WO2010079331A1 - Interlayer formulation for flat films - Google Patents
Interlayer formulation for flat films Download PDFInfo
- Publication number
- WO2010079331A1 WO2010079331A1 PCT/GB2010/000020 GB2010000020W WO2010079331A1 WO 2010079331 A1 WO2010079331 A1 WO 2010079331A1 GB 2010000020 W GB2010000020 W GB 2010000020W WO 2010079331 A1 WO2010079331 A1 WO 2010079331A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- composition
- solvent
- hole transport
- layer
- transport material
- Prior art date
Links
- 239000000203 mixture Substances 0.000 title claims abstract description 87
- 238000009472 formulation Methods 0.000 title description 18
- 239000011229 interlayer Substances 0.000 title description 14
- 239000000463 material Substances 0.000 claims abstract description 99
- 239000002904 solvent Substances 0.000 claims abstract description 75
- 230000005525 hole transport Effects 0.000 claims abstract description 55
- 238000002347 injection Methods 0.000 claims abstract description 24
- 239000007924 injection Substances 0.000 claims abstract description 24
- 238000009835 boiling Methods 0.000 claims abstract description 16
- 238000007639 printing Methods 0.000 claims abstract description 14
- RDOXTESZEPMUJZ-UHFFFAOYSA-N anisole Chemical compound COC1=CC=CC=C1 RDOXTESZEPMUJZ-UHFFFAOYSA-N 0.000 claims abstract description 8
- LTEQMZWBSYACLV-UHFFFAOYSA-N Hexylbenzene Chemical compound CCCCCCC1=CC=CC=C1 LTEQMZWBSYACLV-UHFFFAOYSA-N 0.000 claims abstract description 6
- XSIFPSYPOVKYCO-UHFFFAOYSA-N butyl benzoate Chemical compound CCCCOC(=O)C1=CC=CC=C1 XSIFPSYPOVKYCO-UHFFFAOYSA-N 0.000 claims abstract description 6
- MTZQAGJQAFMTAQ-UHFFFAOYSA-N ethyl benzoate Chemical compound CCOC(=O)C1=CC=CC=C1 MTZQAGJQAFMTAQ-UHFFFAOYSA-N 0.000 claims abstract description 6
- QPJVMBTYPHYUOC-UHFFFAOYSA-N methyl benzoate Chemical compound COC(=O)C1=CC=CC=C1 QPJVMBTYPHYUOC-UHFFFAOYSA-N 0.000 claims abstract description 6
- NIEHEMAZEULEKB-UHFFFAOYSA-N ortho-ethylanisole Natural products CCC1=CC=CC=C1OC NIEHEMAZEULEKB-UHFFFAOYSA-N 0.000 claims abstract description 6
- UZKWTJUDCOPSNM-UHFFFAOYSA-N methoxybenzene Substances CCCCOC=C UZKWTJUDCOPSNM-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000002861 polymer material Substances 0.000 claims abstract description 4
- LBNXAWYDQUGHGX-UHFFFAOYSA-N 1-Phenylheptane Chemical compound CCCCCCCC1=CC=CC=C1 LBNXAWYDQUGHGX-UHFFFAOYSA-N 0.000 claims abstract description 3
- BLMBNEVGYRXFNA-UHFFFAOYSA-N 1-methoxy-2,3-dimethylbenzene Chemical compound COC1=CC=CC(C)=C1C BLMBNEVGYRXFNA-UHFFFAOYSA-N 0.000 claims abstract description 3
- DTFKRVXLBCAIOZ-UHFFFAOYSA-N 2-methylanisole Chemical compound COC1=CC=CC=C1C DTFKRVXLBCAIOZ-UHFFFAOYSA-N 0.000 claims abstract description 3
- UDEWPOVQBGFNGE-UHFFFAOYSA-N benzoic acid n-propyl ester Natural products CCCOC(=O)C1=CC=CC=C1 UDEWPOVQBGFNGE-UHFFFAOYSA-N 0.000 claims abstract description 3
- HHNHBFLGXIUXCM-GFCCVEGCSA-N cyclohexylbenzene Chemical compound [CH]1CCCC[C@@H]1C1=CC=CC=C1 HHNHBFLGXIUXCM-GFCCVEGCSA-N 0.000 claims abstract description 3
- 229940095102 methyl benzoate Drugs 0.000 claims abstract description 3
- OLXYLDUSSBULGU-UHFFFAOYSA-N methyl pyridine-4-carboxylate Chemical compound COC(=O)C1=CC=NC=C1 OLXYLDUSSBULGU-UHFFFAOYSA-N 0.000 claims abstract description 3
- VXNSQGRKHCZUSU-UHFFFAOYSA-N octylbenzene Chemical compound [CH2]CCCCCCCC1=CC=CC=C1 VXNSQGRKHCZUSU-UHFFFAOYSA-N 0.000 claims abstract description 3
- FBXWCEKQCVOOLT-UHFFFAOYSA-N octylcyclohexane Chemical compound CCCCCCCCC1CCCCC1 FBXWCEKQCVOOLT-UHFFFAOYSA-N 0.000 claims abstract description 3
- QTFAGJWQYORRKM-UHFFFAOYSA-N 1,1-dicyclohexyl-4-hexylcyclohexane Chemical group C1(CCCCC1)C1(CCC(CC1)CCCCCC)C1CCCCC1 QTFAGJWQYORRKM-UHFFFAOYSA-N 0.000 claims abstract 2
- 238000000034 method Methods 0.000 claims description 33
- 229920000642 polymer Polymers 0.000 claims description 31
- 238000007641 inkjet printing Methods 0.000 claims description 26
- 238000000151 deposition Methods 0.000 claims description 20
- 239000011248 coating agent Substances 0.000 claims description 6
- 238000000576 coating method Methods 0.000 claims description 6
- WCOYPFBMFKXWBM-UHFFFAOYSA-N 1-methyl-2-phenoxybenzene Chemical group CC1=CC=CC=C1OC1=CC=CC=C1 WCOYPFBMFKXWBM-UHFFFAOYSA-N 0.000 claims description 5
- 230000008021 deposition Effects 0.000 claims description 5
- 238000003618 dip coating Methods 0.000 claims description 5
- 125000005259 triarylamine group Chemical group 0.000 claims description 5
- 229920001577 copolymer Polymers 0.000 claims description 4
- 238000005507 spraying Methods 0.000 claims description 3
- 125000003983 fluorenyl group Chemical group C1(=CC=CC=2C3=CC=CC=C3CC12)* 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 claims description 2
- 239000010410 layer Substances 0.000 description 108
- 239000000758 substrate Substances 0.000 description 21
- 239000010408 film Substances 0.000 description 20
- 229910052751 metal Inorganic materials 0.000 description 13
- 239000002184 metal Substances 0.000 description 13
- 239000000976 ink Substances 0.000 description 11
- 229920001609 Poly(3,4-ethylenedioxythiophene) Polymers 0.000 description 10
- 239000011159 matrix material Substances 0.000 description 10
- 230000008719 thickening Effects 0.000 description 9
- 125000003118 aryl group Chemical group 0.000 description 8
- 239000011368 organic material Substances 0.000 description 8
- 239000007787 solid Substances 0.000 description 8
- 239000000243 solution Substances 0.000 description 8
- 239000011521 glass Substances 0.000 description 7
- 125000001072 heteroaryl group Chemical group 0.000 description 7
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 6
- 238000001035 drying Methods 0.000 description 6
- -1 poly(ethylene dioxythiophene) Polymers 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 125000000217 alkyl group Chemical group 0.000 description 5
- 239000004411 aluminium Substances 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 5
- 239000008393 encapsulating agent Substances 0.000 description 5
- 239000000178 monomer Substances 0.000 description 5
- 239000004033 plastic Substances 0.000 description 5
- 229920003023 plastic Polymers 0.000 description 5
- 229920002098 polyfluorene Polymers 0.000 description 5
- 125000003545 alkoxy group Chemical group 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 229910052736 halogen Inorganic materials 0.000 description 4
- 150000002367 halogens Chemical class 0.000 description 4
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 229920000412 polyarylene Polymers 0.000 description 4
- 238000004528 spin coating Methods 0.000 description 4
- 125000001424 substituent group Chemical group 0.000 description 4
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical group [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 3
- 239000004642 Polyimide Substances 0.000 description 3
- 125000004429 atom Chemical group 0.000 description 3
- 230000004888 barrier function Effects 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 229920000547 conjugated polymer Polymers 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 3
- 238000005401 electroluminescence Methods 0.000 description 3
- AMGQUBHHOARCQH-UHFFFAOYSA-N indium;oxotin Chemical compound [In].[Sn]=O AMGQUBHHOARCQH-UHFFFAOYSA-N 0.000 description 3
- 229920002120 photoresistant polymer Polymers 0.000 description 3
- 229920001467 poly(styrenesulfonates) Polymers 0.000 description 3
- 229920001721 polyimide Polymers 0.000 description 3
- 239000011970 polystyrene sulfonate Substances 0.000 description 3
- 229960002796 polystyrene sulfonate Drugs 0.000 description 3
- 230000005855 radiation Effects 0.000 description 3
- 238000010129 solution processing Methods 0.000 description 3
- NQMUGNMMFTYOHK-UHFFFAOYSA-N 1-methoxynaphthalene Chemical compound C1=CC=C2C(OC)=CC=CC2=C1 NQMUGNMMFTYOHK-UHFFFAOYSA-N 0.000 description 2
- 101100512907 Arabidopsis thaliana MES9 gene Proteins 0.000 description 2
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- 239000004793 Polystyrene Substances 0.000 description 2
- 150000004996 alkyl benzenes Chemical class 0.000 description 2
- CHFKDIRTBQUUCE-UHFFFAOYSA-N anisole;1-methyl-3-phenoxybenzene Chemical compound COC1=CC=CC=C1.CC1=CC=CC(OC=2C=CC=CC=2)=C1 CHFKDIRTBQUUCE-UHFFFAOYSA-N 0.000 description 2
- 239000010405 anode material Substances 0.000 description 2
- 229910052788 barium Inorganic materials 0.000 description 2
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 2
- QVQLCTNNEUAWMS-UHFFFAOYSA-N barium oxide Chemical compound [Ba]=O QVQLCTNNEUAWMS-UHFFFAOYSA-N 0.000 description 2
