GB2453387A

GB2453387A - OLED with fullerene charge transporting layer

Info

Publication number: GB2453387A
Application number: GB0720078A
Authority: GB
Inventors: Poopathy Kathirgamanathan
Original assignee: OLED-T Ltd
Current assignee: OLED-T Ltd
Priority date: 2007-10-15
Filing date: 2007-10-15
Publication date: 2009-04-08
Also published as: GB0720078D0; GB2453387A8

Abstract

The OLED has electrodes between which is a fullerene charge transporting layer and an electroluminescent material layer. The OLED has in order an anode, a fullerene hole transporting layer, the electroluminescent layer, a fullerene electron transporting layer and a cathode. The hole transporting layer may have one or more adjacent hole transporting layers and the electron transporting layer may have one or more adjacent electron transporting layers. The fullerene may be mixed with polymers and/or doped with metal.

Description

Electroluminescent Devices The present invention relates 10 an electroluminescent device which can emit light of different colours.

Materials which emit light when an electric current is passed through them are well known and used in a wide range of display applications. Liquid crystal devices and devices which are based on inorganic semiconductor systems are widely used, however these suffer from the disadvantages of high energy consumption, high cost of manufacture, low quantum efficiency and the inability to make flat panel displays.

Patent application W098/58037 describes a range of Ianthanide complexes which can be used ira electroluminescent devices which have improved properties and give better results. Patent Applications PCT/GB98/O1 773, PCT/0B99/036 19, PCT/G1399/04030, PCT/0B99/04028, PCT/GBOO/00268 describe electroluminescent complexes, structures and devices using rare earth chelates.

Typical electroluminescent devices which are commonly referred to as optical light emitting diodes (OLEDS) comprise an anode, normally of an electrically light transporting material, a layer of a hole transporting material, a layer of the electroluminescent material, a layer of an electron transporting material and a metal cathode.

US Patent 5128587 discloses an electroluminescent device which consists of an organometallic complex of rare earth elements of the lanihanide series sandwiched between a transparent electrode of high work function and a second electrode of low work function with a hole conducting layer interposed between the electroluminescent layer and the transparent high work function electrode and an electron conducting layer interposed between the electroluminescent layer and the electron injecting low work function anode. The hole conducting layer and the electron conducting layer are required to improve the working and the efficiency of the device. The hole conducting or transportation layer serves to transport holes and to block the electrons, thus preventing electrons from moving into the electrode without recombining with holes. The electron conducting or transporting layer serves to transport electrons and to block the holes, thus preventing holes from moving into the electrode without recombining with holes. The recombination of carriers therefore mainly or entirely takes place in the emitter layer.

As described in US Patent 6333521 this mechanism is based upon the radiative recombinalion of a trapped charge. Specifically, OLEDs are comprised of at least two thin organic layers between an anode and a cathode. The material of one of these layers is specifically chosen based on the material's ability to transport holes, a "hole transporting layerTM (HTL), and the material of the other layer is specifically selected according to its ability to transport electrons, an electron transporting layer" (ETL).

With such a construction, the device can be viewed as a diode with a forward bias when the potential applied to the anode is higher than the potential applied to the cathode. Under these bias conditions, the anode injects holes (positive charge carriers) into the HTL, while the cathode injects electrons into the ETL. The portion of the luminescent medium adjacent to the anode thus forms a hole injecting and transporting zone while the portion of the luminescent medium adjacent to the cathode forms an electron injecting and transporting zone. The injected holes and electrons each migrate toward the oppositely charged electrode. When an electmn and bole localize on the same molecule, a Frenkel Cxciton is formed. These excitons are trapped in the material which has the lowest energy. Recombination of the short-lived exeitons may be visualized as an electron dropping from its conduction potential to a valcnce band, with relaxation occurring, under certain conditions, preferentially via a photoemissive mechanism.

