Organic electroluminescent materials and devices

Cyclometallated iridium complexes having triphenylene or aza triphenylene and bulky alkyl substitution that can be used as emitters in OLEDs to improve the external quantum efficiency (EQE) and lifetime of OLEDs are disclosed.

FIELD

The present invention relates to compounds for use as emitters, and devices, such as organic light emitting diodes, including the same.

BACKGROUND

SUMMARY

The present disclosure is directed to cyclometallated iridium complexes having triphenylene or aza triphenylene and bulky alkyl substitution that can be used as emitters in OLEDs to improve the external quantum efficiency (EQE) and lifetime of OLEDs.

A novel compound of Formula I

is disclosed. In Formula I, n=0, 1, or 2; Z1to Z16are each independently C or N; any of Z13to Z16is C when it forms a bond with Ir, or when it forms a bond with the ring having R1; any chelate ring comprising Ir is a 5-membered ring; R1to R6each independently represents mono to the maximum allowable substitution, or no substitution; each R1to R6is independently hydrogen or a substituent selected from the group consisting of the general substituents defined above; any two substituents may be joined or fused together to form a ring; and at least one of R1and R2is an alkyl or cycloalkyl group comprising five or more C atoms.

An OLED comprising the compound of the present disclosure in an organic layer therein is also disclosed.

A consumer product comprising the OLED is also disclosed.

DETAILED DESCRIPTION

The term “ester” refers to a substituted oxycarbonyl (—O—C(O)—Rsor —C(O)—O—Rs) radical.

The term “ether” refers to an —ORsradical.

The term “sulfinyl” refers to a —S(O)—Rsradical.

The term “sulfonyl” refers to a —SO2—Rsradical.

The term “phosphino” refers to a —P(Rs)3radical, wherein each Rscan be same or different.

The term “silyl” refers to a —Si(Rs)3radical, wherein each Rscan be same or different.

The term “alkenyl” refers to and includes both straight and branched chain alkene radicals. Alkenyl groups are essentially alkyl groups that include at least one carbon-carbon double bond in the alkyl chain. Cycloalkenyl groups are essentially cycloalkyl groups that include at least one carbon-carbon double bond in the cycloalkyl ring. The term “heteroalkenyl” as used herein refers to an alkenyl radical having at least one carbon atom replaced by a heteroatom. Optionally the at least one heteroatom is selected from O, S, N, P, B, Si, and Se, preferably, O, S, or N. Preferred alkenyl, cycloalkenyl, or heteroalkenyl groups are those containing two to fifteen carbon atoms. Additionally, the alkenyl, cycloalkenyl, or heteroalkenyl group is optionally substituted.

The term “alkynyl” refers to and includes both straight and branched chain alkyne radicals. Preferred alkynyl groups are those containing two to fifteen carbon atoms. Additionally, the alkynyl group is optionally substituted.

The terms “aralkyl” or “arylalkyl” are used interchangeably and refer to an alkyl group that is substituted with an aryl group. Additionally, the aralkyl group is optionally substituted.

The term “heterocyclic group” refers to and includes aromatic and non-aromatic cyclic radicals containing at least one heteroatom. Optionally the at least one heteroatom is selected from O, S, N, P, B, Si, and Se, preferably, O, S, or N. Hetero-aromatic cyclic radicals may be used interchangeably with heteroaryl. Preferred hetero-non-aromatic cyclic groups are those containing 3 to 7 ring atoms which includes at least one hetero atom, and includes cyclic amines such as morpholino, piperidino, pyrrolidino, and the like, and cyclic ethers/thio-ethers, such as tetrahydrofuran, tetrahydropyran, tetrahydrothiophene, and the like. Additionally, the heterocyclic group may be optionally substituted.

In some instances, the preferred general substituents are selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, alkoxy, aryloxy, amino, silyl, aryl, heteroaryl, sulfanyl, and combinations thereof.

In yet other instances, the more preferred general substituents are selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, aryl, heteroaryl, and combinations thereof.