- 239000002585 base Substances 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- SESFRYSPDFLNCH-UHFFFAOYSA-N benzyl benzoate Chemical compound C=1C=CC=CC=1C(=O)OCC1=CC=CC=C1 SESFRYSPDFLNCH-UHFFFAOYSA-N 0.000 description 2
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 2
- 229910052794 bromium Inorganic materials 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- MHDVGSVTJDSBDK-UHFFFAOYSA-N dibenzyl ether Chemical compound C=1C=CC=CC=1COCC1=CC=CC=C1 MHDVGSVTJDSBDK-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006870 function Effects 0.000 description 2
- 238000004770 highest occupied molecular orbital Methods 0.000 description 2
- 229910010272 inorganic material Inorganic materials 0.000 description 2
- 239000011147 inorganic material Substances 0.000 description 2
- 238000003780 insertion Methods 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- AUHZEENZYGFFBQ-UHFFFAOYSA-N mesitylene Substances CC1=CC(C)=CC(C)=C1 AUHZEENZYGFFBQ-UHFFFAOYSA-N 0.000 description 2
- 125000001827 mesitylenyl group Chemical group [H]C1=C(C(*)=C(C([H])=C1C([H])([H])[H])C([H])([H])[H])C([H])([H])[H] 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 238000000059 patterning Methods 0.000 description 2
- 238000000206 photolithography Methods 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 229920000767 polyaniline Polymers 0.000 description 2
- 229920002223 polystyrene Polymers 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 229920005604 random copolymer Polymers 0.000 description 2
- 238000007650 screen-printing Methods 0.000 description 2
- 125000003107 substituted aryl group Chemical group 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 239000008096 xylene Substances 0.000 description 2
- 125000001140 1,4-phenylene group Chemical group [H]C1=C([H])C([*:2])=C([H])C([H])=C1[*:1] 0.000 description 1
- XHLHPRDBBAGVEG-UHFFFAOYSA-N 1-tetralone Chemical compound C1=CC=C2C(=O)CCCC2=C1 XHLHPRDBBAGVEG-UHFFFAOYSA-N 0.000 description 1
- UXKWZAANEMJTCK-UHFFFAOYSA-N 3,4-dihydro-2h-naphthalen-1-one;1,3,5-trimethylbenzene Chemical group CC1=CC(C)=CC(C)=C1.C1=CC=C2C(=O)CCCC2=C1 UXKWZAANEMJTCK-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 101150037847 MES1 gene Proteins 0.000 description 1
- AFVFQIVMOAPDHO-UHFFFAOYSA-N Methanesulfonic acid Chemical compound CS(O)(=O)=O AFVFQIVMOAPDHO-UHFFFAOYSA-N 0.000 description 1
- 229910015711 MoOx Inorganic materials 0.000 description 1
- 229920000557 Nafion® Polymers 0.000 description 1
- 229920000265 Polyparaphenylene Polymers 0.000 description 1
- NRCMAYZCPIVABH-UHFFFAOYSA-N Quinacridone Chemical compound N1C2=CC=CC=C2C(=O)C2=C1C=C1C(=O)C3=CC=CC=C3NC1=C2 NRCMAYZCPIVABH-UHFFFAOYSA-N 0.000 description 1
- 229910019897 RuOx Inorganic materials 0.000 description 1
- 101100097991 Schizosaccharomyces pombe (strain 972 / ATCC 24843) rar1 gene Proteins 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 150000001454 anthracenes Chemical class 0.000 description 1
- 150000004984 aromatic diamines Chemical class 0.000 description 1
- 125000003710 aryl alkyl group Chemical group 0.000 description 1
- JXLHNMVSKXFWAO-UHFFFAOYSA-N azane;7-fluoro-2,1,3-benzoxadiazole-4-sulfonic acid Chemical compound N.OS(=O)(=O)C1=CC=C(F)C2=NON=C12 JXLHNMVSKXFWAO-UHFFFAOYSA-N 0.000 description 1
- OYLGJCQECKOTOL-UHFFFAOYSA-L barium fluoride Chemical compound [F-].[F-].[Ba+2] OYLGJCQECKOTOL-UHFFFAOYSA-L 0.000 description 1
- 229910001632 barium fluoride Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229960002903 benzyl benzoate Drugs 0.000 description 1
- 229920001400 block copolymer Polymers 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- ZADPBFCGQRWHPN-UHFFFAOYSA-N boronic acid Chemical compound OBO ZADPBFCGQRWHPN-UHFFFAOYSA-N 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 150000004696 coordination complex Chemical class 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 238000002484 cyclic voltammetry Methods 0.000 description 1
- 239000000412 dendrimer Substances 0.000 description 1
- 229920000736 dendritic polymer Polymers 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- USIUVYZYUHIAEV-UHFFFAOYSA-N diphenyl ether Chemical compound C=1C=CC=CC=1OC1=CC=CC=C1 USIUVYZYUHIAEV-UHFFFAOYSA-N 0.000 description 1
- 239000002019 doping agent Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000005227 gel permeation chromatography Methods 0.000 description 1
- 238000009499 grossing Methods 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 125000005843 halogen group Chemical group 0.000 description 1
- RBTKNAXYKSUFRK-UHFFFAOYSA-N heliogen blue Chemical compound [Cu].[N-]1C2=C(C=CC=C3)C3=C1N=C([N-]1)C3=CC=CC=C3C1=NC([N-]1)=C(C=CC=C3)C3=C1N=C([N-]1)C3=CC=CC=C3C1=N2 RBTKNAXYKSUFRK-UHFFFAOYSA-N 0.000 description 1
- 125000004446 heteroarylalkyl group Chemical group 0.000 description 1
- QHWAQXOSHHKCFK-UHFFFAOYSA-N hexylcyclohexane Chemical compound CCCCCCC1CCCCC1 QHWAQXOSHHKCFK-UHFFFAOYSA-N 0.000 description 1
- 229920001519 homopolymer Polymers 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 230000002209 hydrophobic effect Effects 0.000 description 1
- 230000005661 hydrophobic surface Effects 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- PNDPGZBMCMUPRI-UHFFFAOYSA-N iodine Chemical compound II PNDPGZBMCMUPRI-UHFFFAOYSA-N 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000004768 lowest unoccupied molecular orbital Methods 0.000 description 1
- 150000002736 metal compounds Chemical class 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- YCWSUKQGVSGXJO-NTUHNPAUSA-N nifuroxazide Chemical group C1=CC(O)=CC=C1C(=O)N\N=C\C1=CC=C([N+]([O-])=O)O1 YCWSUKQGVSGXJO-NTUHNPAUSA-N 0.000 description 1
- 239000002674 ointment Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000012044 organic layer Substances 0.000 description 1
- 125000002524 organometallic group Chemical group 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- IEQIEDJGQAUEQZ-UHFFFAOYSA-N phthalocyanine Chemical compound N1C(N=C2C3=CC=CC=C3C(N=C3C4=CC=CC=C4C(=N4)N3)=N2)=C(C=CC=C2)C2=C1N=C1C2=CC=CC=C2C4=N1 IEQIEDJGQAUEQZ-UHFFFAOYSA-N 0.000 description 1
- 238000005240 physical vapour deposition Methods 0.000 description 1
- 238000009832 plasma treatment Methods 0.000 description 1
- 239000004584 polyacrylic acid Substances 0.000 description 1
- RKCAIXNGYQCCAL-UHFFFAOYSA-N porphin Chemical compound N1C(C=C2N=C(C=C3NC(=C4)C=C3)C=C2)=CC=C1C=C1C=CC4=N1 RKCAIXNGYQCCAL-UHFFFAOYSA-N 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000005258 radioactive decay Effects 0.000 description 1
- 150000003384 small molecules Chemical class 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 125000000547 substituted alkyl group Chemical group 0.000 description 1
- 150000003460 sulfonic acids Chemical class 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- JOXIMZWYDAKGHI-UHFFFAOYSA-N toluene-4-sulfonic acid Chemical compound CC1=CC=C(S(O)(=O)=O)C=C1 JOXIMZWYDAKGHI-UHFFFAOYSA-N 0.000 description 1
- 229910000314 transition metal oxide Inorganic materials 0.000 description 1
- ITMCEJHCFYSIIV-UHFFFAOYSA-M triflate Chemical compound [O-]S(=O)(=O)C(F)(F)F ITMCEJHCFYSIIV-UHFFFAOYSA-M 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
- H10K71/10—Deposition of organic active material
- H10K71/12—Deposition of organic active material using liquid deposition, e.g. spin coating
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
- H10K71/10—Deposition of organic active material
- H10K71/12—Deposition of organic active material using liquid deposition, e.g. spin coating
- H10K71/15—Deposition of organic active material using liquid deposition, e.g. spin coating characterised by the solvent used
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
- H10K50/14—Carrier transporting layers
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
- H10K71/10—Deposition of organic active material
- H10K71/12—Deposition of organic active material using liquid deposition, e.g. spin coating
- H10K71/13—Deposition of organic active material using liquid deposition, e.g. spin coating using printing techniques, e.g. ink-jet printing or screen printing
- H10K71/135—Deposition of organic active material using liquid deposition, e.g. spin coating using printing techniques, e.g. ink-jet printing or screen printing using ink-jet printing
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/10—Organic polymers or oligomers
- H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
- H10K85/113—Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
- H10K85/1135—Polyethylene dioxythiophene [PEDOT]; Derivatives thereof
Definitions
- a typical organic light-emitting device comprises a substrate, on which is supported an anode, a cathode and a light-emitting layer situated in between the anode and cathode and comprising at least one polymeric electroluminescent material.
