Organic polymeric bi-metallic composites

Abstract

Organic polymeric bi-metallic alkoxide or aryloxide composites are used as dielectric materials in various devices with improved properties such as improved mobility. These composites comprise a poly(meth)acrylate or polyester having metal coordination sites, and the same or different bi-metallic alkoxide or aryloxide molecules that are coordinated with the organic polymer. The bi-metallic alkoxide or aryloxide molecules can be represented by Structure (I) shown herein. Such composites are generally soluble at room temperature in various organic solvents and be provided in homogeneous organic solvent solutions that can be suitably applied to a substrate to form dielectric materials.

Claims

1. An organic polymeric bi-metallic alkoxide or aryloxide composite, comprising: a poly(meth)acrylate or polyester comprising metal coordination sites, and one or more of the same or different bi-metallic alkoxide or aryloxide complexed molecules that are coordinated with the poly(meth)acrylate or polyester, the bi-metallic alkoxide or aryloxide complexed molecules being selected from the group consisting of barium titanium (methoxyisopropanol).sub.6, barium titanium (triethylene glycol ethyl ether).sub.6, strontium titanium (methoxyisopropanol).sub.6, and barium titanium (diethylene glycol monoethyl ether).sub.6.

2. The organic polymeric hi-metallic alkoxide or aryloxide composite of claim 1 comprising a poly(meth)acrylate or a copolymer derived at least in part from an alkyl (meth)acrylate.

3. A homogeneous organic solvent solution of an organic polymeric bi-metallic alkoxide or aryloxide composite that is dissolved at room temperature within an organic solvent medium, comprising: an poly(meth)acrylate or polyester comprising metal coordination sites, and one or more of the same or different bi-metallic alkoxide or aryloxide complexed molecules that are coordinated with the poly(meth)acrylate or polyester, the bi-metallic alkoxide or aryloxide complexed molecules being selected from the group consisting of barium titanium (methoxyisopropanol).sub.6, barium titanium (triethylene glycol ethyl ether).sub.6, strontium titanium (methoxyisopropanol).sub.6, and barium titanium (diethylene glycol monoethyl ether).sub.6.

4. The homogeneous organic solvent solution of claim 3, wherein the organic solvent medium comprises one or more organic solvents selected from the group consisting of anisole, toluene, any xylene, N,N-dimethyl formamide, dimethyl sulfoxide, tetrahydrofuran, 1-methoxy-2-propanol, 2-methoxyethanol, 1,2-dichloroethane, methylene chloride, chloroform, chlorobenzene, and 1,2,-dichlorobenzene.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1a through 1d illustrate cross-sectional views of four possible configurations for an organic field effect transistor that is one embodiment of the present invention. FIGS. 1a and 1b illustrate a device having a bottom gate configuration and FIGS. 1c and 1d illustrate a device having a top gate configuration.

(2) FIGS. 2a and 2b are graphical representations of the output and transfer characteristics of the device described below in Invention Example 10.

DETAILED DESCRIPTION OF THE INVENTION

(3) Definitions

(4) As used herein to define various components of the composites, dielectric compositions, semi-conductor compositions and layers, unless otherwise indicated, the singular forms “a,” “an,” and “the” are intended to include one or more of the components (that is, including plurality referents).

(5) Each term that is not explicitly defined in the present application is to be understood to have a meaning that is commonly accepted by those skilled in the art. If the construction of a term would render it meaningless or essentially meaningless in its context, the term's definition should be taken from a standard dictionary.

(6) The use of numerical values in the various ranges specified herein, unless otherwise expressly indicated otherwise, are considered to be approximations as though the minimum and maximum values within the stated ranges were both preceded by the word “about.” In this manner, slight variations above and below the stated ranges can be used to achieve substantially the same results as the values within the ranges. In addition, the disclosure of these ranges is intended as a continuous range including every value between the minimum and maximum values.

(7) As used herein, the terms “over,” “above,” and “under” and other similar terms, with respect to layers in the devices described herein, refer to the order of the layers, wherein the organic thin film layer is above the gate electrode, but do not necessarily indicate that the layers are immediately adjacent or that there are no intermediate layers.

(8) Unless otherwise noted in this application, the term “composite” refers to an organic polymeric bi-metallic alkoxide or aryloxide composite of this invention.

(9) Moreover, unless otherwise indicated, percentages refer to percents by total dry weight, for example, weight % based on total solids of either a layer or formulation used to make a layer. Unless otherwise indicated, the percentages can be the same for either the dry layer or the total solids of the formulation used to make that layer.

(10) For clarification of definitions for any terms relating to polymers, reference should be made to “Glossary of Basic Terms in Polymer Science” as published by the International Union of Pure and Applied Chemistry (“IUPAC”), Pure Appl. Chem. 68, 2287-2311 (1996). However, any definitions explicitly set forth herein should be regarded as controlling.

(11) The term “polymer” refers to high and low molecular weight polymers including oligomers and includes homopolymers and copolymers. The term “copolymer” refers to polymers that are derived from two or more different monomers.

(12) The term “backbone” refers to the chain of atoms (carbon or heteroatoms) in a polymer to which a plurality of pendant groups are attached. One example of such a backbone is an “all carbon” backbone obtained from the polymerization of one or more ethylenically unsaturated polymerizable monomers. However, other backbones can include heteroatoms wherein the polymer is formed by a condensation reaction or some other means.

(13) Periodic Table refers to the well known chemical arrangement of chemical elements.

(14) The above described features and advantages of the present invention will become more apparent when taken in conjunction with the following description and drawings wherein identical reference numerals have been used, where possible, to designate identical or analogous features that are common to the Figures.

(15) Organic Polymeric Bi-Metallic Alkoxide or Aryloxide Composites

(16) The composites of this invention comprise one or more organic polymers, each of which comprises metal coordination sites for the two different metals formed in the compositions as described below. Such coordination sites include but are not limited to, inorganic and organic groups that are generally pendant to the organic backbone of the polymers. Examples of inorganic groups include but are not limited to, siloxane and phosphoric esters. Examples of organic groups include but not limited to, amines, pyridines, alkoxy, carbonyls, esters, ethers, carboxylic acids, and aromatic groups that are pendant to the organic polymer backbone or as part of the backbone. A given organic polymer can have more than one type of metal coordination site. Particularly useful metal coordination sites are esters, ethers, carbonyl, and pyridine groups.

