KR20210012774A - Thermoelectric module - Google Patents

Abstract

According to an embodiment of the present invention, provided is a thermoelectric module which can effectively prevent heat diffusion of an electrode layer material. The thermoelectric module comprises: a plurality of thermoelectric material layers including a thermoelectric material; an electrode layer connecting the plurality of thermoelectric material layers; and a diffusion prevention layer positioned between each of the thermoelectric material layers and the electrode layer, wherein the diffusion prevention layer includes a Mo-Ti alloy, wherein the Mo-Ti alloy has a Mo content of 70 atomic% or more, and Ti The content is 30 atomic% or less.

Description

Thermoelectric module {THERMOELECTRIC MODULE}

The present invention relates to a thermoelectric module, and more specifically, to a thermoelectric module that has excellent thermal and electrical characteristics, prevents deformation of a thermoelectric element even under high temperature conditions, and is capable of stably driving.

In recent years, while interest in the development and saving of alternative energy is increasing, research and research on efficient energy conversion materials are being actively conducted. In particular, research on thermoelectric materials, which are thermo-electric energy conversion materials, is accelerating.

When there is a temperature difference at both ends of a material in a solid state, a difference in concentration of carriers (electrons or holes) having a heat dependence occurs, which is an electrical phenomenon called thermoelectric force, that is, a thermoelectric phenomenon. As such, the thermoelectric phenomenon refers to a reversible and direct energy conversion between a temperature difference and an electric voltage. These thermoelectric phenomena can be classified into thermoelectric power generation, which produces electrical energy, and thermoelectric cooling/heating, which causes a temperature difference at both ends by supplying electricity.

A thermoelectric material exhibiting such a thermoelectric phenomenon is a material having a function of directly converting heat into electricity or electricity into heat, and has an advantage that power generation is possible only by providing a temperature difference. Thermoelectric materials were developed to have a high thermoelectric figure of merit with the development of semiconductors from the late 1930s after the discovery of the Seebeck effect, Peltier effect, and Thomson effect, which are thermoelectric phenomena in the early 19th century. Has become.

Thermoelectric materials exhibiting thermoelectric phenomena have an eco-friendly and sustainable advantage in power generation and cooling processes, so many studies are being conducted. Moreover, since it is possible to directly generate electric power from industrial waste heat and automobile waste heat, interest in thermoelectric materials is increasing as a useful technology for improving fuel efficiency or reducing CO ₂ .

Meanwhile, a thermoelectric module is generally composed of a plurality of thermoelectric devices, and power generated by each thermoelectric device is collected and used. The thermoelectric device has a thermoelectric material layer in charge of generating power and an electrode layer for moving carriers (electrons or holes) between the thermoelectric material layers as a basic configuration. The thermoelectric material layer is divided into a p-type thermoelectric material layer in which holes move to transfer thermal energy and an n-type thermoelectric material layer in which electrons move to transfer thermal energy, and a pair of p-n thermoelectric material layers can be a basic unit. A thermoelectric module that generates electricity using a temperature difference is used in an environment where the temperature difference between the high temperature and low temperature regions is large to obtain high thermoelectric efficiency. The thermoelectric material layer using the commonly used Bismuth Telluride (Bi-Te) thermoelectric material is used in the temperature range of about 200 to 300℃, and the thermoelectric material layer using the Skutterudite (Co-Sb) thermoelectric material is about 500~ It is driven in a temperature range of 600°C.

Since the thermoelectric module is used at such a high temperature, mutual diffusion between the thermoelectric material and the electrode material, which is a component, occurs when the thermoelectric module is driven, which is known as one of the main causes of deteriorating the performance of the thermoelectric module. In order to suppress such mutual diffusion, a diffusion barrier layer is inserted between the thermoelectric material layer and the electrode layer, and a bonding layer for improving bonding strength between the diffusion barrier layer and the electrode material may be added.

Therefore, it is necessary to develop a new diffusion barrier layer having excellent electrical properties and suppressing mutual diffusion between a thermoelectric material layer, a bonding layer, or an electrode layer, which are components of a thermoelectric module in a high temperature environment.