- OLED organic light-emitting device
- holes are injected into the device through the anode and electrons are injected into the device through the cathode.
- the holes and electrons combine in the light-emitting layer to form an exciton which then undergoes radioactive decay to emit light.
- a layer of hole injection material such as poly(ethylene dioxythiophene)/polystyrene sulphonate (PEDOT/PSS) may be provided between the anode and the light- emitting layer to assist injection of holes from the anode to the light-emitting layer.
- a hole transport layer made from a hole transport material may be provided between the anode and the light-emitting layer to assist transport of holes to the light-emitting layer.
- Luminescent conjugated polymers are an important class of materials that will be used in organic light emitting devices for the next generation of information technology based consumer products.
- OLEDs organic light emitting diodes
- conjugated polymers may be readily formed by Suzuki or Yamamoto polymerisation. This enables a high degree of control over the regioregulatory of the resultant polymer.
- Conjugated polymers may be solution processable due to the presence of appropriate solubilising groups.
- Suitable solvents for polyarylenes, in particular polyfluorenes include mono- or poly-alkylbenzenes such as toluene and xylene.
- Particularly preferred solution deposition techniques are spin- coating and inkjet printing.
- Spin-coating is particularly suitable for devices wherein patterning of the electroluminescent material is unnecessary, for example for lighting applications or simple monochrome segmented displays.
- InkJet printing is particularly suitable for high information content displays, in particular full colour displays.
- solution deposition techniques include dip-coating, roll printing and screen printing.
- the luminescent layer is made from an organic compound. It is taught that a composition of an organic luminescent material suitable for ink jet printing needs to satisfy the conditions given on a numerical range for at least one of contact angle, viscosity and surface tension. The range given for contact angle is 30 to 170 degrees. The range given for viscosity is 1 to 20cp. The range given for surface tension is 20 to 70 dyne/cm. A preferred embodiment is said to be where the organic luminescent compound is a hole injection and transfer type material. A separate hole injection and transfer layer laminated to the luminescent layer also is disclosed.
- hole injection and transfer layer No particular limitation is imposed upon the forming method for such a hole injection and transfer layer, but it is said that it is possible to form the layer using the ink-jet method for example.
- materials constituting the hole injection and transfer layer are given as aromatic diamine based compounds such as TPD; MTDATA; quinacridone; bisstil anthracene derivatives; PVK; phthalocyanine based complex such as copper phthalocyanine; porphin based compound; NPD; TAD; polyaniline; and the like.
- WO 2006/123167 also discloses a composition comprising an organic electroluminescent material and a high boiling point solvent having a boiling point higher than water. There is no disclosure nor suggestion in WO 2006/123167 of depositing a semiconducting hole transport material by ink-jet printing to form a separate hole transport layer.
- ink jet printing The key reasons for the interest in ink jet printing are scalability and adaptability.
- the former allows arbitrarily large sized substrates to be patterned and the latter should mean that there are negligible tooling costs associated with changing from one product to another since the image of dots printed on a substrate is defined by software. At first sight this would be similar to printing a graphic image - commercial print equipment is available that allows printing of arbitrary images on billboard sized substrates.
- the significant difference between graphics printers and display panels is the former use substrates that are porous or use inks that are UV curable resulting in very little effect of the drying environment on film formation.
- the inks used in fabricating OLED displays are ink jet printed onto non-porous surfaces and the process of changing from a wet ink to dry film is dominated by the drying environment of the ink in the pixel. Since the printing process involves printing stripes (or swathes) of ink (corresponding to the ink jet head width) there is an inbuilt asymmetry in the drying environment. In addition OLED devices require the films to be uniform to nanometer tolerance. It follows that to achieve scalability and adaptability requires control of the film forming properties of the ink and a robustness of this process to changes in pixel dimensions and swathe timing.
- the present inventors have accordingly identified a need to provide further compositions suitable for deposition by ink-jet printing to achieve flat films and which overcome the above identified problems.
- the second solvent will have a dielectric constant in the range from 1 to 2.2 or from 20 to 32.
- the first solvent has a dielectric constant in the range of from above 2.2 and to below 20.
- the first solvent can be any of cyclohexylbenzene, methylanisole, methylbenzoate, butylbenzoate, ethyl benzoate, propyl benzoate, ethylanisole, dimethylanisole, anisole, hexylbenzene, heptylbenzene, octylbenzene.
- the second solvent can be for example dicyclohexyl, monohexylcyclohexane, monooctylcyclohexane.
- the amount of second solvent is 1 to 99% by volume of the composition.
- the amount of second solvent is 20 to 80% by volume of the composition and even more preferably the amount of second solvent is 30 to 70% by volume of the composition.
- the first solvent has a boiling point between 100 and 200 0 C.
- the second solvent has a boiling point between 210 and 35O 0 C.
- the composition comprises a third solvent which is miscible with the first and second solvents and which has a higher boiling point than the first solvent.
- the third solvent can act as a film smoothing agent to further reduce any roughness.
- the third solvent is 0.01 to 10% by volume of the composition. Even more preferably the third solvent is 0.5 to 2% by volume of the composition.
- a composition comprising a light-emitting material and a solvent has a solids content of around 1 w/v %. This range is imposed due to limitations of molecular weight of the emitter and viscosity of the composition, which needs to be within the viscosity threshold of the inkjet print head.
- the concentration of light-emitting material in an inkjet composition is typically maximised such that as much light-emitting material is deposited in each drop of the composition. Even so, two or three passes of the inkjet head are generally necessary for a sufficient quantity of light-emitting material to be deposited to produce a light-emitting layer having a thickness of about 60 nm, which is the thickness required for optimal device performance.
- the present inventors have found that a hole transport layer may provide optimal performance at much lower thickness (around 10 nm). Hole transporting compositions may therefore be provided at much lower concentration.
- the semiconducting hole transport material is a polymer in that much higher molecular weight semiconducting hole transport polymers may be used than the corresponding molecular weight of a light-emitting polymer.
- the semiconducting hole transport polymer may have a molecular weight in the range 40,000 to 400,000 Daltons.
- Such a semiconducting hole transport polymer preferably has a molecular weight of at least 350,000 Daltons(unless stated otherwise, polymer molecular weights provided herein are weights in Daltons relative to polystyrene measured by gel permeation chromatography). This is particularly beneficial if the polymer of the composition comprises crosslinkable groups because there is a higher number of crosslinkable groups per polymer chain in a higher molecular weight polymer.
- Devices comprising light-emitting polymers with molecular weights of less than 250,000 Daltons suffer from poor device performance, and so light- emitting compositions suitable for inkjet printing are not formulated with such low molecular weight polymers.
- the present inventors have found that no such poor device performance is found for hole transporting polymers.
- the jetting properties of the composition are strongly dependent on the solids content (the solids content of a composition may be determined simply by evaporating the solvent and weighing the remaining solid).
- a composition containing a luminescent material for ink-jet printing will have a higher solids content of about 1 w/v%.
- concentration of the semiconducting hole transport material in the composition is 0.8 w/v% or less.
- the semiconducting hole transport material may be cross linkable due to the presence of cross linkable groups.
- the semiconducting hole transport material preferably comprises a polymer.
- Preferred semiconducting hole transport polymers comprise a triarylamine repeat unit.
- Preferred triarylamine repeat units satisfy general Formula 1 :
- Ar 1 and Ar 2 are optionally substituted aryl or heteroaryl groups, n is greater than or equal to 1 , preferably 1 or 2, and R is H or a substituent, preferably a substituent.
- R is preferably alkyl or aryl or heteroaryl, most preferably aryl or heteroaryl. Any of the aryl or heteroaryl groups in the unit of formula 1 may be substituted.
- Preferred substituents include alkyl and alkoxy groups. Any of the aryl or heteroaryl groups in the repeat unit of Formula 1 may be linked by a direct bond or a divalent linking atom or group.
- Preferred divalent linking atoms and groups include O; S; substituted N; and substituted C.
- Particularly preferred units satisfying Formula 1 include units of Formulae 2-4:
- Ar 1 and Ar 2 are as defined above; and Ar 3 is optionally substituted aryl or heteroaryl.
- preferred substituents for Ar 3 include alkyl and alkoxy groups.
- Particularly preferred hole transporting polymers of this type are copolymers (particularly AB copolymers) of a triarylamine repeat unit and a second repeat unit.
- the second repeat unit preferably is a fluorene repeat unit, more preferably a repeat unit of Formula 5:
- R 1 and R 2 are independently selected from hydrogen or optionally substituted alkyl, alkoxy, aryl, arylalkyl, heteroaryl and heteroarylalkyl. More preferably, at least one of R 1 and R 2 comprises an optionally substituted C 4 - C 2O alkyl or aryl group.
- a second aspect of the present invention relation is a method of forming an organic light-emitting device including the steps of: a. providing an anode layer; b. optionally providing a conducting hole injecting layer on the anode layer; c. depositing a composition as defined in any one of claims 1 to 15 on the anode or hole injecting layer by ink-jet printing to form a semiconducting hole transport layer, provided that when the semiconducting hole transport material is deposited by ink-jet printing then the semiconducting hole transport material is deposited on a hole injecting layer.
- a third aspect of the present invention is a method of forming an organic light- emitting device including the step of:
- a method according to the second or third aspects of the invention includes a further step of baking the semiconducting hole transport layer by heating.
- Baking conditions should be selected so that at least a part of the semiconducting hole transport layer is rendered insoluble so that the luminescent layer can be deposited without dissolving the semiconducting hole transport layer.