The materials that function as the ETL or FITL of an OLED may also serve as the medium in which exciton formation and electroluminescent emission occur. Such OLEDs are referred to as having a single heterostructure" (SH). Alternatively, the electroluminescent material may be present in a separate emissive layer between the HTL and the EU in what is referred to as a double heterostructure (DH).

In a single heterostructure OLED, either holes are injected from the HTL into the ETL where they combine with electrons to form excitons, or electrons are injected from the ETL into thc I-ITL where they combine with holes to form excitons. Because excitons are trapped in the material having the lowest energy gap, and conimoniy used EU materials generally have smaller energy gaps than commonly used HTL materials, the emissive layer of a single heterostructure device is typically the ETL. In such an OLED, the materials used for the EU and HTL should be chosen such that holes can be injected efficiently from the tilL into the ETL. Also, the best OLEDs are believed to have good energy level alignment between the highest occupied molecuJar orbital (1-LOMO) levels of the HTL and ETL materials.

In a double heterostructure OLED, holes are injected from the HTL and electrons are injected from the ETL into the separate emissive layer, where the holes and electmns combine to form excitons.

Various compounds have been used as HL materials or ETL materials. HTL materials mostly consist of triaiyl ainines in various forms which show high hole mobilities (-1 0 cm2 fVs), There is somewhat more variety in the ETLs used in OLEDs, Aluminium tris(8-hydroxyquinolate) (A1q3) is the most common EU material, and others include oxidiazol, triazol, and triazine.

A well documented cause of OLED failure is thermally induced deformation of the organic layers (e.g. melting, crystal formation, thermal expansion, etc.). This failure mode can be seen in the studIes that have been carried out with hole transporting materials, K. Naito and A. Miura, J. Phys. Chem. (1993), 97, 6240-6248; S. Tokito, H. Tanaka, A. Okada and Y. Taga. App!. Phys. Lett. (1996), 69, (7), 878-880; Y. Shirota, T Kobata and N. Noma, Chem. Lett. (1989), 1145-1148; T. Noda, I. Lmae, N. Noma and Y. Shirota, Adv. Mater. (1997), 9, No. 3; E. Han, L. Do, M. Fujihira, 1-1.

inada and Y. Shirota, J. App!. Phys. (1996), 80, (6) 3297-701; T. Nods, H. Ogawa, N. Norna and Y. Shirota, Appi. Phys. Left. (1997), 70, (6), 699-701; S. Van Slyke, C. Chen and C. Tang, Appi. Phys. Left. (1996), 69, 15, 2160-2162; and U.S. Pat. No. 5,061,569.

In order to overcome this problem US Patent 6333521 discloses organic materials that are present as a glass, as opposed to a crystalline or polycrystallinc form, are disclosed for use in the organic layers of an OLED, since glasses arc capable of providing higher transparency as well as producing superior overall charge carrier characteristics as compared with the polycrystallinc materials that are typically produced when thin films of the crystalline form of the materials are prepared.

However, thermally induced deformation of the organic layers may Lead to catastrophic and irreversible failure of the OLED if a glassy organic layer is heated above its T8. In addition, thermally induced deformation of a glassy organic layer may occur at temperatures lower than Tg, and the rate of such deformation may be dependent on the difference between the temperature at which the deformation occurs and Tg. Consequently, the lifetime of an OLEI) may be dependent on the T5 of the organic layers even if the device is not heated above T5. As a result, there is a need for organic materials having a high Tg that can be used in the organic layers of an OLED.

However there is a general inverse correlation between the I and the hole transporting properties of a material, i.e., materials having a high T5 generally have poor hole transporting properties. Using an HTL with good hole transporting properties leads to an OLED having desirable properties such as higher quantum efficiency, lower resistance across the OLED, higher power quantum efficiency, and higher luminance.

We have now devised an electroluminescent device using HTLs and/or ETLs which reduce this problem.

According to the invention there is provided an electroluminescent device which comprises (i) a first electrode (ii) a layer incorporating a fullerene charge transporting material (iii) a layer of an electroluminescent material and (iv) a second electrode.