Embodiments of the present invention are to provide a thermoelectric module capable of effectively preventing thermal diffusion of an electrode layer material and a method of manufacturing the same.

However, the problems to be solved by the embodiments of the present invention are not limited to the above-described problems and may be variously expanded within the scope of the technical idea included in the present invention.

A thermoelectric module according to an embodiment of the present invention includes a plurality of thermoelectric material layers including a thermoelectric material; An electrode layer connecting the plurality of thermoelectric material layers; And a diffusion barrier layer positioned between each thermoelectric material layer and the electrode layer, wherein the diffusion barrier layer includes a Mo-Ti alloy, and the Mo-Ti alloy has a Mo content of 70 atomic% or more, and Ti The content of is less than 30 atomic%.

The Mo-Ti alloy may have a Mo content of 80 atomic% or more and a Ti content of 20 atomic% or less.

The thickness of the diffusion barrier layer may be 100 nm to 100 μm.

The thickness of the diffusion barrier layer may be 150 nm to 10 μm.

The thermoelectric module may further include a bonding layer positioned between the diffusion barrier layer and the electrode layer.

The bonding layer may include at least one of Ti, Ni, Cu, Fe, Ag, and Sn.

The thermoelectric material may include at least one of Bi-Te-based, Co-Sb-based, silicide-based, half-whistler-based, PbTe-based, Si-based, and SiGe-based.

According to embodiments of the present invention, by including a diffusion barrier layer having excellent diffusion prevention properties, it is possible to effectively prevent heat diffusion of the electrode layer material under a high temperature environment.

In addition, since a diffusion barrier layer having excellent electrical conductivity characteristics due to low specific resistance is implemented, it may be more advantageous for electrical connection between the thermoelectric material layer and the electrode layer.

1 is a diagram schematically illustrating a part of a thermoelectric module according to an embodiment of the present invention.
2 is a photograph showing a cross section of the diffusion barrier layer of Example 2.
3 is a photograph showing a cross section of the diffusion barrier layer of Comparative Example 3.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

In order to clearly describe the present invention, parts irrelevant to the description have been omitted, and the same reference numerals are assigned to the same or similar components throughout the specification.

In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of description, so the present invention is not necessarily limited to the illustrated bar. In the drawings, the thicknesses are enlarged to clearly express various layers and regions. And in the drawings, for convenience of description, the thickness of some layers and regions is exaggerated.

In addition, when a part of a layer, film, region, plate, etc. is said to be "on" or "on" another part, this includes not only "directly above" another part, but also a case where another part is in the middle. . Conversely, when one part is "directly above" another part, it means that there is no other part in the middle. In addition, to be "on" or "on" the reference part means that it is located above or below the reference part, and means that it is located "above" or "on" in the direction opposite to gravity. no.

In addition, throughout the specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless otherwise stated.

1 is a schematic diagram of a part of a thermoelectric module 100 according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a thermoelectric module 100 according to an embodiment of the present invention includes: a plurality of thermoelectric material layers 300 including a thermoelectric material; An electrode layer 200 for connecting between the plurality of thermoelectric material layers 300; Each thermoelectric material layer 300 includes a diffusion barrier layer 500 positioned between the electrode layer 200, and the diffusion barrier layer 500 includes a Mo-Ti alloy. The diffusion prevention layer 500 is for preventing material diffusion between the thermoelectric material layer 300 and the electrode layer 200, and is composed of a material constituting the thermoelectric material layer 300 and a material constituting the electrode layer 200. It is possible to prevent heat diffusion, and is particularly effective in preventing heat diffusion of materials constituting the electrode layer 200.

Since Mo-Ti alloy has excellent high-temperature stability and diffusion-preventing properties, when applied as a diffusion-preventing layer for Bi-Te-based thermoelectric materials, there is no change in the durability test at 300°C for 100 hours.

In addition, a method of sputtering or e-beam evaporation may be used to form the diffusion barrier layer. When the Mo metal is deposited by the above method, it tends to grow in a column shape, that is, a column shape. In the diffusion preventing layer grown in a columnar shape, the thermoelectric material or the bonding layer material may diffuse through the gap between the pillars and the pillars, and thus there is a problem that the diffusion preventing function is deteriorated.

