JP2013539198A - Organic light emitting compositions, devices and methods - Google Patents

Abstract

  A composition comprising a triplet acceptor unit comprising a fluorescent material and an optionally substituted compound of formula (I). The composition can be used in an organic light emitting device, and the optionally substituted compound of formula (I) can be blended or combined with a fluorescent material. The composition can be deposited by solution deposition.

Description

  This application is based on British Patent Application No. 1010741.5 filed on June 25, 2010, British Patent Application No. 1010742.3 filed on June 25, 2010, and British Patent Application No. 1010745 filed on June 25, 2010. No. 6, British Patent Application No. 1010743.1 filed on June 25, 2010 and British Patent Application No. 1101642.5 filed on January 31, 2011. The contents of each of the applications forming the aforementioned priority are hereby incorporated by reference in their entirety.

  The present invention relates to an organic light emitting composition, an organic light emitting device containing the organic light emitting composition, and a method for producing the device.

  Electronic devices containing active organic materials for use in devices such as organic light emitting diodes, organic photovoltaic devices, organic photodetectors, organic transistors and memory array devices are gaining increasing attention. Devices comprising organic materials offer benefits such as low weight, low power consumption and flexibility.

  Furthermore, the use of soluble organic materials allows the use of solution processing, such as ink jet printing or spin coating, in the manufacture of devices.

  Common organic light emitting devices (“OLEDs”) are fabricated on glass or plastic substrates that are coated with a transparent anode such as indium tin oxide (“ITO”). A thin film layer of at least one electroluminescent organic material is disposed on the first electrode. Finally, a cathode is disposed on the layer of electroluminescent organic material. A charge transport layer, charge injection layer or charge blocking layer can be disposed between the anode and the electroluminescent layer and / or between the cathode and the electroluminescent layer.

  During operation, holes are injected into the device through the anode and electrons are injected into the device through the cathode. Holes and electrons combine in the organic electroluminescent layer to form excitons, which then emit radiation that decays.

In WO90 / 13148, the organic light emitting material is a conjugated polymer such as poly (phenylene vinylene). In US Pat. No. 4,539,507, organic light emitting materials are a class of materials known as low molecular weight materials such as tris- (8-hydroxyquinoline) aluminum (“Alq ₃ ”).

  These materials produce electroluminescence due to radiative decay of singlet excitons (fluorescence), but according to spin statistics, up to 75% of excitons are non-radiatively decayed triplet excitons, ie fluorescent It has been determined that for OLEDs, the quantum efficiency can be as low as 25%. For example, Chem. Phys. Lett. 1993, 210, 61, Nature (London), 2001, 409, 494, Synth. Met. 2002, 125, 55 and references thereof.

  The presence of triplet excitons that can have relatively long-lived triplet excited states can be detrimental to the lifetime of OLEDs as a result of triplet-triplet or triplet-singlet interaction. ("Lifetime", as used herein in the context of OLED, means the length of time it takes for the brightness of an OLED at a constant current to drop by 50% from its original brightness value. , “Lifetime”, as used herein in the context of the lifetime of a triplet excited state, means the half-life of the triplet exciton). US Patent Application No. 2007/145886 discloses an OLED comprising a triplet quenching material to prevent or reduce triplet and triplet or triplet and singlet interactions.

  OLEDs containing luminescent anthanthrene, including blue luminescent anthanthrene, are described in U.S. Patent No. 7,135,243, U.S. Patent Application No. 2006/141287 and Shah et al., J Phys Chem A 2005, 109, 7777-7681. Is disclosed.

  OLEDs have a high potential for display and lighting applications. However, there is still a need to improve the performance of these devices.

  In a first aspect, the present invention provides a composition comprising a fluorescent material and a triplet accepting unit comprising an optionally substituted compound of formula (I).

  Optionally, the fluorescent material is a polymer that includes a fluorescent repeating unit.

Optionally, the compound of formula (I) is
Alkyl (one or more non-adjacent C atoms may be replaced with O, S, substituted N, C═O and —COO—, and one or more H atoms may be replaced with F; Or aryl, heteroaryl, arylalkyl or heteroarylalkyl, each optionally substituted with halogen, cyano or alkyl (one or more non-adjacent C atoms are O , S, substituted N, C═O and —COO— may be substituted))
Substituted with one or more substituents selected from the group consisting of

  Optionally, the compound of formula (I) comprises formula (Ia).

Wherein each R ³ is independently selected from H and a substituent selected from the group of claim 3, wherein at least one R ³ is not H.

Optionally, the substituent R ³ that is not H is present in the 2-position and / or 8-position of the compound of formula (I).

  Optionally, the composition comprises a luminescent material and a physical mixture of a compound of formula (I).

  Optionally, the triplet accepting unit is chemically bound to the fluorescent material.

  Optionally, the triplet acceptor unit is attached in the main chain of the polymer or as a side chain group or end group of the polymer.

  Optionally, the triplet accepting unit is attached in the main chain of the polymer through its 2 and 8 positions, or as a side chain or end group of the polymer through its 2 or 8 positions. doing.

  Optionally, the luminescent material comprises an amine.

  Optionally, the luminescent material is a polymer comprising amine repeat units.

  Optionally, the triplet accepting unit is present in an amount of at least 0.1 mol% relative to the luminescent material.

  In a second aspect, the present invention provides a solution comprising a solvent and the composition of any preceding claim.

  In a third aspect, the present 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 the composition of the first aspect.

  In a fourth aspect, the present invention provides a method of forming the organic light emitting device of the third aspect, comprising depositing the solution of the second aspect and evaporating the solvent.

  In a fifth aspect, the present invention provides a composition of formula (I) optionally substituted for accepting triplet excitons generated by a luminescent material in a composition comprising a triplet accepting unit and a luminescent material. Provides use of units.

  Optionally, according to the fifth aspect, the composition comprises a luminescent material and a physical mixture of the compound of formula (I).

