High-Current OTFT Device with a Vertical Design Structure and Donor-Acceptor Based Organic Semiconductor Materials

Abstract

This document describes an electronic device comprising a heterocyclic organic compound. More specifically, this document describes an organic electronic system combined with a donor-acceptor organic semiconductor, a method for manufacturing the device, and its uses.

Description

Background Technical Field

[0002] This disclosure describes electronic devices that include heterocyclic organic compounds. More specifically, this disclosure describes organic electronic systems that incorporate donor-acceptor organic semiconductors, methods for fabricating such devices, and their uses. Background Art

[0004] The great interest in organic electronic devices has led to extensive research on organic semiconductor devices such as organic light-emitting diodes, organic field-effect transistors (OFETs), organic chemical sensors, and polymer solar cells. Organic semiconductor devices can open up entirely new paradigms for manufacturing processes and applications. If organic semiconductors can be deposited from solution, it is conceivable that their cost could be significantly reduced compared to their inorganic counterparts (such as silicon), as this would enable rapid, large-area manufacturing routes such as spin coating, inkjet printing, gravure printing, transfer printing, and other printing processes, and could be applied to smart cards, security labels, low-cost sensors, and switching elements in flat panel display substrates. Newly developed disposable products, such as organic radio frequency identification (RFID) devices, can be attached to the packaging of items. Flexible organic electronic devices can be rollable and applied to non-planar surfaces.

[0005] One of the key components of a flexible electronic device is a field-effect transistor (FET), which is a horizontal device having source and drain electrodes in the same plane. In the "off" state, there is no carrier channel accumulation between the source and drain electrodes in the FET, while in the "on" state, current flows between the source and drain electrodes and is controlled by the gate voltage applied to the gate electrode. Such devices typically operate in the accumulation mode, where the gate bias induces a carrier channel at the insulator-semiconductor interface.

[0006] In the case of organic field-effect transistors (OFETs), two parameters used to characterize their usefulness are the current ratio between the on-state and the off-state (on / off ratio) and the field-effect mobility. So far, OFETs have shown low current output because of inherently low carrier mobility due to weak wavefunction overlap between molecules and film disorder. The low carrier mobility also greatly limits the operating frequency to below 100 kHz. Moreover, OFETs tend to be unstable because the conduction channel is confined to a few monolayers at the semiconductor-dielectric interface, where adsorbed oxygen, moisture, and other chemicals can have a great impact on transistor characteristics. To obtain the desired current output, it is often necessary to operate OFETs at voltages exceeding 20 volts. In the past decade, great efforts have been made to improve the performance of field-effect transistors by increasing mobility, reducing the gate dielectric thickness, and reducing the channel length. However, there is still a need for OFET devices that provide high relative current density at low voltages. Summary of the Invention

[0007] Disclosed herein are polymer compositions comprising heterocyclic organic compounds such as fused thiophene compounds, methods for their preparation, and their uses. The compositions and methods described herein have many advantages over compositions and methods of the prior art. For example, the substituted fused thiophene compositions described herein can be more soluble and more suitable for processing than similar unsubstituted thiophene compositions. Polymers and oligomers comprising the fused thiophene moieties described herein can be processed using conventional spin-coating operations. Additionally, the compositions described herein can be prepared under conditions substantially free of β-H, thus significantly improving the oxidative stability of the compositions.

[0008] In some embodiments, a device includes: a substrate; a collector layer; an emitter layer that is positively biased relative to the collector; a metal grid including a metal layer having openings, the metal grid being located between the collector and the emitter but not in direct contact with the collector and the emitter, wherein the length of each opening along its longest dimension is from about 50 nm to about 800 nm; and a semiconductor layer located between the collector and the emitter, the semiconductor layer comprising an organic semiconductor polymer having the following structure:

[0009]

[0010] Wherein, each D is an independently selected conjugated electron-donating aromatic or heteroaromatic group having 5 to 50 backbone atoms, and each D group is optionally substituted with one or more electron-donating substituents or electron-withdrawing substituents, provided that even when substituted, the electronic property of each D remains electron-donating; each A is an independently selected conjugated electron-accepting aromatic or heteroaromatic group having 5 to 50 backbone atoms or a vinylene group substituted with one or two electron-withdrawing substituents, each A is optionally substituted with one or more electron-donating substituents or electron-withdrawing substituents, provided that even when substituted, the electronic property of each A is electron-accepting; a and b are each an integer from 1 to 4, and n is an integer from 2 to 10,000.

[0011] In one aspect, which can be combined with any other aspect or embodiment, each D is independently a compound in Table 1.

[0012] In one aspect, which can be combined with any other aspect or embodiment, each A is independently a compound in Table 2.

[0013] In one aspect, which can be combined with any other aspect or embodiment, the organic semiconductor polymer consists of one of the polymers listed in Table 3.

[0014] In one aspect, which can be combined with any other aspect or embodiment, one or more of R1, R2, R3, R4, and R6 are optionally substituted C 15 -C 35 alkyl.

[0015] In one aspect, which can be combined with any other aspect or embodiment, one or more of R1, R2, or R3 can be optionally substituted C 15 -C 35 alkyl.

[0016] In one aspect, which can be combined with any other aspect or embodiment, each of R1 and R2 is independently optionally substituted C 15 -C 35 alkyl.

[0017] In one aspect, which can be combined with any other aspect or embodiment, each of R1 and R2 is independently optionally substituted C 15 -C 35 alkyl having at least one branching point.