The term charge transporting material includes both hole transporting materials and electron transporting materials. When the first electrode is the anode and the second electrode is the cathode the charge transporting material will be a hole transporting material and when the first electrode is a cathode and the second electrode is the anode the charge transporting material will be an electron transporting material.

The invention also provides an electroluminescent device which comprises (i) a first electrode which is the anode (ii) a layer of a fuflerene hole transporting material (HTL) (iii) a layer of an electroluminescent material (iv) a layer of a fullerene electron transporting material (ETL) and (v) a second electrode which is the cathode.

A fullerene is a third form of pure carbon dilThrent from graphite and diamond, the only two forms known before 1985. In 1985, Richard Smalley and a team of chemists at Rice University identified the structure of one ftillerene that contained 60 carbon atoms. This C molecule has come to be known 1buckminsterfullerene.' See "Fullcrenes,' Curl, R. F. and Smalley, R. E, Scientific American, Oct., 1991, pp. 54- 63, incorporated herein by reference, and references cited therein.

A fullerene structure is characterized in that each carbon atom is bonded to three other carbon atoms. The carbon atoms so joined curve around to form a molecuLe with a cage-like structure and aromatic properties. A fullerene molecule with 60 carbon atoms resembles the familiar shape of a soccer ball. Fullerenes may contain even numbers of carbon atoms totaLling from 20 to 500 or more. Known fullerenes are C, C78, C82, C, Cs6 C, C90 and C96 fullerenes. Fullerenes are not necessarily spherical. They may take the form of long tubular structures with hemispherical caps at each end of the tube. Hyperfullerene structures also exist wherein one structure is contained within a second larger structure. For generally spherical molecular structures, these hypcrfullerenes resemble an onion layered structure. Tubular structures within larger structures are also possible. Fullerenes are more fully described in the literature cited above.

The molecular structure for buckminsterfiillerene was first identified in 1985, sec NATURE, C flBuckniinsterfullerenew, Kroto, H. W., Heath, J. R., O'Brien S. C., Curl, P.. F. and Smalley, R. E., Vol. 318, No. 6042, pp. 162-163, Nov. 14, 1985. The process desciibed therein for maldng fullerenes involves vaporizing the carbon from a rotating solid disk of graphite into a high-density helium flow using a focused pulsed laser.

Another method of making fullerenes was describe in THE JOURNAL OF PHYSICAl CHEMISTRY, "Characterization of the Soluble All-Carbon Molecules C60 and C70, AJIE et. a!, Vol. 94, No. 24, 1990, pp. 8630-8633.

The original method of preparation of buckminsterfulierene was in a molecular beam, and only very small quantities could be made. However, it was soon found that the molecules were produced in large numbers in an electric arc between two carbon electrodes in a helium atmosphere as described in US Patent 5227038.

Whether a fullerene is used as a hole transporting material or as an electron transporting material will depend on the properties of the fullercnc. For usc as ETLs the C60 fullerenes are preferred and for use as HTLs the C70 fullerenes are preferred.

The invention also provides:-An electroluminescent device which comprises (i) a first electrode (ii) a layer incorporating a C,0 flullerene hole transporting material (iii) a layer of an electroluminescent material and (iv) a second electrode.

An electroluminescent device which comprises (i) a first electrode (ii) a layer of an electroluminescent material (iii) a layer incorporating a C60 fullerene electron transporting material and (iv) a second electrode.

An electroluminescent device which comprises (i) a first electrode (ii) a layer incorporating a C,0 fullerene hole transporting material (iii) a layer of an electroluminescent material (iv) a layer incorporating a C60 fullerene electron transporting material and (v) a second electrode.

There can be one or more other hole transporting layers adjacent the fuflerene hole transporting material and one or more other electron transporting material adjacent to the fullerene electron transporting material, e.g. 1101 C70 HTLj EU E111 C Metal; ITOI HILl C EU Eu C6 Metal, 1101 C70J HILl ELI C6oI HTLI Metal; 1101 Hill C70 ELI C60 I ETLJ Metal where ITO is an indium tin oxide anode, HTL is a hole transporting layer, EL is a layer of an organic electroluminescent material, ETL is an electron transporting layer and Metal is a metal cathode.