  Optionally, according to the fifth aspect, the unit of formula (I) is chemically bound to the fluorescent material.

  Optionally, according to the fifth aspect, the luminescent material is a polymer and the unit of formula (I) is bound in the main chain of the polymer or bound as a side chain group or end group of the polymer doing.

  Optionally, according to the fifth aspect, the unit of formula (I) quenches triplet excitons generated by the luminescent material.

  Optionally, according to the fifth aspect, the unit of formula (I) mediates the triplet-triplet annihilation of the triplet exciton transferred from the light emitting polymer to the triplet accepting unit.

  In a sixth aspect, the present invention provides a luminescent composition comprising a polymer and an optionally substituted luminescent unit of formula (I).

  Optionally, the composition of the sixth aspect comprises a blend of a polymer and a compound of formula (I).

  Optionally, according to the sixth aspect, the units of formula (I) are bonded in the main chain of the polymer, or are bonded as side groups or terminal groups of the polymer.

  In a seventh aspect, the present invention provides a compound of formula (I) substituted with at least one solubilizing group.

Optionally, the solubilizing group is selected from alkyl and arylalkyl.

In a first aspect of the invention, it will be appreciated that the invention relates to a composition in which the triplet acceptor unit of formula (I) does not substantially emit light. Energy level of the excited singlet state of the luminescent material (S ₁₎ is prevented from any substantial movement of singlet excitons from S ₁ energy level to the S ₁ level of the triplet-receiving material of a light-emitting material Therefore, it is lower than the energy level of the corresponding triplet accepting unit, and preferably lower than this energy level.

  In the case of the second embodiment of the present invention in which the unit of formula (I) is a luminescent material, the opposite is true.

  “Aryl” and “heteroaryl” as used herein include both fused and unfused aryl and heteroaryl groups, respectively.

  A “triplet accepting unit” as used herein means a unit that can accept a triplet exciton from a light emitting unit. The triplet accepting unit prevents the reverse transfer of triplet excitons from the triplet accepting unit to the luminescent unit, preferably lower than the energy level of the triplet excited state of the luminescent unit, in order to function efficiently. Therefore, it has an energy level T1 of a triplet excited state at least kT lower.

1 is a schematic diagram of triplet quenching by a compound of formula (I). FIG. 1 is a schematic diagram of a first triplet-triplet annihilation mechanism comprising a compound of formula (I). FIG. It is a figure which shows the 2nd triplet-triplet annihilation mechanism containing the compound of a formula (I). 1 is a diagram illustrating an organic light emitting device according to an embodiment of the present invention. FIG. 5 shows the electroluminescence spectrum of an exemplary OLED of the present invention compared to the electroluminescence spectrum of a comparative device. FIG. 4 shows the lifetime of four exemplary OLEDs of the present invention compared to the electroluminescence spectrum of a comparative device. FIG. 4 shows the T ₉₀ lifetime (ie, time to decay to 90% of the initial luminescence) of four exemplary OLEDs of the present invention compared to the electroluminescence spectrum of a comparative device. FIG. 6 shows current density versus voltage for an exemplary device and a comparative device. FIG. 6 illustrates external quantum efficiency versus voltage for an exemplary device and a comparative device.

  The invention is described in detail below with respect to the composition of (A) (compound of formula (I) is a triplet acceptor material) and the composition of (B) (compound of formula (I) is a luminescent material). .

A. Antanthrenes as triplet acceptor materials We have identified several pathways that can cause decay of triplet excitons in order to reduce or eliminate decay due to pathways that lead to shortened lifetime of the device. Some of these paths allow the decay of radioactive excitons by delayed fluorescence that can provide better device efficiency compared to non-radiative decay paths.

  Without being bound to any theory, the mechanism of triplet quenching and delayed fluorescence that may occur is described below.

Triplet Quench FIG. 1 shows a first energy transfer mechanism of an exemplary OLED. In order to avoid suspicion, the scale of energy levels including FIG. 1 is not described in this specification. FIG. 1 shows the energy transfer of an OLED in which a light emitting material having an energy level S _{1E in} a singlet excited state and an energy level S _0E in a singlet ground state is arranged. Singlet excitons having energy S _1E are attenuated by the fluorescence emission hv indicated by the solid line arrow between S _1E and S _0E in FIG. Triplet and triplet exciton interactions or triplet and singlet exciton interactions can create a “superexcited” state on the luminescent material. Without being bound by any theory, it is believed that the formation of these high energy “superexcited” states on the luminescent material can be detrimental to the operational lifetime of the material. However, by providing a triplet acceptor unit with an excited triplet state energy level T _1A lower than T _1E , it is possible to transfer a triplet exciton to a triplet acceptor unit for non-radiative quenching. This is an alternative to the radiation decay from T _1E to S _0E , which is the spin forbidden process indicated by the dotted line in FIG. The S ₁ and T ₁ levels can be measured from the fluorescence and phosphorescence spectra, respectively.

The triplet accepting unit has a singlet excited state energy level higher than the singlet excited state energy level S _1E in order to substantially or completely prevent the transfer of singlet excitons from S _1E to S _1A . _{Has the} position S _1A . Preferably, S _1A is at an energy at least kT higher than S _1E to prevent any substantial reverse movement of excitons. Similarly, T _1E is preferably at an energy at least kT higher than T _1A .

Triplet-triplet annihilation FIG. 2 shows a second energy transfer mechanism of an exemplary OLED.

According to this embodiment, the triplet-triplet annihilation (TTA) caused by the interaction between two triplet accepting units is a maximum of 2 × T _1A (T _1A is the triplet excited state of the triplet acceptor material). Resulting in a triplet-triplet annihilation type singlet exciton having an energy of 1). This singlet exciton formed on the first triplet accepting unit of the two triplet accepting units has an energy level _SnA that is at a higher energy than S _1A and S _1E , and therefore This singlet exciton can move to S _1A and then to S _1E , from which light hv can be emitted as delayed fluorescence. Triplet excitons on the second triplet accepting unit of the two triplet accepting units can decay to the ground state T _0A .