[0018] In one aspect, which can be combined with any other aspect or embodiment, each of R1 and R2 is independently optionally substituted C 15 -C 35 alkyl having at least one branching point, wherein the branching point is at least 4 carbons away from the base molecule.

[0019] In one aspect, which can be combined with any other aspect or embodiment, at least one D is:

[0020]

[0021] wherein each X is independently NR6, S, Se or O; and each R1 is independently hydrogen, C1-C 40 alkyl, C1-C 40 alkenyl, C1-C 40 alkynyl, C1-C 40 alkoxy, C1-C 40 cycloalkyl, C1-C 40 aryl, C1-C 40 heteroaryl, C1-C 40 heterocycloalkyl, C1-C 40 a conjugated group - any of which may be optionally substituted, or a halogen; and each R6 is independently hydrogen, C1-C 40 alkyl.

[0022] In one aspect, which can be combined with any other aspect or embodiment, at least one A is:

[0023]

[0024] where each x is independently NR5, S, Se or O; each R5 is independently hydrogen, C1-C 40 alkyl.

[0025] In one aspect, which can be combined with any other aspect or embodiment, A is:

[0026]

[0027] and D is:

[0028]

[0029] wherein each X is independently NR6, S, Se or O; and each R1 is independently hydrogen, C1-C 40 alkyl, C1-C 40 alkenyl, C1-C 40 alkynyl, C1-C 40 alkoxy, C1-C 40 cycloalkyl, C1-C 40 aryl, C1-C 40 heteroaryl, C1-C 40 heterocycloalkyl, C1-C 40 a conjugated group - any of which may be optionally substituted, or a halogen; and each R6 is independently hydrogen, C1-C 40 alkyl.

[0030] In one aspect that can be combined with any other aspect or embodiment, each R1 is independently an optionally substituted C having at least one branching point 15 -C 35 alkyl group.

[0031] In one aspect that can be combined with any other aspect or embodiment, the collector comprises a metal, such as aluminum.

[0032] In one aspect that can be combined with any other aspect or embodiment, the emitter comprises a transparent conductive oxide, such as indium tin oxide, or an organic polymer, such as poly(3,4-ethylenedioxythiophene) doped with polystyrenesulfonic acid.

[0033] In one aspect that can be combined with any other aspect or embodiment, the openings in the metal grid are substantially circular openings, and the length of the longest dimension is from 100 nm to 800 nm or from 200 nm to 500 nm.

[0034] In one aspect that can be combined with any other aspect or embodiment, the metal layer of the metal grid comprises aluminum.

[0035] In one aspect that can be combined with any other aspect or embodiment, the organic semiconductor polymer is:

[0036]

[0037]

[0038]

[0039]

[0040] wherein n is from 2 to 10,000.

[0041] In one aspect that can be combined with any other aspect or embodiment, the collector layer is configured to have an output current density of at least 100 mA / cm for an operating voltage below 1.5 V 2 of.

[0042] In some embodiments, a method of fabricating a device includes: providing a substrate having an emitter layer disposed thereon; spin-coating an insulating layer over the emitter layer; modifying the insulating layer by any of the following: disposing a polymer layer on top of the insulating layer or subjecting the insulating layer to an etching process; coating the insulating layer with polymeric nanospheres; coating the polymeric nanospheres with a patterned metal mask layer; removing the polymeric nanospheres after the patterned metal mask layer is disposed to form voids in the insulating layer; coating the patterned metal mask layer with a donor-acceptor organic semiconductor (OSC) layer; and disposing a patterned collector layer on the OSC layer.

[0043] In one aspect, which can be combined with any other aspect or embodiment, the insulating layer is polyvinylpyrrolidone (PVP).

[0044] In one aspect, which can be combined with any other aspect or embodiment, the polymer layer is poly(3-hexylthiophene-2,5-diyl) (P3HT) and the etching process includes reactive ion etching (RIE).

[0045] In one aspect, which can be combined with any other aspect or embodiment, the polymeric nanospheres comprise polystyrene.

[0046] Other features and advantages are given in the following detailed description, some of which will be readily apparent to those skilled in the art or will be recognized by practicing the written description and its claims and the embodiments described in the drawings.

[0047] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary and are intended to provide an overall review or framework for understanding the nature and characteristics of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings, which are incorporated in and constitute a part of this specification, provide further understanding of the present disclosure. The drawings are not necessarily to scale, and the dimensions of various elements may be distorted for clarity. The drawings illustrate one or more embodiments and, together with the description, serve to explain the principles and operations of the various embodiments.

[0049] Figure 1 A device design for an organic polymer-based vertical transistor, as described in an embodiment, is described.

[0050] Figure 2A and 2B show the I-V curves of vertical transistors containing the following polymers, as described in an embodiment, in chlorobenzene:

[0051]

[0052] Among them Figure 2A shows the output characteristics, and Figure 2B shows the on / off current ratio.

[0053] Figure 3A and 3B shows the I-V curve of a vertical transistor containing PTDC8BC8C10DPPTDC17FT4 in tetralin, where Figure 3A shows the output characteristics, and Figure 3B shows the on / off current ratio.

[0054] Figure 4A and 4B shows the I-V curve of a vertical transistor containing PTDC8BC8C10DPPTDC17FT4 in cyclooctane, where Figure 4A shows the output characteristics, and Figure 4B shows the on / off current ratio.