(17) Useful classes of organic polymers with metal coordination sites include but are not limited to, poly(meth)acrylates formed from one or more methacrylic acid esters or acrylic acid esters, polystyrenes including halogenated polystyrenes, hydroxylated polystyrenes and other organic polymers derived from styrene derivatives, poly(meth)acrylamides, and poly(propylene oxide). For example, poly(methyl methacrylate) (PMMA) and organic copolymers derived at least in part from methyl and other alkyl methacrylates are particularly useful. Other organic polymers that are useful include but not limited to, aliphatic polycarbonates such as poly(propylene carbonate) and poly(ethylene carbonate), polyesters, polyimides, polyamides, polysulfones, polylactides, polylactones, poly(arylene ethers), polyphenylenes, poly(phenyl quinoxalines), poly(vinyl alcohol), poly(vinyl acetate), poly(vinyl phenol), poly(vinyl cinnamate), poly (2-vinyl pyridine), and poly (4-vinyl pyridine). Still other useful organic polymers are poly(styrene-co-alpha-methyl styrene) and poly(styrene-ethylene oxide). Polyesters and poly(meth)acrylates are particularly useful.

(18) Such useful organic polymers can be obtained from various commercial sources or they are readily prepared by polymer chemists using readily available reaction materials and known polymerization conditions.

(19) Some particularly useful ethylenically unsaturated polymerizable monomers that can be used to provide recurring units in poly(meth)acrylates include but are not limited to, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, octadecyl methacrylate, decyl methacrylate, hexadecyl methacrylate, dodecyl methacrylate, cyclohexyl methacrylate, cyclooctyl methacrylate, 4-octylphenyl methacrylate, docosonyl methacrylate, 2-octyl-1-dodecanyl methacrylate, 4-octylcyclohexyl methacrylate, 2-ethylhexyl methacrylate, eicosanyl methacrylate, and corresponding acrylates.

(20) Useful poly(meth)acrylates may have only up to 25 mol % of recurring units derived from an alkyl acrylate or alkyl methacrylate, and the remainder of the polymer backbone can have any suitable “additional” recurring units, generally in random order with each other, derived from other ethylenically unsaturated polymerizable monomers. The organic polymers can have at least 75 mol % and up to 99.5 mol %, or typically at least 80 mol % and up to and including 95 mol %, of these additional recurring units in the backbone, based on the total moles of recurring units in the polymer backbone. Such additional recurring units can be derived, for example, from ethylenically unsaturated polymerizable monomers, which monomers can be substituted or unsubstituted.

(21) More generally, useful additional recurring units can be defined as those that, when present as the only recurring units in a homopolymer, this homopolymer should have a glass transition temperature (T.sub.g) at least 25° C. and up to any temperature that is a practical limit so that the resulting organic polymers have the desired dielectric properties in the devices described herein. This “homopolymer T.sub.g feature” can be determined using DSC.

(22) Some particularly useful additional recurring units can be derived from 1-diadamantyl methacrylate, 1-adamantyl methacrylate, methyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, n-butyl acrylate, phenyl methacrylate, 2-phenylethyl methacrylate, 1-diadamantyl acrylate, 1-adamantyl acrylate, styrene, 4-methylstyrene, norbornyl methacrylate, 4-t-butylstyrene, 2-vinyl naphthalene, 1-vinyl naphthalene, or 4-vinyl biphenyl.

(23) The organic polymers described above can be purchased or prepared using known starting materials (for example, ethylenically unsaturated polymerizable monomers) and free radical polymerization initiators. Similarly, living free radical polymerization techniques such as atom transfer radical polymerization (ATRP), nitroxide-mediated polymerization (NMP), or reversible addition-fragmentation chain transfer (RAFT) polymerization can be used. Other organic polymers useful in the practice of this invention can be prepared using condensation polymerization techniques with the appropriate starting materials (for example diols and diacids for polyesters). A skilled worker in polymer chemistry would be able to use the description in this application as guidance to prepare any of the organic polymers useful for practice in this invention.

(24) The most useful organic polymers for preparing the composites of this invention are poly(meth)acrylates (both homopolymers and copolymers derived from (meth)acrylate monomers) and polyesters.

(25) The organic polymeric bi-metallic alkoxide or aryloxide composite also includes bi-metallic alkoxide or aryloxide molecules that are coordinated with the organic polymer. Thus, the composite can be represented by the following Structure (I):

(26) ##STR00002##

(27) In Structure (I), M.sub.1 metals are selected from Group 3 to Group 12 metals in Rows 4 and 5 of the Periodic Table. Particularly useful second M metals include but are not limited to, titanium, zirconium, nickel, copper, zinc, palladium, silver, lanthanum, and combinations thereof (two or more of these metals). Thus, organic polymeric bi-metallic alkoxide or aryloxide composite can comprise molecules with different M.sub.1 metals. Titanium, zirconium, and zinc (or combinations of two or more thereof) are particularly useful metals of this type.

(28) In addition, in Structure (I), M.sub.2 is a metal selected from Group 2 of the Periodic Table including but not limited to, barium, strontium, or calcium, or a combination thereof (two or more of these metals). Thus, organic polymeric bi-metallic alkoxide or aryloxide composite can comprise molecules with different M.sub.2 metals. Barium and strontium (or a combination of both metals) are particularly useful Group 2 metals.

(29) Particularly useful combinations of M.sub.1 and M.sub.2 metals to provide the desired metal alkoxides and metal aryloxides include but are not limited to, barium with titanium, barium with zirconium, strontium with titanium, strontium with zirconium, barium and titanium with zirconium, and barium and strontium with titanium.

(30) Structure (I) also includes the R.sub.1 and R.sub.2 groups that can be the independently (same or different) substituted or unsubstituted alkyl groups or substituted or unsubstituted aryl groups.

(31) The useful R.sub.1 and R.sub.2 substituted or unsubstituted alkyl groups can be linear or branched, cyclic or acyclic, and comprise at least 1 to and including 24 carbon atoms, and typically at least 1 to and including 8 carbon atoms. Representative substituted or unsubstituted alkyl groups include but are not limited to methyl, ethyl, n-propyl, isopropyl, t-butyl, n-hexyl, cyclopentyl, and cyclohexyl. Other particularly useful alkyl groups are substituted or unsubstituted alkyl ethers of ethylene and diethylene glycols including alkyl ethers such as monomethyl ether, monoethyl ether, monopropyl ether, monoisopropyl ether, monobutyl ether, monophenyl ether, and monobenzyl ether. Esters of ethylene glycol and diethylene glycol are also useful in present invention.

(32) Useful R.sub.1 and R.sub.2 substituted or unsubstituted aryl groups in the composite include substituted or unsubstituted carbocyclic aromatic groups having 6 or 10 carbon atoms in the aromatic ring, such as substituted or unsubstituted phenyl, naphthyl, 4-methylphenyl, phenol, 2-methoxyphenol, monophenyl ether, monobenzyl ether, and similar groups.

