ORGANIC ELECTROLUMINESCENT MATERIALS AND DEVICES

Metal complexes with cyclic ligands having Formula (I),

are disclosed. Ligands with cyclic structure are believed to be beneficial to the rigidity and stability of the metal complexes, which is desirable for improving OLED device performance.

FIELD

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

BACKGROUND

SUMMARY

A compound comprising a ligand LA of Formula (I),

is disclosed. In Formula (I), G1 has at least one 5-membered or 6-membered carbocyclic or heterocyclic ring; G2 has at least two 5-membered or 6-membered carbocyclic or heterocyclic ring fused together; G1 and G2 are linked by a chemical group L having at least three backbone atoms; L is not fused with G1 or G2; LA is coordinated to a metal M; LA is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand; and M is optionally coordinated to other ligands.

According to another aspect, an OLED comprising an anode, a cathode, and an organic layer, disposed between the anode and the cathode, is disclosed. The organic layer comprises a compound comprising a ligand LA of Formula (I),

wherein G1 has at least one 5-membered or 6-membered carbocyclic or heterocyclic ring; G2 has at least two 5-membered or 6-membered carbocyclic or heterocyclic ring fused together; G1 and G2 are linked by a chemical group L having at least three backbone atoms; L is not fused with G1 or G2; wherein LA is coordinated to a metal M; wherein LA is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand; and wherein M is optionally coordinated to other ligands.

A consumer product is also disclosed which comprises an OLED comprising an anode, a cathode, and an organic layer, disposed between the anode and the cathode. The organic layer comprises a compound comprising a ligand LA of Formula (I),

wherein G1 has at least one 5-membered or 6-membered carbocyclic or heterocyclic ring; G2 has at least two 5-membered or 6-membered carbocyclic or heterocyclic ring fused together; G1 and G2 are linked by a chemical group L having at least three backbone atoms; wherein L is not fused with G1 or G2; the ligand LA is coordinated to a metal M; LA is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand; and wherein M is optionally coordinated to other ligands.

Metal complexes having the disclosed ligands with cyclic structure are believed to be beneficial to the rigidity and stability of the metal complexes, which is desirable for improving OLED device performance.

DETAILED DESCRIPTION

FIG. 1 shows an organic light emitting device 100. The figures are not necessarily drawn to scale. Device 100 may include a substrate 110, an anode 115, a hole injection layer 120, a hole transport layer 125, an electron blocking layer 130, an emissive layer 135, a hole blocking layer 140, an electron transport layer 145, an electron injection layer 150, a protective layer 155, a cathode 160, and a barrier layer 170. Cathode 160 is a compound cathode having a first conductive layer 162 and a second conductive layer 164. Device 100 may be fabricated by depositing the layers described, in order. The properties and functions of these various layers, as well as example materials, are described in more detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which are incorporated by reference.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210, a cathode 215, an emissive layer 220, a hole transport layer 225, and an anode 230. Device 200 may be fabricated by depositing the layers described, in order. Because the most common OLED configuration has a cathode disposed over the anode, and device 200 has cathode 215 disposed under anode 230, device 200 may be referred to as an “inverted” OLED. Materials similar to those described with respect to device 100 may be used in the corresponding layers of device 200. FIG. 2 provides one example of how some layers may be omitted from the structure of device 100.

The term “halo,” “halogen,” or “halide” as used herein includes fluorine, chlorine, bromine, and iodine.

The term “cycloalkyl” as used herein contemplates cyclic alkyl radicals. Preferred cycloalkyl groups are those containing 3 to 10 ring carbon atoms and includes cyclopropyl, cyclopentyl, cyclohexyl, adamantyl, and the like. Additionally, the cycloalkyl group may be optionally substituted.

The term “alkenyl” as used herein contemplates both straight and branched chain alkene radicals. Preferred alkenyl groups are those containing two to fifteen carbon atoms. Additionally, the alkenyl group may be optionally substituted.

The term “alkynyl” as used herein contemplates both straight and branched chain alkyne radicals. Preferred alkynyl groups are those containing two to fifteen carbon atoms. Additionally, the alkynyl group may be optionally substituted.

The terms “aralkyl” or “arylalkyl” as used herein are used interchangeably and contemplate an alkyl group that has as a substituent an aromatic group. Additionally, the aralkyl group may be optionally substituted.