[0055] Figure 5A and 5B shows the I-V curve of a vertical transistor containing PTDC8BC8C10DPPTDC17FT4 in decalin, where Figure 5A shows the output characteristics, and Figure 5B shows the on / off current ratio.

[0056] Figure 6 is a graph showing the lifetime of the characteristics of a vertical transistor containing PTDC8BC8C10DPPTDC17FT4.

[0057] Figure 7 is a graph showing the lifetime of the characteristics of a vertical transistor containing the following substances:

[0058]

[0059] Figure 8 is a scanning electron microscope (SEM) image of a vertical transistor containing PTDC8BC8C10DPPTDC17FT4.

[0060] Figure 9 is a scanning electron microscope (SEM) image of a vertical transistor containing PTDC16DPPTDC17FT4.

[0061] Figure 10 is a graph showing the output current of the characteristics of a vertical transistor without a poly(3-hexylthiophene-2,5-diyl) (P3HT) interlayer disposed above polyvinylpyrrolidone (PVP).

[0062] Figure 11is a graph showing the output current of the vertical transistor characteristics including the following substances:

[0063] Detailed implementation mode

[0064] Before disclosing and describing the materials, articles and / or methods of the present invention, it should be understood that the aspects described below are not limited to specific compounds, synthesis methods or uses, as these can of course vary. It should also be understood that the terms used herein are only for describing specific aspects and are not intended to be restrictive.

[0065] Many terms will be mentioned in this specification and the claims that follow, and these terms shall have the following definitions:

[0066] Throughout the specification, unless the context requires otherwise, the word "comprising" or variations thereof such as "comprises" or "containing" shall be understood to imply the inclusion of the stated integer or step or group of integers or steps, but not the exclusion of any other integer or step or group of integers or steps.

[0067] It should be noted that, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" used in this specification and the appended claims include plural referents. Thus, for example, reference to "a carrier" includes a mixture of two or more such carriers, etc.

[0068] "Optional" or "optionally" means that the subsequent described event or circumstance may or may not occur, and this description includes the case where the event or circumstance occurs and the case where the event or circumstance does not occur.

[0069] If a numerical range including an upper limit value and a lower limit value is listed herein, then unless otherwise indicated in a specific case, this range is intended to include the endpoints of the range and all integers and fractions within this range. The scope of the claims is not limited to the specific values recited when defining the range. Additionally, when a quantity, concentration or other numerical value or parameter is given in the form of a range, one or more preferred ranges or a list of upper preferred values and lower preferred values, this should be understood to explicitly disclose all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value, whether or not these pairings are individually disclosed.

[0070] When the term "about" is used to describe a value or endpoint of a range, it is understood that the present disclosure includes the specific value or endpoint being referenced. When a numerical value or endpoint of a range is not used with "about", the numerical value or endpoint of the range is intended to include two embodiments: one modified with "about" and the other not modified with "about". It should also be understood that each endpoint value of a range is meaningful both in relation to and independent of another endpoint value.

[0071] As used herein, the term "alkyl" may be a branched or unbranched saturated hydrocarbon group having 1 to 40 carbon atoms (or having the number of carbon atoms as defined by the nomenclature C γ -C ζ where γ and ζ are numerical values and γ < ζ), such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, decyl, or tetradecyl, etc. When not specifically limited, the alkyl may be substituted or unsubstituted. The term "unsubstituted alkyl" is defined herein as an alkyl containing only carbon and hydrogen. The term "substituted alkyl" is defined herein as an alkyl in which one or more hydrogen atoms are replaced by a "substituent", and the "substituent" consists of the following: C1-C 20 alkyl, C1-C 20 alkenyl, C1-C 20 alkynyl, C3-C 20 cycloalkyl, halogen, hydroxy, C6-C 20 aryl, C6-C 20 heteroaryl, alkoxy, carboxyl, carboxylic acid, cyano, or heterocyclic group. Unless otherwise restricted by definition, all substituents may optionally be further substituted by 1, 2, or 3 substituents selected from C1-C 20 alkyl, hydroxy, halogen, or CF3.

[0072] The term "alkyl" as defined herein also includes cycloalkyl, and the cycloalkyl may optionally be substituted by the substituents defined above. The term "cycloalkyl" as used herein refers to a non-aromatic carbon-based ring composed of at least 3 carbon atoms (in some embodiments, 3 - 20 carbon atoms). Examples of cycloalkyl include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, etc. The term cycloalkyl also includes heterocycloalkyl, wherein at least one carbon atom of the ring may be substituted by a heteroatom, such as, but not limited to, nitrogen, oxygen, sulfur, or phosphorus.

[0073] As used herein, the term "aryl" can be any carbon-based aromatic group, fused carbon-based aromatic group, including but not limited to benzene, naphthalene, etc. The term "aryl" also includes "heteroaryl", which means an aromatic ring composed of at least three carbon atoms containing at least one heteroatom in the aryl ring. Examples of heteroatoms include but are not limited to nitrogen, oxygen, sulfur, and phosphorus. The aryl can be substituted or unsubstituted. The aryl can be substituted by one or more groups, including but not limited to C1-C 20 alkyl, C1-C 20 alkynyl, C1-C 20 alkenyl, halogen, nitro, amino, or hydroxyl. In some embodiments, the term "aryl" can be limited to substituted or unsubstituted aromatic and heteroaromatic rings having 6 to 40 carbon atoms.