(33) Combinations of substituted or unsubstituted alkyl groups and substituted or unsubstituted aryl groups, such as alkaryl groups or aralkyl groups, can also be used, and such groups can also include substituents attached via oxygen atoms, such as alkoxy groups, aryloxy groups, or alkyloxyalkyl groups.

(34) In particularly useful organic polymeric bi-metallic alkoxide or aryloxide composites of this invention, the alkyloxide comprises one or more substituted or unsubstituted alkyl groups having 1 to 24 carbon atoms, or the aryloxide comprises one or more substituted or unsubstituted phenyl groups. Other useful embodiments include both a substituted or unsubstituted alkyl group and a substituted or unsubstituted aryl group, including substituted alkyl and aryl groups having alkoxy or alkyleneoxyalkyl substituents.

(35) The organic polymeric bi-metallic alkoxide or aryloxide composites of the present invention can be prepared in any suitable manner, but a particularly useful synthetic method comprises:

(36) mixing a non-aqueous solution of a suitable organic polymer (or a mixture of organic polymers) comprising metal coordination sites with one or more bi-metallic alkoxides or aryloxides in a suitable organic solvent medium for a suitable time and temperature, and

(37) removing the organic solvent medium, in a suitable manner such as evaporation or other drying means.

(38) For example, the mixing of the organic polymer(s) and bi-metallic alkoxide or aryloxide of Structure (I) can be carried out at a temperature of at least 30° C. and up to and including 100° C. In particular, the mixing can be carried out at a temperature of at least 30° C. to and including 60° C. Thus, either the mixing of the removal of the organic solvent medium, or both, can be carried out at a temperature of at least 30° C.

(39) The mixing of the reactants can be carried out for at least 10 minutes and up to and including 24 hours, usually with stirring or mechanical mixing. Suitable reaction conditions are provided below in the Syntheses before the Invention Examples.

(40) A homogeneous organic solvent solution of the organic polymeric bi-metallic alkoxide or aryloxide composite can be prepared by dissolving the composite at room temperature within an organic solvent medium (comprising one or more organic solvents). As noted above, this composite comprises:

(41) an poly(meth)acrylate or polyester comprising metal coordination sites, and

(42) one or more of the same or different bi-metallic alkoxide or aryloxide that are coordinated with the poly(meth)acrylate or polyester, each of the bi-metallic alkoxide or aryloxide complexed molecules being represented by Structure (I) described above.

(43) The homogeneous organic solvent solution is an organic solvent medium that comprises one or more organic solvents, for example selected from the group consisting of anisole, toluene, any xylene, N,N-dimethyl formamide, dimethyl sulfoxide, tetrahydrofuran, 1-methoxy-2-propanol, 2-methoxy-ethanol, 1,2-dichloroethane, methylene chloride, chloroform, chlorobenzene, and 1,2,-dichlorobenzene.

(44) The term “homogeneous” means that the organic polymeric bi-metallic alkoxide or aryloxide composite is soluble in the organic solvent medium of choice at room temperature (20-25° C.) at up to 50 weight % for at least 7 days.

(45) In some embodiments, the organic polymeric bi-metallic alkoxide or aryloxide composite can be provided in the form of a solid film. In other words, the homogeneous organic solvent solution described above can be coated onto a suitable substrate and dried under suitable conditions.

(46) Electronic Devices

(47) The composites of the present invention can be used in a method of making an OFET, the method comprising:

(48) providing a substrate,

(49) forming a gate electrode on the substrate,

(50) forming a composite gate dielectric layer (according to the present invention) on the gate electrode by applying inventive organic polymeric bi-metallic alkoxide or aryloxide composite (having a thickness less than 1 μm) interposed between the gate electrode and an organic semiconductor layer,

(51) depositing an organic semiconductor layer adjacent to the composite gate dielectric layer, and

(52) depositing a source electrode and a drain electrode contiguous to the organic semiconductor layer.

(53) Any organic polymeric bi-metallic alkoxide or aryloxide composite described herein can be used to prepare the gate dielectric layer in the OFET's, or a combination of two or more of such composites can be used. An integrated circuit comprising a plurality of OFET's can also be provided.

(54) Any known thin film transistor or field effect transistor configuration is possible. For example, the source and drain electrodes may be adjacent to the gate dielectric with the organic semiconductor layer over the source and drain electrodes, or the organic semiconductor layer may be interposed between the source and drain electrodes and the gate dielectric. In each option, a composite dielectric layer can be provided between the organic semiconductor layer and the gate dielectric.

(55) Each organic field effect transistor (OFET) illustrated in FIGS. 1a-1d contains source electrode 40, drain electrode 50, gate electrode 60, gate dielectric 20, substrate 10, and semiconductor organic layer 30 in the form of a film connecting source electrode 40 to drain electrode 50, which organic semiconductor layer comprises a compound as described below. When the OFET operates in an accumulation mode, the charges injected from source electrode 40 into the organic semiconductor layer 30 are mobile and a current flows from source 40 to drain 50, mainly in a thin channel region within about 100 Angstroms of the semiconductor-dielectric interface. In the configuration of FIG. 1a, the charge need only be injected laterally from source electrode 40 to form the channel. In the configuration of FIG. 1b, the charge is injected vertically for source electrode 40 into organic semiconductor layer 30 to form the channel. In the absence of a gate field, the channel ideally has few charge carriers and as a result there is ideally no source-drain conduction.

(56) The off current is defined as the current flowing between source electrode 40 and drain electrode 50 when charge has not been intentionally injected into the channel by the application of a gate voltage. For an accumulation-mode TFT, this occurs for a gate-source voltage more negative, assuming an n-channel, than a certain voltage known as the threshold voltage. The “on” current is defined as the current flowing between source electrode 40 and drain electrode 50 when charge carriers have been accumulated intentionally in the channel by application of an appropriate voltage to gate electrode 60, and the channel is conducting. For an n-channel accumulation-mode TFT, this occurs at gate-source voltage more positive than the threshold voltage. It is desirable for this threshold voltage to be zero or slightly positive for n-channel operation. Switching between on and off is accomplished by the application and removal of an electric field from gate electrode 60 across gate dielectric 20 to the semiconductor-dielectric interface, effectively charging a capacitor.

(57) The composites of this invention can be used to provide dielectric layers (also known as gate dielectrics or gate insulator layers) in the devices described herein, to improve electrical properties, without the need for additional surface treatment or coating another layer on the surface to which the composite formulations are applied.

(58) For example, a gate dielectric or gate insulator layer can be prepared by:

(59) depositing on or applying to a suitable substrate, a liquid formulation can consists essentially of one or more composites of this invention and optionally one or more suitable organic solvents, and

(60) removing any organic solvent from the applied liquid layer to form a solid gate dielectric or gate insulator layer. This process is described in more detail below.

