JP2015040154A - Czts-based compound semiconductor material and use of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CZTS-based compound semiconductor material, which can be sintered at lower firing temperature, for a solar battery.SOLUTION: A CZTS-based compound semiconductor material having Cu, Zn, Sn and S as main components is made to include a CZTS-based compound, and one or both of Sn and Zn as a sintering aid, and a dense sintered compact is obtained by firing at a low temperature of 500 to 670°C. 1 to 9 mass%, preferably 4 to 7 mass% or less of Sn or Zn is contained in the sintered compact based on the CZTS-based compound. In addition, the CZTS-based compound semiconductor material is fired at a firing temperature of preferably 500-670°C, or more preferably at a firing temperature of 550-570°C.

Description

  The present specification relates to a CZTS compound semiconductor material and use thereof.

  Solar cells are expected to contribute to the prevention of global warming and the like because they emit less carbon dioxide per power generation and do not require fuel for power generation. At present, single-junction solar cells having a pair of pn junctions using single crystal silicon or polycrystalline silicon are the mainstream among solar cells in practical use. In addition, in recent years, research and development has been actively promoted for thin-film solar cells that do not depend on silicon.

  In particular, there is a CZTS thin film solar cell that uses a compound semiconductor (referred to as a CZTS compound semiconductor in this specification) using Cu, Zn, Sn, and S instead of silicon for a light absorption layer. Since these materials are easily available and inexpensive, this type of solar cell has attracted attention.

  As a technique related to the CZTS-based thin film solar cell, for example, Patent Document 1 discloses sulfide firing in which powders of cupric sulfide, zinc sulfide, and zinc sulfide are mixed and then fired over 10 Mpa by a hot press method. A method for manufacturing a bonded target is disclosed.

JP 2010-245238 A

  As disclosed in Patent Document 1, in order to manufacture a dense sintered body of a CZTS-based compound semiconductor, it was necessary to fire at a temperature of 675 ° C. or higher. On the other hand, when using a CZTS type compound semiconductor for a solar cell, the form which forms a CZTS type compound semiconductor in the surface of an electrode is assumed. In such a laminated structure, an unfired CZTS-based compound semiconductor film applied to the surface of the electrode is fired at 675 ° C. or higher and sintered.

  However, for example, when a Mo electrode is used as an electrode, the reaction proceeds at the interface between the CZTS-based compound semiconductor and the Mo electrode and a different phase is formed when the firing temperature is 570 ° C. or higher. Therefore, it has been difficult for the CZTS-based thin film solar cell provided with the CZTS-based compound semiconductor film on the electrode surface to exhibit its original performance.

  The present specification provides a CZTS-based compound semiconductor material that can be sintered at a lower firing temperature and use thereof.

  As a result of various studies, the present inventors have obtained knowledge that a CZTS compound semiconductor can be densified as a sintered body at a lower firing temperature by adding a specific sintering aid and firing. It was. Based on this finding, the present specification provides the following means.

(1) A CZTS compound semiconductor material containing Cu, Zn, Sn, and S as main components,
A CZTS-based compound containing Cu, Zn, Sn and S as main components;
Either or both of Sn and Zn;
Including, material.
(2) The material according to (1), further comprising SnS.
(3) The material according to (1) or (2), wherein the Sn is contained in an amount of 1% by mass to 9% by mass with respect to the CZTS compound.
(4) The material according to any one of (1) to (3), wherein the Sn is contained in an amount of 4% by mass to 7% by mass with respect to the CZTS compound.
(5) The material according to any one of (1) to (4), wherein the Zn is contained in an amount of 1% by mass to 9% by mass with respect to the CZTS compound.
(6) The material according to any one of (1) to (5), wherein the Zn is contained in an amount of 4% by mass to 7% by mass with respect to the CZTS compound.
(7) A method for producing a CZTS-based compound semiconductor comprising Cu, Zn, Sn and S as main components,
Firing a sintered body containing Cu, Zn, Sn and S in the presence of either or both of Sn and Zn;
A method comprising:
(8) The method according to (7), wherein the object to be sintered is a CZTS-based compound.

