Sputter protective layer for organic electronic devices
The present invention provides an organic gate insulator (OGI) layer having a low dielectric constant (k), said organic gate insulator layer being over-coated with a cross-linked organic layer (OSPL) having a relatively high permittivity (k). The present invention also provides an electronic device comprising such an organic thin film transistor. The invention also provides a solution for producing said OSPL, and a process for producing said OSPL.
1 . A thin film transistor, comprising a substrate, one or more source/drain electrodes, at least one gate electrode, an organic semiconductor layer, and an organic gate insulator (OGI) layer;
wherein the organic gate insulator (OGI) layer has a dielectric constant (k)<3.0 @ 1000 Hz, said organic gate insulator layer being over-coated with a cross-linked organic layer (OSPL);
wherein the cross-linked layer is a free-radical photocured layer;
wherein the cross-linked organic layer thereon has a permittivity (k)>3.3 @ 1000 Hz;
preferably wherein the cross-linked organic layer thereon has a permittivity (k)>3.5 at 1000 Hz;
more preferably wherein the cross-linked organic layer thereon has a permittivity (k)>4.0 at 1000 Hz;
wherein the cross-linked organic layer thereon is obtainable by polymerising a solution comprising at least one multi-functional acrylate, a fluorosurfactant and an acrylate and/or methacrylate-functionalised silicone surfactant, and one or more initiators;
wherein the organic semiconductor layer comprises one or more material selected from the group consisting of tetracene, chrysene, pentacene, diketopyrrolopyrroles, substituted benzothienobenzothiophenes (C8-BTBT), dinaphthothienothiophenes (DNTT), pyrene, perylene, coronene, or substituted derivatives of these; oligomeric para substituted phenylenes such as p-quaterphenyl (p-4P), p-quinquephenyl (p-5P), p-sexiphenyl (p-6P), or soluble substituted derivatives of these, poly(3-substituted thiophene), poly(3,4-bisubstituted thiophene), polybenzothiophene, polyisothianapthene, poly([Lambda]/-substituted pyrrole), poly(3-substituted pyrrole), poly(3,4-bisubstituted pyrrole), polyfuran, polypyridine, poly-1,3,4-oxadiazoles, polyisothianaphthene, poly([Lambda]/-substituted aniline), poly(2-substituted aniline), poly(3-substituted aniline), poly(2,3-bisubstituted aniline), polyazulene, polypyrene; pyrazoline compounds; polyselenophene; polybenzofuran; polyindole; polypyridazine; benzidine compounds; stilbene compounds; triazines; substituted metallo- or metal-free porphines, phthalocyanines, fluorophthalocyanines, naphthalocyanines, naphthalene diimides or fluoronaphthalocyanines; C60 and C70 fullerenes; A/.[Lambda]/′-dialkyl, substituted dialkyl, diaryl or substituted diaryl-1,4,5,8-naphthalenetetracarboxylic diimide and fluoro derivatives; [Lambda]/.[Lambda]/′-dialkyl, substituted dialkyl, diaryl or substituted diaryl 3,4,9,10-perylenetetracarboxylicdiimide; bathophenanthroline; diphenoquinones; 1,3,4-oxadiazoles; 11,11,12,12-tetracyanonaptho-2,6-quinodimethane; [alpha], [alpha]′-bis(dithieno[3,2-b2′,3′-d]thiophene); dithieno[2,3-d;2′,3′-d′]benzo[1,2-b;4,5-b′]dithiophene (DTBDT); poly dithienobenzodithiophene-co-diketopyrrolopyrrolebithiophene (PDPDBD); isoindigo-Bithiophene-(IIDDT-C3), thieno[3,2-b]thiophene-5-fluorobenzo[c][1,2,5]thiadiazole copolymers, di(thiophen-2-yl)thieno[3,2-b]thiophene (DTTT); 2,8-dialkyl, substituted dialkyl, diaryl or substituted diaryl anthradithiophene; 2,2′-bibenzo[1,2-b:4,5-b′jdithiophene, benzothienobenzothiophene (BTBT) polymers benzodithiazole polymers, and mixtures thereof.
2 . The thin film transistor of claim 1 , wherein the OGI layer material is selected from the group consisting of perfluoropolymers, benzocyclobutene polymers (BCB), parylene, polyvinylidene fluoride (PVDF) polymers, cyclic olefin copolymers (e.g. norbornene), perfluoro cyclic olefin polymers, adamantyl polymers, perfluorocyclobutylidene polymers (PFCB), siloxane polymers (such as polymethylsiloxane), and mixtures thereof.
3 . The thin film transistor according to claim 1 , wherein the cross-linked organic layer thereon is 50-4000 nm thick.
4 . The thin film transistor according to claim 1 , wherein the surface free energy of OGI is 15-22 mN/m.
5 . The thin film transistor according to claim 1 , wherein the surface free energy of cross-linked-organic layer thereon is between 16-35 mN/m.
6 . The thin film transistor according to claim 1 , wherein the permittivity of the cross-linked organic layer on the OGI is ≥4.
7 . The thin film transistor according to claim 1 , wherein the cross-linked organic layer thereon is obtainable by polymerising a solution further comprising an acrylate functional oligomer and/or a non-acrylate organic solvent.
8 . An electronic device comprising a thin film transistor according to claim 1 .
9 . The thin film transistor according to claim 2 , wherein the surface free energy of the OGI is 15-22 mN/m.
10 . A process for solution deposition of a cross-linkable organic layer on to a low surface energy organic gate insulator, wherein the solution comprises at least one fluorosurfactant, at least one acrylate- and/or methacrylate-functionalised silicone surfactant, at least one multi-functional acrylate, and one or more initiators.
11 . A process according to claim 10 , wherein the fluorosurfactant has a 0.1% solution surface tension (mN/m) in toluene of less than 24 mN/m.