(61) The devices described herein can comprise the composite dielectric materials described herein and such devices can be electronic device including but not limited to, organic field effect transistors (OFET's), optical devices such as organic light emitting diodes (OLED's), photodetectors, sensors, logic circuits, memory elements, capacitors, and photovoltaic (PV) cells. Particularly useful electronic devices are OFET's that are described in more detail below. However, just because other devices are not described in detail, it is not contemplated that the present invention is useful only in OFET's. A skilled artisan in the various arts would know how to use the dielectric composites of this invention for those other types of devices.

(62) The present invention can be used in a method for the production of an organic polymeric hi-metallic alkoxide or aryloxide composite dielectric layer and electronic devices incorporating such components. In one embodiment, a suitable substrate is provided and a solution or dispersion of the composite of the present invention is applied to the substrate and dried to remove any organic solvent(s), and suitable electrical contacts are made with the layer. The particular method to be used can be determined by the structure of the desired semiconductor component. In the production of an organic field effect transistor, for example, a gate electrode can be first deposited on a flexible substrate, a homogeneous organic solvent solution or composite of this invention can then be applied on it to form a dielectric layer, and then source and drain electrodes and a layer of a suitable semiconductor material can be applied on top of the dielectric layer.

(63) The structure of such a transistor and hence the sequence of its production can be varied in the customary manner known to a person skilled in the art. Thus, alternatively in another embodiment, a gate electrode can be formed first, followed by a gate dielectric of the composite of this invention, then the organic semiconductor layer can be formed, and finally the contacts for the source electrode and drain electrode can be formed on the organic semiconducting layer.

(64) A third embodiment can have the source and drain electrodes formed first, then the organic semiconductor layer can be formed, followed by forming the dielectric layer, and a gate electrode can be formed on the dielectric layer.

(65) A skilled artisan would recognize that other useful structures can be constructed or intermediate surface modifying layers can be interposed between the above-described components of the thin film transistor. In most embodiments, a field effect transistor comprises the organic polymeric bi-metallic alkoxide or aryloxide composite dielectric layer, a gate electrode, a organic semiconductor layer, a source electrode, and a drain electrode, wherein the composite dielectric layer, the gate electrode, the organic semiconductor layer, the source electrode, and the drain electrode are arranged in any sequence as long as the gate electrode, and the organic semiconductor layer both contact the organic polymeric bi-metallic alkoxide or aryloxide composite dielectric layer, and the source electrode and the drain electrode both contact the organic semiconductor layer.

(66) Substrate

(67) A substrate (also known as a support) can be used for supporting the OFET or other device during manufacturing, testing, or use. A skilled artisan would appreciate that a substrate that is selected for commercial embodiments can be different from a substrate that is selected for testing or screening various embodiments. In other embodiments, a temporary substrate can be detachably adhered or mechanically affixed to another substrate. For example, a flexible polymeric substrate can be adhered to a rigid glass substrate that can be removed.

(68) In some embodiments, the substrate does not provide any necessary electrical function (such as electrical conductivity) for the device such as an organic field effect transistor. This type of support is considered a “non-participating support”.

(69) Useful substrate materials include both organic and inorganic materials including but not limited to, inorganic glasses, silicon wafer, ceramic foils, polymeric films, filled polymeric materials, coated metallic foils, acrylics, epoxies, polyamides, polycarbonates, polyimides, polyketones, poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene) [sometimes referred to as poly(ether ether ketone) or PEEK], polynorbornenes, polyphenyleneoxides, poly(ethylene naphthalenedicarboxylate) (PEN), poly(ethylene terephthalate) (PET), poly(phenylene sulfide) (PPS), and fiber-reinforced plastics (FRP).

(70) A flexible substrate can be used in some embodiments to allow for roll processing, which can be a continuous process, and providing economy of scale and manufacturing compared to flat or rigid supports. The flexible substrate can be designed to be wrapped around the circumference of a cylinder of less than 50 cm in diameter, or typically less than 25 cm in diameter, without distorting or breaking, using low force. A flexible substrate can be rolled upon itself.

(71) In some useful devices, a substrate is optional. For example, in a top construction as illustrated in FIG. 1b, when the gate electrode or gate dielectric provides sufficient support for the intended use of the resultant TFT, a substrate is not needed. In addition, the substrate can be combined with a temporary support in which the support is detachably adhered or mechanically affixed to the substrate, such as when the support is desired for a temporary purpose, for example, for manufacturing, testing, transport, or storage. Thus, a flexible polymeric temporary support can be adhered to a rigid glass substrate, which flexible polymeric temporary support could be removed at an appropriate time.

(72) Gate Electrode

(73) The gate electrode for the OFET's can be composed of any useful conductive material. A variety of useful gate materials include but are not limited to, metals, degenerately doped semiconductors, conducting polymers, and printable materials such as carbon ink or a silver-epoxy. For example, the gate electrode can comprise doped silicon, or a metal such as aluminum, chromium, gold, silver, nickel, palladium, platinum, tantalum, or titanium, or mixtures thereof. Conductive polymers also can be used, including but not limited to, polyaniline, polypyrrole, and poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS). In addition, alloys, combinations, and multilayers of these materials can be used in the gate electrode.

(74) In some embodiments, the same material can provide the gate electrode function and also provide a supporting (substrate) function. For example, doped silicon can function as the gate electrode and the substrate for an OFET.

(75) Gate Dielectric

(76) The gate dielectric is provided on a gate electrode to electrically insulate the gate electrode from the rest of the electronic device (such as an OFET device). The gate dielectric is provided as a separate layer comprising one or more of the organic polymeric bi-metallic alkoxide or aryloxide composites of this invention. In most embodiments, the dielectric layer consists essentially of one of more of these composites with only non-essential materials as additional components. In yet other embodiments, the dielectric layer consists only of one or more of the composites.

(77) The gate dielectric layers described herein exhibit a suitable dielectric constant that does not vary significantly with frequency. The gate dielectric layer can have a resistivity of at least 10.sup.14 ohm-cm for OFET devices.

(78) In some embodiments, the organic polymeric bi-metallic alkoxide or aryloxide composite gate dielectric prepared using the composite of this invention can possess one or more of the following characteristics: coatability out of solution, crosslinkable, photo-patternable, high thermal stability (for example, stable up to a temperature of at least 250° C.), low processing temperatures (for example, less than 150° C., or less than 100° C.), and compatibility with flexible substrates.

