GB2525219A - Polymer and organic light-emitting device - Google Patents

Abstract

A composition comprises a phosphorescent compound of formula (I) and a polymer comprising a repeat unit of formula (II) Ar1 is an aryl or heteroaryl group; R2 is a substituent; A is independently in each occurrence N or CR3 wherein R3 is H or a substituent; M is a transition metal or metal ion; x is a positive integer of at least 1; y is 0 or a positive integer; LI is a mono- or polydentate ligand; RI is a substituent; z is 0 or a positive integer; X is 0 or S. The phosphorescent compound of formula (I) may be mixed with the polymer or may be covalently bound thereto. The composition may be used in the light-emitting layer between the anode and the cathode of an organic light-emitting device.

Description

Polymer and Organic Light-Emitting Device

Background of the Invention

Electronic devices containing active organic materials are attracting increasing attention for use in devices such as organic light emitting diodes (OLEDs), organic photoresponsive devices (in particular organic photovoltaic devices and organic photosensors), organic transistors and memory array devices. Devices containing active organic materials offer benefits such as low weight, low power consumption and flexibility. Moreover, use of soluble organic materials allows use of solution processing in device manufacture, for example inkjet printing or spin-coating.

An OLED may comprise a substrate carrying an anode, a cathode and one or more organic light-emitting layers between the anode and cathode.

Holes are injected into the device through the anode and electrons are injected through the cathode during operation of the device. Holes in the highest occupied molecular orbital (HOMO) and electrons in the lowest unoccupied molecular orbital (LIJMO) of a light-emitting material combine to form an exciton that releases its energy as light.

A light emitting layer may comprise a semiconducting host material and a light-emitting dopant wherein energy is transferred from the host material to the light-emitting dopant.

For example, J. Appl. Phys. 65, 3610, 1989 discloses a host material doped with a fluorescent light-emitting dopant (that is, a light-emitting material in which light is emitted via decay of a singlet exciton).

Phosphorescent dopants are also known (that is, a light-emitting dopant in which light is emitted via decay of a triplet exciton).

A hole-transporting layer may be provided between the anode and light-emitting layer of an OLED.

Suitable light-emitting materials include small molecule, polymeric and dendrimeric materials. Suitable light-emitting polymers include poly(arylene vinylenes) such as poly(p-phenylene vinylenes) and polymers containing arylene repeat units, such as fluorene repeat units. Blue light-emitting fluorene homopolymer is disclosed in WO 97/05184.

WO 2010/085676 discloses host materials for electrophosphorescent devices. A copolymer formed by copolymerization of I,6-his(3-(4,4,5,5-tetramethyl-[ 1,3,2]- dioxahorolan-2-yl)phenoxyl)hexane and 2-(4-(3-(3,6-dihromocarhazol-9-yl)propyl)phenyl)-4,6-di(3-methylphenyl)-I, 3,5-triazine is disclosed.

WO 2008/025997 discloses the following monomer for use in preparation of a polymeric host: c'.Br N...-N C6 H13 WO 2013/191088 discloses a high molecular compound including a group of formula (II): 0 (Ar' )nl t wherein n I is an integer of 1-3; Ar' is an arylene group, a divalent aromatic heterocyclic group, or a divalent aromatic amine residue: and R1' is H, alkyl, aryl, heteroaryl or aralkyl, and at least three of the groups are alkyl, aryl, heteroaryl or aralkyl -EP1245659 discloses a polymer having a phosphorescent metal complex in the main chain or in a side chain of the polymer.

Huang et al, Polymer (2009), 50(25), 5945-5958 discloses a polymer having fluorene repeat units, dibenzothiophene repeat units and a benzimidazole-based iridium complex repeat unit.

Mikroyannidis et al, J. Poly. Sci., Part A: Polymer Chemistry (2006), 44(23). 6790-6800 discloses poly(fluorene vinylene-alt-dibenzothiophene vinylene)s. OLEDs containing these polymers showed electroluminescence with maxima at 530 and 540 nm.

Mikroyannidis et al, Synth. Met. 2004, 142(1-3), 113-120 discloses fluorescent poly(p-phenylenes) hearing dihenzothiophene moieties along the main chain and having a photoluminescence maximum near 510 nm.

Yang et al, Synth. Met. 2003, 135-136, 183-184 discloses copolymers of fluorene and dibenzothiophene, and fluorescent OLEDs formed for these copolyrners.

Yang et al, J. Mater. Chem. 2003, 13(6), 1351-1355 discloses copolymers of 9,9-dioctyli'luorelle and dibenzothiophene.

Nemoto, J. Poly. Sci., Part A: Polymer Chemistry 2003, 41(10), 1521-1526 discloses a polymer formed by Suzuki polycondensation of a 2,8-dihoronic ester dihenzothiophene with 2,7-dibromo-9,9-dioctylfluorene and and 3,6-dibrorno-9-octylcarbazole or 1,4-dihromo-2,5-dioctyl oxyhenzene.

Summary of the Invention

In a first aspect the invention provides a composition comprising a phosphorescent compound of formula (I) and a polymer comprising a repeat unit of formula (II) (L1) Mc:IIIIIIcç -R) (I) (II) wherein: Ar1 is an aryl or heteroaryl group that may be unsubstituted or substituted with one or R2 is a stibstiwent; A is independently in each occurrence N or CR3 wherein R3 is H or a substituent; M is a transition metal or metal ion; x is a positive integer of at least 1; y is 0 or a positive integer; and each L' is independently a mono-or polydentate ligand different from ligands of formula

N

QA

z is 0 or a positive integer; and X is 0 or S. in a second aspect the invention provides a formulation comprising a composition according to the first aspect and at least one solvent.

in a third aspect the invention provides an organic light-emitting device comprising an anode, a cathode and a light-emitting layer between the anode and cathode wherein the light-emitting layer comprises a composition according to the first aspect.

Description of the Drawings

The invention will now be described in more detail with reference to the drawings in which: Figure 1 illustrates schematically an OLED according to an embodiment of the invention; Figure 2 shows the pliotoluminescence spectra of a composition according to an embodiment of the invention and two comparative compositions; Figure 3 is a graph of current density vs. voltage for an OLED according to an embodiment of the invention and a comparative OLED; Figure 4 is a graph of voltage vs. time for an OLED according to an embodiment of the invention and a comparative OLED; Figure 5 is a graph of EQE vs. current for an OLED according to an embodiment of the invention and a crnnparative OLED; Figure 6 is a graph of luminance vs. time for an OLED according to an embodiment of the invention and a comparative OLED; aild Figure 7 shows the electroluminescent spectra of OLEDs according to embodiments of the invention.

Detailed Description of the Invention

Figure 1 illustrates an OLED 100 according to an embodiment of the invention comprising an anode 101, a cathode 105 and a light-emitting layer 103 between the anode and cathode. The device 100 is supported on a substrate 107, for example a glass or plastic substrate.