Initially, the triplet exciton formed at T _1E moves to T _1A . By providing a triplet acceptor material having an energy level T _1A lower than T _1E , rapid exciton transfer from T _1E to T _1A can occur. This movement is relatively rapid compared to the decay rate of triplet excitons from T _1E to S _0E , which is the spin forbidden process indicated by the dotted arrows in FIG. The energy gap between T _1E and T _1A is preferably greater than kT to avoid reverse exciton migration from T _1A to T _1E . Similarly, the energy gap between S _1A and S _1E is preferably greater than kT to avoid reverse exciton migration from S _1E to S _1A .

The decay path of triplet excitons on T _1A competing with triplet-triplet annihilation is the non-radiative (quenching) path to S _0A previously described with respect to FIG. Several measures can be taken to maximize the potential for TTA rather than attenuation to _SOA . In particular,
i) The triplet absorbing material can be selected such that the triplet excitons on T _1A have a relatively long lifetime τ _TA . The relatively long life, but also means that the rate of reduction of the S _0A is relatively slow, the probability of TTA is meant that relatively high.
ii) The concentration of the triplet absorbing material in the light emitting layer may be relatively high, for example in the range of more than 1 mol%, for example 1-10 mol%.
iii) Two or more triplet receptive materials can be placed in close proximity, eg as described below for units of formula (II).

  Each of these measures can be used alone or in combination.

  FIG. 3 shows a third energy transfer mechanism of an exemplary OLED.

In this case, triplet-triplet annihilation occurs between triplet excitons with energy T _1A located on the triplet accepting unit and triplet excitons with energy T _1E located on the luminescent material. It will be understood that this results in a triplet-triplet annihilation singlet exciton (TTAS) having an energy of maximum T _1E + T _1A . The energy level S _nA of singlet excitons is higher than S _1E, energy level S _nA therefore, moves the energy to the S _1A, it can be moved from S _1A to S _1E, the light therefrom hv can be emitted as delayed fluorescence.

  Without being bound by any theory, it is believed that the lifetime of the device can be improved by avoiding the formation of superexcited states on the light emitting polymer formed during OLED driving. In addition, by utilizing a TTA that produces stable delayed fluorescence, compared to a device where all triplet excitons are quenched (as shown in FIG. 1) or OLED drive with delayed fluorescence intensity at an early stage. There is a potential for improved efficiency compared to devices that do not have triplet acceptor units that can subsequently decline sharply.

  The mechanism for quenching the triplet and two or all three of the aforementioned two TTA mechanisms occur within the same device, and the amount of delayed fluorescence from each of the two mechanisms of TTA depends on the concentration of the luminescent material, the triplet. It will be understood that it depends on factors such as the concentration of the accepting unit, the rate constant of the competitive process and the lifetime of the excited state of the triplet exciton on the luminescent and triplet accepting units. The measures described above with respect to FIG. 2 can be used to increase the likelihood of TTA.

  The rate constant of triplet exciton transfer from the luminescent material to the triplet acceptor material can be selected to exceed the rate constant of quenching of the triplet exciton.

Triplet acceptor material A triplet acceptor anthanthrene may be a compound that is blended with a luminescent material, wherein the luminescent composition comprises one or more additional components, such as one or more charge transport materials, in particular one. Alternatively, a plurality of hole transport materials or electron transport materials can be included. Alternatively, the triplet accepting ananthrene can be bound to the luminescent material or, if present, bound to any of the other components described above.

  When anthanthrene is blended with the luminescent material, it is optionally substituted with a solubilizing group. An anthanthrene compound can have the formula (Ia).

Wherein each R ³ is independently selected from H and a substituent, and at least one R ³ is not H. Preferred substituents R ³ are alkyl and optionally substituted aryl or heteroaryl, especially optionally substituted phenyl.

When R ³ is alkyl, one or more H atoms may be replaced with F, and one or more non-adjacent C atoms may be O, S, substituted N, C═O and — It may be replaced by COO-.

  Particularly preferred alkyl groups are n-butyl, t-butyl, n-hexyl and n-octyl.

Particularly preferred is substitution of R ³ at the 2-position and / or 8-position of the anthanthrene ring.

When R ³ is aryl or heteroaryl, preferred substituents include alkyl groups and alkoxy groups. Exemplary compounds of formula (Ia) include:

Wherein, Ak is alkyl, in particular branched or C ₁ ~ ₁₀ alkyl straight.

When the luminescent material is a polymer, the anthanthrene can be arranged in the main chain of the polymer in the form of repeating units. These repeating units may correspond to compounds of formula (Ia) in which two R ³ groups are replaced by bonds with adjacent repeating units. There is no significant change in the HOMO-LUMO gap of the material due to the linkage through the 2 and / or 8 positions due to the relatively low electron density at these positions compared to the 4 and / or 10 positions. In addition, it is possible to connect with an adjacent aromatic repeating unit, and conjugation with the adjacent aromatic repeating unit hardly or not occurs.

  Exemplary repeat units include the following:

In the formula, ^* indicates a connecting point for connecting repeating units to form a polymer chain, and Ak is as described above.

  Anthanthrene groups are attached in the main chain of the light-emitting polymer by polymerizing monomers containing the repeating units shown above, which are substituted with leaving groups that can participate in metal-catalyzed cross-coupling reactions. be able to. Exemplary leaving groups include halogen groups and boronic acid groups or boronic ester groups for use in Suzuki or Yamamoto polymerization reactions. These reactions are described in more detail below.

  Alternatively or additionally, when the luminescent material is a polymer, the anthanthrene can be arranged in the form of polymer end groups or in the form of side groups that are pendant from the polymer backbone. In this case, exemplary side chain groups or terminal groups include repeating units optionally substituted as follows.