The term “heterocyclic group” as used herein contemplates aromatic and non-aromatic cyclic radicals. Hetero-aromatic cyclic radicals also means 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, such as tetrahydrofuran, tetrahydropyran, and the like. Additionally, the heterocyclic group may be optionally substituted.

The term “aryl” or “aromatic group” as used herein contemplates single-ring groups and polycyclic ring systems. The polycyclic rings may have two or more rings in which two carbons are common to two adjoining rings (the rings are “fused”) wherein at least one of the rings is aromatic, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl, heterocycles, and/or heteroaryls. Preferred aryl groups are those containing six to thirty carbon atoms, preferably six to twenty carbon atoms, more preferably six to twelve carbon atoms. Especially preferred is an aryl group having six carbons, ten carbons or twelve carbons. Suitable aryl groups include phenyl, biphenyl, triphenyl, triphenylene, tetraphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene, preferably phenyl, biphenyl, triphenyl, triphenylene, fluorene, and naphthalene. Additionally, the aryl group may be optionally substituted.

As used herein, “substituted” indicates that a substituent other than H is bonded to the relevant position, such as carbon. Thus, for example, where R1 is mono-substituted, then one R1 must be other than H. Similarly, where R1 is di-substituted, then two of R1 must be other than H. Similarly, where R1 is unsubstituted, R1 is hydrogen for all available positions.

A compound comprising a ligand LA of Formula (I),

is disclosed. In Formula (I), G1 has at least one 5-membered or 6-membered carbocyclic or heterocyclic ring; G2 has at least two 5-membered or 6-membered carbocyclic or heterocyclic ring fused together; G1 and G2 are linked by a chemical group L having at least three backbone atoms; L is not fused with G1 or G2; LA is coordinated to a metal M; LA is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand; and M is optionally coordinated to other ligands.

In some embodiments of the compound, M is selected from the group consisting of Ir, Rh, Re, Ru, Os, Pt, Au, and Cu. In some embodiments, M is Ir or Pt. In some embodiments, L has at least four backbone atoms. In some embodiments, L has at least five backbone atoms. In some embodiments, L is selected from the group consisting of alkyl, cycloalkyl, aryl, heteroaryl, ether, silyl, amine, and combinations thereof.

In some embodiments of the compound, G1 has one 5-membered or 6-membered carbocyclic or heterocyclic ring, and G2 has three 5-membered or 6-membered carbocyclic or heterocyclic ring fused together. In some embodiments of the compound, G1 is selected from the group consisting of phenyl, pyridine, pyrimidine, triazine, imidazole, pyrazole, oxazole, thiazole, imidazole derived carbene, and substituted variants thereof. In some embodiments of the compound, G2 is selected from the group consisting of naphthalene, quinoline, isoquinoline, benzimidazole, benzothiazole, quinazoline, carbazole, dibenzothiophene, dibenzofuran, dibenzoselenophene, triphenylene, aza variants thereof, and substituted variants thereof.

In some embodiments of the compound, the ligand LA is selected from the group consisting of:

In some embodiments of the compound, wherein the ligand LA is selected from the group consisting of:

LA1 to LA3 represented by

wherein in LA2, X = S; and

LA4 to LA6 represented by

wherein in LA5, X = S; and

LA7 to LA9 represented by

wherein in LA8, X = S; and

LA10 to LA12 represented by

wherein in LA11, X = S; and

LA13 to LA15 represented by

wherein in LA14, X = S; and

LA16 to LA18 represented by

wherein in LA17, X = S; and

LA19 to LA21 represented by

wherein in LA20, X = S; and

LA22 to LA24 represented by

wherein in LA23, X = S; and

LA25 to LA27 represented by

LA28 to LA30 represented by

wherein in LA29, X = S; and

LA31 to LA33 represented by

wherein in LA32, X = S; and

LA34 to LA36 represented by

wherein in LA35, X = S; and

LA37 to LA39 represented by

wherein in LA38, X = S; and

LA40 to LA42 represented by

wherein in LA41, X = S; and

LA43 to LA45 represented by

wherein in LA44, X = S; and

LA46 to LA48 represented by

wherein in LA47, X = S; and

LA49 to LA51 represented by

wherein in LA50, X = S; and

LA52 to LA54 represented by

wherein in LA53, X = S; and

LA55 to LA57 represented by

wherein in LA56, X = S; and

LA58 to LA60 represented by

wherein in LA59, X = S; and

LA61 to LA63 represented by

wherein in LA62, X = S; and

LA64 to LA66 represented by

wherein in LA65, X = S; and

LA67 to LA69 represented by

wherein in LA68, X = S; and

LA70 to LA72 represented by

wherein in LA71, X = S; and

LA73 to LA75 represented by

wherein in LA74, X = S; and

LA76 to LA78 represented by

wherein in LA77, X = S; and

LA79 to LA81 represented by

wherein in LA80, X = S; and

LA82 to LA84 represented by

wherein in LA83, X = S; and

LA85 to LA87 represented by

wherein in LA86, X = S; and

LA88 to LA90 represented by

wherein in LA89, X = S; and

LA91 to LA93 represented by

wherein in LA92, X = S; and

LA94 to LA96 represented by

wherein in LA95, X = S; and

LA97 to LA99 represented by

wherein in LA98, X = S; and

LA100 to LA102 represented by

wherein in LA101, X = S; and

LA103 to LA105 represented by

wherein in LA104, X = S; and

LA106 to LA108 represented by

wherein in LA107, X = S; and

LA109 to LA111 represented by

wherein in LA110, X = S; and

LA112 to LA114 represented by

wherein in LA113, X = S; and

LA115 to LA117 represented by

wherein in LA116, X = S; and

LA118 to LA120 represented by

wherein in LA119, X = S; and

LA121 to LA123 represented by

wherein in LA122, X = S; and

LA124 to LA126 represented by

wherein in LA125, X = S; and

LA127 to LA129 represented by

wherein in LA128, X = S; and

LA130 to LA131 represented by

wherein in LA131, X = S; and

LA133 to LA135 represented by

wherein in LA134, X = S; and

LA136 to LA138 represented by

wherein in LA137, X = S; and

LA139 to LA141 represented by

wherein in LA140, X = S; and

LA142 to LA144 represented by

wherein in LA143, X = S; and

LA145 to LA147 represented by

wherein in LA146, X = S; and

LA148 to LA150 represented by

wherein in LA149, X = S; and

LA151 to LA153 represented by

wherein in LA152, X = S; and

LA154 to LA156 represented by

wherein in LA155, X = S; and

LA157 to LA159 represented by

wherein in LA158, X = S; and

LA160 to LA162 represented by

wherein in LA161, X = S; and

wherein in LA164, X = S; and

LA166 to LA168 represented by

wherein in LA167, X = S; and

LA169 to LA171 represented by

wherein in LA170, X = S; and

LA172 to LA174 represented by

wherein in LA173, X = S; and

LA175 to LA177 represented by

wherein in LA176, X = S; and

LA178 to LA180 represented by

wherein in LA179, X = S; and

LA181 to LA183 represented by

wherein in LA182, X = S; and

LA184 to LA186 represented by

wherein in LA185, X = S; and

LA187 to LA189 represented by

wherein in LA188, X = S; and

LA190 to LA192 represented by

wherein in LA191, X = S; and

LA193 to LA195 represented by

wherein in LA194, X = S; and

LA196 to LA198 represented by

wherein in LA197, X = S; and

LA199 to LA201 represented by

wherein in LA200, X = S; and

LA202 to LA204 represented by

wherein in LA203, X = S; and

LA205 to LA207 represented by

wherein in LA206, X = S; and

LA208 to LA210 represented by

wherein in LA209, X = S; and

LA211 to LA213 represented by

wherein in LA212, X = S; and

LA214 to LA216 represented by

wherein in LA215, X = S; and

LA217 to LA219 represented by

wherein in LA218, X = S; and

LA220 to LA222 represented by

wherein in LA221, X = S; and

LA223 to LA225 represented by

wherein in LA224, X = S; and

LA226 to LA228 represented by

wherein in LA227, X = S; and

LA229 to LA231 represented by

wherein in LA230, X = S; and

LA232 to LA234 represented by

wherein in LA233, X = S; and

LA235 to LA237 represented by

wherein in LA236, X = S; and

LA238 to LA240 represented by

wherein in LA239, X = S; and

LA271, and

In some embodiments where LA is one of LA1 to LA272 defined above, the compound has a formula (LA)nIr(LB)3-n, wherein LB is a bidentate ligand, and n is 1, 2, or 3. In some embodiments of the compound, LB has the following formula

and is selected from the group consisting of LB to LB275 as defined below:

1.
H
H
H
H
H

2.
CH3
H
H
H
H

3.
H
CH3
H
H
H

4.
H
H
CH3
H
H

5.
H
H
H
CH3
H

8.
H
CH3
CH
H
H

H
H
H
H

CH3
H
H
H

H
CH3
H
H

H
H
CH3
H

H
H
H

H
H
H

CH3
H
H

H
CH3
H

CH3
H
H

H
CH3
H

32.
H
H

35.
H
H

H
H
H
H

CH3
H
H
H

H
CH3
H
H

H
H
CH3
H

H
H
H

H
H
H

CH3
H
H

H
CH3
H

CH3
H
H

H
CH3
H

56.
H
H

59.
H
H

H
H
H
H

CH3
H
H
H

H
CH3
H
H

H
H
CH3
H

H
H
H

H
H
H

CH3
H
H

H
CH3
H

CH3
H
H

H
CH3
H

80.
H
H

83.
H
H

H
H
H
H

CH3
H
H
H

H
CH3
H
H

H
H
CH3
H

H
H
H

H
H
H

CH3
H
H

H
CH3
H

CH3
H
H

H
CH3
H

104.
H
H

107.
H
H

H
H
H
H

CH3
H
H
H

H
CH3
H
H

H
H
CH3
H

H
H
H

H
H
H

CH3
H
H

H
CH3
H

CH3
H
H

H
CH3
H

128.
H
H

131.
H
H

H
H
H
H

CH3
H
H
H

H
CH3
H
H

H
H
CH3
H

H
H
H

H
H
H

CH3
H
H

H
CH3
H

CH3
H
H

H
CH3
H

152.
H
H

155.
H
H

178.
CD3
H
H
H
H

179.
H
CD3
H
H
H

180.
H
H
CD3
H
H

181.
H
H
H
CD3
H

192.
H
H
H
H
CD3

H
H
H
CD3

H
H
CD3

H
H
CD3

223.
H
H

226.
H
H

H
H
H
CD3

H
H
CD3

H
H
CD3

247.
H
H

250.
H
H

H
H
H
CD3

H
H
CH
CD

H
H
CD3

H
H
CD3

CH
H
CD3

271.
H
H

274.
H
H

In some embodiments of the compound, the compound has a structure according to the formula Ir(LAk)(LBj)2, wherein the compound is selected from the group consisting of Compound x, wherein x is an integer from 1 to 74800, wherein for each Compound x of formula Ir(LAk)(LBj)2, k is an integer from 1 to 272, andj is an integer from 1 to 275; and x=275k+j−275, wherein LAI through LA272 and LB1 through LB275 are as defined above.

In some embodiments of the compound, the compound has formula (LA)mPt(LC)2-m; wherein LC is a bidentate ligand; and m is 1, or 2.

In some embodiments of the compound having the formula (LA)mPt(LC)2-m, m is 1, and LA is connected to Le to form a tetradentate ligand.

According to another aspect, an OLED comprising an anode, a cathode, and an organic layer, disposed between the anode and the cathode, is disclosed. The organic layer comprises a compound comprising a ligand LA of Formula (I),

wherein G1 has at least one 5-membered or 6-membered carbocyclic or heterocyclic ring; G2 has at least two 5-membered or 6-membered carbocyclic or heterocyclic ring fused together; G1 and G2 are linked by a chemical group L having at least three backbone atoms; L is not fused with G1 or G2; wherein LA is coordinated to a metal M; wherein LA is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand; and wherein M is optionally coordinated to other ligands.

In some embodiments, the organic layer is an emissive layer and the compound is an emissive dopant or a non-emissive dopant.

In some embodiments, the organic layer further comprises a host, wherein host comprises at least one selected from the group consisting of metal complex, triphenylene, carbazole, dibenzothiophene, dibenzofuran, dibenzoselenophene, azatriphenylene, azacarbazole, aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene. In some embodiments, the host is selected from the group consisting of:

and combinations thereof.

A consumer product is also disclosed which comprises an OLED comprising an anode, a cathode, and an organic layer, disposed between the anode and the cathode. The organic layer comprises a compound comprising a ligand LA of Formula (I),

wherein G1 has at least one 5-membered or 6-membered carbocyclic or heterocyclic ring; G has at least two 5-membered or 6-membered carbocyclic or heterocyclic ring fused together; G1 and G2 are linked by a chemical group L having at least three backbone atoms; wherein L is not fused with G1 or G2; the ligand LA is coordinated to a metal M; LA is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand; and wherein M is optionally coordinated to other ligands.