Light-emitting layer 103 maybe unpatterned, or maybe patterned to form discrete pixels.

Each pixel may be further divided into subpixels. The light-emitting layer may contain a single light-emitting material, for example for a monochrome display or other monochrome device, or may contain materials emitting different colours, in particular red, green and blue light-emitting materials for a full-colour display.

Light-emitting layer 103 contains a composition of the invention. The light-emitting layer 103 may consist essentially of the composition or may contain one or more further materials, for example one or more charge-transporting materials or one or more further light-emitting materials. The polymer of the composition functions as a host for the compound of formula (1). The triplet energy level of the polymer is preferably no more than 0.1 cv below that of the phosphorescent compound of formula (1), and is more preferably about the same or higher than that of the phosphorescent compound in order to avoid quenching of phosphorescence from the phosphorescent compound. Optionally, the lowest triplet energy level of the host polymer is at least 2.5 cv, optionally at least 2.6 cv.

One or more further layers maybe provided between the anode lOt and cathode I O,for example hole-transporting layers, electron transporting layers, hole blocking layers and electron blocking layers.

Preferred device structures include: Anode / Hole-injection layer I Light-emitting layer / Cathode Anode / Hole transporting layer / Light-emitting layer / Cathode Anode / Hole-injection layer / Hole-transporting layer / Light-emitting layer! Cathode Anode / Hole-injection layer / Hole-transporting layer / Light-emitting layer! Electron-transporting layer I Cathode.

Preferably, at least one of a hole-transporting layer and hole injection layer is present.

Preferably, both a hole injection layer and hole-transporting layer are present.

In operation, substantially all light emitted from the device may be light emitted from the phosphorescent compound of formula (I), or one or more further fluorescent or phosphorescent light-emitting materials may he present.

In embodiments of the invention, substantially all light is emitted from a single light-emitting layer containing a composition of the invention. In other embodiments of the invention, the device may contain a light-emitting layer containing a composition of the invention and at least one further light-emitting layer. The further light-emitting layer may be a charge-transporting layer containing a fluorescent or phosphorescent light-emitting material that emits light when the device is in use.

The OLED may be a white-emitting OLED containing one or more further fluorescent or phosphorescent light-emitting materials that, in combination with the phosphorescent compound of formula (1), produce white light. A white-emitting OLED may contain a single, white-emitting layer or may contain two or more layers that emit different colours which, in combination, produce white light. White light may be produced from a combination of red, green and blue light-emitting materials provided in a single light-emitting layer or distributed within two or more light-emitting layers. In a preferred arrangement, the device has a light-emitting layer comprising a red light-emitting material and a light-emitting layer comprising green and hlLle light-emitting materials.

The red light-emitting material maybe provided as a dopant in a hole-transporting layer.

The light emitted from a white-emitting OLED may have CIE x coordinate equivalent to that emitted by a black body at a temperature in the range of 2500-9000K and a CIE y coordinate within 0.05 or 0.025 of the CIE y co-ordinate of said light emitted by a black body, optionally a CIE x coordinate equivalent to that emitted by a black body at a temperature in the range of 2700-4500K.

The compound of formula (I) is preferably a blue phosphorescent compound. The photoluminescent spectrum of the phosphorescent compound of formula (I) may have a peak in the range of 420-490 nm, more preferably 420 -480 nm.

If present in light-emitting layer 103 or in a separate layer, the one or more further light-emitting materials may be selected from green and red fluorescent or phosphorescent materials.

A green emitting material may have a photolnminescent spectrum with a peak in the range of more than 490nm up to 580 nm, optionally more than 490 nm up to 540 nm.

A red emitting material may optionally have a peak in its photoluminescent spectrum of more than 580 nm up to 630 nm, optionally 585-625 nm.

In a preferred embodiment, the composition contains a blue phosphorescent compound of formula (I) and at least one of red and green phosphorescent compounds.

if present, a charge-transporting layer adjacent to a phosphorescent light-emitting layer preferably contains a charge-transporting material having a T1 excited state energy level that is no more than 0.1 cv lower than, preferably the same as or higher than, the Ti excited state energy level of the phosphorescent compound of formula (1) in order to avoid quenching of triplet excitons migrating from the light-emitting layer into the charge-transporting layer.

Triplet energy levels as described anywhere herein may be as measured from the energy onset (energy at half of the peak intensity on the high energy side) of the phosphorescence spectrum measured by low temperature phosphorescence spectroscopy (Y.V. Romaovskii et al, Physical Review Letters, 2000, 85 (5), Plo27, A. van Dijken et a], Journal of the American Chemical Society, 2004, 126, p77! 8).

Phosphorescent compound of formula (I) The phosphorescent compound of formula (1) may be physically mixed with the polymer or may he covalently hound thereto. The phosphorescent compound of formula (I) may be provided in a side-chain, main chain or end-group of the polymer. Where the phosphorescent material is provided in a polymer side-chain, the phosphorescent material may be directly bound to the backbone of the polymer or spaced apart there from by a spacer group, for example a C120 alkyl spacer group in which one or more non-adjacent C atoms may be replaced by COO, C=O, 0 or S. It will therefore be appreciated that a composition of the present invention may consist of or may be a polymer comprising a repeat unit of formula (II) with a phosphorescent compound of formula (I) covalently bound in the polymer main chain or covalently bound as a side-group or end-group of the polymer.

The compound of formula (1) may make up about 0.05 wt % up to about 50 wt % of the phosphorescent compound + polymer weight.

If more than two phosphorescent materials of different colours are used with a single host material then the emitter with the highest triplet energy level may be provided in a greater amount than the other emitter or emitters, for example in an amount of at least two times or at least 5 times the weight percentage of each of the other emitter or emitters.

Optionally, y of formula (I) is 0.

In the case where y is at least 1, may be a dilcetonate, optionally acac or picolinate.

Optionally, x of formula (1) is 3.

Optionally, M of formula (I) is an iridium ion.

Ar' may be a fused or unfused group. Exemplary aromatic groups Ar' are phenyl that may be unsubstituted or substituted with 1, 2, 3, 4 or 5 substituents and fluorene that may be unsubstituted or substituted with one or more substituents. Exemplary heteroaromatic groups include pyridine and carhazole. Preferably, is a fused or unfused aromatic group.

Substituents of Ar1, where present, may he selected from the group consisting of: -C120 alkyl wherein one or more non-adjacent C atoms of the alkyl group may be replaced by 0, S or COO, C=O, NR6 or SiR62 and one or more H atoms of the C1 alkyl group may be replaced by F wherein R6 is a substituent and is optionally in each occurrence a C14o hydrocarbyl group, optionally a Ci2o alkyl group; -aryl or heteroaryl substituted with one or more C120 alkyl groups; and -a branched or linear chain of two or more aryl or heteroaryl rings, each of which ring may be substituted with one or more substituents.