  As described above, the coupling via the 2-position or 8-position causes little or no conjugation with the adjacent aromatic group.

  Anthanthrene side chain groups or end groups are substituted on the polymer with an anthanthrene compound substituted with an appropriate leaving group that can participate in metal-catalyzed cross-coupling reactions such as halogens or boronic acids or boronic esters. It can be formed by reacting with a leaving group.

Alternatively, anthanthrene side groups can be incorporated into the light emitting polymer by providing them as monomer substituents shown below.
PG-polymerizable unit-PG
｜
In the antanthrene formula, PG represents a polymerizable group such as the aforementioned leaving group or a polymerizable double bond.

As described above, multiple triplet accepting anthanthrene units can be placed in close proximity to increase the possibility of TTA and delayed fluorescence. For example, two anthanthrene groups can be provided with an optionally substituted compound having the formula (II).
Antanthrene-spacer-anthanthrene
(II)
In the formula, “anthanthrene” represents a compound of formula (I), and “spacer” is a spacer group that is conjugated or unconjugated. The spacer group separates the two triplet accepting ananthrene groups and preferably separates their electronic characteristics (eg HOMO and LUMO). Depending on the exact nature of the conjugation and orbital overlap, Sp can optionally include one or more arylene or heteroarylene groups such as substituted phenyl, biphenyl or fluorene. Alternatively, Sp can optionally include an unconjugated linking group such as alkyl, or a linking of another molecule that does not provide a conjugation pathway between anthanthrene and anthanthrene.

  The unit of formula (II) may be a separate compound physically mixed with the luminescent material or may be bound to the luminescent material. When the luminescent material is a polymer, the unit of the formula (II) can be bonded as a repeating unit, a side chain group or a terminal group of the main chain as described above.

Alternatively or additionally, the triplet accepting unit may be an oligomer or polymer comprising a repeating structure of formula (IIb), or a component of the oligomer or polymer.
(Anthanthrene-Spacer) _m
(IIb)
In the formula, m is at least 2. The oligomer or polymer can be mixed with the luminescent material or placed in the polymer backbone.

  Although the coupling of the triplet accepting unit and the light emitting polymer has been described above, it will be understood that the triplet accepting unit can also be coupled to any other component of the composition, if present.

  The concentration of the triplet acceptor unit of formula (I) is optionally in the range of at least 0.1 mol%, or at least 1 mol%, for example 1-10 mol%. The higher the triplet receptive material concentration, the greater the potential for TTA.

  To increase the possibility of TTA, the lifetime of the excited triplet present on the triplet acceptor material is optionally at least 1 microsecond. The lifetime of a triplet exciton is its half-life, which is described in Handbook of Photochemistry, 2nd edition, Steven L Murov, Ian Carmichael and Gordon L Hug and its references, the contents of which are incorporated herein by reference. As described, it can be measured by flash photolysis to measure the lifetime of single molecule triplets.

Anthanthrene has a T ₁ level of 850 nm and an S ₁ level of 430 nm. In comparison, anthracene has a T ₁ level of 670 nm and an S ₁ level of 375 nm. The lower energy T ₁ level of anthanthrene means that it can be used as a triplet absorber with a wider variety of luminescent materials than anthracene.

  Triplet acceptor materials, unlike phosphorescent dopants, do not provide an energetically prone route for absorbed triplets to radiatively decay, resulting in triplet excitons absorbed by the triplet acceptor material. It will be understood that no energy is substantially lost from the triplet acceptor material in the form of light emission from the triplet acceptor material.

  The dynamics of singlet and triplet excitons can be studied using time-resolved electroluminescence and quasi-continuous oscillation (quasi-cw) and time-resolved excited state absorption. The density of triplet excitons on the luminescent material, for example on the polymer backbone of the conjugated luminescent polymer, can be measured using absorption in the quasi-cw excited state.

  Excited state absorption techniques are described elsewhere (King, S., Rothe, C. & Monkman, A. Triple build in and decay of isolated polyspirobifluorine chains in dilute solution. 10808 (2004), and Dhoot, AS, Ginger, DS, Beljonne, D., Shuai, Z. & Greenham, N. C. Triple formation and deci- cation of dehydrated polymer P 195-201 (2002)).

  For example, the triplet state of polyfluorene is well characterized using these techniques by the strong excited state absorption properties peaking at 780 nm due to the triplet state (King, S., Rothe, C. & Monkman, A. Triple build in and isolated polyspirobifluorine chains in dilute solution. J. Chem. Phys. 121, 10803-10. Dias, F. & Monkman, AP Triplet exciton state and related phenomena in the beta-phase of poly 9,9-dioctyl) fluorene.Physical Review B70 (2004 years)).

  Thus, the investigation of the triplet population of polyfluorenes can be performed at 780 nm, but those skilled in the art will be able to adapt this investigation to other emissive materials based on the absorption properties of the excited states of those materials. Will understand.

  FIG. 4 shows the structure of an OLED according to an embodiment of the present invention. The OLED includes a transparent glass or plastic substrate 1, an anode 2, a cathode 4, and a light emitting layer 3 provided between the anode 2 and the cathode 4. Additional layers such as a charge transport layer, charge injection layer or charge blocking layer can be located between the anode 2 and the cathode.

Luminescent materials Suitable luminescent materials for use in layer 3 include small molecules, polymeric materials and dendrimer materials, and compositions thereof. Light emitting polymers suitable for use in layer 3 include poly (arylene vinylenes), and polyarylenes such as polyfluorenes, especially 2,7-linked 9,9 dialkyl polyfluorenes or 2,7-linked 9,9 diaryl polyfluorenes. Polyspirofluorene, in particular 2,7-linked poly-9,9-spirofluorene; polyindenofluorene, in particular 2,7-linked polyindenofluorene; polyphenylene, in particular poly-1 substituted with alkyl or alkoxy , 4-phenylene. Such polymers are described, for example, in Adv. Mater. 2000, 12 (23) 1737-1750 and references therein.