In addition there can be a buffer layer between the ITO and the hole transporting layer.

Preferably the ftillerene is mixed with a polymeric material such as a polyolefin e.g. polyethylene, polypropylene etc. and preferably polystyrene.

The fullerenes can be doped with a metal or metal alloy to modify the properties of the fullerene, any material can be used depending on the application of the fuilerene and the nature of the other materials in the electroluminescent device.

Electroluminescent compounds which can be used as the electroluminescent material in the present invention are of general formula (La)M where M is a rare earth, Ianthanide or an actinide, La is an organic complex and n is the valence state of M. Other organic electroluminescent compounds which can be used in the present invention are of formula (L>-M*---L where La and Lp are organic Iigands, M is a rare earth, transition metal, lanthanide or an actinide and n is the valence state of the metal M. The ligands La can be the same or different and there can be a plurality of ligands Lp which can be the same or different.

For example (Li)(L2)(L3)(L,.)M(Lp) where M is a rare earth, transition metal, lanthanide or an actinide and (Lj)(L2XL3XL...) are the same or different organic complexes and (Lp) is a neutral ligand. The total charge of the ligands (Li)(L2)(L3)(L..) is equal to the valence state of the metal M. Where there are 3 groups La which corresponds to the HI valence state of M the complex has the formula (L1XL2)(L3)M (Lp) and the different groups (Li)(L2XL3) may be the same or different.

Lp can be monodentate, bidentate or polydentate and there can be one or more ligands Lp.

Preferably M is metal ion having an unfilled inner shell and the preferred metals are selected from Sm(11J), Eu(11), Eu(lll), Tb(I11), Dy(IH), Yb(lH), Lu(ITI), Gd (Ill), Gd(ffl) U(Ill), Tm(11I), Ce (111), Pr(ll1), Nd(ilI), Pm(1J1), Dy(lH), 110(111), Er(ll1), Yb(ll1) and more preferably Eu(Ill), Tb(fll), Dy(H1), Gd (111), Er (III), Yt(ffl).

Further organic electroluminescent compounds which can be used in the present invention are of general formula (La)MM2 where M1 is the same as M above, M2 is a non rare earth metal, La is a as above and n is the combined valence state of M1 and M2. The complex can also comprise one or more neutral ligands Lp so the complex has the general formula (La) M1 M2 (Lp), where Lp is as above. The metal M2 can be any metal which is not a rare earth, transition metal, lanthanide or an actinide examples of metals which can be used include lithium, sodium, potassium, rubidium, caesium, beryllium, magnesium, calcium, strontium, barium, copper (1), copper (11), silver, goki, zinc, cadmium, boron, aluminium, gallium, indium, gennanium, tin (II), tin (IV), antimony (11), antimony (IV), lead (II), lead (IV) and metals of the first, second and third groups of transition metals in different valence states e.g. manganese, iron, ruthenium, osmium, cobalt, nickel, palladium(ll), palladium(IV), platinum(lI), platinum(LV), cadmium, chromium, titanium, vanadium, zirconium, tantalum, molybdenum, rhodium, iridium, titanium, niobium, scandium, yttrium.

For example (LiXLiXL3XL..)M (Lp) where M is a rare earth, transition metal, lanthanide or an actinide and (Li)(L2XL3)(L...) and (Lp) arc the same or different organic complexes.

Further organometallic complexes which can be used in the present invention are binuclear, trinuclear and polynuclear organometallic complexes e.g. of formula (Lm), M1 -M2(Ln) e.g. (Lm)XM(M2(Ln) -10 -where L is a bridging ligand and M1 is a rare earth metal and M2 is M1 or a non rare earth metal, Lm and Ln are the same or different organic ligands La as defined above, x is the valence state of M1 and y is the valence state of M2.

