Patent Application
20200055885
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 comprises an anode, a cathode and one or more organic light-emitting layers between the anode and cathode. Non-emissive layers, for example charge transporting layers, may be provided 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 (LUMO) of a light-emitting material combine to form an exciton that releases its energy as light.
Light-emitting materials include small molecule, polymeric and dendrimeric materials. Fluorescent light-emitting polymers include poly(arylene vinylenes) such as poly(p-phenylene vinylenes) and polyarylenes such as polyfluorenes.
A light-emitting dopant, for example a fluorescent or phosphorescent dopant, may be used with a charge-transporting host material.
A significant proportion of light generated within an OLED may reflect or be absorbed within the device, limiting the external quantum efficiency of the device.
Kim et al, Adv. Mater. 26(23), 3844-3847, 2014 “Highly Efficient Organic Light-Emitting Diodes with Phosphorescent Emitters Having High Quantum Yield and Horizontal Orientation of Transition Dipole Moments” discloses a heteroleptic iridium complex having a preferred dipole orientation in the horizontal direction. U.S. Pat. No. 8,809,841 disclose a device wherein a transition dipole moment of a luminescent center material is parallel to a top surface of a substrate, and wherein a transition dipole moment of a host material is parallel to the top surface of the substrate.
Kozhevnikov et al, Chem. Mater., 2013, 25 (11), pp 2352-2358 discloses compounds 1 and 5 of formulae:
It is an object of the invention to improve the efficiency of organic light-emitting devices.
In a first aspect the invention provides a metal complex of formula (I):
M(L1)x(L2)y (I)
wherein:
M is a second or third row transition metal;
L1 in each occurrence is independently a light-emitting ligand;
L2 is an auxiliary ligand;
x is at least 1;
y is at least 1; and
each L1 is a group of formula (IIa) or (IIb):
wherein R1-R10 are each independently H or a substituent with the proviso at least one of R3, R5 and R9 of at least one L1 is a group of formula —(Ar)p wherein Ar in each occurrence is independently an aryl or heteroaryl group that may be unsubstituted or substituted with one or more substituents, and p is at least 2.
In a second aspect the invention provides a metal complex of formula (I):
M(L1)x(L2)y (I)
wherein:
M is a second or third row transition metal;
L1 in each occurrence is independently a light-emitting ligand;
L2 is an auxiliary ligand;
x is at least 1;
y is at least 1;
at least one L1 is substituted with at least one group of formula —(Ar)p wherein Ar in each occurrence is independently an aryl or heteroaryl group that may be unsubstituted or substituted with one or more substituents, and p is at least 2; and
an angle between a transition dipole moment vector of the metal complex and a bond vector of at least one L1-(Ar)p bond is less than 15°.
In a third aspect the invention provides a metal complex of formula (I):
M(L1)x(L2)y (I)
wherein:
M is a second or third row transition metal;
L1 in each occurrence is independently a light-emitting ligand;
L2 is an auxiliary ligand;
x is at least 1;
y is at least 1;
at least one L1 is substituted with at least one group of formula —(Ar)p wherein Ar in each occurrence is independently an aryl or heteroaryl group that may be unsubstituted or substituted with one or more substituents, and p is at least 2, such that an a:b ratio of the metal complex is at least 3:1 wherein a is a dimension of the complex in a direction parallel to a transition dipole moment of the complex and b is a dimension of the complex in any direction perpendicular to the transition dipole moment of the complex.
In a fourth aspect the invention provides a composition comprising a metal complex according to the first, second or third aspect and a host.
In a fifth aspect the invention provides a formulation comprising a composition according to the fourth aspect and at least one solvent.
In a sixth aspect the invention provides an organic light-emitting device comprising an anode, a cathode and a light-emitting layer between the anode and cathode comprising a composition according to the fifth aspect.
In a seventh aspect the invention provides method of forming a device according to the sixth aspect, the method comprising the step of depositing the formulation of the fifth aspect over one of the anode and cathode and evaporating the at least one solvent to form the light-emitting layer, and forming the other of the anode and cathode over the light-emitting layer.
In an eighth aspect the invention provides a light-emitting polymer comprising a light-emitting repeat unit of formula (XIIIa) or (XIIIb):
wherein M is a metal, preferably a transition metal; wherein R1, R2, R3, R4, R6, R7, R8 and R10 are each independently H or a substituent; L2 is a ligand as described with reference to the complex of formula (I); and n is 1 or 2. L2 is different from the ligand of formula (XIIIa) or (XIIIb). Preferably n is 1.
Preferably M is as described with reference to the complex of formula (I). Iridium (III) is particularly preferred.
Preferably R1, R2, R3, R4, R6, R7, R8, and R10 are each independently as described with reference to the ligands of formula (IIa) or (IIb).
The repeat units of formula (XIIIa) or (XIIIb) may be bound directly to an adjacent co-repeat unit or may be spaced apart therefrom, optionally spaced apart by a group of formula (Ar4)z, as described with reference to formulae (XIIIa-m) and (XIIIb-m).
In a ninth aspect the invention provides an organic light-emitting device comprising an anode, a cathode and a light-emitting layer between the anode and the cathode wherein the light-emitting layer comprises a polymer according to the eighth aspect.
In a tenth aspect the invention provides a monomer of formula (XIIIa-m) or (XIIIb-m):
wherein M, R1, R2, R3, R4, R6, R7, R8 and R10, n and L2 are as described with reference to repeat units of formulae (XIIIa) and (XIIIb); LG is a leaving group; Ar4 is an aryl or heteroaryl group; and z is 0, 1, 2 or 3.
Preferably, LG in each occurrence is selected from halogen; boronic acid and esters thereof; and sulfonic acid and esters thereof, more preferably bromine, iodine, boronic acid or boronic ester.
Ar4 is preferably a 1,4-linked phenylene which may be unsubstituted or substituted with one or more substituents, optionally one or more C1-12 alkyl groups wherein one or more non-adjacent C atoms may be replaced with O, S, CO or COO. z is preferably 0 or 1. Two or more substituents of Ar4 may be linked to form, with Ar4, a fused aromatic group which may be unsubstituted or substituted with one or more substituents, optionally one or more C1-12 alkyl groups wherein one or more non-adjacent C atoms may be replaced with O, S, CO or COO.