Exemplary C120 alkyl groups wherein one or more ion-adjacent C atoms of the alkyl group are replaced by 0, S or COO, C=O, NR6 or SiR62 include C120 alkoxy.

Preferably, substituents of Ar1, where present, are selected from C140 hydrocarbyl groups, more preferably from: -C 1-20 alkyl; -unsubstituted phenyl, or phenyl substituted with one or more CL2D alkyl groups: and -a branched or linear chain of two or more phenyl rings, each of which ring may be substituted with one or more C120 alkyl groups.

A branched or linear chain of two or aryl or heteroaryl rings may be a dendron.

A dendron may have optionally substituted formula (XTI) / B\ (XII) wherein BP represents a branching point for attachment to a core and G1 represents first generation branching groups.

The dendron may he a first, second, third or higher generation deridron. 01 maybe sLibstituted with two or more second generation branching groups 02, and so on, as in optionally substituted formula (XTTa): JG3

C

Gci_G2cL4Ga \ C1 G2..

N flCa L2 u

V

(Xlla) wherein ii isO or 1; v isO ifu isO or maybe 1) or I ifu is I; BP represents a branching point for attachment to a core and C1, C2 and C3 represent first, second and third generation dendron branching groups. In one preferred embodiment, each of BP and C1, 02... C is phenyL and each phenyl BP, G, G... is a 3,5-linked phenyl.

BP and / or any group 0 may be substituted with one or more substituents, for example one or more C120 alkyl or alkoxy groups.

Exemplary aromatic slibstitLients of Ar1 include the following, each of which maybe unsubstituted or substituted with one or more substituents, optionally one, two or more C120 alkyl groups: * * * wherein * represents an attachment point of the dendron to An.

Each R2 may be selected from substituents of Ar1 described above. R2 is preferably a hydrocarbyl group as described above with reference to substituents of Ar1.

In an embodiment, each A of formula (I) is CR in another embodiment, one A of formula (1) is CR3 and the other A is N. The heterocyclic ring containing the groups A is not fused.

R3, where present, is preferably selected from the group consisting of C140 hydrocarhyl groups, more preferably C120 alkyl.

Alkyl as described anywhere herein includes linear, branched and cyclic alkyl.

Polymer The polymer comprising repeat units of formula (H) preferably has a LUMO level that is less than 2.1 eV from vacuum level. Preferably, the HOMO of the compound of formula (I) is at least 2.5 eV, optionally at least 2.7 eV deeper (further from vacuum) than the LUMO of the polymer. Without wishing to he hound by any theory, it is believed that this HOMO-LUMO gap reduces the probability of excimer formation between the HOMO of the compound of formula (I) and the LUMO of the polymer. It will be appreciated that a shallower LIJMO of the polymer results in a larger HOMO-LIJMO gap.

The polymer comprising repeat units of formula (H) is preferably a conjugated polymer wherein repeat units of formula (H) are conjugated to adjacent repeat units in the polymer backbone. The polymer may contain repeat units to limit the extent of conj Ligation along the polymer backbone.

Preferably, a polymer comprising repeat units of formula (II) is a co-polymer comprising repeat units of formula (II) and one or more co-repeat units.

Exemplary co-repeat units include arylene co-repeat units that maybe unsubstituted or substituted with one or more substituents. A preferred arylene co-repeat unit is a phenylene repeat unit that may be unsubstituted or substituted with one or more The one or more co-repeat units may include a conjugation-breaking repeat unit, which is a repeat unit that does not provide any conjugation path between repeat units adjacent to the conjugation-breaking repeat unit.

Exemplary conjugation-brealung co-repeat units include co-repeat units of formula (II): (3 srØ (H) wherein: Ar4 ill each occurrence independently represents an aryl or heteroaryl group that may be unsubstituted or substituted with one or more substituents; and Sp represents a spacer group comprising at least one carbon or silicon atom.

Preferably, the spacer group includes at least one sp3-hyhridised carbon atom separating the Ar4 groups.

Preferably Ar4 is an aryl group and the Ar4 groups may he the same or different. More preferably each Ar4 is phenyl.

Each Ar4 may independently be unsubstituted or may be substituted with 1, 2, 3 or 4 substituents. The one or more substituents may be selected from: -C120 alkyl wherein one or more non-adjacent C atoms of the alkyl group may he 6 6 replaced by 0, S or COO, C=O, NR or SiR 2 and one or more H atoms of the Ci alkyl group ma)' he replaced by F wherein R6 is a suhstituent and is optionally in each occurrence a C140 hydrocarhyl group, optionally a Ci_29 alkyl group; and -aryl or heteroaryl substituted with one or more C120 alkyl groups.

Preferred substituents of Ar4 are Ci2o a1ky groups, which may be the same or different in each occurrence.

Exemplary groups Sp include a C120 alkyl chain wherein one or more non-adjacent C 6.6 atoms of the chain maybe replaced with 0, 5, -NR -, -SiR 2, -C(=O)-or -COO-and wherein R6 in each occurrence is as described above.

Exemplary repeat units of formula (II) include the following, wherein R in each occurrence is H or C15 alkyl: -d--ED R2__d)_ -(j,)-+_2__d)_ \ \ \ \ \/ \/ \/ -(-I)---j R6_<f)_ _E5J_-_sj R6_(9_ _(_())_Si -f-p--Si R6_(d_ ±-" oYo--_(?_OT"OTTh_$$)_ (p_i0\i0\y (Ø_/O\JO\Ø _(p_/O\iO\dy so\.so\ Exemplary arylene co-repeat units include 1,2-, 1,3-and i,4-phenylene repeat LInits, 3,6-and 2,7-linked fluorene repeat units, indenofluorene, naphthalene, anthracene and phenanthrene repeat units, each of which may he unsubstituted or substituted with one or more substitutents, for example one or more C140 hydrocarhyl substituents.

One preferred class of arylene repeat units is phenylene repeat units, such as phenylene repeat units of formula (VU: +cL (VI) wherein win each occurrence is independently 0, 1, 2, 3 or 4, optionally I or 2; n is 1, 2 or 3; and R7 independently in each occurrence is a substituent.

Where present, each R7 may independently he selected from the group consisting of: -alkyl, optionally C120 ailcyl, wherein one or more non-adjacent C atoms may be replaced with optionally substituted aryl or heteroaryl, 0, S, substituted N, C=O or -COO-, and one or more H atoms maybe replaced with F; -aryl and heteroaryl groups that may be unsubstituted or substituted with one or more substituents, preferably phenyl substituted with one or more C1.20 alkyl groups; -a linear or branched chain of aryl or heteroaryl groups, each of which groups may independently he substituted, for example a group of formula -(Ar7)r wherein each Ar7 is independently an aryl or heteroaryl group and r is at least 2, preferably a branched or linear chain of phenyl groups each of which may he unsubstituted or substituted with one or more Ci.20 ailcyl groups; and -a crosslinkable-group, for example a group comprising a double bond such and a vinyl or acrylate group, or a henzocyclohutane group.

