Integrated flexible thermoelectric device and method of manufacturing the same

Abstract

An integrated flexible thermoelectric device includes p-type carbon nanoparticle regions and n-type carbon nanoparticle regions which are alternately and continuously connected to each other. In particular, the p-type carbon nanoparticle regions and the n-type carbon nanoparticle regions are formed on the one carbon nanoparticle paper.

Claims

1. A method of manufacturing an integrated flexible thermoelectric device, the method comprising: preparing a carbon nanotube emulsion by dispersing a carbon nanotube in a solvent; forming a p-type carbon nanotube paper by molding a layer using the carbon nanotube emulsion; and forming n-type regions on the p-type carbon nanotube paper by selectively injecting n-type dopants into the n-type regions which are predetermined regions on the p-type carbon nanotube paper, wherein adjacent p-type and n-type regions are in direct contact with one another in a longitudinal direction; and wherein p-type regions which are not injected with the n-type dopants and the n-type regions are alternately and continuously aligned.

2. The method of claim 1, wherein the solvent of the carbon nanotube emulsion comprises one or more selected from the group consisting of dimethyl formamide (DMF), water, methyl pyrrolidone (NMP), methanol, ethanol, propanol, and butanol.

3. The method of claim 1, wherein the forming the p-type carbon nanotube paper comprises performing a vacuum filtration of the carbon nanotube emulsion.

4. The method of claim 1, wherein the n-type dopants comprise triphenylphosphine (TPP) or polyethyleneimine (PEI).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings.

(2) FIG. 1A illustrates an exemplary thermoelectric device that is formed to be flexible and integrating p-type and n-type carbon nanotube regions according to an exemplary embodiment in the present invention, and FIG. 1B illustrates a folded state of the thermoelectric device according to an exemplary embodiment in the present invention.

(3) FIG. 2 shows an exemplary p-type carbon nanotube paper in a ribbon form prepared according to an exemplary embodiment of the present invention.

(4) FIG. 3 illustrates an exemplary process of forming n-type carbon nanotube regions on the exemplary p-type carbon nanotube paper of FIG. 2 according to an exemplary embodiment of the present invention.

(5) FIG. 4 illustrates an exemplary folding process to form an exemplary thermoelectric device integrating p-type and n-type carbon nanotube regions according to an exemplary embodiment of the present invention.

(6) FIG. 5 shows an exemplary an exemplary state of the folded thermoelectric device of FIG. 4 according to an exemplary embodiment of the present invention.

(7) FIG. 6 shows a Seebeck coefficient of an n-type carbon nanotube region according to concentration (wt %) of an n-type dopant solution when the n-type dopant is doped in a p-type carbon nanotube paper according to an exemplary embodiment of the present invention.

(8) FIG. 7 shows an exemplary n-type carbon nanotube paper in a ribbon form prepared according to an exemplary embodiment of the present invention.

(9) FIG. 8 illustrates an exemplary process of forming p-type carbon nanotube regions on the exemplary n-type carbon nanotube paper of FIG. 7 according to an exemplary embodiment of the present invention

DETAILED DESCRIPTION

(10) The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

(11) Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about.”

(12) Hereinafter, some exemplary embodiments of the present invention will be described in detail with reference to the illustrative drawings. It is to be noted that in giving reference numerals to components of each of the accompanying drawings, the same components will be denoted by the same reference numerals even though they are shown in different drawings. Further, in describing exemplary embodiments of the present invention, well-known constructions or functions will not be described in detail in the case in which they may unnecessarily obscure the understanding of the present invention.

(13) FIGS. 1A and 1B illustrate a structure of an integrated flexible thermoelectric device according to an exemplary embodiment in the present invention. FIG. 1A shows a thermoelectric device is formed in a ribbon form and FIG. 1B shows an exemplary thermoelectric device integrating n-type carbon nanotube regions and p-type carbon nanotube regions in alternate manners.

(14) As used herein, the “p-type” carbon nanotube region may be formed of carbon nanotube materials including electron holes as majority carriers (most abundant electron holes). In certain embodiments, the p-type carbon nanotube region may be doped with an impurity (p-type dopant) to create the electron holes in conductive carbon nanotube materials. In certain embodiments, the carbon nanotubes serve to create the electron holes without the p-type dopants, such that those may be referred to as p-type carbon nanotube regions.