In an eleventh aspect the invention provides a method of forming a polymer, the method comprising the step of polymerizing a monomer according to the tenth aspect. Preferably, the monomer according to the tenth aspect is copolymerized with one or more co-monomers for forming one or more co-repeat units.
The invention will now be described in more detail with reference to the Drawings in which:
With reference to
One or more further layers may be provided between the anode and the cathode. Optionally, further layers may be selected from one or more of a hole-injection layer, a hole-transporting layer, an electron-blocking layer, a electron-transporting layer and an electron blocking layer.
Exemplary OLED layer structures include the following:
Anode/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/Cathode.
Preferably, a hole-injection layer is present between the anode and the light-emitting layer.
Preferably, a hole-transporting layer is present between the anode and the light-emitting layer.
Preferably, both of a hole-injection layer and a hole-transporting layer are present.
In one embodiment, substantially all light is emitted from light-emitting layer 103. In other embodiments, one or more further layers may emit light in addition to light-emitting layer 103. Optionally, one of a hole-transporting layer and an electron-transporting layer comprises a light-emitting material and emits light in use.
The light-emitting layer 103 contains a host material and a heteroleptic phosphorescent metal complex wherein the or each substituent X of the ligands of the metal complex are selected such that at least one substituent X is aligned with the S1 transition dipole moment of the metal complex. The light-emitting layer 103 may consist of the host material and metal complex or may comprise one or more further materials, optionally one or more further light-emitting materials.
By “heteroleptic” as used herein is meant that the ligands of the phosphorescent metal complex include at least two ligands having different coordinating groups.
By “aligned with the S1 transition dipole moment” as used herein is meant that at least one substituent X is substituted on a ligand such that an angle between the S1 transition dipole moment vector and the ligand-X bond is no more than 15°, optionally no more than 10°, optionally no more than 5°, optionally 0.
By “light-emitting ligand” as used herein is meant a ligand having molecular orbitals that contribute to the lowest singlet excited state (S1) of the metal complex, for example by MLCT.
By “auxiliary ligand” as used herein is meant a ligand having molecular orbitals that do not contribute to the lowest singlet excited state (S1) of the metal complex, for example by MLCT.
The heteroleptic phosphorescent metal complex may be, without limitation, a red, green or blue light-emitting material.
A blue light emitting material may have a photoluminescent spectrum with a peak in the range of 400-490 nm.
A green light emitting material may have a photoluminescent spectrum with a peak in the range of more than 490 nm up to 580 nm.
A red light emitting material may optionally have a peak in its photoluminescent spectrum of more than 580 nm up to 650 nm, preferably 600-630 nm.
The photoluminescence spectrum of a light-emitting material may be measured by casting 5 wt % of the material in a PMMA film onto a quartz substrate to achieve transmittance values of 0.3-0.4 and measuring in a nitrogen environment using apparatus C9920-02 supplied by Hamamatsu.
The metal complex of formula (I) may be provided with one or more further light-emitting materials that in combination produce white light when the OLED is in use. The 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 2700-6000K.
Further light-emitting materials may be provided in light-emitting layer 103 and/or in another layer or other layers of the device. Further light-emitting materials may be fluorescent or phosphorescent.
The present inventors have found that an OLED having a high external quantum efficiency can be obtained by using phosphorescent metal complexes as described herein a light-emitting materials of the device. Without wishing to be bound by any theory, it is believed that providing substituents X that are aligned with the S1 transition dipole moment causes the S1 transition dipole moment of the metal complex to align with the plane of the surface that the phosphorescent metal complex is deposited onto. Preferably, the light-emitting layer is a film having an anisotropy factor α of less than 0.85, preferably less than 0.50 or 0.40.
Preferably, the complex of formula (I) has an octahedral geometry.
The compound of formula A illustrates a metal complex according to an embodiment of the invention:
The S1 transition dipole moment, as determined by quantum chemical modelling as described herein, extends parallel to the Ir—N bonds of formula (A). The ligand-X bond of formula A and the transition dipole moment are substantially parallel. The same applies to complexes (B) and (C) illustrated below:
At least one substituent X is aligned with the transition dipole moment.
In the case where x of formula (I) is 2, the metal-N bonds are preferably parallel. With reference to Formulae A, B and C, replacing the acac ligand with a further phenylpyridine ligand will produce a complex having an Ir—N bond that is not parallel to the other Ir—N bonds of the complex.
M of formula (I) may be selected from rows 2 and 3 d block elements, and preferably from ruthenium, rhodium, palladium, rhenium, osmium, iridium, platinum and gold. Iridium is particularly preferred.
Optionally, the or each L1 of the compound of formula (I) is selected from ligands of formulae (IIa) or (IIb):
wherein:
R1-R10 are each independently selected from H, a substituent X or a substituent other than X; and
and
R9 is a substituent X; or
Preferably, the compound has formula M(L1)2L2 and only R3 is a group of formula X.
If more than one ligand L1 is present then the substitution of groups X may be the same or different on different ligands L1.
Preferably, each ligand L1 is the same for ease of synthesis.
Groups R1-R10 that are not a substituent X are preferably selected from H, D, F and C1-10 alkyl wherein one or more non-adjacent C atoms may be replaced by O, S, C═O or COO and one or more H atoms may be replaced by F. Two or more adjacent groups R1-R10 that are not alkyl may be linked to form an aromatic or non-aromatic ring, optionally phenyl, that may be unsubstituted or substituted with one or more substituents, optionally one or more C1-20 alkyl groups. More preferably, groups R1-R10 that are not a substituent X are H.
Preferably, the complex of formula (I) has an aspect ratio a:b of at least 3:1 wherein a is a dimension of the complex in a direction parallel to a transition dipole moment of the complex and b is a dimension of the complex in any direction perpendicular to the transition dipole moment of the complex. Optionally, the a:b ratio is at least 4:1 or at least 5:1. The substituent X has formula —(Ar)p wherein p is at least 2, optionally 3, and each Ar is independently an unsubstituted or substituted aryl or heteroaryl group. Dimensions may be determined by molecular modelling as described herein.
p can be 1-10 provided that substituent X has higher T1 than the emitter core.