- This technique of baking the semiconducting hole transport layer is known in the art.
- a suitable temperature for baking is in the range of from 160 to 220 0 C, preferably 180 to 200 0 C.
- deposition of the defined composition will be onto an anode or a conducting hole injecting layer.
- the thickness of the semiconducting hole transport layer is in the range from 5 to 40nm, more preferably 5 to 30 nm, more preferably from 8 to 20 nm, and most preferably about 10nm.
- the solvent can take anything between a few seconds and a few minutes to dry and results in a relatively thin film in comparison with the initial "ink" volume. Often multiple drops are deposited, preferably before drying begins, to provide sufficient thickness of dry material.
- the methods typically will include steps of depositing a luminescent layer on the semiconducting hole transport layer, optionally depositing an electron transport layer on the luminescent layer, and depositing a cathode on the luminescent layer or electron transport layer, where present.
- the methods include a step of removing the solvent from the semiconducting hole transport layer after formation thereof.
- Preferred methods for removing the solvent(s) include vacuum drying at elevated temperature, typically up to 100 0 C depending on vacuum pressure. The provision of a high boiling point solvent increases the drying time of the composition.
- the desired viscosity of the composition will, to some extent, be dependent on the pixel size, drop diameter, drop volume, drop frequency, and wetability of the surface onto which the composition is being deposited. For small pixels a higher solids content is generally used. For larger pixels a lower solid content is used. For larger pixels, the concentration of the composition is reduced to get good film forming properties.
- the composition should have a contact angle with the bank such that it wets the base of the well but does not flood out of the well.
- a fourth aspect of the present invention provides an organic light-emitting device made by a method according to the second or third aspects of the invention.
- the architecture of an electroluminescent device preferably comprises a (typically transparent glass or plastic) substrate 1 , an anode 2 and a cathode 4.
- a luminescent layer 3 is provided between anode 2 and cathode 4.
- At least one of the electrodes is semi-transparent in order that light may be emitted.
- the anode is transparent, it typically comprises indium tin oxide.
- the semiconducting hole transport layer is present between anode 2 and luminescent layer 3. Further layers may be located between anode 2 and cathode 3, such as charge transporting, charge injecting or charge blocking layers.
- a conductive hole injection layer which may be formed from a conductive organic or inorganic material between the anode 2 and the semiconducting hole transport layer to assist hole injection from the anode into the semiconducting hole transport layer.
- the hole transporting layer located between anode 2 and luminescent layer 3 preferably has a HOMO level of less than or equal to 5.5 eV, more preferably around 4.8-5.5 eV. HOMO levels may be measured by cyclic voltammetry, for example.
- an electron transporting layer located between electroluminescent layer 3 and cathode 4 preferably has a LUMO level of around 3-3.5 eV.
- a fifth aspect of the present invention provides a full colour display comprising an organic light-emitting device according to the fourth aspect of the invention.
- a preferred full colour display comprises “red” pixels, "green” pixels and “blue” pixels, each pixel comprising an OLED as defined in relation to the fourth aspect.
- a “red” pixel will have a luminescent layer comprising a red electroluminescent material.
- a “green” pixel will have a luminescent layer comprising a green electroluminescent material.
- a “blue” pixel will have a luminescent layer comprising a blue electroluminescent material.
- the hole transport layer is common to all colours.
- red electroluminescent material an organic material that by electroluminescence emits radiation having a wavelength in the range of 600- 750 nm, preferably 600-700 nm, more preferably 610-650 nm and most preferably having an emission peak around 650-660 nm.
- green electroluminescent material an organic material that by electroluminescence emits radiation having a wavelength in the range of 510- 580 nm, preferably 510-570 nm.
- blue electroluminescent material an organic material that by electroluminescence emits radiation having a wavelength in the range of 400- 500 nm, more preferably 430-500 nm.
- Red, green and blue electroluminescent materials are known in the art.
- Figure 2 shows a vertical cross section through an example of an OLED.
- Figure 3 shows edge thickening in an interlayer of a thin film.
- Figures 4 to 6 show interlayer film profiles resulting from different solvent formulations.
- luminescent layer 3 may consist of luminescent material alone or may comprise the luminescent material in combination with one or more further materials.
- the electroluminescent material may be blended with hole and/or electron transporting materials as disclosed in, for example, WO 99/48160, or may comprise a luminescent dopant in a semiconducting host matrix.
- the luminescent material may be covalently bound to a charge transporting material and/or host material.
- Luminescent layer 3 may be patterned or unpatterned.
- a device comprising an unpatterned layer may be used as an illumination source, for example.
- a white light emitting device is particularly suitable for this purpose.
- a device comprising a patterned layer may 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 typically used in combination with a patterned anode layer and an unpatterned cathode.
- the anode layer is formed of parallel stripes of anode material, and parallel stripes of electroluminescent material and cathode material arranged perpendicular to the anode material wherein the stripes of electroluminescent material and cathode material are typically separated by stripes of insulating material ("cathode separators") formed by photolithography.
- Suitable materials for use in luminescent layer 3 include small molecule, polymeric and dendrimeric materials, and compositions thereof.
- Suitable electroluminescent polymers for use in layer 3 include poly(arylene vinylenes) such as poly(p-phenylene vinylenes) and polyarylenes such as: polyfluorenes, particularly 2,7-linked 9,9 dialkyl polyfluorenes or 2,7-linked 9,9 diaryl polyfluorenes; polyspirofluorenes, particularly 2,7-linked poly-9,9- spirofluorene; polyindenofluorenes, particularly 2,7-linked polyindenofluorenes; polyphenylenes, particularly alkyl or alkoxy substituted poly-1 ,4-phenylene.
- Suitable electroluminescent dendrimers for use in layer 3 include electroluminescent metal complexes bearing dendrimeric groups as disclosed in, for example, WO 02/066552.
- Cathode 4 is selected from materials that have a workfunction allowing injection of electrons into the luminescent layer. Other factors influence the selection of the cathode such as the possibility of adverse interactions between the cathode and the electroluminescent material.
- the cathode may consist of a single material such as a layer of aluminium. Alternatively, it may comprise a plurality of metals, for example a bilayer of a low workf unction material and a high workfunction material such as calcium and aluminium as disclosed in WO 98/10621 ; elemental barium as disclosed in WO 98/57381 , Appl. Phys. Lett.
- 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 will comprise 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.
- 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.
- the substrate may comprise a plastic as in US 6268695 which discloses a substrate of alternating plastic and barrier layers or a laminate of thin glass and plastic as disclosed in EP 0949850.
- the device is preferably encapsulated with an encapsulant (not shown in Figure 1) to prevent ingress of moisture and oxygen.
- encapsulants include a sheet of glass, films having suitable barrier properties such as alternating stacks of polymer and dielectric as disclosed in, for example, WO 01/81649 or an airtight container as disclosed in, for example, WO 01/19142.
- 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.
- Preferred methods for preparation of semiconducting polymers are Suzuki polymerisation as described in, for example, WO 00/53656 and Yamamoto polymerisation as described in, for example, T. Yamamoto, "Electrically Conducting And Thermally Stable ⁇ - Conjugated Poly(arylene)s Prepared by Organometallic Processes", Progress in Polymer Science 1993, 17, 1153- 1205.
- These polymerisation techniques both operate via a "metal insertion" wherein the metal atom of a metal complex catalyst is inserted between an aryl group and a leaving group of a monomer.
- Yamamoto polymerisation a nickel complex catalyst is used; in the case of Suzuki polymerisation, a palladium complex catalyst is used.
- a monomer having two reactive halogen groups is used.
- 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.
- other leaving groups capable of participating in metal insertion include groups include tosylate, mesylate and triflate.
- a single polymer or a plurality of polymers may be deposited from solution to form layer 3.
- Suitable solvents for polyarylenes, in particular polyfluorenes, include mono- or poly-alkylbenzenes such as toluene and xylene.
- Particularly preferred solution deposition techniques are spin-coating and inkjet printing.
- InkJet printing is particularly suitable for high information content displays, in particular full colour displays. InkJet printing of OLEDs is described in, for example, EP 0880303.
- solution deposition techniques include dip-coating, roll printing and screen printing.
- Organic LEDs may be deposited on a substrate in a matrix of pixels to form a single or multi-colour pixellated display.
- a multicoloured display may be constructed using groups of red, green, and blue emitting pixels.
- So-called active matrix displays have a memory element, typically a storage capacitor and a transistor, associated with each pixel whilst passive matrix displays have no such memory element and instead are repetitively scanned to give the impression of a steady image.
- FIG 2 shows a vertical cross section through an example of an OLED device 100.
- an active matrix display part of the area of a pixel is occupied by associated drive circuitry (not shown in Figure 2).
- the structure of the device is somewhat simplified for the purposes of illustration.
- the OLED 100 comprises a substrate 102, typically 0.7 mm or 1.1 mm glass but optionally clear plastic, on which an anode layer 106 has been deposited.
- the anode layer typically comprises around 150 nm thickness of ITO (indium tin oxide), over which is provided a metal contact layer, typically around 500nm of aluminium, sometimes referred to as anode metal.
- ITO indium tin oxide
- a metal contact layer typically around 500nm of aluminium, sometimes referred to as anode metal.
- Glass substrates coated with ITO and contact metal may be purchased from Corning, USA.
- the contact metal (and optionally the ITO) is patterned as desired so that it does not obscure the display, by a conventional process of photolithography followed by etching.
- a substantially transparent conducting hole injection layer 108a is provided over the anode metal, followed by the semiconducting hole transport layer 108b and an electroluminescent layer 108c.
- Banks 112 may be formed on the substrate, for example from positive or negative photoresist material, to define wells 114 into which these active organic layers may be selectively deposited. The wells thus define light emitting areas or pixels of the display.