In these complexes there can be a metal to metal bond or there can be one or more bridging ligands between M1 and M2 and the groups Lm and Ln can be the same or different.

By trinuclear is meant there are three rare earth metals joined by a metal to metal bond i.e. of formula (Lm) M 1 -M3 (in)y _M2 ( Lp) or (Lm)M -,M3 (Ln), M2 (Lp) where M1, M2 and M3 are the same or different rare earth metals and Lm, Ln and Lp are organic ligands Lc& and x is the valence state of M1, y is the valence state of M2 and z is the valence state of M3. Lp can be the same as Lm and Ln or different.

The rare earth metals and the non rare earth metals can be joined together by a metal to metal bond and/or via an intermediate bridging atom, ligand or molecular group.

For example the metals can be linked by bridging Zigands e.g. -11 -(Lm)Mi M3(Ln) M2(U,) or M1:T_U M

L L / I

whei L is a bridging iigand.

By polynuclear is meant there are more than three inetais joined by metal to metal bonds and/or via intermediate ligands or MI-M2-M4_-M3 or . 2 I.. I #.

Ms--M4 or -L... ,.-L\ ,-L...

M2 M4 M3 "-L-' L WhCreMI,M2, M3and M4arercthmeasaniLjsabndgjflgJj -12 -Preferably Li is selected from a diketones such as those of formulae or (I) (II) (LU) where R1, R2 and R3 can be the same or different and are selected from hydrogen, and substituted and unsubstituted hydrocarbyl groups such as substituted and unsubstituted aliphatic groups, substituted and unsubstituted aromatic, heterocyclic and polycyclic ring stnjctures, fluorocarbons such as trifluoryl methyl groups, halogens such as fluorine or thiophenyl groups; R,, R2 and R3 can also form substituted and unsubstituted fused aromatic, beterocyclic and polycyclic ring structures and can be copolymerisable with a monomer e.g. styrene. X is Se, S or 0, Y can be hydrogen, substituted or unsubstituted hydrocarbyl groups, such as substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures, fluorine, fluorocarbons such as trifluoryl methyl groups, halogens such as fluorine or thiophenyl groups or nitrile.

The beta diketones can be polymer substituted beta diketones and in the polymer, oligomer or dendrimer substituted 13 diketone the substituents group can be directly linked to the diketone or can be linked through one or more -CH2 groups i.e. Polymer Polymer (cH2) or (I) (II) - 13 -Polymer (CH2 Polymer im br C R:; (Lila) (Ilib) or through phenyl groups e.g. Polymer \ / Pd)wer Po&mer.. Pomer Polymer or R3 (mc) (Hid) where "polymer" can be a polymer, an oligomer or a dendrimer, (there can be one or two substituted phenyl groups as well as three as shown in (Ilic)) and where R is selected from hydrogen, and substituted and unsubstituted bydrocarbyl groups such as substituted and unsubstituted aliphatic groups, substituted and unsubstituted aromatic, hetcrocyciic and polycyclic ring structures, fluorocarbons such as trifluoryl methyl 1.5 groups, halogens such as fluorine or thiophenyl groups.

Examples of R and/or R. and/or R3 include aliphatic, aromatic and heterocyclic alkoxy, aryloxy and carboxy groups, substituted and substituted phenyl, fluorophenyl, -14 -biphenyl, phenanthrene, anthracene, naphthyl and fluorene groups alkyl groups such as t-butyl, heterocyclic groups such as carbazole.

Some of the different groups La may also be the same or different charged groups such as carboxylate groups so that the group L, can be as defmed above and the groups L2, can be charged groups such as

R-C (IV)

where R is R, as defined above or the groups L1, L2 can be as defined above and L3,, etc. are other charged groups.

R1,R2andR3 canalsobe X whereXisO,S,SeorNH. (V)

A preferred moiety R1 is trifluoromethyl CF3 and examples of such diketones are, banzoyltrifluoroacetone, p-chlorobenzoyltrifluoroacetone, p-bromotrifluoroacetone, p.phenyltrifluoroaeetone 1 -naphthoyltrifluoroacetone, 2-naphthoyltrifluoroacetone, 2-phenathoyltrifluoroacetone, 3-phenanthoyitrifluoroatone, 9-anthroylt1jfluomacetonetrjfluoroetone cinnamoyltrifluoroacetone, and 2-thenoyltrifluoroacetone.