Preferably, each Ar is independently selected from a C6-20 aryl group, optionally phenyl, or a 6-membered heteroaryl of C and N atoms, optionally triazine.
Each Ar is independently unsubstituted or substituted with one or more substituents. Exemplary substituents are C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced by O, S, C═O or COO and one or more H atoms may be replaced with F.
Optionally, a position of the Ar group adjacent to a bond between L1 and X is substituted with such a substituent to create a twist between L1 and X.
Optionally, at least one Ar group is substituted with a C1-20 alkyl group to enhance solubility of the compound of formula (I) in solvents as described herein.
The group of formula —(Ar)p may be a linear or branched chain of Ar groups. A branched chain of —(Ar)p groups may form a dendron.
A dendron may have optionally substituted formula (III)
wherein BP represents a branching point for attachment to a core and G1 represents first generation branching groups.
The dendron may be a first, second, third or higher generation dendron. G1 may be substituted with two or more second generation branching groups G2, and so on, as in optionally substituted formula (Ma):
wherein u is 0 or 1; v is 0 if u is 0 or may be 0 or 1 if u is 1; BP represents a branching point for attachment to a core and G1, G2 and G3 represent first, second and third generation dendron branching groups. In one preferred embodiment, each of BP and G1, G2 . . . Gn is phenyl, and each phenyl BP, G1, G2 . . . Gn-1 is a 3,5-linked phenyl.
Exemplary groups X include the following, each of which may be unsubstituted or substituted with one or more substituents:
wherein * is a point of attachment to L1.
Exemplary ligands L2 are:
N,N-chelating ligands, optionally pyridine carboxamides; pyridyl pyrazolates; pyridyl triazolates; amidates;
N,O-chelating ligands, optionally picolinate or iminophenol; and
O,O-chelating ligands, optionally diketonates; or acetates.
Exemplary diketonates have formula:
wherein R20 and R22 are each independently a substituent; R21 is H or a substituent; and wherein R20 and R21 or R21 and R22 may be linked to form a ring. Preferably, R20, and R22 are each independently a C1-10 alkyl group. Preferably, R21 is H or a C1-10 alkyl group. R20 and R21 may be linked to form a 6-10 membered aromatic or heteroaromatic ring that may be unsubstituted or substituted with one or more substituents, optionally one or more substituents selected from C1-20 hydrocarbyl groups.
Exemplary diketonates are acac and:
N,O-chelating ligands include a ligand of formula (V):
wherein Ar2 is a heteroaryl, preferably a 5-10 membered heteroaryl of C and N atoms that may be unsubstituted or substituted with one or more substituents, optionally one or more C1-10 alkyl groups.
Exemplary N,N-chelating ligands have formula (IV):
wherein Ar20 independently in each occurrence is a 5-10 membered heteroaryl group, optionally a 5-membered heteroaryl containing N and C atoms, optionally pyrazole or triazole.
Ligands of formula (IV) may be unsubstituted or may be substituted with one or more substituents. Exemplary substituents are C6-10 aryl or 5-10 membered heteroaryl groups, optionally phenyl that may be unsubstituted or substituted with one or more substituents, and C1-10 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, C═O or COO H atoms may be replaced with F.
Exemplary ligands of formula (IV) are:
The S1 transition dipole moment vector of a compound of formula (I) may be determined by quantum chemical modelling using Gaussian09 software available from Gaussian, Inc. according to the following steps:
Bond lengths and bond vectors may be determined from this model.
Host The host used with the metal complex of formula (I) may be a small molecule, dendrimeric or polymeric material. Preferably the host is a polymer.
The value of the anisotropy factor α of a film of a composition of a metal complex of formula (I) and a host may be affected by the structure of the host.
Preferably, the host material has an a absorption value measured as described herein of 0.85, preferably less than 0.50 or 0.40.
A polymeric host may have a rod-like backbone.
Optionally, the host polymer is a conjugated polymer comprising arylene or heteroarylene repeat units.
The polymer may comprise co-repeat units of formula (VI):
wherein Ar is an arylene or heteroarylene group, more preferably a C6-20 aryl group, that may be unsubstituted or substituted with one or more substituents, and angle Θ is 140°-180°
Exemplary arylene repeat units of formula (VI) include, without limitation, 1,4-linked phenylene repeat units; 2,7-linked fluorene repeat units; 2-8-linked phenanthrene repeat units; 2,8-linked dihydrophenanthrene repeat units; and 2,7-linked triphenylene repeat units, each of which may be unsubstituted or substituted with one or more substituents.
Optionally, angle Θ is 160°-180°, optionally 170°-180° Optionally, 1-100 mol %, optionally 10-95 mol % or 20-80 mol % of repeat units of the polymer may be repeat units of formula (VI).
The 1,4-phenylene repeat unit may have formula (VII)
wherein w in each occurrence is independently 0, 1, 2, 3 or 4, optionally 1 or 2; and R7 independently in each occurrence is a substituent.
Where present, each R7 may independently be selected from the group consisting of:
alkyl, optionally C1-20 alkyl, wherein one or more non-adjacent C atoms may be replaced with optionally substituted aryl or heteroaryl, O, S, substituted N, C═O or —COO—, and one or more H atoms may be 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; and
—(Ar1)c wherein each Ar1 is independently an aryl or heteroaryl group that may be unsubstituted or substituted with one or more substituents and c is at least 1, optionally 1 2 or 3
Ar1 in each occurrence is preferably a C6-20 aryl group, more preferably phenyl. The group —(Ar1)c may form a linear or branched chain of aryl or heteroaryl groups in the case where c is at least 2. Preferred substituents of Ar1 are C1-20 alkyl groups.
Substituted N, where present, may be —NR2— wherein R2 is C1-20 alkyl; unsubstituted phenyl; or phenyl substituted with one or more C1-20 alkyl groups.