As in the present embodiment, the diffusion barrier layer 500 including the Mo-Ti alloy suppresses columnar growth, so that the interface can be formed smoothly, and the above-described problems can be prevented.

In the Mo-Ti alloy in the diffusion barrier layer 500, the Mo content is preferably 70 atomic% or more, the Ti content is 30 atomic% or less, the Mo content is 80 atomic% or more, and the Ti content is 20 More preferably, it is atomic% or less. When Mo and Ti in the alloy are formed in the range of the atomic ratio as described above, excellent diffusion preventing properties may be exhibited even in a high temperature environment. This will be described later in Evaluation Example 1 below.

In addition, since the diffusion barrier layer composed of the Mo-Ti alloy in the above composition range exhibits a relatively lower specific resistance, charge carriers can smoothly move the diffusion barrier layer when the thermoelectric module 100 is driven, so that the thermoelectric material layer and the electrode layer It may be more advantageous for the electrical connection between. That is, a diffusion barrier layer having excellent electrical properties as well as diffusion prevention properties can be implemented. This will be described later in Evaluation Example 2 below.

In addition, the diffusion barrier layer composed of a Mo-Ti alloy has the advantage of being advantageous in forming a smooth interface because columnar growth is limited. In the case of an irregular columnar interface, there may be a problem in that the material of the electrode layer is diffused between the interfaces, but the diffusion preventing layer in the present embodiment can prevent such a problem from occurring. This will be described later in Evaluation Example 3 below.

Meanwhile, the thickness of the diffusion barrier layer 500 including the Mo-Ti alloy may be 100 nm to 100 μm. When the thickness of the diffusion barrier layer 500 is within the above range, oxidation of the thermoelectric material layer 300 can be effectively suppressed, and film stress due to the difference in thermal expansion coefficient with the thermoelectric material layer 300 is relieved to prevent membrane separation. can do. Considering the remarkable improvement effect through the use of the alloy material in the diffusion barrier layer 500 and the combined thickness control as described above, the thickness of the diffusion barrier layer is more specifically 150 nm to 100 μm, and even more specifically 150 nm to 10 μm. I can.

The diffusion preventing layer 500 may be formed in the form of a sputtering layer, an electroplating layer, or a sintered layer.

In the case of applying in the form of a sintered layer, the Mo and Ti metals are prepared in powder form, and a paste composition is prepared in which a binder or a solvent is mixed, and then applied to the surface of a thermoelectric element or a bonding layer to be described later. , A method of sintering, etc. can be used.

In the case of sputtering, first remove the oxide film on the surface of the deposition target by plasma treatment, and proceed with the deposition process by using a sputtering device to set the power applied to the deposition target in the range of about 0.1 to about 10 W/cm ² . I can. The deposition time may vary depending on the deposition material and the thickness of the deposition film and the sputtering process conditions, but may proceed for about 10 to about 300 minutes, for example, and the pressure during operation may be about 0.1 to about 50 mTorr.

In addition, a specific process in each method for depositing a metal compound may be used without particular limitation as long as it is generally used in the field to which the present invention belongs.

Meanwhile, in the thermoelectric module 100 according to the embodiment of the present invention, the thermoelectric material layer 300 is divided into a p-type thermoelectric material layer and an n-type thermoelectric material layer according to its role, and alternately positioned pn thermoelectric material layers. One pair of material layers is the basic unit. In FIG. 1, only one thermoelectric material layer 300 is illustrated for convenience of description.

The type of thermoelectric material included in the thermoelectric material layer 300 is not particularly limited, and specifically, Bi-Te-based, Co-Sb-based, silicide-based, half-whisler-based, PbTe-based, Si It may include at least one of a material based on SiGe and SiGe.