(9) The method according to (7) or (8), wherein the firing step is further performed in the presence of SnS.
(10) The method according to any one of (7) to (9), wherein the baking step is a step of baking the CZTS compound at a temperature of 500 ° C. or higher and 670 ° C. or lower.
(11) The method according to any one of (7) to (10), wherein the baking step is a step of baking the CZTS compound at a temperature of 500 ° C. or higher and 570 ° C. or lower.
(12) The method according to any one of (7) to (11), wherein the baking step is a step of baking the CZTS compound at a temperature of 550 ° C. or higher and 570 ° C. or lower.
(13) A CZTS photoelectric conversion device including a CZTS compound semiconductor layer mainly composed of Cu, Zn, Sn, and S,
An electrode layer;
(1) to (6) CZTS-based compound semiconductor material in which the CZTS-based compound semiconductor material is integrated with the electrode layer by firing;
An apparatus comprising:
(14) The device according to (12), wherein the electrode layer includes Mo.
(15) A method for producing a CZT photoelectric conversion device comprising a CZTS compound semiconductor layer containing Cu, Zn, Sn and S as main components,
Supplying the CZTS compound semiconductor material according to any one of (1) to (6) to the electrode layer to form a CZTS compound semiconductor material layer;
Firing the electrode layer and the CZTS-based compound semiconductor material layer at a temperature of 500 ° C. or higher and 670 ° C. or lower;
A method comprising:
(16) A sintering aid for CZTS compounds,
A sintering aid containing either or both of Sn and Zn.
(17) The sintering aid according to (16), further comprising SnS.

It is a figure which shows the effect of Sn addition amount with respect to a CZTS type compound. It is a figure which shows Sn addition amount (SnS3 mass% addition) with respect to a CZTS type compound. It is a figure which shows the effect of Sn addition amount (SnS3 mass% addition) with respect to a CZTS type compound, and a calcination temperature. It is a figure which shows the effect of the Zn addition amount with respect to a CZTS type compound. It is a figure which shows Zn addition amount (SnS3 mass% addition) with respect to a CZTS type compound. It is a figure which shows the relationship between a calcination temperature, a sintering auxiliary agent, and a relative density. It is a figure which shows the relationship between the addition amount of SnS, and a relative density. It is a figure explaining the relationship between a calcination temperature and a relative density.

  The present disclosure relates to a CZTS-based compound semiconductor material with improved sinterability and use thereof.

  The CZTS-based compound semiconductor material disclosed in the present specification can contain either or both of Sn and Zn that function as a sintering aid in addition to the CZTS-based compound. Thereby, the sinterability of a CZTS type compound can be improved. That is, the CZTS compound can be sintered at a lower firing temperature and / or can be obtained as a sintered body having a higher density.

  In addition, by applying the CZTS-based compound semiconductor material disclosed in this specification to a CZTS-based thin film solar cell, an excellent battery utilizing the original characteristics of the compound semiconductor and the electrode can be obtained. Since CZTS compound semiconductor materials can be sintered at a lower temperature than conventional ones, for example, there is a possibility of decomposition and reaction at the sintering temperature of conventional CZTS compound semiconductors such as Mo (above 675 ° C.). This is because even if the composition is supplied directly to an electrode containing a certain metal and fired at once, it does not react with Mo or the like in the electrode to form a different phase. Hereinafter, the disclosure of this specification will be described in detail.

(CZTS compound semiconductor materials)
The material disclosed in the present specification is a material for obtaining a CZTS-based compound semiconductor containing Cu, Zn, Sn, and S as main components, the CZTS-based compound, and one or both of Sn and Zn, Can be included. By including Sn and / or Zn, the present material promotes the sintering of the CZTS-based compound and enables sintering at a lower firing temperature.

Examples of the CZTS compound include Cu _{2 + x} Zn _{1 + y} Sn _{1 + z} S _{4 + δ} (−0.1 ≦ x ≦ 0.1, −0.1 ≦ y ≦ 0.1, −0. 1 ≦ z ≦ 0.1, 0.1 ≦ δ ≦ 0.1). Among them, typically, Cu ₂ ZnSnS ₄ and Cu ₂ Zn (Sn, S) ₄ are listed. Cu ₂ ZnSnS ₄ is preferable.