Preferably, each R7 is independently selected from C1-40 hydrocarbyl, and is more preferably selected from C1-20 alkyl; unsubstituted phenyl; and phenyl substituted with one or more C1-20 alkyl groups; and a linear or branched chain of phenyl groups, wherein each phenyl may be unsubstituted or substituted with one or more substituents.
Substituents R7 of formula (VII), if present, are adjacent to linking positions of the repeat unit, which may cause steric hindrance between the repeat unit of formula (VII) and adjacent repeat units, resulting in the repeat unit of formula (VII) twisting out of plane relative to one or both adjacent repeat units.
A particularly preferred repeat unit of formula (VII) has formula (VIIa):
A 2,7-linked fluorene repeat unit may have formula (IX):
wherein R8 in each occurrence is the same or different and is a substituent wherein the two groups R8 may be linked to form a ring; R7 is a substituent as described above; and d is 0, 1, 2 or 3.
Each R8 may independently be selected from the group consisting of:
Preferably, each R8 is independently a C1-40 hydrocarbyl group.
Different groups R8 are disclosed in WO 2012/104579 the contents of which are incorporated in entirety by reference.
Substituted N, where present, may be —NR2— wherein R2 is as described above.
Exemplary substituents R7 are alkyl, for example C1-20 alkyl, wherein one or more non-adjacent C atoms may be replaced with O, S, C═O and —COO—, optionally substituted aryl, optionally substituted heteroaryl, fluorine, cyano and arylalkyl. Particularly preferred substituents include C1-20 alkyl and substituted or unsubstituted aryl, for example phenyl. Optional substituents for the aryl include one or more C1-20 alkyl groups.
The extent of conjugation of repeat units of formula (IX) to aryl or heteroaryl groups of adjacent repeat units in the polymer backbone may be controlled by substituting the repeat unit with one or more substituents R8 in or more positions 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 C1-20 alkyl substituent in one or both of the 3- and 6-positions.
The repeat unit of formula (VI) may have formula (X) or (XI):
wherein R7, R8 and d are as described with reference to formulae (VII) and (IX) above.
Any of the R7 groups of formulae (X) and (XI) 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 C1-20 alkyl groups.
Any of the R8 groups of formula (XI) may be linked to any other of the R8 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 C1-20 alkyl groups.
The host polymer may contain repeat units of formula (X):
wherein Ar8, Ar9 and Ar10 are each independently unsubstituted or substituted with one or more, optionally 1, 2, 3 or 4, substituents, z in each occurrence is independently at least 1, optionally 1, 2 or 3, preferably 1, and Y is N or CR14 wherein R14 is H or a substituent, preferably H or C1-10 alkyl and with the proviso that at least one Y is N. Preferably, Ar8, Ar9 and Ar10 of formula (X) are each phenyl, each phenyl being optionally and independently substituted with one or more C1-20 alkyl groups.
Substituents of Ar8, Ar9 and Ar10 may be selected from substituted or unsubstituted alkyl, optionally C1-20 alkyl, wherein one or more non-adjacent C atoms may be replaced with optionally substituted aryl or heteroaryl (preferably phenyl), O, S, C═O or —COO— and one or more H atoms may be replaced with F.
Preferred substituents of Ar8, Ar9 and Ar10, if present, are C1-40 hydrocarbyl, preferably C1-20 alkyl or a hydrocarbyl crosslinking group.
In one preferred embodiment, all 3 groups Y are N.
Ar10 of formula (X) is preferably phenyl, and is optionally substituted with one or more C1-20 alkyl groups or a crosslinkable unit. The crosslinkable unit may be bound directly to Ar10 or spaced apart from Ar10 by a spacer group.
Preferably, z is 1 and each of Ar8, Ar9 and Ar10 is unsubstituted phenyl or phenyl substituted with one or more C1-20 alkyl groups.
A particularly preferred repeat unit of formula (X) has formula (Xa), which may be unsubstituted or substituted with or more substituents R5, preferably one or more C1-20 alkyl groups:
The metal complex of formula (I) may be provided in an amount in the range of 0.1-40 wt % in a composition comprising the host and the metal complex of formula (I).
The lowest triplet excited state energy level of the host material is at least the same as or higher than that of the metal complex. Triplet energy levels may be measured from the energy onset of the phosphorescence spectrum measured by low temperature phosphorescence spectroscopy (Y. V. Romaovskii et al, Physical Review Letters, 2000, 85 (5), p 1027, A. van Dijken et al, Journal of the American Chemical Society, 2004, 126, p 7718).
The metal complex may be admixed with the host or may be covalently bound to the host. In the case of a host polymer the metal complex may be provided as a side-group or end group of the polymer backbone or as a repeat unit in the backbone of the polymer.
Light Emitting Polymer
The light-emitting polymer comprising a light-emitting repeat unit of formula (XIIIa) or (XIIIb) preferably has an anisotropy factor α of no more than 0.8, preferably no more than 0.7, more preferably no more than 0.5. The value of the anisotropy factor α may be affected by the structure and/or molar percentage of the light-emitting repeat unit and/or co-repeat units. Co-repeat units may be selected to give, in combination with an aligned light-emitting repeat unit, a required anisotropy factor α of the polymer.
Suitable co-repeat units include electron-transporting co-repeat units; hole-transporting co-repeat units; and light-emitting co-repeat units wherein the transition dipole moment of the light-emitting co-repeat unit is not aligned with the polymer backbone.
The co-repeat units may form a rod-like backbone.
Preferably, the light-emitting polymer may comprise co-repeat units of formula (VI). Co-repeat units of formula (VI) are as described above in relation to a host.
The light-emitting polymer comprising a light-emitting repeat unit of formula (XIIIa) or (XIIIb) optionally has a polystyrene-equivalent number-average molecular weight (Mn) measured by gel permeation chromatography in the range of about 1×103 to 1×108, and preferably 1×103 to 5×106. The polystyrene-equivalent weight-average molecular weight (Mw) of the polymers described herein may be 1×103 to 1×108, and preferably 1×104 to 1×107.
