroleum ether:dichloromethane (v:v = 1:5) mixture as eluent to give 455 mg of a white solid, in 32% yield. 1 H NMR (400MHz, CD2Cl2) δ7.86 (d, J=8.8Hz, 2H), 7.14 (dd, J1=8.8Hz, J2=4.8Hz, 4H), 7.02–6.96 (m, 6H).

[0045] Example 2

[0046] The compounds TTT-TPA-F and TTT-1-Me obtained in Example 1 were dissolved in chlorobenzene to prepare a 10 mg / ml solution. The solution was then spin-coated onto a quartz plate using a spin coater at a speed of 700 rpm. The UV-Vis absorption was measured. Figure 1 The UV-Vis absorption spectrum of thin films generally has two types of absorption peaks: the absorption peaks below short wavelength (300 nm) are mainly attributed to the π-π* transition absorption of molecules; the absorption peaks of long wavelength (350 nm-360 nm) are mainly attributed to the charge transfer (ICT) transition absorption peaks from donor units to acceptor units within molecules.

[0047] Example 3

[0048] The compound TTT-1-Me obtained in Example 1 was dissolved in chlorobenzene to prepare a 10 mg / ml solution. This solution was then spin-coated onto a quartz plate at 700 rpm using a spin coater, and its photoluminescence spectrum was measured. Figure 2 We know that the emission peak of TTT-1-Me is at 468 nm, and that of TTT-TPA-F is at 458 nm. It is clear that the donor portion of the fluorescent material exhibits a blue shift in the photoluminescence spectrum of the entire fluorescent molecule, and under photoexcitation, all compounds are in the blue light region.

[0049] Example 4

[0050] The photoluminescence properties of compounds TTT-TPA-F and TTT-1-Me in Example 1 were tested in different solvents. Compounds TTT-TPA-F and TTT-1-Me were dissolved in n-hexane, toluene, chloroform, tetrahydrofuran, and dichloromethane, respectively, to prepare solutions of 10... -5 Solution M was excited by light at 350 nm and 310 nm, respectively, to obtain Figure 3 , Figure 4 As shown in the figure, in different solvents, the emission wavelength of the compound exhibits a certain red shift with the increase of solvent polarity, and the full width at half maximum (FWHM) also changes accordingly. This indicates that these compounds have strong intramolecular charge transfer. The red shift and FWHM change of TTT-TPA-F with increasing solvent polarity are lower than those of TTT-T-Me, indicating that its intramolecular charge transfer (CT) effect is stronger than that of TTT-TPA-F.

[0051] Example 5

[0052] In Example 1, the absorption of compound TTT-TPA-F and the emission of CBP showed good overlap. Figure 5 This indicates that there is a good energy transfer between the two.

[0053] Example 6

[0054] In Example 1, compound TTT-1-Me and PO-T2T were blended at a mass ratio of 85:15, and their photoluminescence spectra were measured. Figure 6 The emission peak of TTT-1-Me is located at 468 nm, while that of the blend system is at 523 nm. This shows a significant redshift and increased full width at half maximum (FWHM) of the blend system compared to the original material. This indicates that the blending of the two compounds forms a new system—an excitocomplex. The spectral change is mainly due to the fact that the formation of the excitocomplex involves charge transfer between the donor and acceptor molecules, and this charge transfer force is generally stronger than that between unimolecular molecules.

[0055] Example 7

[0056] The fluorescence lifetime of compound TTT-1-Me in Example 1 was tested under a nitrogen atmosphere. Figure 7 As shown, the fitted compound TTT-1-Me has a lifetime of 0.7 μs, which is a long lifetime.

[0057] Example 8

[0058] The blend film formed from compounds TTT-1-Me and PO-T2T in an 85:15 mass ratio in Example 1 was tested for its lifetime under a nitrogen atmosphere. Figure 8 It can be determined through fitting that the lifetime of the excitocomplex of TTT-1-Me and PO-T2T is 6.1 μs, which is a long lifetime.