- a cathode layer 110 is then applied by, say, physical vapour deposition.
- the cathode layer typically comprises a low work function metal such as calcium or barium covered with a thicker, capping layer of aluminium and optionally including an additional layer immediately adjacent the electroluminescent layer, such as a layer of lithium fluoride, for improved electron energy level matching.
- a low work function metal such as calcium or barium covered with a thicker, capping layer of aluminium and optionally including an additional layer immediately adjacent the electroluminescent layer, such as a layer of lithium fluoride, for improved electron energy level matching.
- Mutual electrical isolation of cathode lines may achieved through the use of cathode separators.
- a number of displays are fabricated on a single substrate and at the end of the fabrication process the substrate is scribed, and the displays separated.
- An encapsulant such as a glass sheet or a metal can is utilized to inhibit oxidation and moisture ingress.
- the edges or faces of the banks are tapered onto the surface of the substrate as shown, typically at an angle of between 10 and 40 degrees.
- the banks present a hydrophobic surface in order that they are not wetted by the solution of deposited organic material and thus assist in containing the deposited material within a well.
- a bank material such as polyimide
- an 0 2 /CF 4 plasma as disclosed in EP 0989778.
- the plasma treatment step may be avoided by use of a fluorinated material such as a fluorinated polyimide as disclosed in WO 03/083960. Numerous other bank structures are known to the skilled person.
- the bank may comprise a plurality of layers of the same or different materials, for example a hydrophilic layer capped with a hydrophobic layer.
- the bank may also comprise an undercut, i.e. the aperture defined by the bank is smaller than the surface area of the base of the well as disclosed in, for example, WO 2005/076386.
- the bank and separator structures may be formed from resist material, for example using a positive (or negative) resist for the banks and a negative (or positive) resist for the separators; both these resists may be based upon polyimide and spin coated onto the substrate, or a fluorinated or fluorinated- like photoresist may be employed.
- interlayer 1 An interlayer formulation for an interlayer material (hole transport material) termed interlayer 1 is a solution of solid material at 0.28% solids in Anisole/Phenoxytoluene 1-1). When printed this formulation gave film profiles (15nm) with edge thickening (up to 40nm). Edge thickening is detrimental to device performance as: i) the EL ink is printed causing a decrease in device lifetime ii) The film profile of the subsequently printed EL layer is dependent on the IL profile. Therefore if the IL film edge thickens then the EL layer will show edge thinning. Variation in the thickness of the EL film across a pixel leads to non-uniform emission and a decrease in device efficiency and lifetime.
- Table 1 shows the physical properties of the solvents used in the novel compositions in accordance with the present invention. All these formulations were successful in eliminating edge thickening.
- Figure 4 shows derived interlayer film profiles when printed onto PEDOT (PD239).
- the A/P1 formulation which is in its current use shows edge thickening whereas the two new formulations (A/DC1 and TET/MES9) give slight edge thinning.
- the A/DC1 formulation also gave rough films probably caused by the insolubility of the polymer in this particular solvent.
- A/P1 Anisole-3-Phenoxytoluene (1-1)
- A/DC1 Anisole-Dicyclohexyl (1-1)
- Figure 5 shows the results of different amounts of Phenoxytoluene which was added to the A/DCI to reduce the roughness. It can be seen from the graph below that only 0.5% addition of the Phenoxytoluene (P/DC/A 81 : (NEW FORMULATION 1)) decreases the roughness sufficiently and maintains the slightly domed profile.
- Figure 6 shows the results of the effect of 1-tetralone (high boiling point solvent which has a high viscosity and high surface tension) being confirmed by two more formulations.
- MON/MES1 1-methoxynaphthalene (50%):Mesitylene (50%) (NEW FORMULATION 3)
- MES/BZB2 Mesitylene (60%):Benzylbenzoate (40%) (NEW FORMULATION 4)
Abstract
A composition suitable for printing of an opto-electrical device comprises a semiconducting hole transport material, hole injection material, light-emitting polymer material, electron transport material, or electron injection material, a first solvent and a second solvent wherein the solvents are miscible with one another, the first solvent has a lower boiling point than the second solvent and the hole transport material has a higher solubility in the first solvent than in the second solvent. The second solvent has a dielectric constant in the range from 1 to 2.2 or from 20 to 32 and the first solvent has a dielectric constant in the range of from above 2.2 and to below 20. The first solvent is any of cyclohexylbenzene, methylanisole, methylbenzoate, butylbenzoate, ethyl benzoate, propyl benzoate, ethylanisole, dimethylanisole, anisole, hexylbenzene, heptylbenzene, octylbenzene, and the second solvent is dicyclohexyl monohexylcyclohexane, or monooctylcyclohexane.
Description
INTERLAYER FORMULATION FOR FLAT FILMS
The present invention is concerned with a composition comprising a hole transport material, hole injection material, light-emitting polymer material, electron transport material, or electron injection layer material, said composition being suitable for deposition by ink jet printing, nozzle coating, spray coating, roll printing, dip coating, slot coating, or flexographic printing in the manufacture of an organic light-emitting device.
BACKGROUND OF THE INVENTION
A typical organic light-emitting device (OLED) comprises a substrate, on which is supported an anode, a cathode and a light-emitting layer situated in between the anode and cathode and comprising at least one polymeric electroluminescent material. In operation, holes are injected into the device through the anode and electrons are injected into the device through the cathode. The holes and electrons combine in the light-emitting layer to form an exciton which then undergoes radioactive decay to emit light.
Other layers may be present in the OLED, for example a layer of hole injection material, such as poly(ethylene dioxythiophene)/polystyrene sulphonate (PEDOT/PSS), may be provided between the anode and the light- emitting layer to assist injection of holes from the anode to the light-emitting layer. Further, a hole transport layer made from a hole transport material may be provided between the anode and the light-emitting layer to assist transport of holes to the light-emitting layer.
Luminescent conjugated polymers are an important class of materials that will be used in organic light emitting devices for the next generation of information technology based consumer products. The principle interest in the use of polymers, as opposed to inorganic semiconducting and organic dye materials, lies in the scope for low-cost device manufacturing, using solution-processing of film-forming materials. Since the last decade much effort has been devoted to the improvement of the emission efficiency of organic light emitting diodes
(OLEDs) either by developing highly efficient materials or efficient device structures.
A further advantage of conjugated polymers is that they may be readily formed by Suzuki or Yamamoto polymerisation. This enables a high degree of control over the regioregulatory of the resultant polymer.
Conjugated polymers may be solution processable due to the presence of appropriate solubilising groups. Suitable solvents for polyarylenes, in particular polyfluorenes, include mono- or poly-alkylbenzenes such as toluene and xylene. Particularly preferred solution deposition techniques are spin- coating and inkjet printing.
Spin-coating is particularly suitable for devices wherein patterning of the electroluminescent material is unnecessary, for example for lighting applications or simple monochrome segmented displays.
InkJet printing is particularly suitable for high information content displays, in particular full colour displays.
Other solution deposition techniques include dip-coating, roll printing and screen printing.
InkJet printing of luminescent layers of OLEDs is described in, for example, EP 0880303. It is said that the luminescent layer is made from an organic compound. It is taught that a composition of an organic luminescent material suitable for ink jet printing needs to satisfy the conditions given on a numerical range for at least one of contact angle, viscosity and surface tension. The range given for contact angle is 30 to 170 degrees. The range given for viscosity is 1 to 20cp. The range given for surface tension is 20 to 70 dyne/cm. A preferred embodiment is said to be where the organic luminescent compound is a hole injection and transfer type material. A separate hole injection and transfer layer laminated to the luminescent layer also is disclosed. No particular limitation is imposed upon the forming method for such a hole injection and transfer layer, but it is said that it is possible to form the layer using the ink-jet method for example. Examples of materials constituting the hole injection and transfer layer are given as aromatic diamine based compounds such as TPD; MTDATA; quinacridone; bisstil anthracene
derivatives; PVK; phthalocyanine based complex such as copper phthalocyanine; porphin based compound; NPD; TAD; polyaniline; and the like.
In Example 2 of EP 0880303, a PVK hole injection layer is deposited on red and green luminescent layers by ink jet printing. The physical properties (viscosity, surface tension, contact angle) of the PVK are not provided. In Example 3 of EP 0880303, a hole injection layer material is mixed with the red, green and blue luminescent materials to form red, green and blue luminescent layers by using an ink-jet device.
WO 2006/123167 is concerned with compositions for ink jet printing conductive or semi-conductive organic material for use in manufacturing opto- electrical devices. It is said in WO 2006/123167 that a charge injecting layer may be deposited as a composition comprising a conductive organic material in a high boiling point solvent. PEDOTPSS is exemplified as a conductive organic material. A method of forming a device by ink jet printing of a formulation comprising PEDOT (or possibly other hole injection materials) and a high boiling point solvent is disclosed.
WO 2006/123167 also discloses a composition comprising an organic electroluminescent material and a high boiling point solvent having a boiling point higher than water. There is no disclosure nor suggestion in WO 2006/123167 of depositing a semiconducting hole transport material by ink-jet printing to form a separate hole transport layer.
The key reasons for the interest in ink jet printing are scalability and adaptability. The former allows arbitrarily large sized substrates to be patterned and the latter should mean that there are negligible tooling costs associated with changing from one product to another since the image of dots printed on a substrate is defined by software. At first sight this would be similar to printing a graphic image - commercial print equipment is available that allows printing of arbitrary images on billboard sized substrates. However the significant difference between graphics printers and display panels is the former use substrates that are porous or use inks that are UV curable resulting in very little effect of the drying environment on film formation. In
comparison, the inks used in fabricating OLED displays are ink jet printed onto non-porous surfaces and the process of changing from a wet ink to dry film is dominated by the drying environment of the ink in the pixel. Since the printing process involves printing stripes (or swathes) of ink (corresponding to the ink jet head width) there is an inbuilt asymmetry in the drying environment. In addition OLED devices require the films to be uniform to nanometer tolerance. It follows that to achieve scalability and adaptability requires control of the film forming properties of the ink and a robustness of this process to changes in pixel dimensions and swathe timing.