Polymerisation Method
Conjugated polymers as described herein may be formed by metal catalysed polymerisations such as Yamamoto polymerisation and Suzuki polymerisation as disclosed in WO 00/53656, WO 03/091355 and EP1245659, the contents of which are incorporated herein by reference.
Preferably, the polymer is formed by polymerising monomers comprising leaving groups that leave upon polymerisation of the monomers. Preferably, the polymer is formed by polymerising monomers comprising boronic acid and ester groups bound to aromatic carbon atoms of the monomer with monomers comprising leaving groups selected from halogen, sulfonic acid or sulfonic ester, preferably bromine or iodine, bound to aromatic carbon atoms of the monomer in the presence of a palladium (0) or palladium (II) catalyst and a base.
Exemplary boronic esters have formula (XII):
wherein R6 in each occurrence is independently a C1-20 alkyl group, * represents the point of attachment of the boronic ester to an aromatic ring of the monomer, and the two groups R6 may be linked to form a ring.
Solution Processing
A light-emitting layer as described herein may be formed by depositing a solution of the compound of formula (I), the host and, if present, any other components of the light-emitting layer dissolved in a solvent or solvent mixture.
Exemplary solvents are benzenes substituted with one or more substituents selected from C1-10 alkyl, C1-10 alkoxy and chlorine, for example toluene, xylenes and methylanisoles.
Exemplary solution deposition techniques include printing and coating techniques such spin-coating, dip-coating, flexographic printing, inkjet printing, slot-die coating and screen printing. Spin-coating and inkjet printing are particularly preferred.
Spin-coating is particularly suitable for devices wherein patterning of the light-emitting layer is unnecessary—for example for lighting applications or simple monochrome segmented displays.
The light-emitting layer may be annealed following deposition. Preferably, annealing is below the glass transition temperature of the polymer.
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 be 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 be closed or open at the channel ends.
Additional layers between the anode and cathode of an OLED, where present, may be formed by a solution deposition method as described herein.
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 and the light-emitting layer or layers of an OLED to improve 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 sulfonic acid, for example Nafion®; polyaniline as disclosed in U.S. Pat. Nos. 5,723,873 and 5,798,170; 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 (1996), 29(11), 2750-2753.
Where a hole-transporting layer is present, a hole-injection layer may be provided between the anode and the hole-transporting layer.
Charge Transporting and Charge Blocking Layers
A hole transporting layer may be provided between the anode and the light-emitting layer or layers. An electron transporting layer may be provided between the cathode and the light-emitting layer or layers.
An electron blocking layer may be 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 may be used in combination. Depending on its HOMO and LUMO levels, a single layer may both transport one of holes and electrons and block the other of holes and electrons.
A hole transporting layer preferably has a HOMO level of less than or equal to 5.5 eV, more preferably around 4.8-5.5 eV as measured by cyclic voltammetry. The HOMO level of the hole transport layer may be selected so as to be within 0.2 eV, optionally within 0.1 eV, of an adjacent layer (such as a light-emitting layer) in order to provide a small barrier to hole transport between these layers. The hole-transporting layer may be a polymer comprising repeat units of formula (I) as described above.
An electron transporting layer located between the light-emitting layers and cathode preferably has a LUMO level of around 2.5-3.5 eV as measured by cyclic voltammetry. For example, a layer of a silicon monoxide or silicon dioxide or other thin dielectric layer having thickness in the range of 0.2-2 nm may be provided between the light-emitting layer nearest the cathode and the cathode. HOMO and LUMO levels may be measured using cyclic voltammetry.
A hole-transporting polymer may be a homopolymer or copolymer comprising a repeat unit of formula (VIII):
wherein Ar8, Ar9 and Ar10 in each occurrence are independently selected from substituted or unsubstituted aryl or heteroaryl, g is 0, 1 or 2, preferably 0 or 1, R13 independently in each occurrence is H or a substituent, preferably a substituent, and c, d and e are each independently 1, 2 or 3.
R13, which may be the same or different in each occurrence when g is 1 or 2, is preferably selected from the group consisting of alkyl, for example C1-20 alkyl, Ar11, a branched or linear chain of Ar11 groups, or a crosslinkable unit that is bound directly to the N atom of formula (VIII) or spaced apart therefrom by a spacer group, wherein Ar11 in each occurrence is independently optionally substituted aryl or heteroaryl. Exemplary spacer groups are C1-20 alkyl, phenyl and phenyl-C1-20 alkyl. Any two aromatic or heteroaromatic groups selected from Ar8, Ar9, and, if present, Ar10 and Ar11 directly bound to the same N atom may be linked by a direct bond or a divalent linking atom or group to another of Ar8, Ar9, Ar10 and Ar11. Preferred divalent linking atoms and groups include O, S; substituted N; and substituted C.
Ar8 and Ar10 aryl, more preferably C6-20 phenyl, that may be are preferably C6-20 unsubstituted or substituted with one or more substituents.
In the case where g=0, Ar9 is preferably C6-20 aryl, more preferably phenyl, that may be unsubstituted or substituted with one or more substituents.
In the case where g=1, Ar9 is preferably C6-20 aryl, more preferably phenyl or a polycyclic aromatic group, for example naphthalene, perylene, anthracene or fluorene, that may be unsubstituted or substituted with one or more substituents.
R13 is preferably Ar11 or a branched or linear chain of Ar11 groups. Ar11 in each occurrence is preferably phenyl that may be unsubstituted or substituted with one or more substituents.
Exemplary groups R13 include the following, each of which may be unsubstituted or substituted with one or more substituents, and wherein * represents a point of attachment to N:
c, d and e are preferably each 1.
Ar8, Ar9, and, if present, Ar10 and Ar11 are each independently unsubstituted or substituted with one or more, optionally 1, 2, 3 or 4, substituents. Exemplary substituents may be selected from:
Preferred substituents of Ar8, Ar9, and, if present, Ar10 and Ar11 are C1-40 hydrocarbyl, preferably C1-20 alkyl or a hydrocarbyl crosslinking group.