The terms “substituted” and “substitution” refer to a substituent other than H that is bonded to the relevant position, e.g., a carbon or nitrogen. For example, when R1represents mono-substitution, then one R1must be other than H (i.e., a substitution) Similarly, when R1represents di-substitution, then two of R1must be other than H. Similarly, when R1represents no substitution, R1, for example, can be a hydrogen for available valencies of ring atoms, as in carbon atoms for benzene and the nitrogen atom in pyrrole, or simply represents nothing for ring atoms with fully filled valencies, e.g., the nitrogen atom in pyridine. The maximum number of substitutions possible in a ring structure will depend on the total number of available valencies in the ring atoms.

In some instance, a pair of adjacent substituents can be optionally joined or fused into a ring. The preferred ring is a five, six, or seven-membered carbocyclic or heterocyclic ring, includes both instances where the portion of the ring formed by the pair of substituents is saturated and where the portion of the ring formed by the pair of substituents is unsaturated. As used herein, “adjacent” means that the two substituents involved can be on the same ring next to each other, or on two neighboring rings having the two closest available substitutable positions, such as 2,2′ positions in a biphenyl, or 1,8 position in a naphthalene, as long as they can form a stable fused ring system.

The present disclosure discloses cyclometallated iridium complexes with (aza)triphenylene and bulky alkyl (no less than four carbon atoms) substitution and their use as emitters in organic electroluminescence devices (OLEDs). The unique fused ring of (aza)triphenylene improves the stability of the complexes and thus extending the operational lifetime of the OLEDs, and the bulky substitution improves the EQE of the emitter complexes by promoting the emitter complexes to align in the emissive layer of the OLEDs.

According to an embodiment of the present disclosure, a compound of (LA)3-nIr(LB)nof Formula I

is disclosed. In Formula I, n=0, 1, or 2; Z1to Z16are each independently C or N; any of Z13to Z16is C when it forms a bond with Ir, or when it forms a bond with the ring having R1; any chelate ring comprising Ir is a 5-membered ring; R1to R6each independently represents mono to the maximum allowable substitution, or no substitution; each R1to R6is independently hydrogen or a substituent selected from the group consisting of the general substituents defined above; any two substituents may be joined or fused together to form a ring; and at least one of R1and R2is an alkyl or cycloalkyl group comprising five or more C atoms.

In some embodiments of the compound of Formula I, each R1to R6is independently hydrogen, or a substituent selected from the group consisting of the preferred general substituents defined above.

In some embodiments of the compound, at least one R1or R2comprises a cyclic or polycyclic alkyl. In some embodiments, at least one R1or R2is a methyl group. In some embodiments, at least one R1or R2is fully or partially deuterated.

In some embodiments of the compound, at least one of R1and R2is an alkyl or cycloalkyl group comprising six or more C atoms. In some embodiments of the compound, at least one of R1and R2is an alkyl or cycloalkyl group comprising seven or more C atoms. In some embodiments of the compound, at least one of R1and R2is an alkyl or cycloalkyl group comprising eight or more C atoms.

In some embodiments of the compound, at least one of R1and at least one of R2are an alkyl or cycloalkyl group comprising five or more C atoms. In some embodiments of the compound, at least one of R1and at least one of R2are an alkyl or cycloalkyl group comprising six or more C atoms. In some embodiments of the compound, at least one of R1and at least one of R2are an alkyl or cycloalkyl group comprising seven or more C atoms. In some embodiments of the compound, at least one of R1and at least one of R2are an alkyl or cycloalkyl group comprising eight or more C atoms.

In some embodiments of the compound, n=0. In some embodiments, n=1. In some embodiments, n=2.

In some embodiments of the compound, Z1to Z16are each C. In some embodiments, at least one of Z1to Z16is N.

In some embodiments, the compound is selected from the group consisting of compounds II-1 to II-1488 that are based on

compounds III-1 to III-1488 that are based on

compounds IV-1 to IV-1488 that are based on

compounds V-1 to V-1488 that are based on

compounds VI-1 to VI-1488 that are based on

compounds VII-1 VII-1488 that are based on

compounds VIII-1 to VIII-1488 that are based on

compounds IX-1 to IX-1488 that are based on

compounds X-1 to X-1488 that are based on

compounds XI-1 to XI-1488 that are based on

compounds XII-1 to XII-1488 that are based on

compounds XIII-1 to XIII-1488 that are based on

compounds XIV-1 to XIV-1488 that are based on

compounds XV-1 to XV-1488 that are based on

compounds XVI-1 to XVI-1488 that are based on

compounds XVII-1 to XVII-1488 that are based on

compounds XVIII-1 to XVIII-1488 that are based on

compounds XIX-1 to XIX-1488 that are based on

where for each of the compounds II-1 to XIX-1488, R1a, R1b, R2a, and R2bin each compound are defined as provided in the following table in which m is II to XIX:

In some embodiments, the compound is defined in the above table corresponding to those substituents selected from the group consisting of:

In some embodiments, LBis selected from the group consisting of:

In some embodiments, LBis selected from the group consisting of:

In some embodiments, LBis selected from the group consisting of:

An organic light emitting device (OLED) incorporating the novel compound of Formula I is also disclosed. The OLED comprises: an anode; a cathode; and an organic layer, disposed between the anode and the cathode. The organic layer comprising a compound of Formula I

where all of the variables are as defined above.

In some embodiments of the OLED, the compound is a sensitizer and the OLED further comprises an acceptor; and where the acceptor is selected from the group consisting of fluorescent emitter, delayed fluorescence emitter, and combination thereof.

A consumer product comprising the OLED incorporating the novel compound of Formula I is also disclosed. All of the variables in Formula I is as defined above.

In some embodiments, the compound can be an emissive dopant. In some embodiments, the compound can produce emissions via phosphorescence, fluorescence, thermally activated delayed fluorescence, i.e., TADF (also referred to as E-type delayed fluorescence; see, e.g., U.S. application Ser. No. 15/700,352, published on Mar. 14, 2019 as U.S. patent application publication No. 2019/0081248, which is hereby incorporated by reference in its entirety), triplet-triplet annihilation, or combinations of these processes. In some embodiments, the emissive dopant can be a racemic mixture, or can be enriched in one enantiomer. In some embodiments, the compound can be homoleptic (each ligand is the same). In some embodiments, the compound can be heteroleptic (at least one ligand is different from others).

When there are more than one ligand coordinated to a metal, the ligands can all be the same in some embodiments. In some other embodiments, at least one ligand is different from the other ligand(s). In some embodiments, every ligand can be different from each other. This is also true in embodiments where a ligand being coordinated to a metal can be linked with other ligands being coordinated to that metal to form a tridentate, tetradentate, pentadentate, or hexadentate ligands. Thus, where the coordinating ligands are being linked together, all of the ligands can be the same in some embodiments, and at least one of the ligands being linked can be different from the other ligand(s) in some other embodiments.

In some embodiments, the compound can be used as a phosphorescent sensitizer in an OLED where one or multiple layers in the OLED contains an acceptor in the form of one or more fluorescent and/or delayed fluorescence emitters. In some embodiments, the compound can be used as one component of an exciplex to be used as a sensitizer. As a phosphorescent sensitizer, the compound must be capable of energy transfer to the acceptor and the acceptor will emit the energy or further transfer energy to a final emitter. The acceptor concentrations can range from 0.001% to 100%. The acceptor could be in either the same layer as the phosphorescent sensitizer or in one or more different layers. In some embodiments, the acceptor is a TADF emitter. In some embodiments, the acceptor is a fluorescent emitter. In some embodiments, the emission can arise from any or all of the sensitizer, acceptor, and final emitter.

In some embodiments, the compound of the present disclosure is neutrally charged.

According to another aspect, a formulation comprising the compound described herein is also disclosed.

The organic layer can also include a host. In some embodiments, two or more hosts are preferred. In some embodiments, the hosts used maybe a) bipolar, b) electron transporting, c) hole transporting or d) wide band gap materials that play little role in charge transport. In some embodiments, the host can include a metal complex. The host can be a triphenylene containing benzo-fused thiophene or benzo-fused furan. Any substituent in the host can be an unfused substituent independently selected from the group consisting of CnH2n+1, OC2n+1, OAr1, N(CnH2n+1)2, N(Ar1)(Ar2), CH═CH—CnH2n+1, C≡C—CnH2n+1, Ar1, Ar1—Ar2, and CnH2n+—Ar1, or the host has no substitutions. In the preceding substituents n can range from 1 to 10; and A1and Ar2can be independently selected from the group consisting of benzene, biphenyl, naphthalene, triphenylene, carbazole, and heteroaromatic analogs thereof. The host can be an inorganic compound. For example a Zn containing inorganic material e.g. ZnS.