(79) For OFET's for example, the dielectric layer generally can have a dry thickness of at least 3,500 Angstroms (Å) and up to and including 15,000 Angstroms (Å), or typically up to and including 10,000 Å, or at least 5,000 Å. The dry thickness can be determined using known methods such as ellipsometry and profilometry. For embedded capacitors and printed circuit board applications, the dry dielectric layer thickness can include those described above for OFET's, but can also be at least 10 μm or at least 20 μm and up to and including 50 μm.

(80) Source and Drain Electrodes

(81) The source electrode and drain electrode are separated from a gate electrode by the gate dielectric while the organic semiconductor layer can be over or under the source electrode and drain electrode. The source and drain electrodes can be composed of any useful conductive material including but not limited to, those materials described above for the gate electrode, for example, aluminum, barium, calcium, chromium, gold, silver, nickel, palladium, platinum, titanium, polyaniline, PEDOT:PSS, graphene, reduced graphene oxide (r-GO), composites of graphene, composites of reduced graphene oxide, other conducting polymers, composites thereof, alloys thereof, combinations thereof, and multilayers thereof.

(82) The thin film electrodes (for example, gate electrode, source electrode, and drain electrode) can be provided by any useful means such as physical vapor deposition (for example, thermal evaporation, sputtering), microcontact printing, or ink jet printing. The patterning of these electrodes can be accomplished by known methods such as shadow masking, additive photolithography, subtractive photolithography, printing, microcontact printing, and pattern coating.

(83) The organic semiconductor layer can be provided over or under the source and drain electrodes, as described above in reference to the thin film transistor article.

(84) Useful materials that can be formed into n-type or p-type organic semiconductor layers are numerous and described in various publications. For example, useful semiconductor materials can be prepared using poly(3-hexylthiophene)(P3HT) and its derivatives, the tetracarboxylic diimide naphthalene-based compounds described in U.S. Pat. No. 7,422,777 (Shukla et al.), the N,N′-diaryl-substituted 1,4,5,8-naphthalene tetracarboxylic acid diimides having electron withdrawing groups as described in U.S. Pat. No. 7,629,605 (Shukla et al.), N,N′-1,4,5,8-naphthalene tetracarboxylic acid diimides having fluoroalkyl-substituted cycloalkyl groups as described in U.S. Pat. No. 7,649,199 (Shukla et al.), heteropyrenes in p-type semiconductors as described in U.S. Pat. No. 7,781,076 (Shukla et al.), cyclohexyl-substituted naphthalene tetracarboxylic acid diimides as described in U.S. Pat. No. 7,804,087 (Shukla et al.), heterocyclyl-substituted naphthalene tetracarboxylic acid diimides as described in U.S. Pat. No. 7,858,970 (Shukla et al.), and N,N′-arylalkyl-substituted naphthalene-based tetracarboxylic acid diimides as described in U.S. Pat. No. 7,981,719 (Shukla et al.). All of the publications noted in this paragraph are incorporated herein by reference.

(85) The present invention also provides integrated circuits that can comprise a plurality of OFET's prepared according to this invention.

(86) Processing

(87) Organic polymeric bi-metallic alkoxide or aryloxide dielectric layers can be readily processed and are thermally and chemically stable to hot or cold organic solvents. Such composite dielectric layer(s) in the gate dielectric can be deposited by spin coating, ink jetting, or blade coating. The entire process of making the thin film transistors or integrated circuits can be carried out below a maximum support temperature of generally 450° C. or less, or typically at 250° C. or less, or even at 150° C. or less. The temperature selection generally depends on the substrate and processing parameters chosen for the given device, once a skilled artisan has the knowledge contained herein. These temperatures are well below traditional integrated circuit and semiconductor processing temperatures, which enables the use of any of a variety of relatively inexpensive supports, such as flexible polymeric supports. Thus, the composites of the present invention enable the production of relatively inexpensive integrated circuits containing organic thin film transistors (OFET's) with significantly improved performance.

(88) In the embodiments where materials of semiconductor layers are soluble in coating solvents, both the organic semiconductor layer and the composite gate dielectric layer can be deposited from solution, making the coating of large areas less difficult.

(89) In one embodiment, an OFET structure illustrated in FIG. 1a is prepared by spin coating an organic semiconductor layer onto a dielectric layer prepared using a composite of this invention, which has pre-patterned source and drain electrodes. In another embodiment, an OFET structure illustrated in FIG. 1c is prepared by spin coating an organic semiconductor layer onto the substrate with pre-patterned source and drain electrodes. Then, an organic polymeric bi-metallic alkoxide or aryloxide composite prepared according to this invention is spin coated (for example, in a homogeneous organic solvent solution) onto the organic semiconductor layer followed by the deposition of the gate electrode by vacuum deposition or liquid deposition of a conductive metal or metal dispersion, respectively.

(90) Electronic devices in which OFET's and other devices are useful include, for example, more complex circuits such as shift registers, integrated circuits, logic circuits, smart cards, memory devices, radio-frequency identification tags, backplanes for active matrix displays, active-matrix displays (for example liquid crystal or OLED), solar cells, ring oscillators, and complementary circuits, such as inverter circuits. In an active matrix display, a thin film transistor can be used as part of voltage hold circuitry of a pixel of the display. In devices containing OFET's, the OFET's are operatively connected by means known in the art.

(91) A composite of the present invention can be embodied in an article that comprises one or more of the described thin film transistors. For example, electronic devices can be integrated circuits, active-matrix displays, and solar cells comprising a multiplicity of thin-film transistors. In some embodiments, the multiplicity of the thin-film transistors is on a non-participating support that is optionally flexible. The composites of the present invention also can be used to prepare an integrated circuit comprising a plurality of thin-film transistors.

(92) The following Examples are provided to illustrate the practice of this invention and are not meant to be limiting in any manner.

(93) The bi-metallic alkoxides used in the following examples were prepared by following the general method reported by Nagao et al in Polymer Int. 60, 1180 (2011). Specific examples are described below.

Bi-Metallic Synthesis 1: Synthesis of Barium Titanium (methoxyisopropanol)6(BaTi(MIP)6)

(94) Barium metal (5 g) was added to 2-methoxy isopropanol (30 ml) and dissolved by heating under nitrogen for 2 hours. After cooling, titanium isopropoxide (10.36 g) was slowly added and reaction mixture was refluxed under nitrogen atmosphere for 4-8 hours. The resulting solution of BaTi(MIP).sub.6 in 2-methoxy isopropanol had 12.5 weight % of barium was used as such to prepare organic polymeric bi-metallic alkoxide composites of this invention.