-:1.5 -The different groups L may be the same or different ligands of formulae (VI) whereXisO, S, or Se and R1 R2and R3 are as above.

The different groups La may be the same or different quinolate derivatives such as or (VII) (VIII) where R is hydrocarbyl, aliphatic, aromatic or heterocyclic carboxy, aryloxy, hydroxy or alkoxy e.g. the 8 hydroxy quinolatc derivatives or R1 o RB O-or R20 -(IX) (X) -1.6 -where R, R1, and R2 are as above or are H or F e.g. R, and R2 are alkyl or alkoxy groups CF S-o s-0 / 8-0 a 0 CF R or (XI) (XII) As stated above the different groups La may also be the same or different carboxylate groups e.g. R5_C(E (Xffl) where R5 is a substituted or unsubstituted aromatic, polycyclic or heterocyclic ring a polypyridyl group, R5 can also be a 2-ethyi hexyl group so L is 2-ethyihexanoate or R5 can be a chair structure so that L is 2-acetyl cyclobexanoate or La can be (XIV) -17 -where R is as above e.g. alkyl, allenyl, amino or a fused ring such as a cyclic or polycyclic ring.

The different groups La may also be R2-4 \ R ( 2 R1 / R2 \;1or (XV) (XVI) (XVII) R 2 (XVIJa) Where R, R1 and R2 are as above.

-18 -The groups Lp can be selected from Ph Ph

I I

O==P -N P Ph

I I Ph Ph

S (XVIII) Where each Ph which can be the same or different and can be a phenyl (OPNP) or a substituted phenyl group, other substituted or unsubstituted aromatic group, a substituted or unsubstituted heterocyclic or polycyclic group, a substituted or unsubstituted fused aromatic group such as a naphthyl, anthracene, pheianthrene or pyrene group. The substituents can be for example an alkyl, aralkyl, alkoxy, aromatic, heterocyclic, polycyclic group, halogen such as fluorine, cyano, amino. Substituted amino etc. Examples are given in figs. 1 and 2 of the drawings where R. R1 R2, R3 and R can be the same or different and are selected from hydrogen, hydrocarbyl groups, substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures, fluorocarbons such as trifluoiyl methyl groups, halogens such as fluorine or thiophenyl groups; R, R1 R2 R and R4 can also form substituted and unsubstitutcd fused aromatic, heterocyclic and polycyclic ring structures and can be copolymerisable with a monomer e.g. styrene. R, K1, R2, R3 and It4 can also be unsaturated alkylerie groups such as vinyl groups or groups -C----CH2=CH2-R where R is as above.

-19 -L can also be compounds of formulae R2 -: R2 or R1 R1 (XV[V) (XX) (XXI) where R,, R2 and R3 are as referred to above, for example bathophen sho in fig. 3 of the drawings in which R. is as above or R1R1 RIRR Q(U) (Xfl where R1, R2 azid R3 are as referred to above.

Lcanalsobe Ph Ph Ph Ph

I -__ I I -I

s=P-N PS j I Ph Ph or Ph Ph (XXJV) (XXV) where Ph is as above.

-20 -Other examples of L chelates are as shown in figs. 4 and fluorene and fluorene derivatives e.g. a shown in figs. 5 and compounds of formulae as shown as shown in figs. 6 to 8.

Specific examples of La and Lp are tripyridyl and TM}ID, and TMHD complexes, a, ci', a'' tripyridyl, crown ethers, cyclans, cryptans phthalocyanans, porphoryins ethylene diamine tetramine (EDTA), DCTA, DTPA and TTHA. Where TMHD is 2,2,6,6-tetramethyl-3,5-heptanedionato and OPNP is diphenyiphosphonimide triphenyl phosphorane. The formulae of the polyamines are shown in fig. 9.