In addition, in the thermoelectric module 100 according to the present embodiment, the electrode layer 200 is electrically connected in series between a plurality of thermoelectric material layers, specifically, a p-type thermoelectric material layer and an n-type thermoelectric material layer. For this purpose, it is positioned above and below the thermoelectric material layer, and may include a conductive material. In FIG. 1, only the electrode layer 200 positioned below the thermoelectric material layer 300 is shown, but another electrode layer (not shown) is also positioned thereon.

The conductive material is not particularly limited, and specifically, copper (Cu), copper-molybdenum (Cu-Mo), silver (Ag), gold (Au), platinum (Pt), etc. may be mentioned. Any one or a mixture of two or more may be used. Among these, the electrode may include copper (Cu) having high electrical conductivity and thermal conductivity.

Meanwhile, a bonding layer 400 for improving bonding strength may be positioned between the diffusion barrier layer 500 and the electrode layer 200.

The bonding layer 400 may be a metal soldering layer or a metal sintering layer. More specifically, one or more metal powders, such as titanium (Ti), nickel (Ni), copper (Cu), iron (Fe), silver (Ag) or tin (Sn), are selectively used with a binder, a dispersant, and a solvent. It may be formed by sintering a metal paste for forming a bonding layer prepared by mixing, and may be formed by a soldering method in which the metal is melted and joined using a solder paste such as Sn-based solder paste or Pb-based solder paste.

The dispersant serves to improve dispersibility of the metal powder in a solvent in a metal paste without a binder resin, and may be present in a form adsorbed on the surface of the metal powder.

This dispersant may be an aliphatic acid having 12 to 20 carbon atoms, or an alkali metal salt or alkaline earth metal salt thereof, and more specifically, stearic acid, oleic acid, oleylamine, palmitic acid ( palmitic acid), dodecanoic acid, isostearic acid, sodium stearate, sodium dodecanoate, and the like.

In addition, the dispersant may be included in an amount of about 0.1 to about 5% by weight, preferably about 0.5 to about 1.5% by weight, based on the total weight of the metal paste.

The solvent imparts wettability to the metal paste and serves as a vehicle for holding the first and second metal powders. In particular, since the boiling point is 150 to 350°C, the drying process and bonding at a low temperature of less than 350°C The process can be carried out.

In addition, such a solvent may include one selected from the group consisting of alcohols, carbonates, acetates, and polyols, and more specifically dodecanol ), propylene carbonate, diethylene glycol monoethyl acetate, tetrahydrofurfuryl alcohol, terpineol, dihydro terpineol, ethylene It may be glycol (ethylene glycol), glycerin (glycerin), tridecanol (tridecanol) or isotridecanol (isotridecanol) and the like.

When forming by the sintering, using a transient liquid phase sintering (TLPS), an intermetallic compound composed of different kinds of metals is generated, which is sintered to form a bonding layer. do.

Meanwhile, although not specifically shown, a second diffusion barrier layer may be further positioned between the bonding layer 400 and the diffusion barrier layer 500 or between the thermoelectric material layer 300 and the diffusion barrier layer 500.

The second diffusion barrier layer is for supplementing the diffusion barrier property of the diffusion barrier layer 500 and may include at least one of Mo, Ti, W, and Co.

Hereinafter, a thermoelectric module according to the present invention will be described through specific examples and comparative examples. However, the following examples are merely illustrative of the present invention, and the contents of the present invention are not limited by the following examples.

Example 1

On the Si substrate, Cu having a thickness of 100 nm serving as an electrode layer was deposited, and a diffusion barrier layer of Mo-Ti alloy was deposited through a sputtering method. The sputtering method of deposition was performed using a sputtering device under conditions where the power applied to the deposition target was 4.4 W/cm ² and the process pressure was 3 mTorr. At this time, the thickness of the diffusion barrier layer was 340 nm, and the Mo-Ti alloy composition of the diffusion barrier layer was 80 atomic% Mo and 20 atomic% Ti.

Example 2

A diffusion barrier layer of Mo-Ti alloy was deposited on the Bi-Ti-based thermoelectric material through sputtering. In the sputtering method, a diffusion barrier layer of Mo-Ti alloy was deposited using a sputtering device under conditions of 4.4 W/cm ² and a process pressure of 3 mTorr.

