Organic thin film transistor and preparation method thereof

Abstract

The invention discloses an organic thin film transistor and a preparation method thereof. The organic thin film transistor comprises a substrate; the source electrode and the drain electrode are located above the substrate, and the source electrode and / or the drain electrode are / is a base metal electrode, a base metal oxide electrode, a base metal nitride electrode or a base metal carbide electrode; the SAMs modification layer is at least located on the source electrode and / or the drain electrode; the organic semiconductor layer is located above the substrate and at least partially covers the SAMs modification layer on the source electrode and / or the drain electrode; and the grid electrode is positioned above the organic semiconductor layer or between the organic semiconductor layer and the substrate. The SAMs modification layer is prepared on the electrode made of a base metal material, so that the SAMs modification layer can replace a noble metal electrode to serve as a source electrode and a drain electrode of the organic thin film transistor, the cost is reduced, and further development of the organic thin film transistor is promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductors, and in particular relates to an organic thin film transistor and a preparation method thereof. Background Art

[0002] Organic semiconductor (OSC) materials have shown great potential in the field of flexible devices due to their excellent properties. In the context of low carbon and cost reduction, organic thin film transistors (OTFTs) based on organic semiconductors have received more and more attention from the industry.

[0003] However, since organic semiconductor materials are incompatible with existing photolithography processes, the photolithography process will damage organic semiconductor materials. Therefore, typical organic semiconductor devices represented by OTFTs usually use a bottom contact structure when integrated for application, that is, the source and drain electrodes of the device are pre-deposited on the substrate, and the organic semiconductor layer is deposited after the source and drain electrodes are deposited.

[0004] This bottom-contact device structure places higher demands on the application of organic semiconductor devices represented by OTFTs. Common high-performance organic semiconductors are generally p-type semiconductors. Due to the lack of efficient electrode contact doping methods in the bottom-contact device structure, in order to reduce contact resistance and achieve efficient carrier injection and collection, it is usually necessary to use precious metal high work function materials such as Ag, Au, Pt as source and drain electrodes. This dependence on precious metals greatly limits the large-scale application of organic optoelectronic devices represented by OTFTs.

[0005] Therefore, in view of the above technical problems, it is necessary to provide an organic thin film transistor and a method for preparing the same. Summary of the invention

[0006] The object of the present invention is to provide an organic thin film transistor and a preparation method thereof, which can reduce the dependence of the device on precious metals.

[0007] In order to achieve the above purpose, the technical solution provided by an embodiment of the present invention is as follows:

[0008] An organic thin film transistor, comprising:

[0009] substrate;

[0010] A source electrode and a drain electrode located above the substrate, wherein the source electrode and / or the drain electrode is a base metal electrode, a base metal oxide electrode, a base metal nitride electrode or a base metal carbide electrode;

[0011] A SAMs modified layer, at least located on the source electrode and / or the drain electrode;

[0012] An organic semiconductor layer is located above the substrate and at least partially covers the SAMs modified layer on the source electrode and / or the drain electrode;

[0013] The gate is located above the organic semiconductor layer or between the organic semiconductor layer and the substrate.

[0014] In one embodiment, the SAMs modification layer includes an anchoring group, a connecting group and a terminal group, the anchoring group is in contact with the source electrode and / or the drain electrode, the terminal group is in contact with the organic semiconductor layer, and the anchoring group and the terminal group are connected via the connecting group.

[0015] In one embodiment, the terminal group is a -PO3H2 group, a -SO3H group, a -COOH group, a -CF3 group, a -CN group, a -NO2 group, a -Br group, a -I group, a -F group or a -OCH3 group.

[0016] In one embodiment, the material of the SAMs modification layer is selected from any one or more of the following:

[0017]

[0018] In one embodiment, the thickness of the SAMs modification layer is 0.4 nm to 10 nm.

[0019] In one embodiment, the organic semiconductor layer is a P-type organic semiconductor layer.

