JPH03211776A - Thermoelectric transducer - Google Patents

Abstract

PURPOSE:To provide a thermoelectric transducer having an increased heat transfer efficiency by using an arragnement, in which pairs of thermoelectic elements forming a ribbon are arranged thermally in parallel and connected electrically in series, and a predetermined area of the ribbon is coated with an infrared-transmitting film in specific thickness. CONSTITUTION:A thin-film ribbon includes pairs of L-shaped and inverse L- shaped semiconductor members, each pair having a laminated structure of n-type semiconductor, metal, and p-type semiconductor. These semiconductor members are arranged thermally in parallel and connected electrically in series. The L shaped members face an infrared absorber 4 at their corners or striped parts. The striped corners of the ribbon are coated with a 0.2-0.7mum thick film 8. A thermoelectric transducer having such an infrared transmitting film S has an electric generation efficiency six times as large as the conventional one. Therefore, it is possible to obtain a very quick response for infrared detection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermoelectric conversion device suitable for a non-contact infrared detection device.

[Prior Art] FIGS. 2(a) and 2(b) show an example of a typical structure of a conventional thermoelectric conversion module for an infrared sensor.

Semiconductor (n-type) semiconductor (p-type) thin film semiconductor elements (hereinafter referred to as thin film ribbons) 2 are formed radially on an insulating substrate 1 by vapor deposition or sputtering, with each radial piece serving as a basic element. , a plurality of them are electrically coupled in series.

Note that the materials used for the thin film ribbon 2 include semiconductors such as Bi, Sb, and Te, which have large Seebeck coefficients, and compounds thereof.

As a high heat source part of the thin film ribbon 2, an infrared absorber 4 is arranged in the central region of the thermoelectric conversion module. As the infrared absorber 4, "black gold" having a high infrared absorption rate is used.

The principle of power generation of a thermoelectric conversion module used as an infrared sensor is as follows. The infrared rays emitted by the object to be detected are first absorbed by the infrared absorber 4. This causes the temperature of the infrared absorber 4 to rise. Thermal energy using this as a heat source is transmitted to the high heat source portion of the thin film ribbon 2 mainly by thermal conduction.

Increase temperature.

On the other hand, the radially outer portion of the thin film ribbon 2 acts as a low heat source and is maintained at a constant temperature by a heat sink 5 attached to the lower surface of the insulating substrate. As a result, a temperature difference ΔT is generated between the high heat source portion and the low heat source portion of the thin film ribbon 2, and power generation based on the Seebeck effect occurs.

The gap between the infrared absorber 4 and the thermoelectric conversion element is approximately 5
It is about 0 to 100 μm.

[Problems to be Solved by the Invention] However, in the heat transfer mechanism as described above, thermal energy is dispersed, which significantly reduces the heat transfer efficiency to the high heat source portion of the thermoelectric conversion element.

Therefore, one technical problem of the present invention is to improve the heat transfer mechanism from the conventional infrared absorber to the high heat source part of the thermoelectric conversion element,
The object of the present invention is to provide a thermoelectric conversion device with improved heat transfer efficiency.

[Means for Solving the Problems] According to the present invention, a plurality of thermoelectric conversion elements including a pair of semiconductor (n-type)-metal-semiconductor (p-type) thin film ribbons are electrically connected in series, and In a thermally arranged thermoelectric conversion device, the thin film ribbon in a predetermined area has a thickness of 0.7
A thermoelectric conversion device is obtained which is characterized in that it is coated with an infrared transmitting film having a film thickness of ~2 μm.

[Principle of the invention] Professor H. T. Abor of the National Physical Laboratory of Israel.

A thin layer was created on the surface by electroplating black nickel onto a nickel or silver plate, or by chemically blackening the surface of an electrolytic aluminum plate. The thickness of the layer is greater than the wavelength of visible light but much smaller than the wavelength of thermal radiation.

At this time, visible light is well absorbed, but it is almost transparent to long wavelength infrared rays, revealing the properties of the underlying metal. Therefore, it has been reported that it does not emit long-wavelength radiation at room temperature, and when exposed to sunlight, it becomes much hotter than a simply black surface.

We focused on this experiment and decided to apply this principle to improving the heat collection effect of thermoelectric conversion devices for infrared sensors.

The black gold thin film used as an infrared absorber also
It has become clear that by appropriately adjusting the film thickness, the infrared transmittance can be significantly different.

FIG. 4 shows the relationship between the spectral radiant emittance of a black body and the wavelength λ. As is clear from the figure, depending on the temperature.

The spectral radiant emittance is different.