Comparative Example 1

In Example 1, a diffusion barrier layer was prepared in the same manner as in Example 1, except that the alloy composition of the diffusion barrier layer was changed to 60 atomic% Mo and 40 atomic% Ti.

Comparative Example 2

In Example 1, a diffusion barrier layer was prepared in the same manner as in Example 1, except that the alloy composition of the diffusion barrier layer was changed to 20 atomic% Mo and 80 atomic% Ti.

Comparative Example 3

In Example 2, a diffusion barrier layer was prepared in the same manner as in Example 2, except that a diffusion barrier layer was formed by sequentially depositing a Mo layer and a Ti layer through sputtering deposition.

Evaluation Example 1: Comparison of anti-diffusion properties

For each of the diffusion barrier layers in Example 1, Comparative Example 1, and Comparative Example 2, the degree of diffusion of Cu elements after heat treatment was measured. This is to evaluate the diffusion prevention performance of the Mo-Ti diffusion prevention layer by measuring the degree of heat diffusion of the material constituting the electrode layer, that is, Cu.

Specifically, after heat-treating each sample at 300°C in a nitrogen atmosphere, the concentration of Cu from the surface to the inside of the diffusion barrier layer is measured using X-ray photoelectron spectroscopy (XPS). First, after measuring the Cu concentration on the surface of the diffusion barrier layer, etching is performed using Ar ions for a certain period of time to measure the Cu concentration again. Thereafter, etching is performed again for a predetermined time and the Cu concentration is measured.

After repeating the concentration measurement through etching and XPS as described above, when Si used as a substrate is detected in XPS, the measurement is completed.

Tables 1 to 3 below are Si,Cu concentration measurement results for Example 1, Comparative Example 1, and Comparative Example 2, respectively.

Etching time(s) Si (atomic%) Mo (atomic%) Ti (atomic%) Cu (atomic%) 0 0.3 21.2 7.9 0.04 50 0.0 74.8 16.5 0.0 500 0.0 78.0 17.6 0.0 1000 0.0 78.1 16.8 0.0 1500 0.0 79.0 16.5 0.0 1600 0.0 77.1 17.3 0.0 1700 0.0 78.5 16.6 0.0 1800 0.0 78.3 16.9 0.0 1900 0.0 78.4 16.9 0.0 2000 0.0 77.9 16.1 0.2 2250 2.5 51.9 10.5 30.9 2500 8.6 10.9 1.4 78.0 2750 49.3 1.5 0.1 47.1 3000 91.9 0.5 0.1 6.5

Etching time(s) Si (atomic%) Mo (atomic%) Ti (atomic%) Cu (atomic%) 0 0.0 8.5 14.2 0.0 50 0.0 42.6 29.3 0.0 500 0.0 54.5 37.1 0.4 1000 0.0 55.3 38.0 0.1 1300 0.0 56.0 37.0 0.4 1400 0.0 55.7 37.8 0.2 1500 0.0 55.2 37.6 0.3 1600 0.0 55.7 38.1 0.4 1700 0.0 55.7 37.7 0.5 1800 0.0 54.8 36.3 0.9 1900 0.0 54.7 37.0 2.0 2000 0.0 52.0 34.3 6.1 2100 0.8 44.8 29.0 19.2 2200 3.8 33.0 19.9 39.1 2300 5.8 20.6 11.7 59.2 2500 12.3 5.7 2.6 77.6 2750 66.4 0.8 0.3 30.7 3000 93.7 0.3 0.0 4.9

Etching time(s) Si (atomic%) Mo (atomic%) Ti (atomic%) Cu (atomic%) 0 0.0 1.7 17.7 0.05 50 0.0 8.5 33.9 0 500 0.0 18.1 63.8 0 1000 0.0 19.5 64.7 0.05 1300 0.0 20.1 66.8 0.6 1400 0.0 20.1 67.5 0.5 1500 0.0 20.4 68.2 0.6 1600 0.0 20.3 67.7 0.7 1700 0.0 20.4 68.1 0.8 1800 0.0 20.6 68.3 0.7 1900 0.0 20.5 68.2 0.8 2000 0.0 20.1 68.1 1.2 2100 0.0 19.6 68.2 3.5 2200 0.0 16.1 51.1 23.0 2300 5.7 8.6 23.3 58.2 2500 11.6 1.1 2.6 83.7 2750 71.7 0.0 0.5 25.9 3000 95.5 0.0 0.3 3.3

