Compound semiconductor and use thereof

Abstract

A novel compound semiconductor which can be used for a solar cell, a thermoelectric material, or the like, and the use thereof.

Claims

1. A compound semiconductor represented by the following Chemical Formula 1, comprising: a Co—Sb skutterudite compound; Sn and S that are included in internal voids of the Co—Sb skutterudite compound; and Q that is substituted with Sb of the Co—Sb skutterudite compound:
Sn.sub.xS.sub.yCo.sub.4Sb.sub.12-zQ.sub.z  [Chemical Formula 1] wherein, in Chemical Formula 1, Q is at least one selected from the group consisting of O, Se, and Te, wherein 0<x<0.2, 0<y≤1, and 0<z<12, and the molar ratio of x to 1 mol of y is 0.1 mol to 0.9 mol.

2. The compound semiconductor of claim 1, wherein in Chemical Formula 1, the molar ratio of x to 1 mol of y is 0.2 mol to 0.8 mol.

3. The compound semiconductor of claim 1, wherein in Chemical Formula 1, z is in the range of 0<z≤4.

4. The compound semiconductor of claim 1, wherein in Chemical Formula 1, the molar ratio of x to 1 mol of z is 0.01 mol to 0.5 mol.

5. The compound semiconductor of claim 1, wherein in Chemical Formula 1, the molar ratio of x to 1 mol of z is 0.05 mol to 0.3 mol.

6. The compound semiconductor of claim 1, wherein the Co—Sb skutterudite compound comprises two voids per unit lattice.

7. The compound semiconductor of claim 1, wherein the compound semiconductor is an N-type compound semiconductor.

8. A method for preparing the compound semiconductor of claim 1 comprising the steps of: forming a mixture containing Sn, S, Co, Sb, and at least one element selected from the group consisting of O, Se and Te; and thermally treating the mixture.

9. The method for preparing the compound semiconductor of claim 8, wherein the thermal treatment step is performed at 400° C. to 800° C.

10. The method for preparing the compound semiconductor of claim 8, wherein the thermal treatment step comprises two or more thermal treatment steps.

11. The method for preparing the compound semiconductor of claim 8, further comprising a pressure-sintering step after thermally treating the mixture.

12. A thermoelectric conversion device comprising the compound semiconductor according to claim 1.

13. A solar cell comprising the compound semiconductor according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates the unit lattice of the compound of Example 1.

(2) FIG. 2 illustrates the unit lattice of the skutterudite compound.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) The present invention will be described in more detail by way of examples. However, these examples are given for illustrative purposes only, and the scope of the invention is not intended to be limited by these examples

EXAMPLES 1 to 3

Preparation of Compound Semiconductors

Example 1

(4) A Co.sub.4Sb.sub.12 skutterudite compound; and Sn.sub.0.05S.sub.0.2Co.sub.4Sb.sub.11.4Te.sub.0.6 in which Sn and S were filled into internal voids of the Co.sub.4Sb.sub.12 skutterudite compound and Te was doped at a Sb site of the Co.sub.4Sb.sub.12 skutterudite compound, were synthesized by the following method.

(5) Sn, S, Co, Sb, and Te in a powder form were weighed, and then they were put into an alumina mortar, following by mixing. The mixed materials were put into a hard mold, formed into pellets, put into a fused silica tube, and vacuum-sealed. Then, the resultant product was put into a box furnace and heated at 680° C. for 15 hours, and then slowly cooled down to room temperature to synthesize Sn.sub.0.05 S.sub.0.2Co.sub.4Sb.sub.11.4Te.sub.0.6.

(6) Next, the synthesized compound was filled into a graphite mold for spark plasma sintering, and then subjected to spark plasma sintering at a temperature of 650° C. under a pressure of 50 MPa for 10 minutes to prepare the compound semiconductor of Example 1. At this time, the relative density of the compound semiconductor was measured to be 98% or more.

Example 2

(7) A compound semiconductor was prepared in the same manner as in Example 1, except that the mixture composition was changed to Sn.sub.0.1S.sub.0.2Co.sub.4Sb.sub.11.4Te.sub.0.6.

Example 3

(8) A compound semiconductor was prepared in the same manner as in Example 1, except that the mixture composition was changed to Sn.sub.0.15S.sub.0.2Co.sub.4Sb.sub.11.4Te.sub.0.6.

COMPARATIVE EXAMPLES 1 TO 3

Preparation of Compound Semiconductors

Comparative Example 1

(9) A compound semiconductor was prepared in the same manner as in Example 1, except that S, Co, Sb, and Te were prepared as reagents, and the mixture composition was changed to S.sub.0.2Co.sub.4Sb.sub.11.4Te.sub.0.6.