Preferred repeat units of formula (VIII) include units of formulae 1-3:
Preferably, Ar8, Ar10 and Ar11 of repeat units of formula 1 are phenyl and Ar9 is phenyl or a polycyclic aromatic group.
Preferably, Ar8, Ar9 and Ar11 of repeat units of formulae 2 and 3 are phenyl.
Preferably, Ar8 and Ar9 of repeat units of formula 3 are phenyl and R11 is phenyl or a branched or linear chain of phenyl groups.
A polymer comprising repeat units of formula (VIII) may be a homopolymer or a copolymer containing repeat units of formula (VIII) and one or more co-repeat units.
In the case of a copolymer, repeat units of formula (VIII) may be provided in a molar amount in the range of about 1-99 mol %, optionally about 1-50 mol %.
Exemplary co-repeat units include arylene repeat units, optionally arylene units as described above.
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.
Cathode
The cathode is selected from materials that have a workfunction allowing injection of electrons into the light-emitting layer. 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, for example a plurality of conductive metals such a bilayer of a low workfunction material and a high workfunction material such as calcium and aluminium as disclosed in WO 98/10621. The cathode may comprise a layer of 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. 1-5 nm) layer of metal compound between the organic semiconducting layers and one or more conductive cathode layers, in particular an oxide or fluoride of an alkali or alkali earth metal, to assist electron injection, for example lithium fluoride, for example as disclosed in WO 00/48258; barium fluoride, for example as disclosed in Appl. 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 3 eV. Work functions of metals can be found in, for example, Michaelson, J. Appl. Phys. 48(11), 4729, 1977.
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 be 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, of course, a fully transparent device is desired), and so the transparent anode used for bottom-emitting devices may be replaced or supplemented with a layer of reflective material such as a layer of aluminium. Examples of transparent cathode devices are disclosed in, for example, GB 2348316.
Encapsulation
Organic optoelectronic devices tend to be sensitive to moisture and oxygen. Accordingly, the substrate preferably has good barrier properties for prevention of ingress of moisture and oxygen into the device. The substrate is commonly glass, however alternative substrates may be used, in particular where flexibility of the device is desirable. For example, the substrate may comprise one or more plastic layers, for example a substrate of alternating 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/or oxygen that may permeate through the substrate or encapsulant may be disposed between the substrate and the encapsulant.
Measurements
Anisotropy factor α is measured using emission spectroscopy as described in M Flämmich et al, Organic Electronics 12, 2011, p. 1663-1668 the contents of which are incorporated herein by reference. The average dipole orientation can be represented by a vector (x,y,z) where the z direction is normal to the plane of the thin film. This can be further parameterised as the ratio of parallel to perpendicular components p∥:p⊥=(x+y):z as used in Flämmich et al, or alternatively as an anisotropy factor α=z/x=z/y, as used throughout this document. In this way, isotropic orientation can be represented by (1,1,1), where p∥:p⊥=2:1 and α=1. Additionally, an example of a anisotropic orientation can be represented as (0.3571, 0.3571, 0.2858), where p∥:p⊥=2.5:1 and α=0.8.
Absorption anisotropy is measured by analysis of the lowest energy absorption peak using the spectroscopic ellipsometry method described in Ramsdale et al., Advanced Materials vol. 14 (3), p 212 (2002).
Unless stated otherwise, a values provided herein are as measured by emission spectroscopy as described above.
Square wave cyclic voltammetry as described anywhere herein may be performed by ramping a working electrode potential linearly versus time. When square wave voltammetry reaches a set potential the working electrode's potential ramp is inverted. This inversion can happen multiple times during a single experiment. The current at the working electrode is plotted versus the applied voltage to give the cyclic voltammogram trace.
Apparatus to measure HOMO or LUMO energy levels by CV may comprise a cell containing a tert-butyl ammonium perchlorate/or tertbutyl ammonium hexafluorophosphate solution in acetonitrile, a glassy carbon working electrode where the sample is coated as a film, a platinium counter electrode (donor or acceptor of electrons) and a reference glass electrode no leak Ag/AgCl. Ferrocene is added in the cell at the end of the experiment for calculation purposes.
Measurement of the difference of potential between Ag/AgCl/ferrocene and sample/ferrocene.
Method and settings:
3 mm diameter glassy carbon working electrode
Ag/AgCl/no leak reference electrode
Pt wire auxiliary electrode
0.1 M tetrabutylammonium hexafluorophosphate in acetonitrile
LUMO=4.8−ferrocene (peak to peak maximum average)+onset
Sample: 1 drop of 5 mg/mL in toluene spun at 3000 rpm LUMO (reduction) measurement:
A good reversible reduction event is typically observed for thick films measured at 200 mV/s and a switching potential of −2.5V. The reduction events should be measured and compared over 10 cycles, usually measurements are taken on the 3rd cycle. The onset is taken at the intersection of lines of best fit at the steepest part of the reduction event and the baseline. HOMO and LUMO values may be measured at ambient temperature.
Steps 1-4 were carried out according to the following reaction scheme:
Step 1: Synthesis of Intermediate 2
Apparatus Set-Up:
A 5 L 3-necked round-bottomed flask, equipped with a mechanical overhead stirrer, thermo socket, nitrogen inlet and exhaust.
Experimental procedure:
Step 2:
Apparatus Set-Up:
A 5 L 3-necked round-bottomed flask, equipped with a mechanical overhead stirrer, nitrogen inlet and exhaust.
Experimental Procedure:
1H-NMR (400 MHz, CDCl3): δ [ppm] 7.43 (dd, J=1.76, 5.28 Hz, 1H), 7.47-7.53 (m, 3H), 7.93 (d, J=1.72 Hz, 1H), 7.98-8.00 (m, 2H), 8.53 (d, J=5.28 Hz, 1H).
Step 3: Synthesis of Intermediate 3
Apparatus Set-Up:
A 3 L 4-necked round-bottomed flask, equipped with a mechanical overhead stirrer, condenser, nitrogen inlet and exhaust.