Other organic electroluminescent materials which can be used include metal quinolates such as lithium quinolate, and non rare earth metal complexes such as aluminium, magnesium, zinc and scandium complexes such as complexes of -diketones e.g. Iris -(I,3-diphenyl-1-3-pmpanedione) (DBM) and suitable metal complexes are Al(DBM)3, Zn(DBM)2 and Mg(DI3M)2. Sc(DBM)3 etc. Other organic electroluminescent materials which can be used include the metal complexes of formula Mç7' j (XXV!) -21 -where M is a metaL other than a rare eaith, a transition metal, a lanthariide or an actmide; n is the valency of M; R1, R2 and R3 which may be the same or different are selected from hydrogen, hydrocarbyl groups, substituted and unsubstituted aliphatic groups substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures, fluorocarbons such as trifluoryl methyl groups, halogens such as fluorine or thiophenyl groups or nitrile; R1 and R3 can aiso be form ring structures and R1, R2 and R3 can be copolymerisable with a monomer e.g. styrene. Preferably M is aluminium and R3 is a phenyl or substituted phenyl group.

Claims

-22 -Claims 1. An electroluminescent device which comprises (i) a first electrode (ii) a layer of a fullerene charge transporting material (iii) a layer of an electroluminescent material and (iv) a second electrode.
2. An electroluminescent device which comprises (i) a first electrode which is the anode (ii) a layer of a fullerene hole transporting material (HTL) (iii) a layer of an electroluminescent material (iv) a layer of a fullerene electron transporting material (ETh) and (v) a second electrode which is the cathode.
3. An electroluminescent device as claimed in claim 1 or 2 in which the fullerene is a C, C70, C75, C82, C, C85 C88, C90 or C% fullerene.
4. An electroluminescent device as claimed in claim 2 in which the fullerene hole transporting material is a C70 fullerene.
5. An electroluminescent device as claimed in claim 4 in which fullerene electron transporting material is a C fullerene.
6. An electroluminescent device as claimed in any one of the preceding claims in which there is one or more other hole transporting layers adjacent the fullerene hole transporting material.
7. An electroluminescent device as claimed in any one of the preceding claims in which there is one or more other electron transporting material adjacent the fullerene electron transporting material.

-23 -
8. An electroluminescent device as claimed in any one of the preceding claims of sucture 1101 C701 FITLI ELI EUF C Metal; 1101 HTLI C ELI ETLI C601 Metal, 1101 C70j HTLI ELI C60j Hill Metal or 1101 HTL C, oI ELI Co ETL Metal where ITO is an indium tin oxide anode, HTL is a hole transporting layer, EL is a layer of an organic electroluminescent material, ETL is an electron transporting layer and Metal is a metal cathode C70 is a C70 fullerene and C60 is a C fullerene.
9. An electroiwninescent device as claimed in any one of the preceding claims in which there is a buffer layer between the first electrode and the hole transporting layer.
10. An electroluminescent device as claimed in any one of claims 2 to 5 in which the thickness of the fullerene HTL and ETL layer is from 2 to 100 nm.
11. An electroluminescent device as claimed in any one of claims I to 5111 which the fullerene is mixed with a polymeric material and/or other additives.
12. An electroluminescent device as claimed in any one of claims 1 to 11 in which the fullerene is doped with a metal.
13. An electroluminescent device as claimed in any one of the preceding claims in which the electroluminescent material is an organo metallic complex of formula (Lcc)>M L where La and Lp are organic tigands, M is a rare earth, transition metal, lanthanide or an actinide and n is the valence state of the metal M and in which the ligands La are the same or different.