Bi-Metallic Synthesis 2: Synthesis of Barium Titanium (triethylene glycol ethyl ether)6(BaTi(TGEE)6)

(95) Barium metal (5.5 g) was added to a solution of titanium isopropoxide (11.4 g) in triethylene glycol ethyl ether (52 ml) and dissolved by heating under nitrogen for 24 hours. After cooling, a dark yellow solution of BaTi(TGEE).sub.6 having 8.67 weight % of barium in triethylene glycol ethyl ether was obtained, which was then used as such to prepare organic polymeric bi-metallic alkoxide composites of this invention.

Bi-Metallic Synthesis 3: Synthesis of Strontium Titanium (methoxyisopropanol)6(SrTi(MIP)6)

(96) Strontium (2.93 g) was added to 2-methoxy isopropanol (30 ml) under an argon atmosphere and heated to reflux. After approximately 4 hours, a clear yellow solution was obtained. Titanium isopropoxide (9.5 g) was added to the reaction mixture using a cannula and the reaction mixture refluxed for 3 hours. After cooling, a pale yellow solution of SrTi(MIP).sub.6, which had 7.47 weight % of strontium in 2-methoxy isopropanol was obtained, which was then used as such to prepare organic polymeric bi-metallic composites of this invention.

Bi-Metallic Synthesis 4: Synthesis of Barium Titanium (diethylene glycol monoethyl ether)6(BaTi(CARB)6)

(97) Barium (2.93 g) was added to diethylene glycol monoethyl ether (30 ml) under argon atmosphere and heated to reflux. After approximately 4 hours, a clear yellow solution was obtained. Titanium isopropoxide (9.5 g) was added to the reaction mixture and the reaction mixture refluxed for 3 hours. After cooling, a pale yellow solution of BaTi(CARB).sub.6 was obtained, which had 7.47 weight % of barium in diethylene glycol monoethyl ether, and was then used to prepare organic polymeric hi-metallic composites of this invention.

Polymer Synthesis 1: Polymerization of Methyl Methacrylate (91%), Octadecyl Methacrylate (6%), and 2-Hydroxyethyl Methacrylate (3%)

(98) A mixture of methyl methacrylate (20.00 g, 199.8 mmol), octadecyl methacrylate (1.38 g, 4.1 mmol), 2-hydroxyethyl methacrylate (0.70 g, 5.3 mmol), 2,2″-azobis(2-methylbutyronitrile) (0.10 g, 0.53 mmol), and chlorobenzene (30 ml) was deaerated with argon for 5 minutes, and then heated under argon in a 70° C. oil bath for 18 hours. The reaction mixture was cooled to room temperature, and the resulting organic polymer was precipitated into excess methanol. The resulting white powder was collected, washed with methanol, and air-dried. The product was re-dissolved in dichloromethane and again precipitated into excess methanol, collected, washed with methanol, and dried in a vacuum oven at 60° C. for 24 hours. The product was obtained as a white powder, 17.5 g (79%). Analysis by size exclusion chromatography (SEC) indicated a weight average molar mass of 153,000 (polystyrene standards). The glass transition temperature was determined to be 112° C. by differential scanning calorimetry (DSC).

Polymer Synthesis 2: Polymerization of Methyl Methacrylate (93%), Octyl Methacrylate (4%), and 2-Hydroxyethyl Methacrylate (3%)

(99) The synthetic procedure of Polymer Synthesis 1 was followed using methyl methacrylate (20.00 g, 199.8 mmol), octyl methacrylate (0.872 g, 4.40 mmol), 2-hydroxyethyl methacrylate (0.65 g, 4.99 mmol), 2,2′-azobis(2-methylbutyronitrile) (0.10, 0.53 mmol), and chlorobenzene (30 ml). The resulting organic polymer product was obtained as a white powder, 16.4 g (77%). Analysis by size exclusion chromatography (SEC) indicated a weight average molar mass of 186,000 (polystyrene standards). The glass transition temperature was determined to be 118° C. by differential scanning calorimetry (DSC).

Polymer Synthesis 3: Polymerization of Methyl Methacrylate (94%), Pentadecafluorooctyl Methacrylate (3%), and 2-Hydroxyethyl Methacrylate (3%)

(100) The procedure of Polymer Synthesis 1 was followed using methyl methacrylate (21.0 g, 209.8 mmol), pentadecafluorooctyl methacrylate (0.67 g, 1.47 mmol), 2-hydroxyethyl methacrylate (0.67 g, 5.13 mmol), 2,2′-azobis(2-methylbutyronitrile) (0.10 g, 0.53 mmol), and chlorobenzene (30 nil). The organic polymeric product was obtained as a white powder, 17.4 g (78%). Analysis by size exclusion chromatography (SEC) indicated a weight average molar mass of 199,000 (polystyrene standards). The glass transition temperature was determined to be 124° C. by differential scanning calorimetry (DSC).

Polymer Synthesis 4: Copolymerization of Methyl Methacrylate (98%) with 2-Vinyl Pyridine (2%)

(101) The procedure of Polymer Synthesis 1 was followed using methyl methacrylate (20.0 g, 199.8 mmol), 2-vinyl pyridine (0.44 g, 4.19 mmol), 2,2′-azobis(isobutyronitrile) (0.335 g, 2.04 mmol), and dimethyl formamide (75 ml). The organic polymeric product was obtained as a white powder, 15.3 g (75%). Analysis by size exclusion chromatography (SEC) indicated a weight average molar mass of 40,400 (polystyrene standards). The glass transition temperature was determined to be 120° C. by differential scanning calorimetry (DSC).

Invention Example 1: Preparation of Poly(methyl methacrylate)(PMMA)-BaTi(MIP)6 Composite

(102) To a 10 ml solution of PMMA (20 weight %) in anisole, 2.5 ml solution of BaTi(MIP).sub.6 prepared in Bi-Metallic Synthesis 1 was added to obtain a PMMA-BaTi(MIP).sub.6 composite that contained 8.5 weight % of barium. The resulting homogeneous organic solvent solution was diluted by addition of 10 ml of anisole followed by addition of 2.3 ml of 2-methoxy isopropanol and 1.5 ml of carbitol. The solution was mixed by stirring for 12 hours to prepare the desired organic polymeric bi-metallic alkoxide composite.

Invention Example 2: Preparation of Poly(methyl methacrylate)(PMMA)-BaTi(TGEE)6 Composite

(103) To an 18 ml solution of PMMA (20 weight %) in anisole, a 3.5 ml solution of BaTi(TGEE).sub.6 prepared in Bi-metallic Synthesis 2 was added to obtain a PMMA-BaTi(TGEE).sub.6 composite that contained 7.0 weight % of barium. The homogeneous organic solvent solution was stirred for 2 hours then diluted by addition of 19 ml anisole followed by 3 ml of carbitol. The solution was mixed by stirring for additional 2 hours to provide the desired organic polymeric bi-metallic alkoxide composite.