Experimental Procedure:
Step 4
Apparatus Set-Up:
A 5 L 4-necked round-bottomed flask, equipped with a mechanical overhead stirrer, condenser, nitrogen inlet and exhaust.
Experimental Procedure:
1H-NMR (400 MHz, CDCl3): δ [ppm] 2.31 (s, 3H), 7.14-7.19 (m, 2H), 7.43-7.52 (m, 5H), 7.67 (s, 1H), 8.03 (d, J=7.60 Hz, 2H), 8.75 (d, J=5.20 Hz, 1H).
Step 5
5 g (15.4 mmol) 2-phenyl-4-(2-methyl-4-bromophenyl)pyridine and 4′-n-octyl biphenyl-4-boronic acid pinacol ester (1.2 equivalents) were dissolved in Toluene (50 mL) and bubbled with nitrogen for 1 hr. Pd2(dba)3 (0.01 eq.) and SPhos (0.02 eq.) were added and the mixture was bubbled with nitrogen for a further 10 min. Et4NOH (20% aq solution; 4 eq.) was degassed by bubbling with nitrogen and added to the reaction and the mixture was stirred and heated at 115° C. for 20 hr.
After cooling to room temperature, the organic part was separated and washed with water and then the solvent removed giving a grey solid. This was purified by precipitation from dichloromethane solution into acetonitrile, followed by trituration with methanol. Finally, the material was dissolved in ethyl acetate and residual undissolved material removed by filtration. Removal of the solvent from the filtrate gave 5.7 g white solid (73% yield).
Step 6
5.7 g of starting material (11.18 mmol) and iridium(III)chloride (0.4 equivalents) were placed in a flask and suspended in a mixture of 2-ethoxyethanol and water (76 mL 3:1 mix). The mixture was bubbled with nitrogen for 1 hr while stirring and then heated to 120° C. for 17 hr. After cooling to room temperature 200 mL water was added and the mixture stirred for 30 min. The yellow precipitate was collected by filtration. The product was purified by precipitation from dichloromethane into heptane, followed by precipitation from toluene into methanol. This gave 3.27 g yellow solid (85% yield).
Step 7
3.27 g (1.31 mmol) starting material, sodium carbonate (5 eq.), 2,2,6,6-tetramethyl heptan-3,5-dione (5 eq.) and 2-ethoxyothanol (65 mL) were placed in a flask and bubbled with nitrogen for 1 hr. The reaction was then stirred and heated at 120° C. for 20 hr. After cooling to room temperature, 200 mL water was added to the flask then the mixture poured a beaker containing 400 mL water. The resulting precipitate was collected in a Buchner funnel and washed with methanol. The resulting yellow solid was purified by recrystallisation in a mixture of dichloromethane and heptane giving 1.85 g product (51% yield).
The product is illustrated in
1H NMR (600 MHz, CHLOROFORM-d) δ=8.46 (2H, d, J2, 2′3, 3′=5.8 Hz, H-2, 2′), 7.84 (2H, s, H-5, 5′), 7.74-7.77 (4H, m, H-21′″, 21′, 21, 21″), 7.70-7.73 (4H, m, H-22′″, 22′, 22, 22″), 7.65 (2H, s, H-17, 17′), 7.63 (2H, d, J=7.8 Hz, H-15, 15′), 7.61 (1H, s, H-9′, 9), 7.60 (5H, d, J=7.8 Hz, H-25′″, 25′, 25, 25″), 7.48 (2H, d, J14, 14′, 12, 12′=7.7 Hz, H-14, 14′), 7.26-7.32 (4H, m, H-26′″, 26′, 26, 26″), 7.11 (2H, dd, J3, 3′, 2, 2′=5.8 Hz, J=1.8 Hz, H-3, 3′), 6.85 (2H, t, J10, 10′,11,11′=7.3 Hz, H-10, 10′), 6.76 (2H, t, J11, 11′,10,10′=7.4 Hz, H-11, 11′), 6.57 (2H, d, J12, 12′, 14, 14′=8.1 Hz, H-12, 12′), 5.55 (1H, s, H-38), 2.68 (4H, t, J28′, 28,29′, 29=7.8 Hz, H-28′, 28), 2.49 (6H, s, H-19′, 19), 1.68 (4H, quin, J29′, 29,28′, 28=7.6 Hz, H-29′, 29), 1.30-1.41 (12H, m, H-32′, 32, 31′, 31, 30′, 30), 1.26-1.31 (5H, m, H-33′, 33), 1.25-1.42 (4H, m, H-34′, 34), 0.95 (18H, s, H-43′, 43, 43′″, 41′, 41, 41″), 0.87-0.93 (6H, m, H-35′, 35)
Step 1: Synthesis of Intermediate 3
Apparatus Set-Up:
A 2 L 3-necked round-bottomed flask, equipped with a mechanical overhead stirrer, condenser, nitrogen inlet and exhaust.
Experimental Procedure:
Step 2: Synthesis of Intermediate 4
Apparatus Set-Up:
A 2 L 3-necked round-bottomed flask, equipped with a mechanical overhead stirrer and condenser.
Experimental Procedure:
1H-NMR (400 MHz, DMSO-d6): δ [ppm] 8.47 (d, J=7.88 Hz, 4H), 7.68 (d, J=7.92 Hz, 4H), 1.36 (s, 18H).
Step 3: Synthesis of Intermediate 6
Apparatus Set-Up:
A 2 L 3-necked round-bottomed flask, equipped with a mechanical overhead stirrer, condenser, nitrogen inlet and exhaust.
Experimental Procedure:
Step 4: Synthesis of Intermediate 7
Apparatus Set-Up:
A 2 L 3-necked round-bottomed flask, equipped with a mechanical overhead stirrer, condenser, nitrogen inlet and exhaust.
Experimental Procedure:
Step 5: Synthesis of Intermediate 8
Apparatus Set-Up:
A 2 L 4-necked round-bottomed flask, equipped with a mechanical overhead stirrer, condenser, nitrogen inlet and exhaust.
Experimental Procedure:
Step 6
Apparatus Set-Up:
A 2 L 3-necked round-bottomed flask equipped with a mechanical stirrer, nitrogen inlet and exhaust.