(15) Further, the “n-type” carbon nanotube region may be formed of carbon nanotube materials including free electrons or shared electrons as majority carriers (most abundant free electron donors), and the n-type carbon nanotube region may be doped with an impurity (n-type dopant) to provide greater electron concentration than the normal carbon nanotubes.

(16) Further, in particular, the above carbon nanoparticle region, for example, either p-type or n-type carbon nanotube regions of FIG. 2 and FIG. 7, respectively, may be formed to be in a paper form and to have suitable flexibility, such that the substrate itself or the substrate with the carbon nanoparticle regions can be transformed, folded, or bent when a predetermined pressure or force is applied. In addition, the carbon nanotube paper may have a suitable thickness for providing flexibility as well as rigidity, and the thickness may range from about 5 μm to about 100 μm.

(17) Referring to FIGS. 1A and 1B, the integrated thermoelectric device according to the present exemplary embodiment may include a structure in which p-type carbon nanotube (CNT) regions and n-type carbon nanotube regions are alternately and continuously connected to each other.

(18) In particular, the p-type carbon nanotube regions and the n-type carbon nanotube regions may be integrally formed. The integrated thermoelectric device according to the present exemplary embodiment may have a structure in which a region having p-type characteristics and a region having n-type characteristics are continuously and alternately formed on one carbon nanotube paper (a paper on which a carbon nanotube network is formed), which is different from a conventional thermoelectric device including an additional electrode or a conductive adhesive to couple the p-type carbon nanotube region and the n-type carbon nanotube region. The above-mentioned integrated structure may be formed by partially doping n-type or p-type dopants on the carbon nanotube paper such that the n-type carbon nanotube region and p-type carbon nanotube region may be connected or positioned continuously and alternately on one carbon nanotube paper. For example, the integrated thermoelectric device may be formed by selectively adsorbing (doping) the n-type dopants on a surface of a p-type carbon nanotube paper of a ribbon form to be spaced apart from each other by a predetermined interval in a length direction and converting the corresponding regions into the n-type carbon nanotube regions. Alternatively, the integrated thermoelectric device may be formed by steps comprising injecting the n-type dopants into the overall p-type carbon nanotube paper in the ribbon form such that those regions may be converted into the n-type carbon nanotube paper and then selectively removing the n-type dopants from the n-type carbon nanotube paper by the predetermined interval in the length direction to recover the corresponding regions into the p-type carbon nanotube regions.

(19) Preferably, the n-type dopants may include a monomolecular material (e.g., triphenylphosphine) or a polymer material (e.g., polyethyleneimine) containing a large amount of group 5B, group 6B or group 7B atoms including unshared electron pairs. As a polymer, a setting polymer or a plastic polymer may be used. For example, as the plastic polymer, any one of polyimide, polyvinylidene (PVDF), nylon, polyethylene terephthalate, polycarbonate, polystyrene, polymethyl methacrylate (PMMA), polyethylene naphthalate (PEN), and polyethersulfone (PES) may be used. Preferably, polyvinylidene (PVDF) may be used, but the examples of the polymers are not limited thereto.

(20) In addition, the n-type dopants may be removed from the n-type carbon nanotube paper by washing the corresponding regions using DMSO or ethanol or performing a surface treatment for the corresponding regions with a carbonyl functional group including carbonyl group such as carboxyl acid, carboxyl halides, or the like using sulfuric acid (H.sub.2SO.sub.4) or thionyl chloride (SOCl.sub.2) may be used. As described above, the regions where the n-type dopants are removed may have p-type characteristics, and become p-type carbon nanotube regions.

(21) As such, the thermoelectric device according to the various exemplary embodiments of the present invention may be integrally formed so as to include both the p-type characteristics and the n-type characteristics in one carbon nanotube paper, such that internal resistance may be present as that of a pure carbon nanotube between the p-type carbon nanotube region and the n-type carbon nanotube region.