Invention Example 3: Preparation of Poly[methyl methacrylate-co-(octyl methacrylate-co-(2-hydroxyethyl methacrylate)]-BaTi(MIP)6 Composite

(104) To a 10 ml solution of the polymer prepared in Polymer Synthesis 2 (20 weight %) in anisole, 5.5 ml of anisole, 3.4 ml of 2-methoxy isopropanol, and 0.4 ml of acetoxy acetone were added. To this solution, 3.0 ml of the solution of BaTi(MIP).sub.6 prepared in Bi-metallic Synthesis 1 was added to obtain a polymer-BaTi(MIP).sub.6 composite that contained 13 weight % of barium. The homogeneous organic solvent solution was further diluted with 12.3 ml of a 1:1 volume % solution of anisole/2-methoxy isopropanol. The solution was mixed by stirring for 12 hours to provide the desired organic polymeric hi-metallic alkoxide composite.

Invention Example 4: Preparation of Poly(methyl methacrylate-2-vinylpyridine)(PMMA-2VP)-BaTi(TGEE)6 Composite

(105) To a 5.0 ml solution of PMMA-2VP copolymer (15 weight %) in 1-methoxy-2-propanol (MIP), a 2.0 ml solution of BaTi(TGEE).sub.6 prepared in Bi-metallic Synthesis 2 was added to obtain a PMMA-2VP-BaTi(TGEE).sub.6 composite that contained 6.0 weight % of barium. The homogeneous organic solvent solution was stirred for 3 hours then diluted by addition of 1.0 ml of MIP. The solution was mixed by stirring for additional 2 hours to provide the desired organic polymeric bi-metallic alkoxide composite in a homogeneous organic solvent solution.

Invention Example 5: Coating of PMMA-BaTi(MIP)6 Composite

(106) The organic polymeric bi-metallic alkoxide composite in a homogeneous organic solvent solution prepared in Invention Example 1 was filtered through a Whatman 0.45 μm glass microfiber filter into a clean glass vial or container. A filtered homogeneous organic solvent solution of the organic polymeric bi-metallic alkoxide composite was spun cast onto samples of a heavily doped silicon wafer substrate for 10 seconds at 2000 rpm and the coating speed was increased over 30 seconds to 4,000 rpm and then spun at this speed for 40 seconds. Each coated doped silicon wafer was then placed onto a hot plate and gradually heated from 50° C. to 120° C. over a period of 10 minutes. The temperature was then increased to 150° C. and was held there for 10 minutes. Each coated sample was gradually cooled to room temperature over a period of 20 minutes. The dry thickness of each organic polymeric bi-metallic alkoxide composite layer was in the range of from 400 nm to 700 nm.

Invention Example 6: Coating of PMMA-BaTi(TGEE)6 Composite

(107) The organic polymeric bi-metallic alkoxide composition prepared as a homogeneous organic solvent solution in Invention Example 2 was filtered through a Whatman 0.45 μm glass microfiber filter into a clean glass vial or container. A filtered homogeneous organic solvent solution of the organic polymeric bi-metallic alkoxide composite was spun cast onto samples of a heavily doped silicon wafer substrate for 10 seconds at 2000 rpm and the coating speed was increased over 30 seconds to 4,000 rpm and spun at this speed for 40 seconds. Each coated doped silicon wafer was then placed on a hot plate and gradually heated from 50° C. to 120° C. over a period of 10 minutes. Finally, the temperature was increased to 150° C. and was held for 10 minutes. Each sample was gradually cooled to room temperature over a period of 20 minutes. The dry thickness of each organic polymeric bi-metallic alkoxide composite layer was in the range of from 400 nm to 700 nm.

(108) Capacitance of each organic polymeric bi-metallic alkoxide composite film (dielectric layer) was measured with an impedance analyzer (Hewlett Packard 4192A) at a frequency of 10 kHz. Each substrate was a heavily doped Si wafer. Silver layers with an area of 5.21×10.sup.−7 m.sup.2 as upper electrodes were patterned on the surface of each composite were deposited in vacuum through a shadow mask. The dielectric constant of the composite film was estimated from the capacitance of the film, area of the silver-electrode, and film thickness.

Invention Example 7: Dielectric Constant Evaluations

(109) PMMA-BaTi(MIP).sub.6 organic polymeric bi-metallic alkoxide composites with varying amounts of BaTi(MIP).sub.6 were prepared as homogeneous organic solvent solution as described in Invention Example 1 noted above. The organic polymeric bi-metallic alkoxide composite homogeneous solutions were filtered through a Whatman 0.45 μm glass and then spun cast onto sample of a heavily doped silicon wafer substrate for 10 seconds at 2000 rpm and the coating speed was increased over 30 seconds to 4,000 rpm and spun at this speed for 40 seconds. Each coated doped silicon wafer was then placed on a hot plate and gradually heated from 50° C. to 120° C. over a period of 10 minutes. Finally, the temperature was increased to 150° C. and was held for 10 minutes. Each coated sample was gradually cooled to room temperature over a period of 20 minutes. The dry thickness of each organic polymeric bi-metallic alkoxide composite gate dielectric layer was in the range of from 0.5 μm to 1.5 μm. Silver contacts were deposited through a shadow mask on top of PMMA-BaTi(MIP).sub.6 composites and the capacitance measured for each sample. The dielectric constant of each composite gate dielectric layer was estimated from the capacitance of the film, area of the silver-electrode, and dry composite thickness. The results are shown below in TABLE I.

(110) TABLE-US-00001 TABLE I Weight % Barium Added as Dielectric Constant @ 10 kHz of BaTi(MIP).sub.6 in PMMA PMMA-BaTi(MIP).sub.6 Composite 0 3.1 12.6 3.55 19 3.7 22 3.84 42 4.76 88 10.6
It is clear from the data presented in TABLE I that the electrical properties of PMMA are improved upon addition of BaTi(MIP).sub.6 in the resulting organic polymeric bi-metallic alkoxide composite of this invention.

Invention Example 8: Preparation of OFET Devices

(111) In order to test the electrical characteristics of the various organic polymeric bi-metallic alkoxide composites of this invention, field-effect transistors were typically made using the top-contact geometry as shown in FIG. 1b. A heavily doped silicon wafer was used as a substrate and it also served as the gate of the transistor.