[0074] The term "halogen" or "halo" refers to a fluorine, bromine, chlorine, or iodine group.

[0075] The term "alkenyl" is defined as a branched or unbranched hydrocarbon group having 2 to 40 carbon atoms and having at least one carbon-carbon double bond in its structural formula, which can be optionally substituted in the same manner as alkyl. The term "alkenyl" as defined herein also includes "cycloalkenyl", which can be optionally substituted by substituents as defined above. The term "cycloalkenyl" refers to a carbocyclic group having 3 to 20 carbon atoms, having a single ring or multiple fused rings and having at least one double bond in the ring structure.

[0076] The term "alkynyl" is defined as a branched or unbranched hydrocarbon group having 2 to 40 carbon atoms and having at least one carbon-carbon triple bond in its structural formula, which can be optionally substituted in the same manner as alkyl.

[0077] The term "conjugated group" is defined as a linear, branched, or cyclic group or a combination thereof in which the p-orbitals of the atoms in the group are connected via electron delocalization, and in which the structure can be described as containing alternating single and double or triple bonds, and can also contain lone pairs, radicals, or carbocations. The conjugated ring group can include one or both of aryl and non-aryl, and can include polycyclic groups or heterocyclic groups, such as diketopyrrolopyrrole. Ideally, the conjugated groups are joined in such a way that the conjugation between the respective thiophene moieties attached to them is continued. In some embodiments, the "conjugated group" can be limited to conjugated groups having 3 to 30 carbon atoms.

[0078] As used herein, "PTDC16DPPTDC17FT4" is an abbreviation or a designated name for the following polymer structure:

[0079]

[0080] In the order from right to left: "P" is a polymer containing one "T" or thiophene unit, "DC16DPP" is diketopyrrolopyrrole (DPP) with two C 16 H 33 groups as N,N'-substituents, "T" represents an inserted thiophene, DC17FT4 represents having four fused rings (FT4), and having two C 17 H 35 groups or chains as β-substituents or having two C 17 H 35 groups or chains of fused thiophene.

[0081] "PTDC8BC8C10DPPTDC17FT4" used herein is an abbreviation or a designated name of the following polymer structure:

[0082]

[0083] In the order from right to left: "P" is a polymer containing one "T" or thiophene unit, "DC8BC8C10DPP" is diketopyrrolopyrrole (DPP) with two C8H 15 (C8H 17 C 10 H 21 ) groups as N,N'-substituents, "T" represents an inserted thiophene, "DC17FT4" represents having four fused rings ("FT4"), and having two C 17 H 35 groups or chains as β-substituents or having two C 17 H 35 groups or chains of fused thiophene.

[0084] "P2TDC8BC8C10DPP2TDC9BC8C10FT4" used herein is an abbreviation or a designated name of the following polymer structure:

[0085]

[0086] In the order from right to left: "P" is a polymer containing two "T" or thiophene units, "DC8BC8C10DPP" is diketopyrrolopyrrole (DPP) with two C8H 15 (C8H 17 C 10 H 21 ) groups as N,N'-substituents, "2T" represents two inserted thiophenes, "DC9BC8C10" represents having four fused rings ("FT4"), and having two C9H 17 (C8H 17C 10 H 21 ) group or chain as a β-substituent or having two C9H at the β-position of the FT4 moiety 17 (C8H 17 C 10 H 21 ) group or chain fused thiophene.

[0087] Devices comprising donor-acceptor polymeric compounds and methods for their manufacture are disclosed. It is to be understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed, while specific individual and joint combinations and permutations of each of these compounds may not be explicitly disclosed specifically, all combinations and permutations are specifically contemplated and included herein. Thus, if a class of molecules A, B, and C is disclosed and a class of molecules D, E, and F and an example of a molecular combination A-D are disclosed, then each molecular combination can be conceived of individually and jointly even if each molecular combination is not stated separately. Thus, in this example, each of the combinations A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F is specifically contemplated and should be considered to be disclosed from the content of A, B, and C; D, E, and F; and the example combination A-D. Similarly, any subset or combination of these subsets is also specifically contemplated and disclosed. Thus, for example, the subgroups A-E, B-F, and C-E are specifically contemplated and should be considered to be disclosed from the content of A, B, and C; D, E, and F; and the exemplary combination A-D. This concept applies to all aspects of the present disclosure, including but not limited to, the steps in the methods of making and using the disclosed compositions. Thus, if there are multiple additional steps that can be performed, it should be understood that each of these additional steps can be performed by any particular embodiment or combination of embodiments of the disclosed methods, and each such combination can be specifically contemplated and should be considered to be disclosed.

[0088] Compound

[0089] Conjugated polymeric compounds that can be used in vertical transistors are described herein, as well as electronic devices comprising such transistors. The compounds are readily synthesizable and solution processable. Thus, transistors comprising these compounds can be fabricated using solution deposition techniques, for example, solution deposition techniques such as inkjet printing, dip coating, and / or spin coating, and screen printing.

[0090] The compounds described herein contain alternating blocks of aromatic, heteroaromatic, or vinylidene electron-withdrawing groups ("A" groups, also referred to as electron-withdrawing or electron-accepting groups, which are referred to as acceptor blocks) and aromatic or heteroaromatic electron-rich donating groups ("D" groups, also referred to as electron-donating groups, which are referred to as donor blocks) along their compound skeletons. The acceptor blocks facilitate electron transport, while the donor blocks facilitate hole transport.