  Suitable luminescent polymers may be luminescent homopolymers containing luminescent repeat units, or luminescent repeat units and additional repeat units such as hole transport and / or electron transport repeat units as disclosed, for example, in WO 00/55927. It may be a copolymer containing. Each repeating unit is provided in the main chain or side chain of the polymer.

Polymers for use as luminescent materials in the devices of the present invention are preferably described in, for example, Adv. Mater. 2000, 12 (23) pp. 1737-1750 and references therein, containing repeat units selected from arylene repeat units. Exemplary first repeat units include J.I. Appl. Phys. 1996, 79, 934; 1,4-phenylene repeating unit; fluorene repeating unit disclosed in European Patent No. 0842208; for example, Macromolecules 2000, 33 (6), indenofluorene disclosed on pages 2016-2020 Repeat units; and spirofluorene repeat units disclosed, for example, in EP 0707020. Each of these repeating units is optionally substituted. Examples of the substituents, C ₁ ~ ₂₀ alkyl or solubilizing groups such as alkoxy; include substituents to increase and the glass transition temperature of the polymer (Tg); fluorine, nitro or electron-withdrawing group such as cyano.

  Particularly preferred polymers comprise optionally substituted 2,7-linked fluorene, most preferably repeating units of formula IV.

In the formula, R ¹ and R ² are independently H or a substituent, and R ¹ and R ² can be linked to form a ring. R ¹ and R ² are preferably hydrogen; optionally substituted alkyl (one or more non-adjacent C atoms are replaced with O, S, substituted N, C═O and —COO— Selected from the group consisting of optionally substituted aryl or heteroaryl, and optionally substituted arylalkyl or heteroarylalkyl. More preferably, at least one of R ¹ and R ² comprises an optionally substituted C ₄ -C ₂₀ alkyl or aryl group.

When R ¹ or R ² is aryl or heteroaryl, preferred optional substituents include alkyl groups (one or more non-adjacent C atoms are O, S, substituted N, C = O and -COO- may be substituted).

Optional substituents on fluorene units other than substituents R ¹ and R ² are preferably alkyl (one or more non-adjacent C atoms are O, S, substituted N, C═O and —COO Optionally substituted aryl), optionally substituted heteroaryl, selected from the group consisting of optionally substituted heteroaryl, alkoxy, alkylthio, fluorine, cyano and arylalkyl.

  Preferably, the polymer comprises the aforementioned arylene repeat units and arylamine repeat units, especially repeat unit V.

Wherein Ar ¹ and Ar ² are optionally substituted aryl or heteroaryl groups, n is 1 or more, preferably 1 or 2, and R is H or a substituent, A substituent is preferred. R is preferably alkyl or aryl or heteroaryl, most preferably aryl or heteroaryl, especially phenyl. Including the case where R comprises aryl or heteroaryl, either the aryl group or heteroaryl group of the unit of formula 1 may be substituted. Preferred substituents are alkyl (one or more non-adjacent C atoms may be replaced by O, S, substituted N, C═O and —COO—), optionally substituted aryl Optionally selected from heteroaryl, alkoxy, alkylthio, fluorine, cyano and arylalkyl. Preferred substituents include alkyl groups and alkoxy groups. Either the aryl group or heteroaryl group of the repeating unit of Formula 1 may be linked by a direct bond or a divalent linking atom or linking group. Preferred divalent linking atoms and linking groups include O, S, substituted N, and substituted C.

  Particularly preferred units that satisfy Formula 1 include units of Formulas 1-3.

Wherein Ar ¹ and Ar ² are as defined above and Ar ³ is an optionally substituted aryl or heteroaryl. When present, preferred substituents for Ar ³ include alkyl groups and alkoxy groups.

  The arylamine repeat unit is preferably present in an amount of up to 30 mol%, preferably up to 20 mol%. These percentages apply to the total number of arylamine units present in the polymer when more than one type of repeating unit of formula (V) is used.

  The polymer can include heteroarylene repeat units for charge transport or emission.

  The combination of anthanthrene and the luminescent material can result in an intramolecular triplet acceptance pathway that is not available in the corresponding mixed system, so that a more efficient triplet compared to mixing anthanthrene with the luminescent material. Can bring acceptance. If a light emitting polymer is used, the anthanthrene is bound to the light emitting repeat unit of the polymer and / or any other repeat unit of the polymer that can be present, such as an electron transport repeat unit and / or a hole transport repeat unit. can do.

  Further, the coupling can be beneficial for processing reasons. For example, if anthanthrene is poorly soluble, when the anthanthrene is coupled to a soluble luminescent material, particularly a soluble luminescent polymer, the luminescent material incorporates anthanthrene units into the solution, and the device is fabricated using solution processing techniques. be able to. Finally, combining anthanthrene units with a luminescent material can prevent phase separation effects in solution processed devices that can be detrimental to device performance.

When the luminescent material is a conjugated polymer comprising a luminescent repeat unit and further repeat units, for example a luminescent amine repeat unit of formula (V) and a fluorene repeat unit of formula (IV), conjugation of an anthanthrene unit to the polymer backbone ( For example, due to conjugation with the fluorene repeating unit, the T ₁ energy level of the anthanthrene unit is lowered, and therefore, energy for moving the triplet exciton from the emitter unit to the anthanthrene unit is likely to occur. This reduction in the T ₁ energy level of an anthanthrene unit allows the use of an anthanthrene unit in combination with a light emitting material having a T ₁ level that is too low to be used with an unconjugated anthanthrene unit. become.