Therefore, based on the experimental results of Professor H. Tabor, the infrared transmitting film differs slightly depending on the temperature of the object to be detected. That is, when the temperature of the object to be detected is high, it is preferable to use a thinner transmission membrane depending on the temperature.

[Example] An example of the thermoelectric conversion device of the present invention is shown in FIGS.
Shown in d).

FIG. 1(a) shows a plan view of an embodiment of a thermoelectric conversion device according to the present invention.

FIG. 1(b) shows a cross-sectional view of the thermoelectric conversion device of FIG. 1(a) taken along line A-A.

The differences from the conventional FIG. 2 will be described in particular detail.

The thermoelectric conversion device according to the present invention includes an infrared absorber 4 formed on the central region of an insulating substrate 1, a thin film formed in a stripe shape on the upper surface of the infrared absorber 4, and a thin film extending in all directions around the infrared absorber 4. A semiconductor element (hereinafter referred to as a thin film ribbon) 2,
It is composed of a heat sink 5, an output terminal 6, and a ground terminal 7 provided on the lower surface of an insulating substrate 1, and an infrared absorbing film 8 formed to cover the striped thin film ribbon 2.

The thin film ribbon 2 is formed by forming a pair of semiconductors (n-type) - metal and semiconductor (p-type) in an L-shape or inverted shape, and thermally heats the plurality of semiconductors as shown in Fig. 1 Ca). electrically connected in parallel and in series. At this time, the bent portion of the L-shaped semiconductor, that is, the striped portion is arranged to face the infrared absorber 4.

The striped portion of the thin film ribbon 2 is further coated with an infrared transmitting film 8 having a film thickness of 0.7 μm to 2 μm.

As shown in FIG. 1(b), a region other than the infrared transmitting film 8 is coated with a transparent insulating film 9 to construct a thermoelectric conversion device.

Output terminals 6 are connected to both ends of the thin film ribbon 2, and an output voltage can be obtained using the same power generation principle as in the conventional example described above.

When using, for example, a hot brake that generates heat)
The thermoelectric conversion device according to the present invention is installed at a position 600 mm away from the center and perpendicular to the plane (230 mm x 230+ m).

Table 1 shows experimental data for thermoelectric conversion devices in which the infrared transmitting film 8 is made of different materials and has different film thicknesses δ. Table 1 shows the output voltage generated by the thermoelectric converter when the temperature of the hot plate surface is 100°C. The applicant obtained the above experimental results by varying the type and thickness δ of the infrared transmitting film in order to enhance the heat collection effect of the thermoelectric converter for an infrared sensor.

As a result, the optimum film thickness is 0.7 to 2μ■, and the power generation efficiency of the thermoelectric conversion element having such an infrared transmitting film 8 can be improved to about six times that of the conventional one. The detection response speed is significantly increased.

FIG. 2 shows a modification of FIGS. 1(a) and (b), in which the reflector 10
is used to enhance the heat collection effect.

C Effects of the Invention According to the present invention, the power generation efficiency of the thermoelectric conversion element used in the thermoelectric conversion device has been improved to about 6 times that of the conventional one, and the response speed of infrared detection has become significantly faster.

[Brief explanation of drawings]

FIG. 1(a) is a plan view of an embodiment of a thermoelectric conversion device for an infrared sensor according to the present invention, and FIG. 1(b) is a plan view of an embodiment of the thermoelectric conversion device for an infrared sensor according to the present invention.
FIG. 2 is a sectional view showing a modification of FIGS. 1(a) and (b), and FIG. 3(a) is a cross-sectional view of a conventional thermoelectric conversion device. The plan view, FIG. 3(b) is a sectional view taken along the line AA in FIG. 3(a), and FIG. 4 is a diagram showing the relationship between the spectral radiant emittance of a black body and the wavelength λ. In the figure. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Thin film semiconductor element (thin film ribbon), 4... Infrared absorber, Gokawa heat sink, 6...
・Output terminal, 7... Earth terminal, 8... Infrared transmitting film. 9...Transparent insulating film, 10...Reflector plate. Figure 1 (α) Figure 2 Figure 3

Claims (2)

[Claims] (1) In a thermoelectric conversion device in which a plurality of thermoelectric conversion elements each consisting of a pair of semiconductor (n-type)-metal-semiconductor (p-type) thin film ribbons are arranged electrically in series and thermally in parallel. , the thin film ribbon in a predetermined area has a thickness of 0.7 to 2
A thermoelectric conversion device characterized by being coated with an infrared transmitting film having a film thickness of μm. (2) The thermoelectric conversion device according to claim 1, wherein a black metal or a black metal compound is used as the infrared transmitting film.