However a key problem with ink jet printing is interlayer edge thickening in flat films. This is clearly seen in Figure 3. Such edge thickening results in edge thinning of the electroluminescent layer. Variation in the thickness of the electroluminescent film across a pixel leads to non-uniform emission and a decrease in device efficiency and lifetime.
There is a need therefore to provide formulations for ink jet printing which can produce flat edges or even thinner edge interlayers for flat film devices.
The present inventors have accordingly identified a need to provide further compositions suitable for deposition by ink-jet printing to achieve flat films and which overcome the above identified problems.
SUMMARY OF THE INVENTION
A first aspect of the present invention provides a composition suitable for ink- jet printing, nozzle coating, spray coating, roll printing, dip coating, slot coating, flexographic printing of an opto-electrical device, which composition comprises a semiconducting hole transport material, hole injection material, light-emitting polymer material, electron transport material, or electron injection layer, a first solvent and a second solvent wherein the solvents are miscible with one another, the first solvent has a lower boiling point than the second solvent and the hole transport material has a higher solubility in the first solvent than in the second solvent.
Use of a high boiling point solvent in which the interlayer polymer is less soluble can be used for solving the above identified problems as the polymer precipitates out more quickly on drying and does not migrate towards the edge of the pixel.
Preferably the second solvent will have a dielectric constant in the range from 1 to 2.2 or from 20 to 32. Typically the first solvent has a dielectric constant in the range of from above 2.2 and to below 20.
Without being especially limited the first solvent can be any of cyclohexylbenzene, methylanisole, methylbenzoate, butylbenzoate, ethyl benzoate, propyl benzoate, ethylanisole, dimethylanisole, anisole, hexylbenzene, heptylbenzene, octylbenzene.
The second solvent can be for example dicyclohexyl, monohexylcyclohexane, monooctylcyclohexane.
The amount of second solvent is 1 to 99% by volume of the composition. Preferably the amount of second solvent is 20 to 80% by volume of the composition and even more preferably the amount of second solvent is 30 to 70% by volume of the composition.
Without being especially limited the first solvent has a boiling point between 100 and 2000C. Typically the second solvent has a boiling point between 210 and 35O0C.
In a preferred embodiment of the first aspect of the present invention the composition comprises a third solvent which is miscible with the first and second solvents and which has a higher boiling point than the first solvent.
The third solvent can act as a film smoothing agent to further reduce any roughness.
Without being especially limited the third solvent can be phenoxytoluene, dibenzylether, phenoxybenzene.
Preferably the third solvent is 0.01 to 10% by volume of the composition. Even more preferably the third solvent is 0.5 to 2% by volume of the composition.
Typically, a composition comprising a light-emitting material and a solvent has a solids content of around 1 w/v %. This range is imposed due to limitations of molecular weight of the emitter and viscosity of the composition, which needs to be within the viscosity threshold of the inkjet print head. The concentration of light-emitting material in an inkjet composition is typically maximised such that as much light-emitting material is deposited in each drop of the composition. Even so, two or three passes of the inkjet head are generally necessary for a sufficient quantity of light-emitting material to be deposited to produce a light-emitting layer having a thickness of about 60 nm, which is the thickness required for optimal device performance. However, the present inventors have found that a hole transport layer may provide optimal performance at much lower thickness (around 10 nm). Hole transporting compositions may therefore be provided at much lower concentration.
A particular benefit of using such low concentrations is found in the case where the semiconducting hole transport material is a polymer in that much higher molecular weight semiconducting hole transport polymers may be used than the corresponding molecular weight of a light-emitting polymer. The semiconducting hole transport polymer may have a molecular weight in the range 40,000 to 400,000 Daltons. Such a semiconducting hole transport polymer preferably has a molecular weight of at least 350,000 Daltons(unless stated otherwise, polymer molecular weights provided herein are weights in Daltons relative to polystyrene measured by gel permeation chromatography). This is particularly beneficial if the polymer of the composition comprises
crosslinkable groups because there is a higher number of crosslinkable groups per polymer chain in a higher molecular weight polymer.
Devices comprising light-emitting polymers with molecular weights of less than 250,000 Daltons suffer from poor device performance, and so light- emitting compositions suitable for inkjet printing are not formulated with such low molecular weight polymers. However, the present inventors have found that no such poor device performance is found for hole transporting polymers.
The jetting properties of the composition are strongly dependent on the solids content (the solids content of a composition may be determined simply by evaporating the solvent and weighing the remaining solid).
Typically, a composition containing a luminescent material for ink-jet printing will have a higher solids content of about 1 w/v%. Preferably the concentration of the semiconducting hole transport material in the composition is 0.8 w/v% or less.
In any of the compositions described herein, the semiconducting hole transport material may be cross linkable due to the presence of cross linkable groups.
In any of the compositions described herein, the semiconducting hole transport material preferably comprises a polymer. Preferred semiconducting hole transport polymers comprise a triarylamine repeat unit.
Preferred triarylamine repeat units satisfy general Formula 1 :
1 wherein Ar1 and Ar2 are optionally substituted aryl or heteroaryl groups, n is greater than or equal to 1 , preferably 1 or 2, and R is H or a substituent, preferably a substituent. R is preferably alkyl or aryl or heteroaryl, most preferably aryl or heteroaryl. Any of the aryl or heteroaryl groups in the unit of formula 1 may be substituted. Preferred substituents include alkyl and alkoxy groups. Any of the aryl or heteroaryl groups in the repeat unit of Formula 1
may be linked by a direct bond or a divalent linking atom or group. Preferred divalent linking atoms and groups include O; S; substituted N; and substituted C.
Particularly preferred units satisfying Formula 1 include units of Formulae 2-4:
2 3 4 wherein Ar1 and Ar2 are as defined above; and Ar3 is optionally substituted aryl or heteroaryl. Where present, preferred substituents for Ar3 include alkyl and alkoxy groups.
Particularly preferred hole transporting polymers of this type are copolymers (particularly AB copolymers) of a triarylamine repeat unit and a second repeat unit. The second repeat unit preferably is a fluorene repeat unit, more preferably a repeat unit of Formula 5:
5 wherein R1 and R2 are independently selected from hydrogen or optionally substituted alkyl, alkoxy, aryl, arylalkyl, heteroaryl and heteroarylalkyl. More preferably, at least one of R1 and R2 comprises an optionally substituted C4- C2O alkyl or aryl group.
A second aspect of the present invention relation is a method of forming an organic light-emitting device including the steps of:
a. providing an anode layer; b. optionally providing a conducting hole injecting layer on the anode layer; c. depositing a composition as defined in any one of claims 1 to 15 on the anode or hole injecting layer by ink-jet printing to form a semiconducting hole transport layer, provided that when the semiconducting hole transport material is deposited by ink-jet printing then the semiconducting hole transport material is deposited on a hole injecting layer.
A third aspect of the present invention is a method of forming an organic light- emitting device including the step of:
1. depositing a composition as defined in any one of claims 1 to 15 by ink-jet printing to form a semiconducting hole transport layer.
Preferably a method according to the second or third aspects of the invention includes a further step of baking the semiconducting hole transport layer by heating.
Baking conditions should be selected so that at least a part of the semiconducting hole transport layer is rendered insoluble so that the luminescent layer can be deposited without dissolving the semiconducting hole transport layer. This technique of baking the semiconducting hole transport layer is known in the art. A suitable temperature for baking is in the range of from 160 to 220 0C, preferably 180 to 200 0C.
In relation to the second and third aspects of the present invention, it will be understood that, typically, deposition of the defined composition will be onto an anode or a conducting hole injecting layer.
Preferably, in the methods according to the second and third aspects of the present invention, the thickness of the semiconducting hole transport layer is in the range from 5 to 40nm, more preferably 5 to 30 nm, more preferably from 8 to 20 nm, and most preferably about 10nm. The solvent can take anything between a few seconds and a few minutes to dry and results in a relatively thin film in comparison with the initial "ink" volume. Often multiple
drops are deposited, preferably before drying begins, to provide sufficient thickness of dry material.
In all of the methods according to the second and third aspects of the present invention, the methods typically will include steps of depositing a luminescent layer on the semiconducting hole transport layer, optionally depositing an electron transport layer on the luminescent layer, and depositing a cathode on the luminescent layer or electron transport layer, where present.
It will be understood that in the second and third aspects of the present invention, preferably, the methods include a step of removing the solvent from the semiconducting hole transport layer after formation thereof. Preferred methods for removing the solvent(s) include vacuum drying at elevated temperature, typically up to 1000C depending on vacuum pressure. The provision of a high boiling point solvent increases the drying time of the composition.
In the methods according to the second and third aspects of the present invention, it will be appreciated that printing generally will be into a pixel defined by bank structures. In this connection, the desired viscosity of the composition will, to some extent, be dependent on the pixel size, drop diameter, drop volume, drop frequency, and wetability of the surface onto which the composition is being deposited. For small pixels a higher solids content is generally used. For larger pixels a lower solid content is used. For larger pixels, the concentration of the composition is reduced to get good film forming properties.
Preferably, the composition should have a contact angle with the bank such that it wets the base of the well but does not flood out of the well.
A fourth aspect of the present invention provides an organic light-emitting device made by a method according to the second or third aspects of the invention.
Preferred features of the device according to the fourth aspect of the present invention are provided below.
With reference to Figure 1 , the architecture of an electroluminescent device according to the fourth aspect of the invention preferably comprises a
(typically transparent glass or plastic) substrate 1 , an anode 2 and a cathode 4. A luminescent layer 3 is provided between anode 2 and cathode 4.