  A preferred method of preparing conjugated luminescent polymers involves “metal insertion” in which the metal atom of the metal complex catalyst is inserted between the aryl or heteroaryl group of the monomer and the leaving group. Exemplary metal insertion methods include, for example, Suzuki polymerisation as described in WO 00/53656, and T.W. Yamamoto, “Electrically Conducting And Thermally Stable π-Conjugated Poly (arylene) s Prepared by Organic Processes, 3rd page, 115th” In the case of Yamamoto polymerization, a nickel complex catalyst is used, and in the case of Suzuki polymerization, a palladium complex catalyst is used.

  For example, in the synthesis of a linear polymer by Yamamoto polymerization, a monomer having two reactive halogen groups is used. Similarly, according to the method of Suzuki polymerisation, at least one reactive group is a boron derivative group such as a boronic acid or boronic ester and the other reactive group is a halogen. Preferred halogens are chlorine, bromine and iodine, most preferably bromine.

  Thus, it will be appreciated that the repeat units shown throughout this application can be derived from monomers bearing appropriate leaving groups. Similarly, end groups or side groups can be attached to the polymer by reaction of a suitable leaving group.

  Suzuki polymerisation can be used to prepare regioregular block copolymers and random copolymers. In particular, homopolymers or random copolymers can be prepared when one reactive group is a halogen and the other reactive group is a boron derivative group. Alternatively, block copolymers or stereoregular copolymers, especially AB copolymers, can be prepared when both reactive groups of the first monomer are boron and both reactive groups of the second monomer are halogen. it can.

  As an alternative to halides, other leaving groups that can participate in metal insertion include groups including tosylate, mesylate and triflate.

  The light-emitting layer 3 can consist only of the light-emitting polymer and the triplet accepting unit, or can comprise these materials in combination with one or more further materials. In particular, the light-emitting polymer can be blended with a hole and / or electron transport material, or can be covalently bonded to the hole and / or electron transport material, for example as disclosed in WO 99/48160.

  The light emitting copolymer can comprise a light emitting region and at least one of a hole transport region and an electron transport region, as disclosed, for example, in WO 00/55927 and US Pat. No. 6,353083. If only one of the hole transport region and the electron transport region is provided, the electroluminescent region can also provide the other of the hole transport functionality and the electron transport functionality, for example, the aforementioned amine unit can be Both hole transport and light emission functionality can be provided. A luminescent copolymer comprising a luminescent repeat unit and one or both of a hole transport repeat unit and an electron transport repeat unit can provide the unit in the polymer backbone, as in US Pat. The unit can be provided from the chain to a polymer side group in a pendant state.

The luminescent material can emit any color, provided that its S ₁ and T ₁ energy levels relative to the anthanthrene unit are as described above, but the luminescent material is preferably a blue luminescent material, In particular, it is a material having photoluminescent emission having a peak wavelength in the range of 400 to 500 nm, preferably 430 to 500 nm.

  The light emitting layer 3 may be patterned or may not be patterned. A device comprising an unpatterned layer can be used, for example, as an illumination light source. White light emitting devices are particularly suitable for this purpose. The device comprising the patterned layer can be, for example, an active matrix display or a passive matrix display. In the case of an active matrix display, a patterned electroluminescent layer is generally used in combination with a patterned anode layer and an unpatterned cathode. In the case of a passive matrix display, the anode layer is formed from parallel stripes of anode material and parallel stripes of electroluminescent and cathode materials arranged perpendicular to the anode material, the electroluminescent and cathode materials The stripes are generally separated by stripes of insulating material (“cathode separator”) formed by photolithography.

B. If anthanthrene anthanthrene compound as a light-emitting material is used as a light emitting material, S ₁ level of anthanthrene compound is less than S ₁ level of the host material (receive singlet excitons from the host material) .

  Preferably, the unit of formula (I) emits blue light.

  The unit of formula (I) may be a compound that is physically mixed with the polymer host material but not chemically bonded, or the unit of formula (I) is chemically bonded to the host material. In that case, the unit of formula (I) can be arranged as a repeating unit of the polymer main chain or can be bonded to the polymer as a side chain group or terminal group. Suitable luminescent compounds of formula (I), repeat units, side chain groups and end groups are as described above for triplet acceptor materials. Surprisingly, we have incorporated an anthanthrene unit into the conjugated polymer, especially by incorporating an anthanthrene unit in the conjugated polymer backbone, especially when the antanthrene unit is linked via its 2 and 8 positions. If so, it has been found that the emission color of the resulting polymer does not shift significantly to red. In particular, this red shift is generally only 10 nm or 5 nm.

  Color shift of the anthanthrene after the substituent by the solubilizing substituent can be avoided by selecting the position of the solubilizing substituent.

Suitable host materials in this case include fluorene homopolymers or copolymers containing fluorene units, and a co-repeat unit of one or more comonomers having an S ₁ level higher than the level of the anthanthrene emitter. ) Is included.

  Exemplary materials, methods and device structures for OLEDs are described in more detail below. The structures of these materials, methods and devices are the same as those of formula (I), regardless of whether the unit comprising the unit of formula (I) functions as an emitter unit or as a triplet accepting unit that does not substantially emit light. It will be understood that the present invention can be applied to an OLED including the following units.

Hole injection layer A conductive hole injection layer, which can be formed from a conductive organic material or an inorganic material, is provided between the anode 2 and the light emitting layer 3, from the anode to one or more layers of the semiconducting polymer. It can be used to inject holes.

  Examples of doped organic hole injection materials include optionally substituted doped poly (ethylenedioxythiophene) (PEDT), particularly as disclosed in EP 0901176 and EP 0947123. PEDT doped with charge balancing polyacids such as polystyrene sulfonate (PSS), polyacrylic acid or fluorinated sulfonic acids such as Nafion®; polyaniline disclosed in US Pat. No. 5,723,873 and US Pat. No. 5,798,170; As well as optionally substituted polythiophene or poly (thienothiophene). Examples of conductive inorganic materials include transition metal oxides such as VOx MoOx and RuOx, such as those disclosed in Journal of Physics D: Applied Physics (1996), 29 (11), pages 2750-2754. included.