(112) Each of several organic polymeric bi-metallic alkoxide composites of the present invention was coated in homogeneous organic solvent solution onto Si wafers as described in Invention Examples 2 and 3 and dried. A 0.3 weight % solution of an organic semiconductor, NDI-TPCHEX (shown below and as disclosed in U.S. Pat. No. 7,804,087 of Shukla et al. that is incorporated herein by reference) in a mixture of solvents 1,2,4-trimethylbenzene and N,N′-dimethylaniline (15 volume %) was spin coated onto the inventive composite dielectric layer at 1000 rpm and dried at 70° C. for 15 minutes. Gold or silver contacts having a thickness of 50 nm were then deposited through a shadow mask. The channel width was held at 1000 μm while the channel lengths were varied between 50 μm and 150 μm.

(113) ##STR00003##

(114) Electrical characterization of the resulting OFET devices was performed with a Hewlett Packard HP 4145B® parameter analyzer. All device measurements were performed in air.

(115) For each analysis performed, between 4 and 12 individual devices were tested using each prepared organic semiconducting layer, and the results were averaged. For each device, the drain current (I.sub.d) was measured as a function of source-drain voltage (V.sub.d) for various values of gate voltage (V.sub.g). For most devices, V.sub.d was swept from 0 V to 80 V for each of the gate voltages measured, typically 0 V, 20 V, 40 V, 60 V, and 80 V. In these measurements, the gate current (Ig) was also recorded in order to detect any leakage current through the device. Furthermore, for each device the drain current was measured as a function of gate voltage for various values of source-drain voltage. For most devices, Vg was swept from 0 V to 80 V for each of the drain voltages measured, typically 40 V, 60 V, and 80 V.

(116) Parameters extracted from the data include field-effect mobility (μ), threshold voltage (V.sub.th), sub-threshold slope (S), and the ratio of I.sub.on/I.sub.off for the measured drain current. The field-effect mobility was extracted in the saturation region, where V.sub.d>V.sub.g−V.sub.th. In this region, the drain current is given by the equation (see Sze in Semiconductor Devices—Physics and Technology, John Wiley & Sons, 1981):

(117) $I_d=\frac{W}{2L}\mu {C_{\mathrm{ox}}\left(V_g-V_{\mathrm{th}}\right)}^2$
wherein W and L are the channel width and length, respectively, and C.sub.ox is the capacitance of the oxide layer, which is a function of oxide thickness and dielectric constant of the material. Given this equation, the saturation field-effect mobility was extracted from a straight-line fit to the linear portion of the √I.sub.d versus Vg curve. The threshold voltage, V.sub.th, is the x-intercept of this straight-line fit. Mobilities can also be extracted from the linear region, where V.sub.d≦V.sub.g−V.sub.th. Here the drain current is given by the equation (see Sze, noted above):

(118) $I_d=\frac{W}{L}\mu C_{\mathrm{ox}}\left[V_d\left(V_g-V_{\mathrm{th}}\right)-\frac{V_d^2}{2}\right]$

(119) For these experiments, mobilities in the linear regime were not extracted, since this parameter is very much affected by any injection problems at the contacts. In general, non-linearities in the curves of I.sub.d versus V.sub.d at low V.sub.d indicate that the performance of the device is limited by injection of charge by the contacts. In order to obtain results that are largely independent of contact imperfections of a given device, the saturation mobility rather than the linear mobility was extracted as the characteristic parameter of device performance.

(120) The log of the drain current as a function of gate voltage was plotted. Parameters extracted from the log I.sub.d plot include the I.sub.on/I.sub.off ratio and the sub-threshold slope (S). The I.sub.on/I.sub.off ratio is simply the ratio of the maximum to minimum drain current, and S is the inverse of the slope of the I.sub.d curve in the region over which the drain current is increasing (that is, the device is turning on).

(121) The following examples demonstrate that OFET devices comprising inventive organic polymeric bi-metallic alkoxide composite as dielectric materials exhibited high mobilities and on/off ratios. The mobilities calculated in the saturation region were between 0.9 and 2 cm.sup.2/V.Math.sec, with on/off ratios of 10.sup.6 to 10.sup.7. In addition to the stable performance, the devices also showed excellent reproducibility.

Invention Example 9

(122) This example demonstrates use of the organic polymeric bi-metallic alkoxide composite of this invention comprising PMMA-BaTi(MIP).sub.6 as a gate dielectric layer in an OFET device.

(123) A 0.3 weight % solution of NDI-TPCHEX in a mixture of solvents 1,2,4-trimethylbenzene-N,N′-dimethylaniline (15 volume %) was spin coated on a PMMA-BaTi(MIP)6 composite dielectric layer as described in Invention Example 3. Silver contacts having a thickness of 50 nm were deposited through a shadow mask. The channel width was held at 1000 μm while the channel lengths were varied between 50 μm and 150 μm. The results are described below in TABLE II.

(124) TABLE-US-00002 TABLE II Dielectric Dielectric Constant Mobility V.sub.th Layer of Composite Layer (cm.sup.2/Vs) (V) I.sub.on/I.sub.off PMMA-BaTi(MIP).sub.6 3.5 0.31 16.4 3 × 10.sup.3 (8.5 wt. % Ba)

Invention Example 10

(125) This example demonstrates the use of another inventive organic polymeric bi-metallic alkoxide composite comprising PMMA-BaTi(CARB).sub.6 as a dielectric layer in an OFET device.

(126) To a 4 ml solution of PMMA (10%) in carbitol, 1.52 ml of a solution of BaTi(CARB).sub.6 (prepared in Bi-Metallic Synthesis 4) was added to obtain a composite homogeneous organic solvent solution that had 19 weight % of barium. This solution was diluted with 0.4 ml of anisole, stirred, and filtered before it was spin casted on a heavily doped Si wafer substrate. The dry thickness of the PMMA-BaTi(CARB).sub.6 dielectric layer was 412 nm.

(127) A 0.3 weight % solution of NDI-TPCHEX in a mixture of solvents 1,2,4-trimethylbenzene and N,N′-dimethylaniline (15 volume %) was jetted using MicroFab's Jetlab® II Table Top Printing Platform onto the PMMA-BaTi(CARB).sub.6 composite dielectric layer. Silver contacts having a thickness of 50 nm were deposited through a shadow mask. The channel width was held at 1000 hem while the channel lengths were varied between 50 μm and 150 μm. The output and transfer characteristics of the device are shown in FIG. 2a and FIG. 2b, respectively. The results are shown below in TABLE III.

(128) TABLE-US-00003 TABLE III Dielectric Dielectric Constant Mobility V.sub.th Layer of Composite Layer (cm.sup.2/Vs) (V) I.sub.on/I.sub.off PMMA- 3.7 1.2 30 1 × 10.sup.3 BaTi(CARB).sub.6 (19 weight % Ba)

(129) These results show that the composites of this invention provide suitable dielectric layers and the resulting devices have significantly improved ambient electrical performance.

(130) The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.