The host can be a compound comprising at least one chemical group selected from the group consisting of triphenylene, carbazole, dibenzothiophene, dibenzofuran, dibenzoselenophene, azatriphenylene, azacarbazole, aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene. The host can include a metal complex. The host can be, but is not limited to, a specific compound selected from the Host Group consisting of:

and combinations thereof.Additional information on possible hosts is provided below.

An emissive region in an OLED is also disclosed. The emissive region comprises a compound of Formula I

where n=0, 1, or 2; Z1to Z16are each independently C or N; any of Z13to Z16is C when it forms a bond with Ir, or when it forms a bond with the ring having R1; any chelate ring comprising Ir is a 5-membered ring; R1to R6each independently represents mono to the maximum allowable substitution, or no substitution; each R1to R6is independently hydrogen or a substituent selected from the group consisting of the general substituents defined above; any two substituents may be joined or fused together to form a ring; and at least one of R1and R2is an alkyl or cycloalkyl group comprising five or more C atoms.

In some embodiments of the emissive region, the compound is an emissive dopant or a non-emissive dopant.

In some embodiments of the emissive region, the emissive region further comprises a host, wherein the host contains at least one group selected from the group consisting of metal complex, triphenylene, carbazole, dibenzothiophene, dibenzofuran, dibenzoselenophene, aza-tripheny lene, aza-carbazole, aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene.

In some embodiments, the emissive region further comprises a host, wherein the host is selected from the Host Group defined above.

In yet another aspect of the present disclosure, a formulation that comprises the novel compound disclosed herein is described. The formulation can include one or more components selected from the group consisting of a solvent, a host, a hole injection material, hole transport material, electron blocking material, hole blocking material, and an electron transport material, disclosed herein.

The present disclosure encompasses any chemical structure comprising the novel compound of the present disclosure, or a monovalent or polyvalent variant thereof. In other words, the inventive compound, or a monovalent or polyvalent variant thereof, can be a part of a larger chemical structure. Such chemical structure can be selected from the group consisting of a monomer, a polymer, a macromolecule, and a supramolecule (also known as supermolecule). As used herein, a “monovalent variant of a compound” refers to a moiety that is identical to the compound except that one hydrogen has been removed and replaced with a bond to the rest of the chemical structure. As used herein, a “polyvalent variant of a compound” refers to a moiety that is identical to the compound except that more than one hydrogen has been removed and replaced with a bond or bonds to the rest of the chemical structure. In the instance of a supramolecule, the inventive compound is can also be incorporated into the supramolecule complex without covalent bonds.

Combination With Other Materials

In one aspect, the metal complexes are:

wherein k is an integer from 1 to 20; L101is an another ligand, k′ is an integer from 1 to 3.
ETL:

Charge Generation Layer (CGL)

EXPERIMENTAL

Synthesis of Materials

4,4,5,5-tetramethyl-2-(triphenylen-2-yl)-1,3,2-dioxaborolane (5.09 g, 14.37 mmol), 2-bromo-4,5-bis(methyl-d3)pyridine (3.04 g, 15.80 mmol), potassium phosphate tribasic monohydrate (6.62 g, 28.7 mmol), dicyclohexyl(2′,6″-dimethoxy-[1,1′-biphenyl]-2-yl)phosphane (0.354 g, 0.862 mmol), toluene (75 ml), and water (25.00 ml) were added to a 300 mL 3-neck flask. Nitrogen was bubbled into the mixture, and then Pd2(dba)3(0.395 g, 0.431 mmol) was added. The reaction mixture was heated to reflux for 16 hours under nitrogen. After the reaction mixture was cooled to room temperature, it was diluted with ethyl acetate and water, and filtered off an insoluble solid. The solvent was removed and the residue was purified by column chromatography on silica gel eluted with 0 to 5% ethyl acetate/DCM to obtain 1.1 g of a yellow solid (23%).