First, referring to Tables 1 to 3, it can be seen that in the case of Example 1, Cu starts to be detected at about 2000 seconds, and in the case of Comparative Examples 1 and 2, Cu starts to be detected at 500 seconds and 1000 seconds, respectively. I can confirm that. At this time, in Tables 1 and 3, Cu detected on the surface of the diffusion barrier layer before etching is not considered as contamination. As the heat diffusion of Cu proceeds smoothly, Cu will be detected near the surface of the diffusion barrier layer, so that Cu is detected It can be interpreted that the shorter the time, the more heat diffusion by Cu occurred. In conclusion, compared to Comparative Examples 1 and 2, the diffusion preventing layer of Example 1 has a longer etching time when Cu is found, and through this, the diffusion preventing property of the diffusion preventing layer of Example 1 is superior to that of Comparative Examples 1 and 2. You can confirm that it is.

Evaluation Example 2: Measurement of electrical resistance of the diffusion barrier layer

For each of the diffusion barrier layers in Example 1, Comparative Example 1 and Comparative Example 2, sheet resistance (Ω/□) and specific resistance (Ωm) were measured and shown in Table 4 below.

Sheet resistance (Ω/□) Resistivity (Ωm) Example 1 4.2 1.4E-06 Comparative Example 1 9.3 3.2E-06 Comparative Example 2 12.0 4.1E-06

Referring to Table 4, the diffusion barrier layer of Example 1 exhibits lower sheet resistance and specific resistance values than the diffusion barrier layers of Comparative Examples 1 and 2. That is, it can be seen that charge carriers may move more smoothly in the diffusion barrier layer of Example 1, and the diffusion barrier layer of Example 1 has better electrical conductivity properties than the diffusion barrier layers of Comparative Examples 1 and 2.

Evaluation Example 3: Cross-sectional photograph

2 and 3 are photographs showing cross-sections of the diffusion barrier layers of Example 2 and Comparative Example 3, respectively.

2 and 3, the diffusion barrier layer containing Mo-Ti alloy formed a smooth interface, whereas the diffusion barrier layer containing Mo formed an irregularly protruding interface due to the columnar growth of Mo. I can confirm. That is, the diffusion barrier layer including the Mo-Ti alloy is advantageous in forming a smoother interface, and diffusion of the thermoelectric material layer or the material of the electrode layer between the interfaces can be prevented.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also present. It belongs to the scope of rights of

100: thermoelectric module
200: electrode layer
300: thermoelectric material layer
400: bonding layer
500: diffusion barrier layer

Claims (7)

A plurality of thermoelectric material layers including a thermoelectric material;
An electrode layer connecting the plurality of thermoelectric material layers; And
And a diffusion barrier layer positioned between each of the thermoelectric material layers and the electrode layer,
The diffusion barrier layer includes a Mo-Ti alloy,
The Mo-Ti alloy is a thermoelectric module having a Mo content of 70 atomic% or more and a Ti content of 30 atomic% or less. In claim 1,
The Mo-Ti alloy is a thermoelectric module having a Mo content of 80 atomic% or more and a Ti content of 20 atomic% or less. In claim 1,
The thickness of the diffusion barrier layer is 100nm to 100μm thermoelectric module. In claim 1,
The thickness of the diffusion barrier layer is 150nm to 10μm thermoelectric module. In claim 1,
Thermoelectric module further comprising a bonding layer positioned between the diffusion barrier layer and the electrode layer. In clause 5,
The bonding layer is a thermoelectric module comprising at least one of Ti, Ni, Cu, Fe, Ag, and Sn. In claim 1,
The thermoelectric material is a thermoelectric module including at least one of Bi-Te-based, Co-Sb-based, silicide-based, half-whistler-based, PbTe-based, Si-based, and SiGe-based.

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