In tile case where R7 comprises an aryl or heteroaryl group, or a linear or branched chain of aryl or heteroaryl groups, the or each aryl or heteroary] group may he substituted with one or more sLibstitlients R8 selected from the group consisting of: alkyl, for example C120 alkyl, wherein one or more non-adjacent C atoms may be replaced with 0, S, substituted N, C=O and -COO-and one or more H atoms of the alkyl group maybe replaced with F; NR92, OR9, SR9, SiR93 and fluorine, nitro and cyano; wherein each R9 is independenfly selected from the group consisting of alkyl, preferably C120 alkyl; and aryl or heteroaryl, preferably phenyl, optionally substituted with one or more C129 alkyl groups.

Substituted N, where present, may be -NR6-wherein R6 is as described above.

Preferably, each R7, where present, is independently selected from Ci4ohydrocarhyl, and is more preferably selected from C120a1ky1: unusubstituted phenyl; phenyl substituted with one or more C12oakyl groups; a linear or branched chain of phenyl groups, wherein each phenyl may be unstibstituted or substituted with one or more substituents; and a crosslinkable group.

if n is 1 then exemplary repeat units of formula (VI) include the following: (R) 4C UR7W A particularly preferred repeat unit of formula (VI) has formula (Via): (Wa) Substituents R7 of formula (VTa) are adjacent to linking positions of the repeat unit, which may cause steric hindrance between tile repeat unit of formula (Via) and adjacent repeat units, resulting in the repeat unit of formula (Via) twisting oLit of plane relative to one or both adjacent repeat units.

Exemplary repeat units where n is 2 or 3 include the following: R7 R7' R7 eo7 R7 1w 1w 1w kII)w 1W A preferred repeat unit has formula (VTh): fd (Vib) The two R7 groups of formula (Vib) may cause steric hindrance between the plienyl rings they are bound to, resulting in twisting of the two phenyl rings relative to one another.

A further class of arylene repeat units are optionally substituted fluorene repeat units, such as repeat units of formula (Vii): R7 R7 (VII) wherein R7 in each occurrence is the same or different axd is a substituellt as described with reference to formula (VI), aild wherein the two groups R7 may be lillked to form a ring; R8 is a substituent; and d is 0, 1, 2 or 3.

The aromatic carbon atoms of the fluorene repeat unit may he unsubstituted, or may he substituted with one or more substituents R8. Exemplary substituents R8 are alkyl, for example C120 alky], wherein one or more non-adjacent C atoms may he replaced with 0, 5, NH or substituted N, C=O and -COO-, optionally sLibstituted aryl, optionally substituted heteroaryl, alkoxy, alkylthio, fluorine, cyano and arylalkyl. Particularly preferred sllbstitLlents include C120 alkyl and substituted or unsubstituted aryl, for example phenyl. Optional substituents for the aryl include one or more C120 alkyl groups.

Substituted N, where present, maybe -NR6-wherein R6 is as described above.

The extent of colljugation of repeat units of formula (VII) to aryl or heteroaryl groups of adjacent repeat units in the polymer backbone may be controlled by (a) linking the repeat ullit through the 3-and I or 6-positions to limit the exteilt of conjugation across the repeat unit, and I or (b) substituting the repeat unit with oiw or more substituents R8 in or more positiolls adjacent to the linking positions in order to create a twist with the adjacent repeat unit or units, for example a 2,7-linked fluorene carrying a C120 alkyl substituent in oiie or both of the 3-and 6-positions.

The repeat unit of formula (VII) may be an optionally substituted 2,7-linked repeat unit of formula (VlIa): N7 N7 (Vila) Optionally, the repeat unit of formula (VTIa) is not substitLited in a position adjacent to the 2-or 7-position. Linkage through the 2-and 7-positions and absence of substituents adjacent to these linking positions provides a repeat unit that is capable of providing a relatively high degree of conjugation across the repeat unit.

The repeat unit of formula (VII) may be an optionally substituted 3,6-linked repeat unit of formula (VITh) R7 N7 (VTTb) The extent of conjugation across a repeat unit of formula (VIIb) may be relatively low as compared to a repeat unit of formula (YJIa).

Another exemplary arylene repeat unit has formula (VIII): (R8)d (R8)d R7 R7 (VIII) wherein R7, R8 and d are as described with reference to formula (Vi) and (Vii) above.

Any of the R7 groups may be linked to any other of the R7 groups to form a ring. The ring so formed may be unsubstituted or may be substituted with one or more substituents, optionally one or more C120 alkyl groups.

Repeat units of formula (Viii) may have formula (Villa) or (V1T1b): (R8)d (R8)d (R8)d (R6)d R7R7 R7R7 (Villa) (VIUb) Further arylene co-repeat units include: phenanthrelle repeat units; naphthalene repeat uiuts; anthracene repeat urnts; and perylene repeat units. Each of these arylelle repeat ullits maybe linked to adjaceilt repeat units through any two of the aromatic carbon atoms of these ullits. Specific exemplary linkages include 9,1O-allthracene; 2,6-anthracene; 1,4-naphthalene; 2,6-naphthalene; 2,7-phenanthrene; and 2,5-perylene. Each of these repeat units may be substituted or unsubstituted, for example sithstituted with one or more Cpo hydrocarbyl groups.

The polymer comprising a repeat unit of formula (TI) may contain one or more hole transporting repeat units. Exemplary hole transporting repeat units maybe repeat units of materials having a electron affinity of 2.9 eV or lower and an ionisation potential of 5-8 eV or lower, preferably 5.7 eV or lower.

Preferred hole-transporting repeat units are (hetero)arylaithne repeat units, including repeat units of formula (TX): ( (Ar8)cf7_(Ar9)d \R13 Ig (IX) wherein Ar8 and Ar9 in each occurrence are independently selected from substituted or unsubstituted aryl or heteroaryl, g is greater than or equal to I, preferably I or 2, R3 is H or a suhstituent, preferably a substituent, and c and dare each independently 1, 2 or 3.

R'3, which may be the same or different in each occurrence when g > 1, is preferably selected from the group consisting of alkyl, for example C170 alkyl, Ar10, a branched or linear chain of Ar10 groups, or a crosslinkable unit that is hound directly to the N atom of formula (IX) or spaced apart therefrom by a spacer group, wherein Ar10 in each occurrence is independently optionally substituted aryl or heteroaryl. Exemplary spacer groups are C120 alkyl, phenyl and plienyl-Ci20 alkyl.