  This material can contain Sn which functions as a sintering aid in addition to the CZTS-based compound. Sn means Sn as a simple substance and does not include a compound such as SnS. Sn is preferably included in the material as a powder.

  This material can contain Zn that functions as a sintering aid in addition to the CZTS-based compound. Zn means Zn as a simple substance and does not include a compound containing Zn. Zn is preferably contained in the material as a powder.

  This material can also contain Sn and Zn each functioning as a sintering aid, or both of them. Preferably, at least Sn is included.

  Since both Sn and Zn are constituent elements of the CZTS-based compound, they can be dissolved in CZTS after sintering to form a chalcopyrite single phase and exhibit the preferable characteristics of the CZTS-based compound.

  Sn in this material can be included with respect to the CZTS compound so that the sintering temperature can be lowered. Preferably, Sn is contained in an amount of 1% by mass to 9% by mass with respect to the CZTS compound. Within this range, even when firing at a temperature of 570 ° C. or lower, the relative density can be improved by adding Sn. If the amount is less than 1% by mass, the addition effect is hardly recognized, and if it exceeds 9% by mass, the relative density addition effect becomes insufficient. More preferably, it is 3 mass% or more, More preferably, it is 4 mass% or more, More preferably, it is 5 mass% or more. More preferably, it is 8 mass% or less, More preferably, it is 7 mass% or less, More preferably, it is 6 mass% or less.

  Moreover, Zn can be included so that a sintering temperature can be lowered | hung with respect to a CZTS type compound. Preferably, Zn is contained in an amount of 1% by mass to 9% by mass with respect to the CZTS compound. Within this range, even when firing at a temperature of 570 ° C. or lower, the relative density can be improved by adding Zn. If the amount is less than 1% by mass, the addition effect is hardly recognized, and if it exceeds 9% by mass, the relative density addition effect becomes insufficient. More preferably, it is 3 mass% or more, More preferably, it is 4 mass% or more, More preferably, it is 5 mass% or more. More preferably, it is 8 mass% or less, More preferably, it is 7 mass% or less, More preferably, it is 6 mass% or less.

  When Sn and Zn are contained in this material, it is preferable that Sn and Zn are contained in a molar ratio of about 1: about 1 in consideration of obtaining a chalcopyrite single phase crystal phase.

  The material can further contain SnS in addition to Sn and / or Zn. SnS can further improve sinterability by combining with Sn or Zn. In particular, in the case of sintering at 570 ° C. or lower, for example, about 500 ° C. or higher and 560 ° C. or lower, a combination of Sn and / or Zn and SnS is preferable. More preferably, they are 500 degreeC or more and 550 degrees C or less, More preferably, it is 540 degrees C or less, More preferably, it is 530 degrees C or less, More preferably, it is 520 degrees C or less.

SnS alone can improve the sinterability of the CZTS compound, but in that case, the amount of SnS added to Cu ₂ ZnSnS ₄ is 1% by mass or more and 9% by mass with respect to the CZTS compound. % Or less, more preferably, the upper limit is 7% by mass or less, and further preferably 5% by mass or less. Moreover, an upper limit is good also as 4 mass% or less. Preferably, the lower limit is 2% by mass or more. More preferably, it is 2% by mass or more and 4% by mass or less, and typically 3% by mass.

  This material can be obtained, for example, by mixing one or two or more selected from CZTS compounds and the above-mentioned sintering aid components. Mixing may be dry or wet, but is preferably dry. Typically, this material can be obtained by mixing with a ball mill for several hours to several tens of hours, preferably within about 30 hours.

  The material may be a mixed powder or a suspension or paste dispersed in a suitable medium such as a slurry. Further, the material may be a sintered compact formed into an appropriate shape (film shape, plate shape, disk shape, etc.). These can be obtained by a general molding method applied to ceramics.