[0091] The repeating unit of the polymeric compound includes an acceptor block containing one or more acceptor groups (A), with donor blocks containing one or more donor groups (D) on each side of the acceptor group, thus providing the following general formula I:

[0092]

[0093] Wherein a and b are integers from 1 to 4, and n is an integer from 2 to 10,000. Each D is an independently selected conjugated electron-donating aromatic or heteroaromatic group having 5 to 50 backbone atoms. Each D group is optionally substituted with one or more electron-donating substituents or electron-withdrawing substituents, provided that even when substituted, the electronic property of each D is electron-donating; each A is an independently selected conjugated electron-accepting aromatic or heteroaromatic group having 5 to 50 backbone atoms or a vinylidene group substituted with one or two electron-withdrawing substituents. Each A is optionally substituted with one or more electron-donating substituents or electron-withdrawing substituents, provided that even when substituted, the electronic property of each A is electron-accepting.

[0094] In some embodiments, each D is independently one or more of the following:

[0095] Table 1

[0096]

[0097]

[0098]

[0099] Wherein each x is independently NR6, S, Se, or O; each R1 is independently hydrogen, C1-C 40 alkyl, C1-C 40 alkenyl, C1-C 40 alkynyl, C1-C 40 alkoxy, C1-C 40 cycloalkyl, C1-C 40 aryl, C1-C 40 heteroaryl, C1-C 40 heterocycloalkyl, C1-C 40Conjugated group - any of which may be optionally substituted, or halogen; each R5 is independently hydrogen, C1-C 40 alkyl, C1-C 40 alkenyl, C1-C 40 alkoxy, C1-C 40 cycloalkyl, C1-C 40 aryl, C1-C 40 heteroaryl or C1-C 40 Conjugated group - any of which may be optionally substituted; and each R6 is independently hydrogen, C1-C 40 alkyl.

[0100] In some embodiments, each A is independently one or more of the following:

[0101] Table 2

[0102]

[0103]

[0104] wherein each x is independently NR5, S, Se or O; each R2 is independently hydrogen, C1-C 40 alkyl, C1-C 40 alkenyl, C1-C 40 alkynyl, C1-C 40 alkoxy, C1-C 40 cycloalkyl, C1-C 40 aryl, C1-C 40 heteroaryl, C1-C 40 heterocycloalkyl, C1-C 40 Conjugated group - any of which may be optionally substituted, or halogen; each R3 is independently hydrogen, C1-C 40 alkyl, C1-C 40 alkenyl, C1-C 40 alkoxy, C1-C 40 cycloalkyl, C1-C 40 aryl, C1-C 40 heteroaryl or C1-C 40 Conjugated group - any of which may be optionally substituted; each R5 is independently hydrogen, C1-C 40 alkyl; each R4 is independently hydrogen, C1-C 40 alkyl, cyano, ester or carboxylic acid; and each R6 is independently hydrogen, C1-C 40 alkyl, cyano, ester or carboxylic acid.

[0105] The side chain, R1, R2, R3, R4, and R6 can play important roles in the solubility, stability, or film-forming properties of the polymer (including structure, viscosity, texture, processability, etc.). In some embodiments, one or more of R1, R2, R3, R4, and R6 are optionally substituted C 15 -C 35 alkyl. In some embodiments, one or more of R1, R2, R3, or R4 are optionally substituted C 15 -C 35 alkyl having at least one branching point. In particular, one or more of R1, R2, or R3 can be optionally substituted C 15 -C 35 alkyl. In some embodiments, each R1 or R2 is independently optionally substituted C 15 -C 35 alkyl. In some embodiments, each R1 or R2 is independently optionally substituted C 15 -C 35 alkyl having at least one branching point. In some embodiments, each R1 or R2 is independently optionally substituted C 15 -C 35 alkyl having at least one branching point, wherein the branching point is at least 4 carbons away from the base molecule.

[0106] Although it was expected that large branched alkyl side chains would inhibit the stacking or structuring of the polymer, these potential problems were not observed. Instead, it is hypothesized that when the branched alkyl chain is at least four carbons away from the main polymer backbone, the polymers as described in the embodiments provide excellent properties, thus not creating steric effects or creating very low steric effects that would interfere with the π-stacking of the polymer backbone, and the presence of four large non-polar branched side chains in one polymer repeat unit significantly increases the solubility of these polymers, thus allowing for an increase in the molecular weight of the polymer, which can achieve enhanced mobility compared to existing high-performance polymers. In some embodiments, the molecular weight of the polymer can be about 30 - 80 kDa or 40 - 60 kDa.

[0107] An exemplary donor-acceptor structure as described in the embodiments is shown below, where n is an integer from 2 to 10,000:

[0108] Table 3

[0109]

[0110]

[0111]

[0112]

[0113] Device

[0114] An organic vertical transistor is similar to a vacuum tube triode in solid state form. The vacuum tube triode consists of a cathode for emitting electrons by heating, an anode for electron collection, and a grid for current modulation. The anode and the cathode are always positively biased. In a vacuum tube triode, both the grid and the anode can control the potential in the device, but the grid is more effective in controlling the potential gradient near the cathode. The on and off states of the vacuum tube triode depend on whether the emitted electrons encounter a large energy barrier between the cathode and the anode. When the grid is at a large negative bias, the electrons experience a negative potential gradient after being emitted from the cathode, and as a result, very few electrons can be collected by the anode. However, if the grid is slightly negatively biased or positively biased, the electrons can find a path through the minimum potential in the grid.