Any of Ar8, Ar9 and, if present, 1O in the repeat unit of Formula (IX) may be linked by a direct bond or a divalerit linking atom or group to another of Ar8, Ar9 and Aj10 Preferred divalent linking atoms and groups include 0, S; substituted N; and substituted C. Any of Ar8, Ar9 and, if present, Ar'° may be substituted with one or more substituents.

Exemplary substituents are substituents R'°, wherein each R'° may indepeildently be selected from the group consisting of: -substituted or unsubstituted alkyl, optionally C1 -20 alkyl, wherein one or more non-adjacent C atoms may he replaced with optionally substituted aryl or heteroaryl, 0, S, substituted N, C=0 or -COO-and one or more H atoms may he replaced with F; and -a crosslinkable group attached directly to the fluorene unit or spaced apart therefrom by a spacer group, for example a group comprising a double bond such and a viny' or acrylate group, or a benzocyclobutane group Preferred repeat units of formu'a (IX) have formulae 1-3: Ar9) (AçAr9) (A)Ar9) Ar1° Ar10 Ar Ar1° 1 2 3 In one preferred arrangement, R'3 is Ar0 and each of Ar8, Ar9 and Ar'0 are independently and optionally substituted with one or more C,2o alkyl groups. Ar8, Ar9 and Ar10 are preferably phenyl.

In another preferred arrangemeilt, the central Ar9 group of formula (IX) linked to two N atoms is a polycyclic aromatic that may he unsubstituted or substituted with one or more substituents R'°. Exemphiry polycyclic aromatic groups are naphthalene, perylene, anthracene and fluorene.

in another preferred arrangement, Ar8 and Ar9 are phenyl, each of which may be substituted with one or more Ci2o alkyl groups, and R'3 is -(Ar'°)r wherein r is at least 2 and wherein the group -(Ar'°)r forms a linear or branched chain of aromatic or heteroaromatic groups, for example 3,5-diphenylbenzene wherein each pheny may be substituted with one or more C12o alkyl groups.ln another preferred arrangement, c, d and g are each 1 and Ar8 aild Ar9 are phenyl lillked by an oxygen atom to form a phenoxazine nllg.

Amine repeat units may be provided in a molar amount in the range of about 0.5 mol % up to about 50 mol %, optionally about 1-25 mol %, optionally about 1-10 mol %.

The polymer may contain one, two or more different repeat units of formula (IX).

Amine repeat units may provide hole-transporting and! or light-emitting functionality.

Preferred light-emitting amine repeat units include a blue light-emitting repeat unit of formula (iXa) and a green light-emitting repeat unit thrmula (iXh): (IXa) (IXb) R'3 of formula (iXa) is preferably a hydrocarhyl, preferably C129 alkyl, phenyl that is LlnsubstitLlted or substituted with one or more C120 alkyl groups, or a branched or linear chain of phenyl groups wherein each said phenyl group is unsubstituted or substituted with one or more C120 alkyl groups.

The repeat unit of formula (IXb) may be unsubstituted or one or more of the rings of the repeat unit of fornmla (iXb) may be substituted with one or more substituents R', preferably one or more C1 -20 alkyl groups.

In one arrangement the phosphorescent material of the composition according to the invention is mixed with the polymer.

in another arrangement the phosphorescent material of the composition according to the invention is covalently bound to the polymer. in this arrangement, the phosphorescent material may be provided as a main-chain repeat unit of the polymer backbone, an end-group of the polymer or a side-group of the polymer that may be directly bound to the polymer backbone or spaced apart from the polymer backbone by a spacer group, for example a Ci2o alkyl group.

Optionally, a light-emitting layer of an OLED according to the invention is formed by depositing a formulation according to the invention comprising the composition and at least one solvent, and evaporating the at least one solvent.

Polymers as described herein suitably have a polystyrene-equivalent number-average molecular weight (Mn) measured by gel permeation chromatography in the range of about ix! o3 to lxi o8, and preferably lxi o3 to 5x 106. The polystyrene-equivalent weight-average molecular weight (Mw) of the polymers described herein may he lxi to I xi O, and preferably I x I o4 to I x I o7.

Polymers described herein are suitably amorphous polymers.

Polymer synthesis One method of forming conjugated or partially conjugated polymers is Suzuki polymerisation, for example as described in WO 00/53656 or US 5777070 which allows formation of C-C bonds between two aromatic or heteroarornatic groups, and so enables formation of polymers having conjugation extending across two or more repeat units.

Suzuki polyrnerisation takes place in the presence of a palladium complex catalyst and a base.

As illustrated in Scheme 1, in the Suzuki polymerisation process a monomer for formillg repeat units RU1 having leaving groups LG1 such as borollic acid or boronic ester oups undergoes polymerisation with a monomer for forming repeat units RU2 having leaving groups LG2 sLich as halogen, sulfonic acid or sulfonic ester to form a carbon-carbon bond between Arylene 1 and Arylene 2: n LGI-RU1-LG1 + n LG2-RU2-LG2 -* -(RU1-RU2)11-Scheme 1 Exemplary boronic esters have formula (V): 0R6 * -B 0R6 (Y) wherein R6 in each occurrence is independently a Ci2o alkyl group, * represents the point of attachment of the boronic ester to an aromatic ring of the monomer, and the two groups may be linked to form a ring, in a preferred embodiment, the two groups are linked to form the pinacol ester of boronic acid: * -B' it will he understood by the skilled person that a monomer LU I -RU! -LU I will not polymerise to form a direct carbon-carbon bond with another monomer LU! -RU I -LU1 -A monomer LU2-RU2-LU2 will not polymerise to form a direct carbon-carbon bond with another monomer LU2-RU2-LU2.

Preferably, one of LG 1 and L02 is bromine or iodine and the other is a boronic acid or horonic ester.

This selectivity means that the ordering of repeat units in the polymer backbone can be controlled such that all or substantially all RU1 repeat ullits formed by polymerisation of LG1-RUI-LG1 are adjacent, on both sides, to RU2 repeat units.

in the example of Scheme 1 above, an AB copolymer is formed by copolymerisation of two monomers in a i:1 ratio, however it will he appreciated that more than two or more than two monomers may be used in the polymerisation, and any ratio of monomers may be used.

The base may he an organic or inorganic base. Exemplary organic bases include tetra-alkylammonium hydroxides, carbonates and hicarhonates Exemplary inorganic bases include metal (for example alkali or alkali earth) hydroxides, carbonates and hicarhonates.

The palladium complex catalyst may be a palladium (0) or palladium (H) compound.

Particularly preferred catalysts are tetrakis(triphenylphosphine)palladium (0) and palladium (H) acetate mixed with a phosphine.

A phosphine may be provided, either as a ligand of the palladium compound catalyst or as a separate compound added to the polymerisation mixture. Exemplary phosphines include triarylphosphines, for example triphenylphosphines wherein each phenyl may independently be unsubstituted or substituted with one or more substituents, for example one or more C15 alicyl or C1. alkoxy groups.