[0020] In one embodiment, the base metal in the base metal electrode, base metal oxide electrode, base metal nitride electrode or base metal carbide electrode includes any one or more combinations of Mo, Ti, Ni, Cu, Sn, Zn, Mg or Al.

[0021] In one embodiment, the gate is located on a substrate, a first insulating layer covering the gate is provided on the substrate, and the source and drain are located on the first insulating layer; or,

[0022] A second insulating layer is disposed on the organic semiconductor layer, and the gate is located on the second insulating layer.

[0023] Another embodiment of the present invention provides a technical solution as follows:

[0024] A method for preparing an organic thin film transistor, the method comprising the following steps:

[0025] providing a substrate;

[0026] Preparing a gate and a first insulating layer on a substrate, wherein the first insulating layer covers the gate;

[0027] preparing a source electrode and a drain electrode on the first insulating layer;

[0028] preparing a SAMs modified layer, wherein the SAMs modified layer is at least located on the source electrode and / or the drain electrode;

[0029] An organic semiconductor layer is prepared on the first insulating layer, and the organic semiconductor layer at least partially covers the SAMs modified layer on the source electrode and / or the drain electrode.

[0030] Another embodiment of the present invention provides a technical solution as follows:

[0031] A method for preparing an organic thin film transistor, the method comprising the following steps:

[0032] providing a substrate;

[0033] preparing a source electrode and a drain electrode on a substrate;

[0034] preparing a SAMs modified layer, wherein the SAMs modified layer is at least located on the source electrode and / or the drain electrode;

[0035] An organic semiconductor layer is prepared on a substrate, wherein the organic semiconductor layer at least partially covers the SAMs modified layer on the source electrode and / or the drain electrode;

[0036] A second insulating layer is formed on the organic semiconductor layer, and a gate is formed on the second insulating layer.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention uses base metal materials to make the source and drain of the organic thin film transistor, and performs SAMs modification, so that the electrodes made of base metal materials with SAMs modification layers can replace precious metal electrodes as the source and drain of the organic thin film transistor, thereby reducing costs and promoting the further development of organic thin film transistors. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 is a schematic diagram of the structure of an organic thin film transistor in Example 1 of the present invention;

[0041] Figure 2 for Figure 1 A partial enlarged view of the middle A;

[0042] Figure 3a to 3e is a process flow chart of the method for preparing an organic thin film transistor in Example 1 of the present invention;

[0043] Figure 4 is a schematic diagram of the structure of an organic thin film transistor in Example 2 of the present invention;

[0044] Figures 5a to 5e is a process flow chart of the method for preparing an organic thin film transistor in Example 2 of the present invention;

[0045] Figure 6 Schematic diagram of the structure of the organic thin film transistor in Comparative Example 1 of the present invention.

[0046] Description of main reference numerals:

[0047] 10-substrate, 201-source electrode, 202-drain electrode, 203-gate electrode, 30-SAMs modification layer, 301-anchoring group, 302-connecting group, 303-terminal group, 40-organic semiconductor layer, 501-first insulating layer, 502-second insulating layer. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0049] The present invention discloses an organic thin film transistor, comprising:

[0050] substrate;

[0051] A source electrode and a drain electrode located above the substrate, wherein the source electrode and / or the drain electrode is a base metal electrode, a base metal oxide electrode, a base metal nitride electrode or a base metal carbide electrode;

[0052] A self-assembled monolayer (SAMs) modification layer, at least located on the source electrode and / or the drain electrode;

[0053] An organic semiconductor layer is located above the substrate and at least partially covers the SAMs modified layer on the source electrode and / or the drain electrode;

[0054] The gate is located above the organic semiconductor layer or between the organic semiconductor layer and the substrate.