The consumer product can be selected from the group consisting of a flat panel display, a curved display, a computer monitor, a medical monitor, a television, a billboard, a light for interior or exterior illumination and/or signaling, a heads-up display, a fully or partially transparent display, a flexible display, a rollable display, a foldable display, a stretchable display, a laser printer, a telephone, a cell phone, tablet, a phablet, a personal digital assistant (PDA), a wearable device, a laptop computer, a digital camera, a camcorder, a viewfinder, a micro-display that is less than 2 inches diagonal, a 3-D display, a virtual reality or augmented reality display, a vehicle, a video wall comprising multiple displays tiled together, a theater or stadium screen, and a sign.

An emissive region of an OLED is disclosed. The emissive region comprising a compound comprising a ligand LA of Formula (I),

is disclosed. In Formula (I), G1 has at least one 5-membered or 6-membered carbocyclic or heterocyclic ring; G2 has at least two 5-membered or 6-membered carbocyclic or heterocyclic ring fused together; G1 and G2 are linked by a chemical group L having at least three backbone atoms; L is not fused with G1 or G2; LA is coordinated to a metal M; LA is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand; and M is optionally coordinated to other ligands.

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

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

and combinations thereof.

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), triplet-triplet annihilation, or combinations of these processes.

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, OCnH2n+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 Ar1 and Ar2 can 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 group consisting of

and combinations thereof.

Additional information on possible hosts is provided below.

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, and an electron transport layer material, disclosed herein.

Combination with Other Materials

In one aspect, Ar1 to Ar9 is independently selected from the group consisting of:

wherein k is an integer from 1 to 20; X101 to X108 is C (including CH) or N; Z101 is NAr1, O, or S; Ar1 has the same group defined above.

wherein Met is a metal, which can have an atomic weight greater than 40; (Y101-Y102) is a bidentate ligand, Y101 and Y102 are independently selected from C, N, O, P, and S; L101 is an ancillary ligand; k′ is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and k′+k″ is the maximum number of ligands that may be attached to the metal.

wherein Met is a metal; (Y103_y104) is a bidentate ligand, Y103 and Y104 are independently selected from C, N, O, P, and S; L101 is an another ligand; k′ is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and k′+k″ is the maximum number of ligands that may be attached to the metal.

In one aspect, the metal complexes are:

Z101 and Z102 is selected from NR101, O, or S.

wherein k is an integer from 1 to 20; L101 is an another ligand, k′ is an integer from 1 to 3.

Charge Generation Layer (CGL)

EXPERIMENTAL

Synthesis of Materials

An example of the inventive compound Ir(LA1)(LB1)2 can be synthesized by the procedure shown in the following scheme.

The intermediate 4-chloro-2-(6-chlorodibenzo[b,d]furan-4-yl)pyridine, which can be prepared by Suzuki coupling reaction using 2-bromo-4-chloropyridine and 2-(6-chlorodibenzo[b,d]furan-4-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, can then react with but-3-en-1-ylzinc(II) bromide using Negishi coupling reaction conditions to afford 4-(but-3-en-1-yl)-2-(6-(but-3-en-1-yl)dibenzo[b,d]furan-4-yl)pyridine. Subjecting the non-conjugated diene intermediate to intramolecular ring-closing metathesis reaction will result in (Z)-1(2,4)-pyridina-2(4,6)-dibenzo[b,d]furanacyclooctaphan-5-ene. Ligand LA1 can then be obtained by hydrogenation using Pd/C catalyst. The inventive example Ir(LA1)(LB1)2 can be synthesized by mixing Ir timer with LA1 in ethanol under reflux condition.

The present invention discloses novel design of a macrocyclic ligand. The key is that two cyclic rings of a bidentate ligand are further connected by a linker unit (L) to form a macrocyclic ligand, e.g., pyridyl and dibenzofuran moieties of the bidentate ligand in LA1 are further connected by a six-carbon aliphatic chain. In LA1, the aliphatic linkage increases the rigidity of the ligand, which will change the vibrational modes and reduces the vibrational relaxation of compound Ir(LA1)(LB1)2 at the excited state. It is known that the vibrational peaks, the reason of the broadness, in the photo- and electro-luminescence correlate to the distortion between the excited and ground state, which is dependent on the vibrational frequencies and their probabilities at the excited state. Therefore, the inventive compound Ir(LA1)(LB1)2 when used as emitters is most likely to exhibit higher photoluminescence quantum yield and narrow emission spectra, which is thought to improve the performance of the OLED device. Furthermore, the linker unit (L) will increase the stability of the ligand and the lifetime of the OLED device.