[0059] Example 9

[0060] Application of compounds TTT-TPA-F and TTT-1-Me in organic light-emitting diodes (OLEDs) in Example 1. Using a blend of TTT-1-Me and PO-T2T as the luminescent material, and a doping system of TTT-TPA-F in the host material CBP as the luminescent layer, organic light-emitting diodes with the structure ITO / PEDOT:PSS (40nm) / TTT-1-Me:PO-T2T (85:15) or (CBP:TTT-TPA-F (x wt%)) (x = 10, 15, 20, 25) (40nm) / TmPyPB (55nm) / LiF (1nm) / Al (100nm) were fabricated. In this configuration, PEDOT:PSS served as the hole injection layer, the blend as the luminescent layer, TmPyPB as the electron transport layer, and LiF / Al as the cathode. Among them, the excitocomplex of compound TTT-1-Me and PO-T2T has the highest efficiency of 16.9% at a mass ratio of 85:15. The external quantum efficiencies at 83:17, 87:13, and 89:11 are 15.4%, 16.1%, and 15.3%, respectively. TTT-TPA-F has a maximum external quantum efficiency of 6.3% with 15wt% doping, and its maximum external quantum efficiencies at doping ratios of 10wt%, 20wt%, and 25wt% are 3.2%, 5.6%, and 5.5%, respectively. Figure 9 , Figure 10 As shown.

[0061] Example 10

[0062] A blend of compounds TTT-1-Me and PO-1-T2T from Example 1 at a mass ratio of 85:15 was used as the main material for BN5. Its photoluminescence spectrum was measured. Figure 11 It can be seen that the photoluminescence spectrum did not change with the increase of BN5 doping concentration, and the emission spectrum showed the intrinsic peak of BN5, all around 508 nm. This indicates that the excitocomplex system formed by BN5 and the two compounds has good energy transfer.

[0063] Example 11

[0064] The performance of an electroluminescent device was investigated using a blend of compound TTT-1-Me and PO-T2T in an 85:15 mass ratio as the host material for BN5. The device structure was ITO / PEDOT:PSS (40nm) / TTT-1-Me:PO-T2T (85:15):BN5 (1wt% / 3wt% / 5wt%) (40nm) / TmPyPB (55nm) / LiF (1nm) / Al (100nm). Figure 12It can be seen that the electroluminescence spectrum is similar to the photoluminescence spectrum, with both peaks being intrinsic peaks of BN5. Furthermore, as the doping concentration of BN5 increases, the peak values ​​are clearly around 514 nm. Figure 13 It can be seen that when the system with TTT-1-Me as the excitocomplex donor is used as the host, and the BN5 doping ratio is 3wt%, the maximum EQE is 20.0%. Device roll-off is achieved through improvements in brightness and external quantum efficiency. Figure 13 We can know that at 1000 cd / cm 2 The brightness rolls off to 6.1% of its original value, even at 2000 cd / cm². 2 The brightness only rolled off by 13%. Meanwhile, its start-up voltage is 3.4V and its maximum brightness is 7195 cd / cm². 2 ( Figure 14 ).

[0065] Example 12

[0066] To verify the stability of the device, the present invention prepared a thin film by mixing compound TTT-1-Me and PO-T2T at a mass ratio of 85:15 and placed it in a nitrogen atmosphere for 0 h, 24 h, and 48 h, and tested its morphological changes by atomic force microscopy. Figure 15 It can be seen that the roughness of the film after 24 hours and 48 hours of storage is not significantly different, with the root mean square roughness being around 0.8 nm. This indicates that the excimer complex has good stability.

Claims

1. The application of a class of excitopolymer donor materials based on tris(triazol)triazine, characterized in that, The application of a blend of the excimer complex TTT-1-Me, ​​based on tris(triazol)triazine, as a donor material and PO-T2T as an acceptor material, as a light-emitting layer in the fabrication of electroluminescent diodes; or the application of a blend of the excimer complex donor material TTT-1-Me and PO-T2T as a host material for the light-emitting guest BN5 in the fabrication of electroluminescent diodes; wherein the excimer complex donor material is an excimer complex donor material constructed with tris(triazol)triazine as an electron acceptor and an acridine derivative as an electron donor, and its molecular structure is shown below: 。 2. The application of the excitopolymer donor material based on tris(triazol)triazine as described in claim 1, characterized in that, When used as a light-emitting layer, the mass ratio of the tri(triazol)triazine-based excitopolymer donor material TTT-1-Me to PO-T2T is 83:17-89:

11.

3. The application of the excitopolymer donor material based on tris(triazol)triazine as described in claim 1, characterized in that, When the blend is used as the main material of BN5, the mass ratio of the excitocomplex donor material TTT-1-Me to PO-T2T is 85:

15.

4. The application of the excitopolymer donor material based on tris(triazol)triazine as described in claim 1, characterized in that, Electroluminescent organic light-emitting diodes are fabricated using solution processing methods.

Images