Charge Transport Layer A hole transport layer can be provided between the anode and the electroluminescent layer. Similarly, an electron transport layer can be provided between the cathode and the electroluminescent layer.

  Similarly, an electron blocking layer can be provided between the anode and the electroluminescent layer, and a hole blocking layer can be provided between the cathode and the electroluminescent layer. The transport layer and blocking layer can be used in combination. Depending on its HOMO and LUMO levels, a single layer can transport one of holes and electrons and block the other of holes and electrons.

  When present, the hole transport layer located between the anode 2 and the electroluminescent layer 3 preferably has a HOMO level of 5.5 eV or less, more preferably about 4.8 to 5.5 eV. The HOMO level can be measured, for example, by cyclic voltammetry.

  When present, the electron transport layer located between the electroluminescent layer 3 and the cathode 4 preferably has a LUMO level of about 3 to 3.5 eV. For example, a layer of silicon monoxide or silicon dioxide or other thin dielectric layer having a thickness in the range of 0.2-2 nm is provided between the electroluminescent layer 3 and the layer 4.

  Polymers for use as charge transport materials can include arylene units such as the fluorene unit of formula (IV) and other units described above.

  The hole transport polymer may comprise a repeat unit of formula (V), such as an arylamine repeat unit, in particular the repeat unit of formulas 1-3 described above. The polymer may be a homopolymer or a copolymer comprising arylene repeat units in an amount up to 95 mol%, preferably up to 70 mol%. These percentages apply to the total number of arylamine units present in the polymer when two or more repeating units of formula (V) are used.

  The charge transport unit can be provided on the polymer main chain or the polymer side chain.

Cathode The cathode 4 is selected from materials having a work function capable of injecting electrons into the electroluminescent layer. Other factors, such as the possibility of deleterious interactions between the cathode and the electroluminescent material, also affect cathode selection. The cathode can be made of a single material such as an aluminum layer.

  Alternatively, the cathode can comprise a plurality of metals, for example, a bilayer of a low work function material and a high work function material, such as calcium and aluminum disclosed in WO 98/10621; WO 98/57381, Appl. Phys. Lett. Elemental barium disclosed in 2002, 81 (4), 634 and WO02 / 84759; or metal compounds, particularly alkali metal or alkaline earth metal oxides, as disclosed in WO00 / 48258, to aid electron injection Or a thin layer of fluoride, such as lithium fluoride; Appl. Phys. Lett. 2001, 79 (5), 2001, barium fluoride; as well as barium oxide. In order to efficiently inject electrons into the device, the cathode preferably has a work function of less than 3.5 eV, more preferably less than 3.2 eV, and most preferably less than 3 eV. Metal work functions are described, for example, in Michaelson, J. et al. Appl. Phys. 48 (11), 4729, 1977.

  The cathode can be opaque or transparent. Transparent cathodes are particularly advantageous in active matrix devices, as light passing through the transparent anode in the active matrix device is at least partially blocked by a drive circuit located under the luminescent pixel. The transparent cathode includes a layer of electron injection material that is sufficiently thin and transparent. In general, the lateral conductivity of this layer is 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 conductive material such as indium tin oxide.

  Transparent cathode devices do not require a transparent anode (unless of course a completely transparent device is desired), and therefore transparent anodes used in bottom light emitting devices are layers of reflective material such as an aluminum layer. It will be understood that can be replaced or supplemented with. An example of a transparent cathode device is disclosed, for example, in GB 2348316.

Sealed OLEDs tend to be sensitive to moisture and oxygen. Thus, the substrate preferably has good barrier properties to prevent moisture and oxygen from entering the device. The substrate is typically glass, but alternative substrates can be used, particularly where device flexibility is desired. For example, the substrate may be a plastic such as in US Pat. No. 6,268,695 which discloses a substrate with alternating plastic and barrier layers, or a thin glass and plastic laminate disclosed in EP 0949850. Can be included.

  The device is preferably sealed with an encapsulant (not shown) to prevent moisture and oxygen ingress. Suitable encapsulants include glass sheets, films with suitable barrier properties such as silicon dioxide, silicon monoxide, silicon nitride, or alternately stacked with polymers and dielectrics as disclosed, for example, in WO01 / 81649 Or hermetic containers disclosed, for example, in WO 01/19142. For transparent cathode devices, a transparent sealing layer such as silicon monoxide or silicon dioxide can be deposited to a micron level thickness, but in a preferred embodiment, the thickness of such layer is 20-300 nm. It is a range. Any atmospheric moisture and / or oxygen getter material that can penetrate the substrate or encapsulant can be deposited between the substrate and encapsulant.

Solution Treatment The light emitting layer 3 can be deposited by any method including vacuum evaporation and deposition from a solution in a solvent. When the emissive layer includes polyarylene such as polyfluorene, suitable solvents for solution deposition include mono- or poly-alkylbenzenes such as toluene and xylene. Particularly preferred solution deposition techniques include printing and coating techniques, preferably spin coating and ink jet printing.

  Spin coating is particularly suitable for devices that do not require patterning of electroluminescent materials, such as lighting applications or simple monochrome segment displays.

  Inkjet printing is particularly suitable for displays with a large amount of information, in particular full color displays. The device prints by providing a patterned layer on the first electrode and defining wells for single color (for monochrome devices) or multiple colors (for multicolor, especially for full color devices) printing Can be inkjet. The layer to be patterned is generally a photoresist layer that is patterned to define wells, for example as described in EP 0880303.

  As an alternative to wells, ink can be printed in channels defined in the patterned layer. In particular, a photoresist can be patterned to form a channel, which, unlike a well, extends over a plurality of pixels and may be closed or open at the end of the channel.