[0055] The present invention also discloses a method for preparing an organic thin film transistor, comprising the following steps:

[0056] providing a substrate;

[0057] A gate and a first insulating layer are prepared on the substrate, wherein the first insulating layer covers the gate;

[0058] preparing a source electrode and a drain electrode on the first insulating layer;

[0059] preparing a SAMs modified layer, wherein the SAMs modified layer is at least located on the source electrode and / or the drain electrode;

[0060] An organic semiconductor layer is prepared on the first insulating layer, and the organic semiconductor layer at least partially covers the SAMs modified layer on the source electrode and / or the drain electrode.

[0061] The present invention also discloses a method for preparing an organic thin film transistor, comprising the following steps:

[0062] providing a substrate;

[0063] preparing a source electrode and a drain electrode on a substrate;

[0064] preparing a SAMs modified layer, wherein the SAMs modified layer is at least located on the source electrode and / or the drain electrode;

[0065] An organic semiconductor layer is prepared on a substrate, wherein the organic semiconductor layer at least partially covers the SAMs modified layer on the source electrode and / or the drain electrode;

[0066] A second insulating layer is formed on the organic semiconductor layer, and a gate is formed on the second insulating layer.

[0067] The present invention is further described below with reference to specific examples.

[0068] Embodiment 1:

[0069] Ginseng Figure 1 As shown, the organic thin film transistor in this embodiment includes:

[0070] Base 10;

[0071] A source electrode 201 and a drain electrode 202 are located above the substrate 10, and the source electrode 201 and / or the drain electrode 202 are base metal electrodes, base metal oxide electrodes, base metal nitride electrodes or base metal carbide electrodes;

[0072] The SAMs modified layer 30 is at least located on the source electrode 201 and / or the drain electrode 202;

[0073] An organic semiconductor layer 40 is located above the substrate 10 and at least partially covers the SAMs modified layer 30 on the source electrode 201 and / or the drain electrode 202;

[0074] The gate 203 is located above the organic semiconductor layer 40 or between the organic semiconductor layer 40 and the substrate 10 .

[0075] Specifically, the organic thin film transistor in this embodiment adopts a bottom-gate bottom-contact structure. The gate 203 is located on the substrate 10 . A first insulating layer 501 covering the gate 203 is provided on the substrate 10 . The source 201 and the drain 202 are located on the first insulating layer 501 .

[0076] Among them, the substrate 10 is any substrate commonly used in organic thin film transistors, including but not limited to hard substrates such as silicon oxide wafers, glass sheets, PCB boards, and flexible substrates such as polyimide (PI) film, polyester (PET) film, polyvinyl alcohol (PVA) film, polyethylene naphthalate (PEN) film, polydimethylsiloxane (PDMS) film, paper and textile material substrates. The first insulating layer includes but is not limited to inorganic insulating layers such as Al2O3 (aluminum oxide) layer, AlN (aluminum nitride) layer, Si3N4 (silicon nitride) layer and SiO2 (silicon oxide) layer, as well as organic insulating layers such as polystyrene (PS) layer, polymethyl methacrylate (PMMA) layer, polyvinyl pyrrolidone (PVP) layer and polyvinyl pyrrolidone (PVP) layer.

[0077] In this embodiment, a SAMs modification layer 30 is prepared on both the source electrode 201 and the drain electrode 202, and both the source electrode 201 and the drain electrode 202 are base metal electrodes, base metal oxide electrodes, base metal nitride electrodes or base metal carbide electrodes. Base metal refers to metals other than precious metals such as Au, Ag, and Pt. Among them, the base metal in this embodiment includes but is not limited to any one or more combinations of Mo, Ti, Ni, Cu, Sn, Zn, Mg, or Al.

[0078] Combination Figure 2 As shown, the SAMs modification layer 30 in this embodiment includes an anchoring group 301, a connecting group 302 and a terminal group 303, the anchoring group 301 is in contact with the source electrode 201 and the drain electrode 202, the terminal group 303 is in contact with the organic semiconductor layer 40, and the anchoring group 301 and the terminal group 303 are connected via the connecting group 302.