(Sintering aid)
The sintering aid disclosed in this specification is a sintering aid for CZTS-based compounds. The present sintering aid can contain either or both of Sn and Zn. According to the present sintering aid, the sinterability of the CZTS-based compound can be improved, the sintering can be performed at a lower firing temperature, and / or the CZTS-based compound can be sintered more densely. .

  About Sn and Zn contained in this sintering aid, it is the same as Sn and Zn in the present composition already explained, and the present composition can contain Sn and Zn alone or both, Furthermore, SnS can be included.

  When this sintering auxiliary agent contains Sn or Zn and SnS, it is preferable to contain so that it may become a suitable ratio with respect to a CZTS type compound. It is preferable that Sn or Zn: SnS is 1-9: 2-4 by mass ratio. More preferably, it can be set to 2-8 / 3 to 8/4 to 7/4 to 6: 2 to 4 with reference to a preferable ratio of Sn or Zn to the CZTS compound in the present composition already described. .

  The present sintering aid may be in the form of one or more kits selected from the group consisting of Sn, Zn and SnS. That is, it can also be set as the kit which contains each metal single-piece | unit and a metal compound as a single formulation, respectively, and uses it combining this suitably.

  The sintering aid is used as a sintering aid by being added to and mixed with the CZTS compound, and also used by being mixed with a firing raw material that can be obtained by firing the CZTS compound.

(CZTS compound semiconductor manufacturing method)
This manufacturing method is a method for manufacturing a CZTS-based compound semiconductor containing Cu, Zn, Sn, and S as main components. In this method, the process of baking the to-be-sintered body containing Cu, Zn, Sn, and S in presence of either or both of Sn and Zn can be provided. Preferably, the firing step is a CZTS-based compound as the sintered body. Further, the firing step is a step of firing the CZTS compound in the presence of SnS. According to this method, since the sintered body containing Cu, Zn, Sn and S is fired in the presence of either or both of Sn and Zn, the sintering temperature of the original CZTS compound (675 ° C.) The sintered body can be sintered at a lower temperature. For this reason, in addition to being advantageous in terms of energy cost, adverse effects on the other materials due to the firing temperature of the CZTS compound are suppressed or avoided when firing integrally with the other materials.

  The to-be-sintered body containing Cu, Zn, Sn, and S refers to a material that becomes a CZTS-based compound densified by firing in addition to the CZTS-based compound described above. For example, in addition to a precursor film formed by a vacuum method such as a sputtering method or a vacuum vapor deposition method before passing through a sulfidation process, a so-called solid phase synthesis method or a CZTS compound synthesized from a liquid phase can be used.

  Various aspects can be applied to Sn, Zn, and SnS used in the firing step, as already described in the description of the present material. That is, the ratio of Sn, Zn, and SnS to the CZTS compound can be applied. Each aspect as already demonstrated is applicable also about a CZTS type compound. In consideration of sinterability, the sintering aid component and the CZTS compound are preferably subjected to the firing step in a mixed state, that is, in a state of various forms of compositions.

  In the firing step, the sintering aid component and the CZTS-based compound can be fired alone, for example, as a film-like body, a plate-like body, a disk-like body, etc., or a laminated layer brought into contact with other elements Alternatively, it can be integrally fired in an integrated state. For example, in order to form this material layer on another material layer, a general method for forming a ceramic thin film can be employed. For example, when manufacturing a photoelectric conversion device such as a CZTS-based thin film solar cell, the material layer can be fired in a state of a CZTS-based compound semiconductor material layer integrated with a Mo (molybdenum) metal layer.

  In the firing step, it is preferable to fire the CZTS-based compound at a temperature of 500 ° C. or higher and 670 ° C. or lower. The sintering temperature of the CZTS compound is 675 ° C., but at least in the presence of Sn and / or Zn, the CZTS compound can be sintered even at 670 ° C. or less. Considering the density of the sintered body, the firing temperature is preferably 520 ° C. or higher, more preferably 530 ° C. or higher, further preferably 540 ° C. or higher, and more preferably 550 ° C. or higher. In consideration of the temperature characteristics of the raw materials contained in the element that is integrally fired, such as Mo, and the characteristics of the integral product obtained by the integral firing, the firing temperature is preferably lower. Specifically, the firing temperature is preferably 650 ° C. or lower, more preferably 600 ° C. or lower, further preferably 580 ° C. or lower, and more preferably 570 ° C. or lower. The firing temperature is preferably 550 ° C. or higher and 570 ° C. or lower in consideration of the sinterability of the CZTS compound.