[0115] Figure 1 An exemplary organic vertical transistor design with functions similar to a vacuum tube triode is shown. The device is on an inert substrate, such as on glass or a polymer. Ultra-thin (e.g., less than 150 μm or 100 μm) and flexible glass can be used to allow the device to be placed in various positions. Electrons are injected from the emitter, pass through the openings in the metal grid and finally reach the collector. The collector can be a metal, alloy or metal oxide that can operate properly at the voltage and current of the device. Exemplary materials that can be used include Al, Au, Ag, Pt, Cu, and stainless steel. The thickness of the emitter can be 10 nm or greater, e.g., 10 nm to 500 nm, where the thickness is determined by the material, signal, current, and voltage.

[0116] Similarly, the metal grid can be made of a metal that can operate properly at the voltage and current of the device, such as Al, Au, Ag, Pt, Cu, and stainless steel. In some embodiments, the metal grid and the collector are made of the same material. The thickness of the metal grid can be 10 nm or greater, e.g., 10 nm to 200 nm, where the thickness is determined by the material, the channel size through the grid, current, and voltage.

[0117] The emitter can be a metal, metal oxide, or polymer with a thickness of 10 nm to 500 nm, where the thickness is also determined by the material, signal, current, and voltage. Exemplary materials for the emitter are poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), transparent conductive oxides such as indium tin oxide (ITO), and metals such as Cu, Pt, Au, Ag, etc.

[0118] The potential between the emitter and the collector can be controlled by the voltages of the grid and the collector. When the voltage between the grid and the collector forms a high potential barrier between the emitter and the opening, few carriers can pass through the opening to reach the collector. On the other hand, if there is no potential barrier, the carriers can pass through the opening and reach the collector. The magnitude of the collector current is determined by the space charge limited current given by the potential difference between the emitter and the center of the opening. The collector current is modulated by the grid bias, which controls the effective potential of the fixed emitter and collector potentials at the opening.

[0119] For a vertical transistor, according to the following space charge limited current relationship, the output current density is proportional to the vertical mobility, and the space charge limited current relationship is:

[0120] J SCLC =(9 / 8)ε0ε r μ(V 2 / L 3 ).

[0121] The advantage of using donor-acceptor organic semiconductor materials in such a system is that the materials produce high current density and high mobility, and are highly stable (long storage life). Since they can be fabricated without an encapsulation layer, it allows for simplified devices. Additionally, many of these polymers can be effectively prepared using non-toxic processes, with high purity and high molecular weight (up to 120,000 Da), and can be effectively prepared using solvent-based printing processes for producing uniform thin semiconducting layers.

[0122] As shown herein, when combined with such a unique vertical transistor structure, using high-performance donor-acceptor type organic semiconductors offers several significant advantages. The operating voltage of the vertical transistor can be 2 V or lower, 1.5 V or lower, 1.25 V or lower, or 1 V or lower. The current density of the donor-acceptor based vertical transistor can be 80 mA / cm 2 , 90 mA / cm 2 , 100 mA / cm 2 , 110 mA / cm 2 , 120 mA / cm 2 , 130 mA / cm 2 , 140 mA / cm 2 , 150 mA / cm 2 or 160 mA / cm 2 . Since no encapsulation layer is required, the device fabrication process is simpler and can be scaled for large areas that require as few as two mask levels and allow the use of various hydrocarbon solvents.

[0123] In particular, vertical transistors provide a unique design that allows for high amplification and improved sensitivity of organic semiconductors in sensor applications. In a vertical transistor design, the current of the device passes through the bulk material and is not hindered by surface effects as in FETs, such as reduced normal field mobility or proximity doping effects. Additionally, the vertical design encapsulates the OSC, thereby enhancing the stability of the device and the OSC material. Finally, vertical OSC transistors occupy a significantly smaller footprint than conventional devices (e.g., FETs). Planar FETs require a footprint size of ~150X to 200X to achieve the same current output.

[0124] Method

[0125] Another aspect includes methods of making the compounds and devices described herein. Based on the cited literature, the disclosed monomers, oligomers, and polymers can be synthesized without undue experimentation. For example, exemplary compounds as described in the embodiments can be found in U.S. Pat. Nos. 7,705,108, 7,838,623, 8,389,669, 7,893,191, and 8,624,232, which are hereby incorporated by reference in their entireties. Alternative designs are also contemplated and can be formed using the methods described herein, methods known in the art, or methods shown in 88 Appl. Phys. Lett. 223510 (2006) and 9 Org. Electron. 310 (2008), both of which are incorporated by reference.

[0126] Devices as described in the embodiments can be constructed using methods known in the art. The substrate is typically an inert non-conductive surface that can withstand the necessary conditions for device fabrication, including high temperatures and organic solvents. Glass, glass ceramics, ceramics, and some plastics can be used. The substrate thickness is based on the needs of the device, such as stability or strength. In some embodiments, the substrate is glass. In some embodiments, the substrate is ultra-thin and / or flexible glass, such as glass. Generally, if the device is to be used in a display or emission-based application, the substrate can preferably be transparent. Subsequently, a conductive layer or emitter layer is placed on the substrate. For example, a transparent conductive oxide can be coated onto the substrate by known methods (e.g., sputter coating). Alternatively, the emitter can comprise a transparent conductive oxide that is sputter coated onto the substrate and then a polymer layer is spin-coated on the transparent conductive oxide (TCO).