Particularly preferred are triphenylphospine and tris(ortho-methoxytriphenyl) phospine.

The polymerisation reaction may take place in a single organic liquid phase in which all components of the reaction mixture are soluble. The reaction may take place in a two-phase aqueous-organic system, in which case a phase transfer agent may be used. The reaction may take place in an emulsion formed by mixing a two-phase aqueous-organic system with an emulsifier.

The polymer may be end-capped by addition of an endcapping reactant. Suitable end-capping reactants are aromatic or heteroaromatic materials substituted with only one leaving group. The end-capping reactants may include reactants substituted with a halogen for reaction with a horonic acid or horonic ester group at a polymer chain end, and reactants substituted with a horonic acid or horonic ester for reaction with a halogen at a polymer chain end. Exemplary end-capping reactants are 1ia1obenzenes,for example hromohenzene, and phenylboronic acid. End-capping reactants may he added during or at the end of the polymerisation reaction.

Charge transporting and charge blocking layers A hole transporting layer may be provided between the anode and the light-emitting layer or layers of an OLED. Likewise, an electron transporting layer may be provided between the cathode and the light-emitting layer or layers.

Similarly, an electron blocking layer may he provided between the anode and the light-emitting layer and a hole blocking layer may be provided between the cathode and the light-emitting layer. Transporting and blocking layers maybe used in combination.

Depending on its HOMO and LIJMO levels, a single layer may both transport one of holes and electrons and block the other of holes and electrons.

A charge-transporting layer or charge-blocking layer may be cross-linked, particularly if a layer overlying that charge-transporting or charge-blocking layer is deposited from a solution. The crosslinkable group used for this crosslinking maybe a crosslinkable group comprising a reactive double bond such and a vinyl or acrylate group, or a henzocyclohutane group.

If present, a hole transporting layer located between the anode and the light-emitting layers preferably has a HOMO level of less than or equal to 5.5 eV, more preferably around 4.8-5.5 eV or 5.1-5.3 eV as measured by cyclic voltammetry. The HOMO level of the hole transport layer maybe selected so as to he within 0.2 cv, optionally within 0.1 eV, of an adjacent layer (such as a light-emitting layer) in order to provide a small harrier to hole transport between these layers.

If present, an electron transporting layer located between the light-emitting layers arid cathode preferably has a LUMO level of around 2.5-3.5 eV as measured by cyclic voltanimetry. For example, a layer of a silicon monoxide or silicon dioxide or other thin dielectric layer having thickness in the range of O.2-2nm may he provided between the light-emitting layer nearest the cathode and the cathode. HOMO and LUMO levels may he measured using cyclic voltammetry.

A hole transporting layer may contain a homopolymer or copolymer comprising a repeat ullit of formula (DC) as described above, for example a copolymer comprising one or more amine repeat ullits of formula (IX) and oe or more arylene repeat units, for example one or more arylelle repeat units selected from formulae (VI), (VII) and (VIII).

An electron transporting layer may contain a polymer comprising a chain of optionally substituted arylene repeat units, such as a chain of fluorene repeat units.

If a hole-or electron-transporting layer is adjacent a light-emitting layer containing a phosphorescent material then the T1 energy level of the material or materials of that layer are preferably higher than that of the phosphorescent emitter in the adjacent light-emitting layer.

Hole injection layers A conductive hole injection layer, which may be formed from a conductive organic or inorganic material, may be provided between the anode 101 and the light-emitting layer 103 of an OLED as illustrated in Figure Ito assist hole injection from the anode into the layer or layers of semiconducting polymer. Examples of doped organic hole injection materials include optionally substituted, doped poly(ethylene dioxythiophene) (PEDT), in particular PEDT doped with a charge-balancing polyacid such as polystyrene sulfonate (PSS) as disclosed in EP 0901176 and EP 0947123, polyacrylic acid or a fluorinated sulfornc acid, for example Nafion ®; polyamline as disclosed in US 5723873 and US 5798170; and optionally substituted polythiophene or poly(thienothiophene). Examples of conductive inorganic materials include transition metal oxides such as VOx MoOx and RuOx as disclosed in Journal of Physics D: Applied Physics (i996), 29(1!), 2750-2753.

Cathode The cathode 105 is selected from materials that have a workfunction allowing injection of electrons into the light-emitting layer of the OLED. Other factors influence the selection of the cathode such as the possibility of adverse interactions between the cathode and the light-emitting material. The cathode may consist of a single material such as a layer of aluminium. Alternatively, it may comprise a plurality of conductive materials such as metals, for example a bilayer of a low workfunction material and a high workfunction material such as calcium and aluminium, for exampleas disclosed in WO 98/1062 1. The cathode may comprise elemental barium, for example as disclosed in WO 98/57381, Appl. Phys. Lett. 2002, 81(4), 634 and WO 02/84759. The cathode may comprise a thin (e.g. 0.5-5 nm) layer of metal compound, in particular an oxide or fluoride of an alkali or alkali earth metal, between the organic layers of the device and one or more conductive cathode layers to assist electron injection, for example lithium fluoride as disclosed in WO 00/48258; barium fluoride as disclosed in AppI. Phys. Lett. 2001,79(5), 2001; and barium oxide. In order to provide efficient injection of electrons into the device, the cathode preferably has a workfunction of less than 3.5 eV, more preferably less than 3.2 eV, most preferably less than 3eV. Work functions of metals can he found in, for example, Michaelson, J. AppI. Phys. 48(! i), 4729, ! 977.

The cathode may be opaque or transparent. Transparent cathodes are particularly advantageous for active matrix devices because emission through a transparent anode in such devices is at least partially blocked by drive circuitry located underneath the emissive pixels. A transparent cathode comprises a layer of an electron injecting material that is sufficiently thin to be transparent. Typically, the lateral conductivity of this layer will he low as a result of its thinness. In this case, the layer of electron injecting material is used in combination with a thicker layer of transparent conducting material such as indium tin oxide.

It will be appreciated that a transparent cathode device need not have a transparent anode (unless a fully transparent device is desired), and so the transparent anode used for bottom-emitting devices maybe replaced or supplemented with a layer of reflective material such as a layer of alLiminiLim. Examples of transparent cathode devices are disclosed in, for example, GB 2348316.

Encapsulation Organic optoelectronic devices tend to he sensitive to moisture and oxygen.

Accordingly, the substrate preferably has good barrier properties for preveiltion of ingress of moisture and oxygen into the device. The substrate is commonly glass, however alternative substrates may be used, ill particular where flexibility of the device is desirable. For example, the substrate may comprise one or more plastic layers, for example a substrate of altemating plastic and dielectric barrier layers or a laminate of thin glass and plastic.