  The firing step is performed in a non-oxidizing gas atmosphere such as a nitrogen gas atmosphere.

  The firing time in the firing step is not particularly limited, but can be appropriately set in consideration of the film thickness and sinterability. For example, the time can be from about one hour to about several tens of hours, and typically about several hours.

(CZTS photoelectric conversion device including a CZTS compound semiconductor layer containing Cu, Zn, Sn and S as main components)
The CZTS-based photoelectric conversion device disclosed in the present specification can include an electrode layer and a CZTS-based compound semiconductor layer in which a CZTS-based compound semiconductor material is integrated with the electrode layer by firing. According to this apparatus, since it is possible to perform integration by sintering at a temperature of 675 ° C. or less, which is the sintering temperature of the CZTS compound, a photoelectric conversion device that can exhibit the original characteristics of the electrode layer and the CZTS compound semiconductor layer It has become. Moreover, since firing at a lower temperature is possible, there is no foreign phase between the electrode layer and the CZTS-based compound semiconductor layer, or the formation of the foreign phase is suppressed.

  The CZTS-based photoelectric conversion device is not particularly limited as long as it includes a CZTS-based compound semiconductor layer as a light absorption layer, but typically, a CZTS-based thin film solar cell can be mentioned. Moreover, although the electrode layer with which this photoelectric conversion apparatus is provided is Mo, Ti, Cr, etc., Preferably it is Mo.

  This device can include other elements necessary as a photoelectric conversion device. For example, in the case of a CZTS-based thin film solar cell, a transparent conductive film such as an ITO thin film or a ZnO film is further provided on the CZTS-based compound semiconductor layer, and a high-resistance buffer layer is provided on the CZTS-based compound semiconductor layer as necessary. Can be provided.

(Manufacturing method of a CZTS photoelectric conversion device including a CZTS compound semiconductor layer containing Cu, Zn, Sn, and S as main components)
A method for producing a CZTS-based photoelectric conversion device disclosed in the present specification includes a step of supplying a CZTS-based compound semiconductor material disclosed in the present specification to an electrode layer to form a CZTS-based compound semiconductor material layer; Firing the electrode layer and the CZTS compound semiconductor material layer at a temperature of 500 ° C. or higher and 670 ° C. or lower. According to this method, since the CZTS compound can be fired and densified at a temperature lower than the original sintering temperature (675 ° C.) of the CZTS compound, the electrode layer and the CZTS compound can be integrated. A photoelectric conversion device that can exhibit the original characteristics of each semiconductor layer can be easily obtained.

  The CZTS photoelectric conversion device can be manufactured by a known method. Typically, an electrode layer is formed on a substrate, and a CZTS-based semiconductor material is supplied on the electrode layer to form the layer. In forming the material layer for the metal electrode layer, various methods used for film formation of ceramics can be appropriately employed.

  The various aspects in the manufacturing method of the CZTS type compound semiconductor already demonstrated can be applied to a baking process. In particular, when Mo is used for the metal electrode, Mo and the CZTS-based compound react at 570 ° C. or more, and a different phase is formed between the electrode layer and the material layer. However, in the case of the present composition layer, it is possible to form a dense CZTS compound semiconductor layer that is sintered while suppressing or avoiding the formation of such undesirable reactions and heterogeneous phases. For this reason, a preferable CZTS type photoelectric conversion device can be produced.

  After forming the CZTS-based compound semiconductor layer by the firing process, a film necessary as a photoelectric conversion device is further formed. For example, in the case of a CZTS-based thin film solar cell, an n-type semiconductor layer such as CdS is formed on the CZTS-based compound semiconductor layer, and a transparent conductive film such as an ITO thin film or a ZnO film is formed on the n-type semiconductor layer. A CZTS-based thin film solar cell can be completed by forming a high resistance buffer layer or the like as necessary.