[0079] Specifically, the terminal group 303 includes but is not limited to a -PO3H2 group, a -SO3H group, a -COOH group, a -CF3 group, a -CN group, a -NO2 group, a -Br group, a -I group, a -F group or a -OCH3 group and other terminal groups having the ability to attract holes.

[0080] In this embodiment, the thickness of the SAMs modification layer 30 is 0.4 nm to 10 nm.

[0081] SAMs are an ordered monolayer formed by spontaneous assembly of molecules with active groups on a solid surface. SAMs can be used to regulate the surface energy of source-drain electrodes made of precious metal materials, and the growth of high-quality OSC films can be achieved by directly modifying SAMs on precious metal electrodes such as Au, Ag, and Pt. In addition, the work function of the electrode can be lowered by modifying SAMs on high-work-function precious metal electrodes such as Au, Ag, and Pt to achieve high-quality electrode contact for n-type OSCs. In this embodiment, SAMs are used to modify the source-drain electrodes made of base metal materials to improve the work function of the source-drain electrodes, thereby replacing the precious metal electrodes.

[0082] Specifically, the SAMs modified layer 30 in this embodiment has a terminal group 303 that attracts holes. After the electrode made of base metal material is modified with SAMs, its work function can be improved, which effectively improves the energy level mismatch problem between the electrode and the highest occupied molecular orbital (HOMO) energy level of the p-type semiconductor material, thereby improving the electrode contact, transforming the electrode contact from Schottky contact to typical ohmic contact, and improving the injection and collection efficiency of holes.

[0083] For example, the material of the SAMs modification layer 30 in this embodiment can be selected from any one or more of the following:

[0084]

[0085] It should be noted that the anchoring group 301 can be selected and regulated according to different electrode materials, and the terminal group 303 is in direct contact with the organic semiconductor layer 40 and is the most important component. The terminal group 303 needs to be reasonably selected so that the work function of the source 201 and the drain 202 made of base metal materials can be increased after modification, thereby achieving the effect of replacing the precious metal electrode.

[0086] More specifically, the organic semiconductor layer 40 in this embodiment is a p-type organic semiconductor layer, including but not limited to a pentacene (Pentacene) layer, a benzothiophene (BT) layer and its derivative layers, a polythiophene (P3HT) layer and its derivative layers, a diketopyrrolopyrrole (DPP) layer and its derivative layers, a 6,13-dichloropentacene (DCP) layer and its derivative layers, and a polyparaphenylenevinylene (PPV) layer and its derivative layers.

[0087] In addition, the SAMs modification layer 30 in this embodiment is only located on the surface of the source 201 and the drain 202 to achieve the best effect. In other embodiments of the present invention, in addition to modifying the source 201 and the drain 202, the SAMs modification layer 30 may also exist on the first insulating layer 501 to simplify the process flow.

[0088] The method for preparing an organic thin film transistor in this embodiment comprises the following steps:

[0089] S1. Figure 3a As shown, a substrate 10 is provided.

[0090] The substrate 10 may be any substrate commonly used in organic thin film transistors, which will not be described in detail here.

[0091] S2, ginseng Figure 3b As shown, a gate 203 and a first insulating layer 501 are prepared on a substrate 10 , and the first insulating layer 501 covers the gate 203 .

[0092] In this embodiment, the preparation process of the gate 203 and the first insulating layer 501 is a conventional process and will not be described in detail here.

[0093] It is worth noting that the above step S1 and step S2 can also be combined into one step, that is, the source electrode 201 and the drain electrode 202 can be directly prepared on the substrate on which the gate electrode 203 and the first insulating layer 501 are prepared in advance.

[0094] S3, ginseng Figure 3c As shown, a source electrode 201 and a drain electrode 202 are prepared on the first insulating layer 501 .

[0095] The method for preparing the source electrode 201 and the drain electrode 202 in this embodiment is a conventional method and will not be described in detail here.

[0096] S4. Figure 3d As shown, a SAMs modification layer 30 is prepared on the source electrode 201 and / or the drain electrode 202 .