-24 -
14. An electroluminescent device as claimed in claim 13 in which there are a plurality of ligands Lp which can be the same or different.
15. An electroluminescent device as claimed in any one of the preceding claims in which the electroluminescent material is an organo metallic complex of formula (L)M1M2 or (L) M1M2 (Lv), where L is Lq L is a neutral ligand M1 is a rare earth, transition metal, lanthanide or an actinide, M2 is a non rare earth metal and n is the combined valence state of M1 and M2.
16. An electroluminescent device as claimed in any one of the preceding claims in which the electroluminescent material is a binuclear, trinuclear or polynuclear organometallic complex of formula (Lm) M1 -M2(Ln) or (Lm) M M2 (Lii), where L is a bridging Ligand and where M1 is a rare earth metal and M2 is M1 or a non rare earth metal, Lm and Ln are the same or different organic ligands La as defined above, x is the valence state of M1 and y is the valence state of M2 or (Lm) M 1 -M3 (Ln) -M2 ( Lp) or (Lm)M i-M3(1) \/ -25 -where M,, M2 and M are the same or different rare earth metals and Lm, Ln and Lp are organic ligands La and x is the valence state of M1, y is the valence state of M2 and z is the valence state of M3 and Lp can be the same as Lm and Ln or different or (Lm)M i M3 (Ln), M2 ( Lp) or

----L

MM

LI

I -I or

M1-M2---M3-M4 or M1-M2-M4-M3 or ,. I -%

Mr--M4 or -L. L\ ,-L', M1 M4 M3 "L -L -26 -where M4 is M1 and L is a bridging ligand and in which the rare earth metals and the non rare earth metals can be joined together by a metal to metal bond andlor via an intermediate bridging atom, ligand or molecular group or in which there are more than three metals joined by metal to metal bonds and/or via intermediate ligands and
17. An electroluminescent device as claimed in claim 15 or 16 in which the non rare earth metal M2 is selected from lithium, sodium, potassium, rubidium. caesium, beryllium, magnesium, calciwn, strontium, barium, copper, silver, gold, zinc, cadmium, boron, aluminium, gallium, indium, germanium, tin, antimony, lead, and metals of the first, second and third groups of transition metals e.g. manganese, iron, ruthenium, osmium, cobalt, nickel, palLadium, platinum, cadmium, chromium.

titanium, vanadium, zirconium, tantulum, molybdenum, rhodium, iridium, titanium, niobium, scandium, and yttrium.
18. An eleciroluminescent device as claimed in any one of claims 13 to 17 in which La has the formula (1) to (XVIIa) herein.
19. An electroluminescent device as claimed in any one of claims 13 to 18 in which Lp has the formula of figs. I to 8 of the accompanying drawings or of formula (XVffl) to (XXV) herein.
20. An electroluminescent device as claimed in any one of claims 13 to 19 in which the said rare earth, transition metal, lanthanide or an actinide is selected from Sm(lll), Eu(11'), Eu(1ll), Tb(ffl), Dy(ffl), Yb(llI), Lu(ll1), Gd (Ill), (3d(II1) U(Hl), Tm(IlI), Ce (Ill), Pr(lLl), Nd(LEI), Pm(llI), Dy(lll), Ho(ffl) and E(lIl).
21. An electroluminescent device as claimed in any one claims I to 7 in which the electroluminescent material is a metal quinolate.

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22. An electroluminescent device as claimed in claim 21 in which the metal quinolate is lithium quinolate or ziTcornum quinolate.
23. An electroluminescent device as claimed in any one claims I to 12 in which the electroluminescent material is an electroluminescent non rare earth metal complex.
24. An electroluminescent device as claimed in claim 23 in which the electroluminescent material is an aluminium, magnesium, zinc or scandium complex.
25. An electroluminescent device as claimed in claim 24 in which the electroluminescent material is a (3-diketone complex.
26. An electroluminescent device as claimed in claim 25 in which the electroluminescent material is Al(DBM)3 Zn(I)BM)2 and Mg(DBM)2 Sc(DBM)3 where (DBM) is Iris -(1,3-diphenyl-1-3-propanedione).
27. An electroluminescent device as claimed in any one of claims 1 to 12 in which the electroluminescent material is a compound of fonnula (XXVI) herein.