  Hereinafter, specific examples embodying the disclosure of the present specification will be described, but these specific examples do not limit the disclosure of the present specification.

In this example, 1 to 10% by mass of Sn powder was added to Cu ₂ ZnSnS ₄ powder, put into a ball mill and mixed for 24 hours in a dry manner. This mixed powder was molded into a disk shape having a diameter of 10 mm, and further CIP molded at 245 MPa to obtain a green compact for firing. The green compact was calcined at 560 ° C. for 2 hours in a nitrogen atmosphere, a sample was taken out, and the density of the sample was measured. The measurement results of the Sn addition amount and the relative density are shown in FIG.

As shown in FIG. 1, when Sn was not added, the relative density was about 70%, but by adding Sn, a high relative density of about 90% at the maximum could be obtained. Further, the relative density of 75% or more can be ensured when the Sn addition amount to the Cu ₂ ZnSnS ₄ powder is in the range of 1% by mass to 9% by mass, and the relative density of 80% by 3% to 8% by mass. It was found that the above can be secured, and a relative density of 80% can be secured at 5% by mass or more and 7% by mass or less.

In this example, 1 to 10% by mass of Sn powder of 3% by mass and 3% by mass of SnS powder were added to Cu ₂ ZnSnS ₄ powder, put into a ball mill, and mixed in a dry process for 24 hours. This mixed powder was molded into a disk shape having a diameter of 10 mm, and further CIP molded at 245 MPa to obtain a green compact for firing. The green compact was calcined at 560 ° C. for 2 hours in a nitrogen atmosphere, a sample was taken out, and the density of the sample was measured. The measurement results of the Sn addition amount and the relative density are shown in FIG.

As shown in FIG. 2, when Sn was not added, the relative density was about 70%. However, by adding Sn, a high relative density of 97% at the maximum could be obtained. Further, the relative density was 93% without addition of Sn but only with the addition of SnS, but it was found that a higher relative density can be obtained by combining with Sn. In addition, the relative density of 93% or more can be ensured when the Sn addition amount with respect to the Cu ₂ ZnSnS ₄ powder is in the range of 1% by mass to 9% by mass, and the relative density of 95% by 3% by mass to 8% by mass. It was found that the above can be secured, and a relative density of 96 to 97% can be secured at 5% by mass to 7% by mass.

  In this example, the sample was taken out in the same manner as in Example 2 except that the firing temperature was 500 ° C., and the density of the sample was measured. The measurement results of the Sn addition amount and the relative density are shown in FIG.

As shown in FIG. 3, even at a firing temperature of 500 ° C., the relative density was about 65% when Sn was not added under the addition of 3% by mass of SnS, but by adding Sn, the relative density was as high as 87% at maximum. The density could be obtained. Further, it was found that the relative density of 85% or more can be ensured when the amount of Sn added to the Cu ₂ ZnSnS ₄ powder is in the range of 3 mass% to 7 mass%. It was also found that the best relative density was obtained at 5% by mass.

In this example, 1 to 10% by mass of Zn powder was added to the Cu ₂ ZnSnS ₄ powder, put into a ball mill, and mixed in a dry manner for 24 hours. This mixed powder was molded into a disk shape having a diameter of 10 mm, and further CIP molded at 245 MPa to obtain a green compact for firing. The green compact was calcined at 560 ° C. for 2 hours in a nitrogen atmosphere, a sample was taken out, and the density of the sample was measured. The measurement results of the Zn addition amount and the relative density are shown in FIG.

As shown in FIG. 4, when Zn was not added, the relative density was about 70%, but by adding Zn, a high relative density of about 78% at the maximum could be obtained. In addition, the relative density of 72% or more can be ensured when the Zn addition amount with respect to the Cu ₂ ZnSnS ₄ powder is 1% by mass or more and 9% by mass or less. It was found that the above can be secured, and a relative density of 78% can be secured at 5% by mass or more and 7% by mass or less.