  Other solution deposition techniques include dip coating, roll printing, nozzle printing and screen printing.

  When multiple layers of an OLED are formed by solution processing, those skilled in the art will know, for example, by cross-linking one layer and then depositing subsequent layers or the material that forms the first layer of the adjacent layer. One will recognize techniques for preventing admixing of adjacent layers by selecting the material of the adjacent layers so that they do not dissolve in the solvent used to deposit the second layer.

Material Examples 1 and 2
Ananthrene compounds 1 and 2 were prepared according to the following synthetic method.

  This synthesis shows substitution at the 2 and 8 positions. Similar substitutions can be provided at the 6,12 and / or 4,10 positions as shown below.

Material Example 3
Anthanthrene compound 3 was prepared starting from commercially available anthanthrene according to the following synthetic method.

Device Example A device having the following structure was formed.
ITO / HIL / HTL / EL / MF / Al
ITO represents an indium tin oxide anode, and HIL is from Plextronics Inc. HTL is a polymer hole transport layer comprising a fluorene repeat unit of formula (IV) and an amine repeat unit of formula (V), and EL is 1 mol% anthanthrene An electroluminescent layer comprising a fluorene repeat unit of formula (IV) and an amine repeat unit of formula (V) blended with compound 3, MF is a metal fluoride, and the MF / Al bilayer is a device The cathode is formed.

As shown in FIG. 5, this device has an electroluminescence spectrum that is substantially identical to the electroluminescence spectrum of the comparative device in the absence of the anthanthrene compound, which indicates that the S ₁ of the anthanthrene compound. It shows that the energy level is higher than the S ₁ energy level of the light emitting unit of the polymer.

As shown in FIG. 6, the T ₅₀ lifetime (ie, the time it takes for the device brightness at a constant current to drop to 50% of its original brightness) is approximately the same as the lifetime of the comparative device, but decaying The curve is extremely flat. In particular, as shown in more detail in FIG. 7, the T ₉₀ lifetime is much longer for the exemplary device compared to the comparative device.

  8 and 9 show that there is little change in current density versus voltage or external quantum efficiency versus voltage for the exemplary device compared to the comparative device.

  Although the invention has been described with reference to specific exemplary embodiments, various modifications, changes and / or combinations of the features disclosed herein can be made from the scope of the invention as set forth in the claims below. It will be understood that it will be apparent to those skilled in the art without departing.

Claims (26)

A composition comprising a triplet acceptor material comprising a fluorescent material and an optionally substituted compound of formula (I).
  The composition according to claim 1, wherein the fluorescent material is a polymer containing a fluorescent repeating unit. The compound of formula (I) is
Alkyl (one or more non-adjacent C atoms may be replaced with O, S, substituted N, C═O and —COO—, and one or more H atoms may be replaced with F; Or aryl, heteroaryl, arylalkyl or heteroarylalkyl, each of which may be substituted with halogen, cyano or alkyl (one or more non-adjacent C atoms are O, S, Substituted with N, C═O and —COO—))
3. A composition according to claim 1 or 2 substituted with one or more substituents selected from the group consisting of. The compound of formula (I) comprises formula (Ia)
4. In any one of claims 1 to 3, wherein each R ³ is independently selected from H and a substituent selected from the group of claim 3, wherein at least one R ³ is not H. The composition as described. Substituents R ³ not H is present in the 2-position and / or 8-position of the compounds of formula (I), A composition according to any one of claims 1 to 4.   6. A composition according to any preceding claim comprising a mixture of a luminescent material and a compound of formula (I).   6. The triplet accepting unit according to any one of claims 1 to 5, wherein the triplet accepting unit is chemically bound to the fluorescent material or, if present, chemically bound to another component of the luminescent composition. Composition.   The composition according to claims 2 and 7, wherein the triplet accepting unit is attached in the main chain of the polymer or as a side group or end group of the polymer.   The triplet accepting unit is attached in the main chain of the polymer via its 2 and 8 positions, or as a side chain group or end group of the polymer via its 2 or 8 position, The composition according to claim 8.   The composition according to claim 1, wherein the luminescent material comprises an amine.   11. A composition according to claim 2 and 10, wherein the luminescent material is a polymer comprising amine repeat units.   12. A composition according to any one of claims 1 to 11, wherein the triplet accepting unit is present in an amount of at least 0.1 mol% relative to the luminescent material.   A solution comprising a solvent and the composition according to claim 1.   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 the composition according to any one of claims 1 to 12.   15. A method of forming an organic light emitting device according to claim 14, comprising depositing the composition of claim 13 and evaporating the solvent. Use of an optionally substituted unit of formula (I) for accepting triplet excitons generated by a luminescent material in a composition comprising a triplet accepting unit and a luminescent material.
  The use according to claim 16, wherein the composition comprises a physical mixture of a luminescent material and a compound of formula (I).   Use according to claim 16, wherein the unit of formula (I) is chemically bound to the fluorescent material.   19. Use according to claim 18, wherein the luminescent material is a polymer and the units of the formula (I) are bound in the main chain of the polymer or are bound as side groups or end groups of the polymer.   20. Use according to any of claims 16 to 19, wherein the unit of formula (I) quenches triplet excitons generated by the luminescent material.   21. Use according to any of claims 16 to 20, wherein the unit of formula (I) mediates the triplet-triplet annihilation of a triplet exciton transferred from the luminescent material to a triplet accepting unit. A luminescent composition comprising a polymer and an optionally substituted luminescent unit of formula (I).
  23. A luminescent composition according to claim 22 comprising a blend of a polymer and a compound of formula (I).   23. A composition according to claim 22, wherein the units of formula (I) are bound in the main chain of the polymer or as side groups or end groups of the polymer. Compound of formula (I)
[Wherein the compound is substituted with at least one solubilizing group].   26. The compound of claim 25, wherein the solubilizing group is selected from alkyl and arylalkyl.