[0127] In some embodiments, an insulating layer may be coated on the emitter layer. The insulating layer may be a polymer layer, such as polyvinylpyrrolidone (PVP), which contains polymer spheres (e.g., made of polystyrene and having a diameter of 30 - 400 nm) that can be removed later. Then, the insulating layer is coated with a metal mask layer, which is formed using one or more known methods including photolithography. Subsequently, the polymer spheres are removed by a solvent, leaving voids in the insulating layer and the mask. Then, the device is coated with a donor - acceptor organic semiconductor, and finally, the collector layer is patterned onto the OSC by a known method (e.g., photolithography).

[0128] In a device without an insulating layer, a first layer of donor - acceptor organic semiconductor may be coated on the emitter. Then, polymer spheres (with a diameter of 30 - 400 nm) may be coated on the OSC and used as a mask for coating a metal mask layer, which is formed using one or more known methods including photolithography. Subsequently, the polymer beads are removed by a solvent, heating, or an adhesive to form a grid. Finally, the collector layer is patterned onto the OSC by a known method (e.g., photolithography).

[0129] Examples

[0130] The following examples are given to fully disclose and describe how the materials, articles, and methods described and claimed herein are made and evaluated to one of ordinary skill in the art. These examples are for illustrative purposes only and are not intended to limit the scope of the specification. Considerable efforts have been made to ensure the accuracy of numerical values (e.g., amounts, temperatures, etc.), but some errors and deviations must be taken into account. Unless otherwise indicated, parts are parts by weight, temperature is in °C or ambient temperature, and pressure is atmospheric or near atmospheric. There can be many variations and combinations of reaction conditions, such as component concentrations, required solvents, solvent mixtures, temperature, pressure, and other reaction ranges and conditions that can be used to optimize the purity and yield of the products obtained by the method. Only reasonable and conventional experimental methods are required to optimize such method conditions.

[0131] Synthesis: Specific exemplary materials - P2TBTD2TDC9BC8C10FT4, PTBTDTDC9BC8C10FT4, and P2TDC8BC8C10DPP2TDC9BC8C10FT4:

[0132]

[0133]

[0134] It can be synthesized by the general procedures disclosed in U.S. Patent Nos. 7,705,108, 7,838,623, 8,389,669, and 7,893,191 and as described herein. A detailed synthesis procedure for PTBTDTDC9BC8C10FT4 is given herein as an example, but it can be varied and applied to other compounds. The monomers and catalyst materials are weighed into a flask and a solvent (m-xylene) is added. Then polymerization is carried out at 125 °C for 1 hour. Subsequently, the material is precipitated, filtered, dried, and then extracted in a Soxhlet extractor to remove any residual monomer and catalyst substances. Finally, the polymer is dissolved out of the Soxhlet extractor, reprecipitated, and dried in vacuo. The organic semiconductor (OSC) is used as the active material of a vertical transistor with high output current density and long storage life without encapsulation.

[0135] Apparatus fabrication, Example 1: The device is fabricated as described below to prepare Figure 1 the device: A polyvinylpyrrolidone (PVP) layer is spin-coated on the ITO emitter from an 8 wt% PVP:PGMEA solution to serve as the insulating layer. A thin surface modification layer [a thin poly(3-hexylthiophene-2,5-diyl) (P3HT) layer] is coated on the PVP to change the surface energy. Then, polystyrene (PS) spheres (diameter: 200 nm) are adsorbed on the substrate. To prepare a layer of self-assembled PS spheres on the PVP substrate, the substrate is immersed in an ethanol solution (1.4 wt%) of PS spheres for 90 seconds. The PS spheres are adsorbed on the substrate surface, and then the wet substrate is taken out of the ethanol and immersed in boiling isopropyl alcohol (IPA) to wash away the unadsorbed spheres. The hot IPA is blown dry using a nitrogen stream to form a monolayer of spheres. The PS spheres are used as a hard mask for the subsequent deposition of a metal grid layer (Al). An Al layer (40 nm) and an SiO layer (50 nm) are deposited as the electrode layer and the insulating layer, respectively. After removing the spheres with Scotch tape (3M), an opening is formed in the metal grid. Oxygen plasma etching is used to open the channel through the PVP and form aluminum oxide on top of the grid. Then the device is completed by depositing a donor-acceptor organic semiconductor layer (~200 - 600 nm thick) as described in the embodiment and then patterning the collector (MoO3 / Al).

[0136] Characterization: An organic vertical transistor as described herein is formed, wherein the organic semiconductor layer comprises PTDC16DPPTDC17FT4 and PTDC8BC8C10DPPTDC17FT4. The output current density of the first organic vertical transistor (solvent: chlorobenzene) comprising PTDC8BC8C10DPPTDC17FT4 is as high as 141 mA / cm 2 ( Figure 2A ) and the on / off current ratio is about 103 ( Figure 2B )。Additional non-toxic solvents tried during the process include tetralin, cyclooctane, and decalin, and the corresponding vertical transistor properties are shown in Figure 3A 、 3B 、4A, 4B, 5A, and 5B. Vertical transistors fabricated with donor-acceptor materials in these solvents show an output current density in the range of 1 - 100 mA / cm 2 and an on / off current ratio of 10 4 - 10 5 . These properties are superior to those shown by conventional P3HT materials, which show an output current density of ~1 mA / cm 2 , and an on / off current ratio of 10 4 - 10 5 . Figure 6 and 7 show the device lifetimes of vertical transistors containing PTDC8BC8C10DPPTDC17FT4 and PTDC16DPPTDC17FT4 without encapsulation, respectively. Figure 8 and 9 show cross-sectional SEM pictures of vertical transistors containing PTDC16DPPTDC17FT4 and PTDC8BC8C10DPPTDC17FT4.