[0097] For example, the SAMs modification layer 30 may be prepared on the source electrode 201 and / or the drain electrode 202 by a gas phase method or a solution method.

[0098] It should be understood that, before the SAMs modification layer 30 is formed, a pre-treatment process such as surface cleaning may be included.

[0099] Specifically, in this embodiment, the SAMs modification layer 30 is only prepared on the source electrode 201 and the drain electrode 202 to achieve the best effect. A patterned photoresist layer is first prepared to expose the surface of the source electrode 201 and the drain electrode 202, and then the SAMs modification is performed; or the surface of the sample is subjected to surface energy treatment so that the SAMs modification layer 30 is preferentially deposited on the electrode. In other embodiments of the present invention, the SAMs modification layer 30 can also be prepared on the first insulating layer 501 at the same time to simplify the process flow.

[0100] Exemplarily, after the preparation of the SAMs modification layer 30 is completed, a process of removing excess SAMs modification layer 30 may also be included.

[0101] S5. Figure 3e As shown, an organic semiconductor layer 40 is prepared on the first insulating layer 501 , and the organic semiconductor layer 40 at least partially covers the SAMs modified layer 30 on the source electrode 201 and / or the drain electrode 202 .

[0102] Specifically, the organic semiconductor layer 40 in this embodiment covers the SAMs modified layer 30 on the source electrode 201 and the drain electrode 202 .

[0103] Embodiment 2:

[0104] Ginseng Figure 4 As shown, the structure and preparation method of the organic thin film transistor in this embodiment are substantially the same as those in Embodiment 1, except that the organic thin film transistor in this embodiment adopts a top-gate bottom-contact structure.

[0105] Specifically, the source electrode 201 and the drain electrode 202 are directly deposited on the substrate, the SAMs modification layer 30 is preferably only located on the source electrode 201 and the drain electrode 202, the organic semiconductor layer 40 is located on the substrate and covers the SAMs modification layer 30 on the source electrode 201 and the drain electrode 202, the second insulating layer 502 is located on the organic semiconductor layer 40, and the gate 203 is located on the second insulating layer 502.

[0106] The method for preparing an organic thin film transistor in this embodiment comprises the following steps:

[0107] S1. Figure 5a As shown, a substrate 10 is provided.

[0108] S2, ginseng Figure 5b As shown, a source electrode 201 and a drain electrode 202 are prepared on the substrate.

[0109] It should be understood that the above-mentioned step S1 and step S2 can be combined, that is, the subsequent process preparation can be directly performed on the substrate 10 that already has the source electrode 201 and the drain electrode 202 .

[0110] S3, ginseng Figure 5c As shown, a SAMs modification layer 30 is prepared on the source electrode 201 and / or the drain electrode 202 .

[0111] Specifically, to achieve the best effect, in this embodiment, the SAMs modification layer 30 is only prepared on the source electrode 201 and the drain electrode 202. The specific preparation method is similar to that in Embodiment 1, and will not be described again here.

[0112] In other embodiments of the present invention, the SAMs modification layer 30 may also exist on the surface of the substrate 10 to simplify the preparation process.

[0113] S4. Figure 5dAs shown, an organic semiconductor layer 40 is prepared on a substrate 10 , and the organic semiconductor layer 40 at least partially covers the SAMs modified layer 30 on the source electrode 201 and / or the drain electrode 202 .

[0114] In this embodiment, the organic semiconductor layer 40 covers the SAMs modified layer 30 on the source electrode 201 and the drain electrode 202 .

[0115] S5. Figure 5e As shown, a second insulating layer 502 is formed on the organic semiconductor layer 40 , and a gate electrode 203 is formed on the second insulating layer 502 .

[0116] The manufacturing process of the gate 203 and the second insulating layer 502 in this embodiment is a conventional process and will not be described in detail here.