In a practical device, at least one of the electrodes is semi-transparent in order that light may be emitted. Where the anode is transparent, it typically comprises indium tin oxide.
The semiconducting hole transport layer is present between anode 2 and luminescent layer 3. Further layers may be located between anode 2 and cathode 3, such as charge transporting, charge injecting or charge blocking layers.
In particular, it is desirable to provide a conductive hole injection layer, which may be formed from a conductive organic or inorganic material between the anode 2 and the semiconducting hole transport layer to assist hole injection from the anode into the semiconducting hole transport layer. Examples of doped organic hole injection materials include 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 US 5723873 and US 5798170; and 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.
The hole transporting layer located between anode 2 and luminescent layer 3 preferably has a HOMO level of less than or equal to 5.5 eV, more preferably around 4.8-5.5 eV. HOMO levels may be measured by cyclic voltammetry, for example.
If present, an electron transporting layer located between electroluminescent layer 3 and cathode 4 preferably has a LUMO level of around 3-3.5 eV.
A fifth aspect of the present invention provides a full colour display comprising an organic light-emitting device according to the fourth aspect of the invention.
A preferred full colour display comprises "red" pixels, "green" pixels and "blue" pixels, each pixel comprising an OLED as defined in relation to the fourth aspect. A "red" pixel will have a luminescent layer comprising a red
electroluminescent material. A "green" pixel will have a luminescent layer comprising a green electroluminescent material. A "blue" pixel will have a luminescent layer comprising a blue electroluminescent material. Preferably, the hole transport layer is common to all colours.
By "red electroluminescent material" is meant an organic material that by electroluminescence emits radiation having a wavelength in the range of 600- 750 nm, preferably 600-700 nm, more preferably 610-650 nm and most preferably having an emission peak around 650-660 nm.
By "green electroluminescent material" is meant an organic material that by electroluminescence emits radiation having a wavelength in the range of 510- 580 nm, preferably 510-570 nm.
By "blue electroluminescent material" is meant an organic material that by electroluminescence emits radiation having a wavelength in the range of 400- 500 nm, more preferably 430-500 nm.
Red, green and blue electroluminescent materials are known in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention now will be described in more detail with reference to the attached Figures, in which:
Figure 1 shows the architecture of a typical OLED; and
Figure 2 shows a vertical cross section through an example of an OLED.
Figure 3 shows edge thickening in an interlayer of a thin film.
Figures 4 to 6 show interlayer film profiles resulting from different solvent formulations.
DETAILED DESCRIPTION
Referring to the device according to the fourth aspect, luminescent layer 3 may consist of luminescent material alone or may comprise the luminescent material in combination with one or more further materials. In particular, the
electroluminescent material may be blended with hole and/or electron transporting materials as disclosed in, for example, WO 99/48160, or may comprise a luminescent dopant in a semiconducting host matrix. Alternatively, the luminescent material may be covalently bound to a charge transporting material and/or host material.
Luminescent layer 3 may be patterned or unpatterned. A device comprising an unpatterned layer may be used as an illumination source, for example. A white light emitting device is particularly suitable for this purpose. A device comprising a patterned layer may 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 typically 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 of parallel stripes of anode material, and parallel stripes of electroluminescent material and cathode material arranged perpendicular to the anode material wherein the stripes of electroluminescent material and cathode material are typically separated by stripes of insulating material ("cathode separators") formed by photolithography.
Suitable materials for use in luminescent layer 3 include small molecule, polymeric and dendrimeric materials, and compositions thereof. Suitable electroluminescent polymers for use in layer 3 include poly(arylene vinylenes) such as poly(p-phenylene vinylenes) and polyarylenes such as: polyfluorenes, particularly 2,7-linked 9,9 dialkyl polyfluorenes or 2,7-linked 9,9 diaryl polyfluorenes; polyspirofluorenes, particularly 2,7-linked poly-9,9- spirofluorene; polyindenofluorenes, particularly 2,7-linked polyindenofluorenes; polyphenylenes, particularly alkyl or alkoxy substituted poly-1 ,4-phenylene. Such polymers as disclosed in, for example, Adv. Mater. 2000 12(23) 1737-1750 and references therein. Suitable electroluminescent dendrimers for use in layer 3 include electroluminescent metal complexes bearing dendrimeric groups as disclosed in, for example, WO 02/066552.
Cathode 4 is selected from materials that have a workfunction allowing injection of electrons into the luminescent layer. Other factors influence the selection of the cathode such as the possibility of adverse interactions between the cathode and the electroluminescent material. The cathode may
consist of a single material such as a layer of aluminium. Alternatively, it may comprise a plurality of metals, for example a bilayer of a low workf unction material and a high workfunction material such as calcium and aluminium as disclosed in WO 98/10621 ; elemental barium as disclosed in WO 98/57381 , Appl. Phys. Lett. 2002, 81(4), 634 and WO 02/84759; or a thin layer of metal compound, in particular an oxide or fluoride of an alkali or alkali earth metal, to assist electron injection, for example lithium fluoride as disclosed in WO 00/48258; barium fluoride 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 will comprise 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.
Optical 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 a plastic as
in US 6268695 which discloses a substrate of alternating plastic and barrier layers or a laminate of thin glass and plastic as disclosed in EP 0949850.
The device is preferably encapsulated with an encapsulant (not shown in Figure 1) to prevent ingress of moisture and oxygen. Suitable encapsulants include a sheet of glass, films having suitable barrier properties such as alternating stacks of polymer and dielectric as disclosed in, for example, WO 01/81649 or an airtight container as disclosed in, for example, WO 01/19142. 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.
Polymerisation methods
Preferred methods for preparation of semiconducting polymers are Suzuki polymerisation as described in, for example, WO 00/53656 and Yamamoto polymerisation as described in, for example, T. Yamamoto, "Electrically Conducting And Thermally Stable π - Conjugated Poly(arylene)s Prepared by Organometallic Processes", Progress in Polymer Science 1993, 17, 1153- 1205. These polymerisation techniques both operate via a "metal insertion" wherein the metal atom of a metal complex catalyst is inserted between an aryl group and a leaving group of a monomer. In the case of Yamamoto polymerisation, a nickel complex catalyst is used; in the case of Suzuki polymerisation, a palladium complex catalyst is used.
For example, in the synthesis of a linear polymer by Yamamoto polymerisation, 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.
It will therefore be appreciated that repeat units and end groups comprising aryl groups as illustrated throughout this application may be derived from a monomer carrying a suitable leaving group.
Suzuki polymerisation may be used to prepare regioregular, block and random copolymers. In particular, homopolymers or random copolymers may be prepared when one reactive group is a halogen and the other reactive group is a boron derivative group. Alternatively, block or regioregular, in particular AB, copolymers may be prepared when both reactive groups of a first monomer are boron and both reactive groups of a second monomer are halogen.
As alternatives to halides, other leaving groups capable of participating in metal insertion include groups include tosylate, mesylate and triflate.
Solution processing
A single polymer or a plurality of polymers may be deposited from solution to form layer 3. Suitable solvents for polyarylenes, in particular polyfluorenes, include mono- or poly-alkylbenzenes such as toluene and xylene. Particularly preferred solution deposition techniques are spin-coating and inkjet printing.
Spin-coating is particularly suitable for devices wherein patterning of the electroluminescent material is unnecessary - for example for lighting applications or simple monochrome segmented displays.
InkJet printing is particularly suitable for high information content displays, in particular full colour displays. InkJet printing of OLEDs is described in, for example, EP 0880303.
Other solution deposition techniques include dip-coating, roll printing and screen printing.
If multiple layers of the device are formed by solution processing then the skilled person will be aware of techniques to prevent intermixing of adjacent layers, for example by crosslinking of one layer before deposition of a subsequent layer or selection of materials for adjacent layers such that the material from which the first of these layers is formed is not soluble in the solvent used to deposit the second layer.
Organic LEDs may be deposited on a substrate in a matrix of pixels to form a single or multi-colour pixellated display. A multicoloured display may be
constructed using groups of red, green, and blue emitting pixels. So-called active matrix displays have a memory element, typically a storage capacitor and a transistor, associated with each pixel whilst passive matrix displays have no such memory element and instead are repetitively scanned to give the impression of a steady image.
Figure 2 shows a vertical cross section through an example of an OLED device 100. In an active matrix display, part of the area of a pixel is occupied by associated drive circuitry (not shown in Figure 2). The structure of the device is somewhat simplified for the purposes of illustration.
The OLED 100 comprises a substrate 102, typically 0.7 mm or 1.1 mm glass but optionally clear plastic, on which an anode layer 106 has been deposited. The anode layer typically comprises around 150 nm thickness of ITO (indium tin oxide), over which is provided a metal contact layer, typically around 500nm of aluminium, sometimes referred to as anode metal. Glass substrates coated with ITO and contact metal may be purchased from Corning, USA. The contact metal (and optionally the ITO) is patterned as desired so that it does not obscure the display, by a conventional process of photolithography followed by etching.
A substantially transparent conducting hole injection layer 108a is provided over the anode metal, followed by the semiconducting hole transport layer 108b and an electroluminescent layer 108c. Banks 112 may be formed on the substrate, for example from positive or negative photoresist material, to define wells 114 into which these active organic layers may be selectively deposited. The wells thus define light emitting areas or pixels of the display.
A cathode layer 110 is then applied by, say, physical vapour deposition. The cathode layer typically comprises a low work function metal such as calcium or barium covered with a thicker, capping layer of aluminium and optionally including an additional layer immediately adjacent the electroluminescent layer, such as a layer of lithium fluoride, for improved electron energy level matching. Mutual electrical isolation of cathode lines may achieved through the use of cathode separators. Typically a number of displays are fabricated on a single substrate and at the end of the fabrication process the substrate is
scribed, and the displays separated. An encapsulant such as a glass sheet or a metal can is utilized to inhibit oxidation and moisture ingress.