[0137] Apparatus fabrication, Example 2: In Example 1, the PVP surface was treated with a thin layer of P3HT before PS nanosphere deposition to enhance surface adhesion. In some instances, P3HT can be replaced by surface treatment with reactive ion etching (RIE) at 70 watts for 5 seconds, followed by PS nanosphere deposition. The PS nanospheres have a diameter of approximately 200 nm and are positively charged. Figure 10 shows the output current of the resulting device. Transistor action indicates that P3HT can be replaced without affecting the electrical properties.

[0138] Apparatus fabrication, Example 3: In the vertical transistors of Examples 2 and 3, commercially available P3HT was used as the active material in the channel, such that the output current density of the collector was approximately 5 mA / cm 2 . Replacing P3HT with the polymer of Equation 1 can provide a higher vertical hole mobility in the channel and, for operating voltages below 1.5 V, increase the output current density of the collector up to 141 mA / cm 2 , as shown in Figure 11 . This is higher than the typical current density of 1 - 10 mA / cm for OLEDs 2Much higher. Therefore, a vertical transistor including the active material of Formula 1 in the channel has the advantage of low-voltage driving for OLED pixels in an active matrix display.

Claims

1. A device, the device comprising: a substrate; a collector layer; an emitter layer that is forward-biased with respect to the collector; a metal grid, which comprises a metal layer having openings, the metal grid being located between the collector and the emitter but not in direct contact with the collector and the emitter, wherein the length of each opening along its longest dimension is from 50 nm to 800 nm; and a semiconductor layer located between the collector and the emitter, the semiconductor layer comprising an organic semiconductor polymer having the following structure: wherein each D is independently wherein each X is independently S, Se or O; and each R1 is independently a C1-C 40 alkyl group; Each A is independently wherein each X′ is independently NR5; each R5 is independently a C1-C 40 alkyl group; a and b are each integers from 1 to 4, and n is an integer from 2 to 10,000.

2. The apparatus according to claim 1, wherein, Each X is S.

3. The apparatus according to claim 1, wherein, Each R1 is independently C 15 -C 35 alkyl group.

4. The device according to claim 2, wherein Each R1 is independently C 15 -C 35 alkyl group.

5. The device according to claim 3, wherein, Each R1 is C 17 H 35 .

6. The device according to claim 4, wherein, Each R1 is C 17 H 35 .

7. The device according to any one of claims 1-6, wherein each R5 is C 16 H 33 or C8H 15 (C8H 17 C 10 H 21 ).

8. The device according to claim 1, wherein The collector comprises metal.

9. The apparatus according to claim 8, wherein, The collector comprises aluminum.

10. The device according to claim 1, wherein, The emitter comprises a transparent conductive oxide.

11. The apparatus according to claim 10, wherein, The emitter comprises indium tin oxide.

12. The apparatus according to claim 1, wherein, The emitter comprises an organic polymer.

13. The device according to claim 12, wherein, The emitter comprises poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid.

14. The device according to claim 1, wherein, The openings in the metal grid include circular openings and have a length in the longest dimension of from 100 nm to 800 nm.

15. The device according to claim 14, wherein, The length of the openings in the longest dimension is from 200 nm to 500 nm.

16. The device according to claim 1, wherein The metal layer of the metal grid comprises aluminum.

17. The device according to claim 1, wherein, The organic semiconductor polymer comprises:

18. The device according to claim 1, wherein, The organic semiconductor polymer comprises:

19. The apparatus according to claim 1, wherein, The organic semiconductor polymer comprises:

20. The device according to claim 1, wherein, The collector layer is configured to have an output current density of at least 100 mA / cm 2 for an operating voltage below 1.5 V.

21. The device according to claim 1, wherein, The device has a current density of 100 mA / cm 2 to 160 mA / cm 2 for an operating voltage below 1.5 V.

22. A method of manufacturing a device, the method comprising: providing a substrate on which an emitter layer is provided; spin-coating an insulating layer on the emitter layer; modifying the insulating layer by any one of the following: providing a polymer layer on top of the insulating layer or subjecting the insulating layer to an etching process; coating the insulating layer with polymeric nanospheres; coating the polymeric nanospheres with a patterned metal mask layer; removing the polymeric nanospheres after the patterned metal mask layer is provided to form voids in the insulating layer; coating the patterned metal mask layer with a donor-acceptor organic semiconductor (OSC) layer; and providing a patterned collector layer on the OSC layer, wherein the OSC layer comprises the organic semiconductor polymer defined in any one of claims 1-7 and claims 17-19.

23. The method according to claim 22, wherein, The insulating layer is polyvinylpyrrolidone (PVP).

24. The method according to claim 22, wherein: the polymer layer is poly(3-hexylthiophene-2,5-diyl) (P3HT), and the etching process comprises reactive ion etching (RIE).

25. The method according to claim 22, wherein, The polymeric nanospheres comprise polystyrene.

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