Comparative Example 2

(10) A compound semiconductor was prepared in the same manner as in Example 1, except that Sn, Co, Sb, and Te were prepared as reagents, and the mixture composition was changed to Sn.sub.0.05Co.sub.4Sb.sub.11.4Te.sub.0.6.

Comparative Example 3

(11) A compound semiconductor was prepared in the same manner as in Example 1, except that the mixture composition was changed to Sn.sub.0.2S.sub.0.2Co.sub.4Sb.sub.11.4Te.sub.0.6.

Experimental Examples

Measurement of Physical Properties of Compound Semiconductors Obtained in Examples and Comparative Examples

(12) The physical properties of the compound semiconductors obtained in the examples and comparative examples were measured by the following methods, and the results are shown in Tables 1 and 2 below.

(13) 1. Lattice Thermal Conductivity (W/mK)

(14) The compound semiconductors obtained in the examples and comparative examples were processed into a coin-type having a diameter of 12.7 mm and a height of 1.5 mm to prepare a specimen. Then, the thermal conductivity of the specimen was calculated from the measured values of thermal diffusivity, specific heat, and density by means of a laser flash (Netzsch, LFA-457) in the range of 50° C. to 500° C. Then, the Lorenz number was calculated and the value thereof was applied to the calculated thermal conductivity to obtain lattice thermal conductivity. The results are shown in Table 1 below.

(15) TABLE-US-00001 TABLE 1 Lattice thermal conductivity of compound semiconductors of examples and comparative examples Temperature Lattice thermal Category (° C.) conductivity (W/mK) Example 1 50 2.00 100 1.86 200 1.65 300 1.49 400 1.38 500 1.30 Example 2 50 1.90 100 1.78 200 1.58 300 1.43 400 1.33 500 1.27 Example 3 50 1.93 100 1.80 200 1.59 300 1.44 400 1.35 500 1.30 Comparative 50 2.19 Example 1 100 2.04 200 1.80 300 1.62 400 1.51 500 1.44 Comparative 50 3.27 Example 2 100 3.00 200 2.56 300 2.23 400 1.99 500 1.85 Comparative 50 2.29 Example 3 100 2.14 200 1.92 300 1.78 400 1.71 500 1.70

(16) As shown in Table 1, it was confirmed that in the case of the compound semiconductors of Examples 1 to 3, as Sn and S were filled simultaneously, the lattice thermal conductivity was lowered over the entire temperature measurement section as compared with those of Comparative Examples 1 and 2.

(17) In addition, when Sn was excessively filled as in Comparative Example 3, it was confirmed that since Sn and S formed a secondary phase such as SnS without being located in internal voids of the Co—SB lattice, the lattice thermal conductivity was increased as compared with those of the examples.

(18) 2. Thermoelectric Performance Index (ZT)

(19) The compound semiconductors obtained in the examples and comparative examples were processed into a rectangular-type having a length of 3 mm, a width of 3 mm, and a height of 12 mm to prepare a specimen. Then, the electrical conductivity and the Seebeck coefficient of the specimen were measured using ZEM-3 (Ulvac-Rico, Inc.) in the range of 50° C. to 500° C.

(20) Next, the thermoelectric performance index (ZT) was calculated from the measured electrical conductivity, Seebeck coefficient, and thermal conductivity value of Experimental Example 1 described above by using the mathematical equation below, and the results are shown in Table 2 below.
ZT=σS.sup.2T/K  [Mathematical Equation]

(21) Herein, ZT represents a thermoelectric performance index, 6 represents electrical conductivity, S represents a Seebeck coefficient, T represents temperature, and κ represents thermal conductivity.

(22) TABLE-US-00002 TABLE 2 Thermoelectric performance index of the compound semiconductors of examples and comparative examples Temperature Thermoelectric Category (° C.) performance index Example 1 50 0.26 100 0.35 200 0.57 300 0.81 400 1.04 500 1.24 Example 2 50 0.27 100 0.36 200 0.58 300 0.82 400 1.05 500 1.26 Example 3 50 0.28 100 0.37 200 0.60 300 0.84 400 1.08 500 1.28 Comparative 50 0.25 Example 1 100 0.34 200 0.54 300 0.76 400 0.98 500 1.18 Comparative 50 0.19 Example 2 100 0.26 200 0.43 300 0.61 400 0.81 500 0.99 Comparative 50 0.23 Example 3 100 0.31 200 0.50 300 0.70 400 0.88 500 1.03

(23) As shown in Table 2, it was confirmed that in the case of the compound semiconductors of Examples 1 to 3, as Sn and S were filled simultaneously, the thermoelectric performance index was enhanced over the entire temperature measurement section as compared with those of Comparative Examples 1 and 2.

(24) In addition, when Sn was excessively filled as in Comparative Example 3, it was confirmed that it could not be used as a thermoelectric material because the thermoelectric performance index was significantly lowered as compared with those of the examples.