Experimental Procedure:
1H-NMR (400 MHz, CDCl3): δ [ppm] 9.03 (s, 1H), 8.97 (d, J=5.04 Hz, 1H), 8.72 (d, J=8.36 Hz, 4H), 8.53 (d, J=5.04 Hz, 1H), 8.20 (d, J=7.16 Hz, 2H), 7.65 (d, J=8.36 Hz, 4H), 7.57-7.61 (m, 2H), 7.52-7.53 (m, 1H), 1.44 (s, 18H).
13C-NMR (100 MHz, CDCl3): δ [ppm] 172.00, 170.06, 158.39, 156.56, 150.42, 144.87, 139.20, 133.11, 129.26, 128.93, 28.86, 127.16, 125.76, 120.80, 119.23, 35.16, 31.22
Step 7
6.45 g Iridium(III) chloride hydrate (18.2 mmol) and starting material (2.2 equivalents) were placed in a flask and suspended in a 3:1 mixture of 2-ethoxyethanol/water (360 mL). The mixture was degassed for 1 h before stirring at 125° C. for 14 hr. The vessel was protected from light for the duration of the reaction. After cooling to room temperature, 200 mL water was added and the mixture stirred for 15 min. The precipitated solid was collected by filtration and washed with 200 mL water followed by 300 mL ethanol and 500 mL methanol. Product used without further purification—18.98 g (85% yield).
Step 8
3 g (1.23 mmol) of starting material and sodium carbonate (10.0 eq) were placed in a flask and suspended in 80 mL 2-ethoxyethanol. In a dropping funnel, 2,2,6,6-tetramethylheptan-3,5-dione (4.0 eq.) was dissolved in 20 mL 2-ethoxyethanol. Both solutions were bubbled with nitrogen for 40 min. The reaction flask was stirred and heated to 60° C. then the solution from the dropping funnel was added. The temperature was increased to 130° C. and the reaction stirred for 18 hr. After cooling to room temperature, 100 mL water was added to the flask and stirred for 20 min. The precipitated product was collected by filtration and washed with water. The resulting deep red solid was purified by column chromatography followed by recrystallisation from toluene/acetonitrile.
The product is illustrated in
1H NMR (600 MHz, CHLOROFORM-d) δ=9.17 (2H, s, H-5, 5′), 8.75 (8H, d, J=8.5 Hz, H-18″, 18′″″, 18′″″″, 18′, 18, 18″″, 18′″, 18″″″), 8.71 (2H, d, J=5.9 Hz, H-2, 2′), 8.37 (2H, dd, J=5.9 Hz, J=1.5 Hz, H-3, 3′), 7.85-7.90 (2H, m, J=7.6 Hz, H-12, 12′), 7.66 (8H, d, J=8.5 Hz, H-19″, 19′″″, 19′″″″, 19′, 19, 19″″, 19′″, 19″″″), 6.92-6.97 (1H, m, M02), 6.94 (2H, t, J=7.3 Hz, H-11, 11′), 6.76 (2H, t, J=7.3 Hz, H-10, 10′), 6.46-6.50 (2H, m, J=7.6 Hz, H-9, 9′), 5.58 (1H, s, H-25), 1.44 (37H, s, H-22″, 22′″″, 22*, 22′, 22′″″″, 22″″″″, 22**, 22, 22″″, 22′″, 22″″″, 22″″″″′), 0.98 (15H, s, H-28″, 28, 28′, 30, 30″, 30′)
A film of a composition of Compound Example 2 (5 wt %) and Host Polymer 1 (95 wt %) was formed by spin-coating and the anisotropy factor α was measured by emission spectroscopy as described herein.
Host Polymer 1 is a polymer formed by Suzuki polymerisation as described in WO00/53656 and comprises repeat units of formulae VIIa (50 mol %), XI (40 mol %) and X (10 mol %) as described above.
The α value was 0.79.
Comparative Composition 1
A film was prepared as described for Composition Example 1 except that Comparative Compound 1, illustrated below, was used in place of Compound Example 2.
The α value was 1.09.
A film of a composition of Compound Example 1 (5 wt %) and Host Polymer 2 (95 wt %) was formed by spin-coating and the anisotropy factor α was measured by emission spectroscopy as described herein.
Host Polymer 2 is a polymer formed by Suzuki polymerisation as described in WO00/53656 and comprises repeat units of formulae VIIa (50 mol %) and XI (50 mol %) as described above.
The α value was 0.33.
Comparative Device 1
An organic light-emitting device having the following structure was prepared:
ITO/HIL/HTL/LEL/Cathode
wherein ITO 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.
A substrate carrying ITO (45 nm) was cleaned using UV/Ozone. A hole injection layer was formed to a thickness of about 65 nm by spin-coating a formulation of a hole-injection material. A hole transporting layer was formed to a thickness of about 22 nm by spin-coating a hole-transporting polymer comprising phenylene repeat units of formula (VII), amine repeat units of formula (VIII-1) and crosslinkable repeat units of formula (IXa) and crosslinking the polymer by heating. The light-emitting layer was formed to a thickness of about 83 nm by spin-coating a mixture of Host Polymer 3:Comparative Compound 2 (70 wt %:30 wt %). A cathode was formed on the light-emitting layer of a first layer of sodium fluoride of about 2 nm thickness, a layer of aluminium of about 100 nm thickness and a layer of silver of about 100 nm thickness.
Host Polymer 3 is a block polymer formed by Suzuki polymerisation as described in WO 00/53656 of a first block formed by polymerisation of the monomers of Set 1, and a second block formed by polymerisation of the monomers of Set 2.
Comparative Compound 2 has the following structure:
A device was prepared as described for Comparative Device 1 except that 5 wt % of Comparative Compound 1 was replaced with 5 wt % of Compound Example 1.
Efficiency of Device Example 1 was about 97 cd/A whereas efficiency of Comparative Device 1 was about 76 cd/A.
With reference to
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1511300.4 | Jun 2015 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2016/051897 | 6/24/2016 | WO | 00 |