In this example, 1 to 10% by mass of Zn powder of 3% by mass of SnS powder was added to Cu ₂ ZnSnS ₄ powder, put into a ball mill, and mixed in a dry process for 24 hours. This mixed powder was molded into a disk shape having a diameter of 10 mm, and further CIP molded at 245 MPa to obtain a green compact for firing. The green compact was calcined at 560 ° C. for 2 hours in a nitrogen atmosphere, a sample was taken out, and the density of the sample was measured. The measurement results of the Zn addition amount and the relative density are shown in FIG.

As shown in FIG. 5, when Zn was not added, the relative density was about 70%, but by adding Zn, a high relative density of 97% at the maximum could be obtained. Further, the relative density was 93% without addition of Sn but only with the addition of SnS, but it was found that a higher relative density can be obtained by combining with Sn. In addition, the relative density of 93% or more can be ensured when the Sn addition amount with respect to the Cu ₂ ZnSnS ₄ powder is in the range of 1% by mass to 9% by mass, and the relative density of 95% by 3% by mass to 8% by mass. It was found that the above can be secured, and a relative density of 96 to 97% can be secured at 5% by mass or more and 7% by mass or less.

Sintering aid (Cu ₂ S, ZnS, SnS and SnS ₂ powders) so that the mass ratio of Cu ₂ ZnSnS ₄ and sintering aid is Cu ₂ ZnSnS ₄ : sintering aid = 100: 3 Was weighed. Then, Cu ₂ ZnSnS ₄ alone or Cu ₂ ZnSnS ₄ and a sintering aid were charged into a ball mill and mixed for 24 hours in a dry manner to obtain a mixed powder. Thereafter, the obtained mixed powder was formed into a disk shape having a diameter of about 10 mm and further subjected to cold isostatic pressing (CIP molding) at a pressure of 245 MPa to obtain a green compact for sintering. The obtained green compact was fired at a firing temperature of 675 ° C. or 560 ° C. for 2 hours in a nitrogen atmosphere, and then the relative density of the sample taken out was measured. The results are shown in FIG.

As shown in FIG. 6, when the firing temperature was 675 ° C., a CZTS-based compound semiconductor having a relative density of about 97% was obtained in the sample to which the sintering aid was not added. In addition, in a sample to which one kind selected from the group consisting of Cu ₂ S, ZnS and SnS ₂ was added as a sintering aid, a CZTS compound semiconductor having a relative density of about 85% was obtained, and SnS was used as a sintering aid. In the sample to which CZTS was added, a CZTS compound semiconductor having a relative density of 98% or more was obtained.

On the other hand, when the firing temperature is 560 ° C., the relative density is about 70% (the minimum is 67.8%, the maximum) in the sample to which the sintering aid is not added and the sample to which Cu ₂ S or ZnS is added as the sintering aid. 70.3%) of CZTS semiconductors were obtained. On the other hand, in the sample to which SnS was added as a sintering aid, a CZTS compound semiconductor having a relative density of about 95% (minimum 94.7%, maximum 95.8%) was obtained. As a sample to which SnS ₂ was added, a CZTS compound semiconductor having a relative density higher than 70% (minimum 73.9%, maximum 80.4%) was obtained. From the above results, it was found that by using SnS or SnS ₂ as a sintering aid, a densified CZTS compound semiconductor can be manufactured even if the firing temperature is reduced.

The SnS powder was weighed so that the mass ratio of Cu ₂ ZnSnS ₄ and SnS was Cu ₂ ZnSnS ₄ SnsS = 100: 1 or more and 13 or less. Then, only the Cu ₂ ZnSnS _4, and the Cu ₂ ZnSnS ₄ and SnS, by mixing for 24 hours in a dry and respectively placed in a ball mill to obtain a mixed powder. Thereafter, the obtained mixed powder was formed into a disk shape having a diameter of about 10 mm and further subjected to cold isostatic pressing (CIP molding) at a pressure of 245 MPa to obtain a green compact for sintering. The obtained green compact was fired at a firing temperature of 560 ° C. for 2 hours in a nitrogen atmosphere, and then the relative density of the sample taken out was measured. The results are shown in FIG. The vertical axis in FIG. 7 is the relative density, and the horizontal axis is the amount of SnS added.