[0117] Comparative Example 1:

[0118] Ginseng Figure 6 As shown, the structure and preparation method of the organic thin film transistor in this comparative example are substantially the same as those in Example 1, except that the source electrode 201 and the drain electrode 202 are not modified with SAMs. The organic thin film transistor in this comparative example is a conventional organic thin film transistor in the prior art. In order to reduce contact resistance and achieve efficient carrier injection and collection, the source electrode 201 and the drain electrode 202 use precious metal electrodes, such as Ag, Au, Pt, etc., which limits the development of organic thin film transistors.

[0119] It can be seen from the above technical solution that the present invention has the following beneficial effects:

[0120] The present invention uses base metal materials to make the source and drain of the organic thin film transistor, and performs SAMs modification, so that the electrodes made of base metal materials with SAMs modification layers can replace precious metal electrodes as the source and drain of the organic thin film transistor, thereby reducing costs and promoting the further development of organic thin film transistors.

[0121] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0122] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An organic thin film transistor, characterized in that: The organic thin film transistor comprises: substrate; A source electrode and a drain electrode located above the substrate, wherein the source electrode and / or the drain electrode is a base metal electrode, a base metal oxide electrode, a base metal nitride electrode or a base metal carbide electrode; A SAMs modified layer, at least located on the source electrode and / or the drain electrode; An organic semiconductor layer is located above the substrate and at least partially covers the SAMs modified layer on the source electrode and / or the drain electrode; The gate is located above the organic semiconductor layer or between the organic semiconductor layer and the substrate.

2. The organic thin film transistor according to claim 1, characterized in that: The SAMs modified layer comprises an anchoring group, a connecting group and a terminal group, wherein the anchoring group is in contact with the source electrode and / or the drain electrode, the terminal group is in contact with the organic semiconductor layer, and the anchoring group and the terminal group are connected via the connecting group.

3. The organic thin film transistor according to claim 2, characterized in that: The terminal group is a -PO3H2 group, a -SO3H group, a -COOH group, a -CF3 group, a -CN group, a -NO2 group, a -Br group, a -I group, a -F group or a -OCH3 group.

4. The organic thin film transistor according to claim 2, characterized in that: The material of the SAMs modification layer is selected from any one or more of the following:

5. The organic thin film transistor according to claim 1, characterized in that: The thickness of the SAMs modification layer is 0.4 nm to 10 nm.

6. The organic thin film transistor according to claim 1, characterized in that: The organic semiconductor layer is a P-type organic semiconductor layer.

7. The organic thin film transistor according to claim 1, characterized in that: The base metal in the base metal electrode, base metal oxide electrode, base metal nitride electrode or base metal carbide electrode includes any one or more combinations of Mo, Ti, Ni, Cu, Sn, Zn, Mg or Al.

8. The organic thin film transistor according to claim 1, characterized in that: The gate is located on a substrate, a first insulating layer covering the gate is provided on the substrate, and the source and drain are located on the first insulating layer; or, A second insulating layer is disposed on the organic semiconductor layer, and the gate is located on the second insulating layer.

9. A method for preparing an organic thin film transistor, characterized in that: The preparation method comprises the following steps: providing a substrate; Preparing a gate and a first insulating layer on a substrate, wherein the first insulating layer covers the gate; preparing a source electrode and a drain electrode on the first insulating layer; preparing a SAMs modified layer, wherein the SAMs modified layer is at least located on the source electrode and / or the drain electrode; An organic semiconductor layer is prepared on the first insulating layer, and the organic semiconductor layer at least partially covers the SAMs modified layer on the source electrode and / or the drain electrode.

10. A method for preparing an organic thin film transistor, characterized in that: The preparation method comprises the following steps: providing a substrate; preparing a source electrode and a drain electrode on a substrate; preparing a SAMs modified layer, wherein the SAMs modified layer is at least located on the source electrode and / or the drain electrode; An organic semiconductor layer is prepared on a substrate, wherein the organic semiconductor layer at least partially covers the SAMs modified layer on the source electrode and / or the drain electrode; A second insulating layer is formed on the organic semiconductor layer, and a gate is formed on the second insulating layer.

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