(22) The above-mentioned integrated flexible thermoelectric device may also be formed in the ribbon form in which the p-type carbon nanotube regions and the n-type carbon nanotube regions are alternately and continuously aligned in a line, as illustrated in FIG. 1A. Further, the thermoelectric device may also be formed in the module form in which the p-type carbon nanotube regions and the n-type carbon nanotube regions are alternately and continuously laminated as illustrated in FIG. 1B by folding interface portions between the p-type carbon nanotube regions and the n-type carbon nanotube regions. However, the folding methods may not be particularly limited thereto.

(23) Although the exemplary embodiments of FIGS. 1A and 1B describes the structure in which two p-type carbon nanotube regions and two n-type carbon nanotube regions are alternately and continuously connected to each other, the number of p-type carbon nanotube regions and n-type carbon nanotube regions is not limited thereto.

(24) In addition, the carbon nanotube paper in the exemplary embodiments described above collectively refers to a material layer (structure body) of a film form on which the carbon nanotube network is formed, and as a carbon nanotube, any one of a single wall carbon nanotube, a double-wall carbon nanotube, a multi-wall carbon nanotube, a thin multi-wall carbon nanotube, and a bundle type carbon nanotube may be used.

(25) In addition, although the exemplary embodiments described above representatively describes the carbon nanotube comprising the carbon nanotubes, however, carbon graphite, graphene, graphene oxide, graphene nanoribbon, carbonblack, or carbon nanoparticle such as carbon nanofiber may also be used instead of the carbon nanotubes to form the paper without limitation.

(26) FIGS. 2 to 5 are process diagrams illustrating processes of manufacturing an integrated flexible thermoelectric device according to an exemplary embodiment of the present invention.

(27) First, referring to FIG. 2, the p-type carbon nanotube paper in the ribbon form is manufactured by dispersing the carbon nanoparticle, for example, the carbon nanotube in a solvent to be separated into particles (nanoparticles) and then by a process of molding a layer using the particles.

(28) For example, carbon nanotube emulsion in which the carbon nanotube is separated (dispersed) into the particles (nanoparticles) is manufactured by adding a powder of the single wall carbon nanotube in dimethyl formamide (DMF) at a concentration of about 0.05 mg/ml, and performing ultra sonication using an ultra sonicator for about 30 minutes. Then, the p-type carbon nanotube paper is manufactured by removing residual solvents from the carbon nanotube emulsion through a vacuum filtration at a temperature of about 80° C. and for about 6 hours using a vacuum oven and then by the process of molding the layer. Preferably, the carbon nanotube paper may be manufactured in a buckypaper form having a thin thickness of about 5 to 100 μm and be formed in the ribbon or belt form. For instance, since the carbon nanotube without any treatment has p-type characteristics, the carbon nanotube paper manufactured with the carbon nanotube may behave the p-type carbon nanotube paper.

(29) Preferably, the solvent for dispersing the powder of the carbon nanotube may include, in addition to dimethyl formamide (DMF) described above, water, methyl pyrrolidone (NMP), methanol, ethanol, propanol, butanol and combinations thereof.

(30) As shown in FIG. 3, the n-type dopants may be doped on the p-type carbon nanotube paper of the ribbon form to be spaced apart from each other by a predetermined interval, such that a p+n integrated carbon nanotube ribbon in which the p-type carbon nanotube regions and the n-type carbon nanotube regions are alternately and continuously aligned may be formed.

(31) For example, predetermined regions of the p-type carbon nanotube paper may be converted into the n-type carbon nanotube regions by dividing and determining the p-type carbon nanotube paper of the ribbon form into p-type regions and n-type regions; and injecting an n-type dopant solution obtained by dissolving the n-type dopants in the solvent into the n-type regions such that the n-type dopants may be adsorbed (doped) in the n-type regions. Preferably, as the n-type dopant solution, for example, a solution in which triphenylphosphine (TPP) is dissolved in dimethylsulfoxide (DMSO) or a solution in which polyethyleneimine (PEI) is dissolved in ethanol may be used. In addition, the dopants may be physically adsorb the corresponding dopant on the surface of the carbon nanotube with any known methods in the related art. For example, one of a method of immersing the corresponding regions of the carbon nanotube paper in a dopant solution, a method of coating the corresponding regions of the carbon nanotube paper with dopants, and a method of vacuum-adsorbing the dopants on the corresponding regions of the carbon nanotube paper, or a combination thereof may be used.