A 3 L 4-neck flask was equipped with a mechanical stirrer, an addition funnel, and a thermocouple, and was charged with 2-chloro-4-iodo-5-methylpyridine (30.0 g, 118.0 mmol, 1.0 equiv) in anhydrous tetrahydrofuran (237 mL). The solution was sparged with nitrogen for 15 minutes then cooled to 0° C. Then, 2-dicyclohexyl phosphino-2′,6′-dimethoxybi-phenyl (SPhos) (2.92 g, 7.1 mmol, 0.06 equiv) and palladium(II) acetate (0.8 g, 3.55 mmol, 0.03 equiv) were added. A 0.61 M solution of cyclohexylzinc(II) bromide in tetrahydrofuran (213.0 mL, 130 mmol, 1.1 equiv) was added drop-wise, maintaining the temperature below 5° C. When addition was completed, the reaction mixture was allowed to warm to room temperature and stirred overnight. Saturated aqueous sodium bicarbonate (200 mL) and ethyl acetate (200 mL) were added. The layers were separated and the aqueous layer was extracted with ethyl acetate (200 mL). The combined organic layers were dried over sodium sulfate, filtered and concentrated under reduced pressure. The crude product was chromatographed on silica gel (500 g), eluting with a gradient of 0-30% ethyl acetate in heptanes (1.0 L of solvent mixture for each 10% increase in polarity), to give 2-chloro-4-cyclohexyl-5-methylpyridine (18.0 g, 73% yield) as a yellow syrup.

A 50 mL, 2-neck round bottom flask, equipped with a condenser, thermocouple and stir bar, was charged with Ir precursor (1.6 g, 1.87 mmol, 1.0 equiv), 4-(cyclohexyl-1-d)-5-(methyl-d3)-2-(triphenylen-2-yl)pyridine (1.4 g, 3.45 mmol, 2.1 equiv), 2-ethoxyethanol (15.0 mL) and N,N-dimethylformamide (15.0 mL). The flask was wrapped with foil to block light and the mixture heated at 85° C. for 7 days, After the reaction mixture was cooled to room temperature, it was filtered and the solid washed with methanol (50 mL). The solid was dissolved in dichloromethane and chromatographed on a short pad of basic alumina (30 g) layered with silica gel (˜30 g), eluting with dichloromethane (200 mL), to give bis[5-(2,2-dimethylpropyl-1,1-d2)-2-(phenyl-2′-yl)ppyridin-1-yl]-[4-(cyclohexyl-1-d)-5-(methyl-d3)-2-((tri-phenylen-2-yl)-3′-yl)pyridin-1-yl]iridium(III) (1.0 g, 51% yield, 99.5% UHPLC purity) as a yellow solid.

Device Examples

All devices were fabricated by high vacuum (<10−7Torr) thermal evaporation. The anode electrode was 80 nm of indium tin oxide (ITO). The cathode electrode consisted of 1 nm of LiQ followed by 100 nm of Al. All devices were encapsulated with a glass lid sealed with an epoxy resin in a nitrogen glove box (<1 ppm of H2O and O2) immediately after fabrication, and a moisture getter was incorporated inside the package.

The organic stack of the device examples consisted of sequentially, from the ITO surface, 10 nm of LG-101 (available from LG Chem. Inc.) as the hole injection layer (HIL), 40 nm of PPh-TPD as the hole transporting layer (HTL), 5 nm of electron blocking layer comprised of (H-3), 40 nm of emissive layer (EML) comprised of premixed host doped with 12 wt % of the invention compound or comparative compound as the emitter, 35 nm of aDBT-ADN with 35 wt % LiQ as the electron-transport layer (ETL). The premixed host comprises of a mixture of HM1 and HM2 in a weight ratio of 7:3 and was deposited from a single evaporation source. The comparative example with Compound A was fabricated similarly to the Device Examples. The chemical structures of the compounds used are shown below:

Provided in Table 1 below is a summary of the device data including emission color, voltage, luminous efficiency (LE), external quantum efficiency (EQE) and power efficiency (PE), recorded at 1000 nits for device examples.

The data in Table 1 show that the device using the inventive compound as the emitter achieved the same color emission but higher efficiency and lower voltage in comparison with the comparative example. The only difference between the inventive example Compound II-1325 and the comparative example compound was the substituent at the R1aposition of Formula II, which is the key to achieving higher device efficiency likely due to the decreased aggregation and enhanced alignment of emitter in the device.