The device may be encapsulated with an encapsulant (not shown) to prevent ingress of moisture and oxygen. Suitable encapsulants include a sheet of glass, films having suitable barrier properties such as silicon dioxide, silicon monoxide, silicon nitride or alternating stacks of polymer and dielectric or an airtight container, in the case of a transparent cathode device, a transparent encapsulating layer such as silicon monoxide or silicon dioxide may be deposited to micron levels of thickness, although in one preferred embodiment the thickness of such a layer is in the range of 20-300 nm. A getter material for absorption of any atmospheric moisture and I or oxygen that may permeate through the substrate or encapsulant may be disposed between the substrate and the encapsulant.

Formulation processing A formulation suitable for forming a light-emitting layer may he formed from the composition or the polymer of the invention, any further components of the layer such as light-emitting dopants, and one or more suitable solvents.

The formulation may be a solution of the composition and any other components in the one or more solvents, or may be a dispersion in the one or more solvents in which one or more components are not dissolved. Preferably, the formulation is a solution.

Solvents suitable for dissolving polymers or phosphorescent compounds carrying non-polar substituents such as alkyl substituents, include henzenes sLibstituted with one or more C19 alkyl or C110 alkoxy groups, for example toluene, xylenes and methylanisoles.

Particularly preferred solution deposition techniques including printing and coating techniques such spin-coating and inkjet printing.

Spin-coating is particularly suitable for devices whereill patterning of the light-emitting layer is unnecessary -for example for lighting applications or simple monochrome segmented displays.

Inkjet printing is particularly suitable for high information content displays, in particular full colour displays. A device may be inkjet printed by providing a patterned layer over the first electrode and defining wells for printing of one colour (in the case of a monochrome device) or multiple colours (in the case of a multicolour, in particular full colour device). The patterned layer is typically a layer of photoresist that is patterned to define wells as described in, for example, EP 0880303.

As an alternative to wells, the ink may he printed into channels defined within a patterned layer. In particular, the photoresist may be patterned to form channels which, unlike wells, extend over a plurality of pixels and which may he closed or open at the channel ends.

Other solution deposition techniques include dip-coating, roll printing, screen printing and slot-die coating.

Examples

Monomer Example 1

To a solution of dibenzothiophene (50 g, 0.271 mol) in 300 ml of chloroform and 300 ml acetic acid was added drop wise bromine (41.8 nil, 0.814 mol) in solution in 40 ml chloroform at 0"C. The resulting mixture was allowed to warm up slowly to room temperature and stirred for 48 hours. CC-MS showed no starting material, mixture of mono and dibromide + some isomers. Reaction mixture was stirred at room temperature for extra 24 hours.

Reaction mixture was quenched by adding drop wise 500 ml of all aqileoLls solution of sodium hydroxide (20% wt/v) at 0°C. Mixture was then poured into 2.5 L of methanol.

Slurry was stirred for I hour and filtered. The solid was the triturated for 30 minutes in IL of methanol, filtered and dried over the week end in vacuum oven at 50°C. Solid was stirred in 800 ml of refluxing chloroform for 2hours and filtered. Resulting solid was stirred in 500 ml of refluxing chloroform for 2hours axd filtered. Solid was then recrystallised 3 times from a mixture of toluene:chloroform to reach the desired purity (99.64% by HPLC, 26.4 g of white solid, 28% yield). Br

Monomer Example 2

To a solution of dibenzofuran (50 g, 0.298 mol) ill 300 ml of chloroform was added drop wise bromine (35.2 ml, 0.684 mol) in solution in 40 ml chloroform at 0°C. The resulting mixture was allowed to warm up slowly to room temperature and stirred for 24 hours.

GC-MS showed no starting material, mixture of mono and dibromide + some isomers.

Reaction mixture was cooled down to 0°C and bromine (7.6 ml, 0.148 mol) iii solution in nil chloroform was added. The resulting mixture was allowed to warm up slowly to room temperature and stirred for 24 hours. GC-MS: 25% monobromide, 70% dibromide + isomers, 2% tribronñde. Reaction mixture was cooled down to OC and bromine (3.0 ml, 0.059 mol) in solution in 5 ml chloroform was added. The resulting mixture was allowed to warm up slowly to room temperature and stirred over night.

Reaction mixture was quenched by adding drop wise 300 in! of an aqueous solution of sodium hydroxide (20% wt/v) at 0°C. Mixture was then poured into 3 L of methanol.

Slurry was stirred for 2 hours and filtered. The solid was the triturated for 1 hour in IL of methanol, filtered and dried over night in vacuum oven at 50°C. Solid was suspended in ml of refluxing chloroform, 600 ml methanol was added followed by 5001111 toluene.

No full di ssol Lition hut mixture was left to cool down to room temperature and filtered.

Solid was then recrystallised from a mixture of toluene methanol, and finally recrystallised from a mixture of toluene hexane to reach the desired purity (9c.73% by HPLC, 32.5 g of white solid, 33% yield). Br

Polymer Examples

Polymers were prepared by Suzuki polymerisation as described in WO 00/53656 of monomers illustrated below in the amounts shown in Table 1. B Br

Monomer Example I

N.....(JZIT Br -B Br C6H13 Comparative Monomer 1 Comparative Monomer 2

BB

Monomer A Monomer B Br Monomer C Lowest excited triplet state (T1) energy levels of the polymers were measured by time-resolved photoluminescence spectroscopy.

Table I

Polymer Boronic ester Dibromo monomer (mol %) LUMO monomer (mol %) level (cv) Polymer Example I Monomer A (IS) Monomer Example 1(50) [85 Monomer B (35) Comparative Monomer A (50) Comparative Monomer 1 (45) 2.61 Polymer 1 Monomer C (5) Comparative Monomer B (50) Comparative Monomer 2 (50) 1.7 Polymer 2 Polymer Example 2 Monomer A (15) Monomer Example 2(50) 1.82 Monomer B (35)

Composition Example

A polymer and Blue Phosphorescent Emitter 1 (95 polymer 5 emitter weight %) were dissolved in a solvent and the formulation was deposited by spin-coating onto a quartz substrate. The solvent was evaporated and the photoluminescent spectrum of the resultant film was measured.

Blue Phosphorescent Emitter I Phosphorescent Emitter I has a HOMO level of 4.82 eV and a LUMO level of 1.86 eV

Table 2

Composition Polymer of the Emitter HOMO -Host composition LUMO gap frY) Composition Example 1 Polymer Example 1 2.97 Comparative Comparative Polymer 1 2.21 Composition 1 Comparative Comparative Polymer 2 3.12 Composition 2 With reference to the photoluminescent spectra of Figure 2, the peak wavelength of Comparative Composition i is at a considerably longer wavelength than, and significantly broader than, that of either Composition Example I or Comparative Composition 2. Without wishing to be bound by any theory, it is believed that the relatively small emitter HOMO -host LUMO gap of Comparative Composition 1 results in exciplex formation, whereas the gaps of Composition Example 1 and Compatative Composition 2 are sufficiently large to avoid significant exciplex formation.