(32) FIG. 6 shows a Seebeck coefficient of the n-type carbon nanotube region according to concentration (wt %) of the n-type dopant solution when the n-type dopant solution is dropped in the p-type carbon nanotube paper. As such, the Seebeck coefficient of the n-type carbon nanotube region may be adjusted by adjusting the concentration of the n-type dopant solution.

(33) When the p-type carbon nanotube paper are determined and divided into the p-type regions and the n-type regions, only the n-type regions may be exposed by masking regions intended to be left as a p-type region from the p-type carbon nanotube paper, for example, using TEFLON™ tape, or the like. In this case, the p-type region and the n-type region may have the same areas to each other or may have different areas.

(34) As shown in FIGS. 4 and 5, a laminated module may be formed by folding interface portions between the p-type carbon nanotube regions and the n-type carbon nanotube regions of the p+n integrated carbon nanotube ribbon so that the p-type carbon nanotube regions and the n-type carbon nanotube regions may be alternately laminated.

(35) FIGS. 7 and 8 illustrate exemplary processes of manufacturing an integrated flexible thermoelectric device according to an exemplary embodiment of the present invention.

(36) As shown in FIG. 7, an n-type carbon nanotube paper of the ribbon form may be manufactured by dispersing the carbon nanoparticle, for example, the carbon nanotube dispersed in the solution including n-type dopants and separated into particles (nanoparticles) may be molded in a layer using the particles.

(37) For example, a carbon nanotube emulsion is manufactured by adding a powder of a single wall carbon nanotube in a solution in which triphenylphosphine (TPP) is dissolved in dimethylsulfoxide (DMSO) or a solution in which polyethyleneimine (PEI) is dissolved in ethanol and then by an ultra sonication as illustrated in FIG. 2, and the n-type carbon nanotube paper is manufactured by removing residual solvents of the carbon nanotube emulsion by a vacuum filtration and then performing a process of molding a layer. Without limitation, the processes as that illustrated in FIG. 2 described above may be performed suitably except that the n-type carbon nanotube emulsion is formed by separating (dispersing) the powder of the carbon nanotube using the n-type dopant solution.

(38) As shown in FIG. 8, the n-type dopants may be removed from the n-type carbon nanotube paper to be spaced apart from each other by a predetermined interval to recover the corresponding regions to the p-type regions, such that a p+n integrated carbon nanotube ribbon in which the p-type carbon nanotube regions and the n-type carbon nanotube regions are alternately and continuously aligned may be formed.

(39) For example, regions to be recovered to the p-type regions may be determined in the n-type carbon nanotube paper of the ribbon form and the corresponding regions are then washed by using DMSO or ethanol, such that n-type dopants (TPP or PEI) of the corresponding regions may be removed. Alternatively, the surface for the corresponding regions may be treated with a carbonyl functional group including a carbonyl group such as carboxyl acid, carboxyl halides, or the like using sulfuric acid (H.sub.2SO.sub.4) or thionyl chloride (SOCl.sub.2) may be used. For example, the p-type regions and the n-type regions may be determined or identified by masking the n-type regions using Teflon tape, or the like so that only the regions to be recovered to the p-type regions from the n-type carbon nanotube paper are exposed.

(40) Thereafter, as in FIGS. 4 and 5 described above, a laminated module may be formed by folding the p+n integrated carbon nanotube ribbon.

(41) The spirit of the present invention has been just exemplified. It will be appreciated by those skilled in the art that various modifications and alterations can be made without departing from the essential characteristics of the present invention.

(42) As described above, according to various exemplary embodiments of the present invention, the internal resistance of the thermoelectric device may be minimized, thereby increasing an amount of power generated from the thermoelectric device.

(43) In addition, according to the present invention, miniaturization and weight reduction of the thermoelectric device may be implemented, such that the thermoelectric device may be applied to various fields.

(44) Accordingly, the exemplary embodiments disclosed in the present invention do not limit but describe the spirit of the present invention, and the scope of the present invention is not limited by the exemplary embodiments. The scope of the present invention should be interpreted by the following claims and it should be interpreted that all spirits equivalent to the following claims fall within the scope of the present invention.