The edges or faces of the banks are tapered onto the surface of the substrate as shown, typically at an angle of between 10 and 40 degrees. The banks present a hydrophobic surface in order that they are not wetted by the solution of deposited organic material and thus assist in containing the deposited material within a well. This is achieved by treatment of a bank material such as polyimide with an 02/CF4 plasma as disclosed in EP 0989778. Alternatively, the plasma treatment step may be avoided by use of a fluorinated material such as a fluorinated polyimide as disclosed in WO 03/083960. Numerous other bank structures are known to the skilled person. For example, the bank may comprise a plurality of layers of the same or different materials, for example a hydrophilic layer capped with a hydrophobic layer. The bank may also comprise an undercut, i.e. the aperture defined by the bank is smaller than the surface area of the base of the well as disclosed in, for example, WO 2005/076386.
The bank and separator structures may be formed from resist material, for example using a positive (or negative) resist for the banks and a negative (or positive) resist for the separators; both these resists may be based upon polyimide and spin coated onto the substrate, or a fluorinated or fluorinated- like photoresist may be employed.
EXAMPLES
An interlayer formulation for an interlayer material (hole transport material) termed interlayer 1 is a solution of solid material at 0.28% solids in Anisole/Phenoxytoluene 1-1). When printed this formulation gave film profiles (15nm) with edge thickening (up to 40nm). Edge thickening is detrimental to device performance as: i) the EL ink is printed causing a decrease in device lifetime
ii) The film profile of the subsequently printed EL layer is dependent on the IL profile. Therefore if the IL film edge thickens then the EL layer will show edge thinning. Variation in the thickness of the EL film across a pixel leads to non-uniform emission and a decrease in device efficiency and lifetime.
This work of the present inventors has demonstrated new solvent combinations for interlayer inks to eliminate interlayer edge thickening.
Table 1 shows the physical properties of the solvents used in the novel compositions in accordance with the present invention. All these formulations were successful in eliminating edge thickening.
Figures 4 to 6 show derived interlayer film profiles when printed onto PEDOT (PD239). The A/P1 formulation which is in current use shows edge thickening whereas the new formulations give slight edge thinning.
Table 1
Figure 4 shows derived interlayer film profiles when printed onto PEDOT (PD239). The A/P1 formulation which is in its current use shows edge thickening whereas the two new formulations (A/DC1 and TET/MES9) give slight edge thinning. The A/DC1 formulation also gave rough films probably caused by the insolubility of the polymer in this particular solvent.
A/P1 = Anisole-3-Phenoxytoluene (1-1)
A/DC1 = Anisole-Dicyclohexyl (1-1)
TET/MES9 = 1-tetralone-Mesitylene (8-2) (NEW FORMULATION 2)
Figure 5 shows the results of different amounts of Phenoxytoluene which was added to the A/DCI to reduce the roughness. It can be seen from the graph below that only 0.5% addition of the Phenoxytoluene (P/DC/A 81 : (NEW FORMULATION 1)) decreases the roughness sufficiently and maintains the slightly domed profile.
Figure 6 shows the results of the effect of 1-tetralone (high boiling point solvent which has a high viscosity and high surface tension) being confirmed by two more formulations.
MON/MES1 : 1-methoxynaphthalene (50%):Mesitylene (50%) (NEW FORMULATION 3)
MES/BZB2: Mesitylene (60%):Benzylbenzoate (40%) (NEW FORMULATION 4)
Claims
1. A composition suitable for ink-jet printing, nozzle coating, spray coating, roll printing, dip coating, slot coating or flexographic printing of an opto-electrical device, which composition comprises a semiconducting hole transport material, hole injection material, light-emitting polymer material, electron transport material, or electron injection layer material, a first solvent and a second solvent wherein the solvents are miscible with one another, the first solvent having a lower boiling point than the second solvent and the hole transport material having a higher solubility in the first solvent than in the second solvent.
2. The composition of claim 1 wherein the second solvent has a dielectric constant in the range from 1 to 2.2 or from 20 to 32 and the first solvent has a dielectric constant in the range of from above 2.2 and to below 20.
3. A composition according to claim 1 or 2 wherein the first solvent is any of cyclohexylbenzene, methylanisole, methylbenzoate, butylbenzoate, ethyl benzoate, propyl benzoate, ethylanisole, dimethylanisole, anisole, hexylbenzene, heptylbenzene, octylbenzene.
4. The composition of any preceding claim wherein the second solvent is dicyclohexyl monohexylcyclohexane, monooctylcyclohexane.
5. The composition of any preceding claim wherein the amount of second solvent is 1 to 99% by volume of the composition.
6. The composition of any preceding claim wherein the amount of second solvent is 20 to 80% by volume of the composition.
7. The composition of any preceding claim wherein the amount of second solvent is 30 to 70% by volume of the composition.
8. The composition of any preceding claim wherein the first solvent has a boiling point between 100 and 2000C.
9. The composition of any preceding claim wherein the second solvent has a boiling point between 210 and 35O0C.
10. The composition of any preceding claim further comprising a third solvent which is miscible with the first and second solvents and which has a higher boiling point than the first solvent.
11. The composition of claim 10 wherein the third solvent is phenoxytoluene.
12. The composition of any of claims 10 to 11 wherein the third solvent is 0.01 to 10% by volume of the composition.
13. The composition of any of claims 10 to 12 wherein the third solvent is 0.5 to 2% by volume of the composition.
14. The composition of any preceding claim comprising a semiconducting hole transport material, wherein the semiconducting hole transport material comprises a polymer having a molecular weight in the range of 40,000 to 400,000 Daltons.
15. The composition of any preceding claim comprising a semiconducting hole transport material, wherein the semiconducting hole transport material comprises a polymer having a molecular weight of at least 350,000 Daltons.
16. A composition according to claim 14 or claim 15, wherein the concentration of the semiconducting hole transport material in the composition is 0.2 to 1 w/v%.
17. The composition of any preceding claim comprising a semiconducting hole transport material,, wherein the semiconducting hole transport material is cross linkable due to the presence of cross linkable groups.
18. The composition of any preceding claim comprising a semiconducting hole transport material, wherein the semiconducting hole transport material comprises a polymer having a triarylamine repeat unit.
19. The composition of any preceding claim comprising a semiconducting hole transport material, wherein the semiconducting hole transport material is a copolymer of a triarylamine repeat unit and a second repeat unit.
20. A composition according to claim 19, wherein the second repeat unit is a fluorene repeat unit.
21. A method of forming an organic light-emitting device including the steps of: a. providing an anode layer; b. optionally providing a conducting hole injecting layer on the anode layer; c. depositing a composition as defined in any one of claims 1 to 20 on the anode or hole injecting layer by ink-jet printing to form a semiconducting hole transport layer, provided that when the semiconducting hole transport material is deposited by ink-jet printing then the semiconducting hole transport material is deposited on a hole injecting layer.
22. A method of forming an organic light-emitting device including the step of:
1. depositing a composition as defined in any one of claims 1 to 20 by ink-jet printing to form a semiconducting hole transport layer.
23. A method according to claim 21 or claim 22, said method including a further step of baking the semiconducting hole transport layer by heating.
24. A method according to claim 23 or claim 24, wherein deposition of the said composition is onto an anode or a conducting hole injecting layer.
25. A method according to any one of claims 21 to 24, further including the steps of: depositing a luminescent layer on the semiconducting hole transport layer, optionally depositing an electron transport layer on the luminescent layer, and depositing a cathode on the luminescent layer or electron transport layer, where present.
26. A method according to any one of claims 21 to 25, further including a step of removing solvent from the semiconducting hole transport layer.
27. An organic light-emitting device made by a method according to any one of claims 21 to 26.
28. A full colour display comprising an organic light-emitting device according to claim 27.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0900452A GB2466843A (en) | 2009-01-12 | 2009-01-12 | Interlayer formulation for flat films |
| GB0900452.4 | 2009-01-12 |
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| WO2010079331A1 true WO2010079331A1 (en) | 2010-07-15 |
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| GB (1) | GB2466843A (en) |
| TW (1) | TW201033301A (en) |
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| WO2019212022A1 (en) * | 2018-05-01 | 2019-11-07 | 三菱ケミカル株式会社 | Composition, and production method for organic-electric-field light-emitting element |
| US11770971B2 (en) | 2015-12-15 | 2023-09-26 | Merck Patent Gmbh | Esters containing aromatic groups as solvents for organic electronic formulations |
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| US8916066B2 (en) * | 2010-05-27 | 2014-12-23 | Corning Incorporated | Polymeric fused thiophene semiconductor formulation |
| GB201210858D0 (en) | 2012-06-19 | 2012-08-01 | Cambridge Display Tech Ltd | Method |
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| GB201418876D0 (en) | 2014-10-23 | 2014-12-03 | Cambridge Display Tech Ltd | Organic light emitting device |
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| WO2019212022A1 (en) * | 2018-05-01 | 2019-11-07 | 三菱ケミカル株式会社 | Composition, and production method for organic-electric-field light-emitting element |
| CN112042275A (en) * | 2018-05-01 | 2020-12-04 | 三菱化学株式会社 | Composition and method for producing organic electroluminescent element |
| JPWO2019212022A1 (en) * | 2018-05-01 | 2021-06-10 | 三菱ケミカル株式会社 | Method for manufacturing composition and organic electroluminescent device |
| JP7415917B2 (en) | 2018-05-01 | 2024-01-17 | 三菱ケミカル株式会社 | Composition and method for producing organic electroluminescent device |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2466843A (en) | 2010-07-14 |
| GB0900452D0 (en) | 2009-02-11 |
| TW201033301A (en) | 2010-09-16 |
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