Device Example I

A white organic light-emitting device having the following structure was prepared: ITO I HIL I HTL! LEL / Cathode wherein TTO is an indium-tin oxide anode; HIL is a hole-injecting layer comprising a hole-injecting material, HTL is a hole-transporting layer, and LEL is a light-emitting layer containing light-emitting metal complexes and a host polymer.

A substrate carrying ITO was cleaned using UV / Ozone. A hole injection layer was formed to a thickness of about 35 nm by spin-coating an aqueous formulation of a hole-injection material available from Plextronics, Inc. A red-emitting hole transporting layer was formed to a thickness of about 22 nm by spin-coating a crosslinkable red-emitting hole-transporting polymer and crosslinking the polymer by heating.

The red-emitting hole transporting polymer was formed by Suzuki polymerisation as described in WO 00/53656 of the following monomers: B 17 0 C3H13 C4H9 C4H9 5Omol% 39.4rnol%

N -N Br r\ /

Br \ / \ / Br Nfl

N N

lOmol% 1.2rnol% The hole transport polymer has the following molecular weight characteristics (GPC relative to polystyrene standard, in Dalton): Mw 129,000, Mp 128,000, Mn 37,000, Pd 3.53.

A green and blue light emitting layer was formed by depositing a light-emitting composition containing Polymer Example 1(74 wt %) doped with Green Phosphorescent Emitter 1(1 wt %) and Blue Phosphorescent Emitter 2 (25 wt %), illustrated below, to a thickness of about 75 nm by spin-coating. An electron-injecting layer was formed by spin-coating Electron injecting Polymer 1, as described in WO 2012/133229. A cathode was formed by evaporation of a layer of sodium fluoride to a thickness of about 2 nrn, a second layer of aluminium to a thickness of about tOO nm and a third layer of silver to a thickness of about tOO nm.

D C

Green Phosphorescent Emitter 1

_-

Blue Phosphorescent Emitter 2 CsO Cs H3C(0C2H4)30 (C2H40)3CH3 Electron bjecting Polymer 1 Comparative Device I For the purpose of comparison, a device was formed as described with reference to Device Example I except that Polymer Example i was replaced with Comparative Polymer 2.

With reference to Figure 3, current density for any voltage between 1-9V is higher for Device Example 1 than for Comparative Device 1.

With reference to Figure 4, Device Example I operates at a lower voltage and voltage rise over time is smaller than for Comparative Device I -With reference to Figure 5, external quantum efficiency at a given current for Device Example 1 is similar to or higher than that of Comparative Device 1.

With reference to Figure 6, the time taken for Device Example 1 to decay to 70% of a starting brightness at constant current is significantly longer than for Comparative Device 1.

Device Example 2

A device was prepared as described in Device Example i except that the green and blue light emitting layer was formed by depositing a light-emitting composition containing Polymer Example 2(74 wt %) doped with Green Phosphorescent Emitter 1(1 wt %) and Blue Phosphorescent Emitter 2 (25 wt %).

With reference to Figure 7, electroluminescent spectra of Device Examples I and 2 are similar.

With reference to Table 3, conductivities and efficiencies of Device Examples 1 and 2 are siniilar.

Table 3

Polymer Voltage J at 1000 V at 10 Efficiency Efficiellcy EQE at Max at 1000 cd/rn2 rna/cm2 at 1000 at 1000 1000 EQE 2 2 cd/rn cd/rn cd/m cd/m (%) (mnlcrn) (V) (Lm!W) (Lm/W) (%) (V) Device 7.41 3.6 8.45 11.58 27.93 11.60 13.5 Exarnple Device 7.47 3.6 8.50 I L26 27.80 I L03 13.7

Example

The time taken for brightness of Device Example 1 to fall to SO % of a starting brightness was approximately 50% longer than for Device Example 2.

Although the present invention has been described in terms of specific exemplary embodiments, it will be appreciated that various modifications, alterations and/or combinations of features disclosed herein will be apparent to those skilled in the art without departing from the scope of the invention as set forth in the following claims.

Claims (19)

1. Claims A composition comprising a phosphorescent compound of formula (1) and a polymer comprising a repeat unit of formula (TI) (L1) (I) (II) wherein: Ar1 is an aryl or heteroaryl group that may be unsubstituted or substituted with A is independently in each occurrence N or CR3 wherein R3 is H or a substituent; M is a transition metal or metal ion; x is a positive integer of at least 1 y is 0 or a positive integer; and each L1 is independently a mono-or polydentate ligand different from ligands of formula

   N Q*A.z is 0 or a positive integer; and Xis 0 or S.
2. 2. A composition according to claim 1 wherein y 0.
3. 3. A composition according to any preceding claim wherein x = 3.
4. 4. A composition according to any preceding claim wherein M is an iridium ion.
5. 5. A composition according to any preceding claim wherein Ar1 is phenyl that may be unsubstituted or substituted with one or more substituents.
6. 6. A composition according to any preceding claim wherein each A is CR3.
7. 7. A composition according to any of claims 1-5 wherein one A is CR3 and the other AisN.
8. 8. A composition according to any preceding claim wherein the polymer has a LUMO level less than 2.0 eV from vacuum level.
9. 9. A composition according to any preceding claim wherein the polymer comprises one or more co-repeat units.
10. 10. A composition according to claim 9 wherein the polymer comprises an arylene co-repeat unit that may he unsubstituted or substituted with one or more suhstituents.
11. 11. A composition according to claim 9 or 10 wherein the one or more co-repeat units include a conjugation-breaking repeat unit that does not provide any conjugation path between repeat units adjacent to the conjugation-breaking repeat unit.
12. 12. A composition according to claim 11 comprising one or more co-repeat units of formula (II): (S Sr®)-(TI) wherein: Ar4 in each occurrence independently represent an aryl or heteroaryl group that may be unsubstituted or substituted with one or tnore substituents; and Sp represents a spacer group comprising at least one carbon or silicon atom.
13. 13. A composition according to any preceding claim wherein the compound of formula (I) is mixed with the polymer.
14. 14. A composition according to any preceding claim wherein the compound of formula (I) is covalently hound to the polymer.
15. 15. A composition according to any preceding claim wherein the phosphorescent material has a photoluminescent spectrum with a peak in the range of 420-490 nm.
16. 16. A formulation comprising a composition according to any preceding claim and at least one solvent.
17. 17. An organic light-emitting device comprising an anode, a cathode and a light-emitting layer between the anode and cathode wherein the light-emitting layer comprises a composition according to any of claims 1-15.
18. 18. An organic light-emitting device according to claim 17 wherein the device comprises a further light-emitting layer between the anode and the cathode.
19. 19. An organic light-emitting device according to claim 17 or 18 wherein the device emits white light.