As shown in FIG. 7, the CZTS compound semiconductor manufactured through the process of firing without adding SnS has a relative density of about 70% (minimum 67.8%, maximum 70.3%). However, by adding 1% by mass or more of SnS to Cu ₂ ZnSnS ₄ and firing, a CZTS compound semiconductor with improved relative density could be produced. In this experiment, the relative density of the CZTS-based compound semiconductor manufactured through the process of adding 3% by mass of SnS to Cu ₂ ZnSnS ₄ and firing was the highest. From the results shown in FIG. 7, the amount of SnS added to Cu ₂ ZnSnS ₄ is preferably 1% by mass or more and 9% by mass or less, more preferably the upper limit is 7% by mass or less, and still more preferably 5% by mass or less. Moreover, an upper limit is good also as 4 mass% or less. It was also found that the lower limit may preferably be 2% by mass or more.

The SnS powder was weighed so that the mass ratio of Cu ₂ ZnSnS ₄ and SnS was Cu ₂ ZnSnS ₄ : SnS = 100: 3. Then, only the well Cu ₂ ZnSnS ₄ and SnS Cu ₂ ZnSnS _4, each placed in a ball mill, by mixing for 24 hours in a dry, to give a mixed powder. Thereafter, the obtained mixed powder was formed into a disk shape having a diameter of about 10 mm and further subjected to cold isostatic pressing (CIP molding) at a pressure of 245 MPa to obtain a green compact for sintering. The obtained green compact was fired at a firing temperature of 500 ° C., 560 ° C., and 675 ° C. for 2 hours in a nitrogen atmosphere, and then the relative density of the sample taken out was measured. The results are shown in FIG. The vertical axis in FIG. 8 is the relative density, and the horizontal axis is the firing temperature.

  As shown in FIG. 8, the CZTS compound semiconductor has a relative density of 96.1% when the firing temperature is set to 500 ° C. and the firing temperature is set to 560 ° C. through the process of firing without adding SnS. The relative density was 68.8%, and it was 96.8% when the firing temperature was 675 ° C. That is, when firing without adding SnS, the relative density could not be increased even when the firing temperature was 560 ° C.

In contrast, a CZTS compound semiconductor manufactured through a process of adding 3% SnS to Cu ₂ ZnSnS ₄ and firing it has a relative density of 69.6% when the firing temperature is 500 ° C. At 560 ° C., it was 95.3%, and at 675 ° C., it was 99.5%. In other words, it was found that the firing temperature at which a dense CZTS compound semiconductor can be obtained can be reduced by 115 ° C. (from 675 ° C. to 560 ° C.) when SnS is not added by adding SnS and firing.

Further, when the generation layer after firing was examined by X-ray diffraction, when fired at was added SnS and 675 ° C. is, SnO ₂ was produced as impurities becomes excessive. On the other hand, when firing at 560 ° C. with SnS added, it was found that no impurity (SnO ₂ ) was generated as in the case of firing without adding SnS.

Claims (17)

A CZTS compound semiconductor material mainly composed of Cu, Zn, Sn and S,
A CZTS compound,
Either or both of Sn and Zn;
Including, material.   Furthermore, the composition of Claim 1 containing SnS.   The composition of Claim 1 or 2 which contains the said Sn 1 mass% or more and 9 mass% or less with respect to the said CZTS type compound.   The composition in any one of Claims 1-3 which contains the said Sn 4 mass% or more and 7 mass% or less with respect to the said CZTS type compound.   The composition in any one of Claims 1-4 which contains the said Zn 1 to 9 mass% with respect to the said CZTS type compound.   The composition in any one of Claims 1-5 which contains 4 to 7 mass% of said Zn with respect to the said CZTS type compound. A method for producing a CZTS compound semiconductor comprising Cu, Zn, Sn and S as main components,
Firing a sintered body containing Cu, Zn, Sn and S in the presence of either or both of Sn and Zn;
A method comprising:   The method according to claim 7, wherein the object to be sintered is a CZTS-based compound.   The method according to claim 7 or 8, wherein the firing step is further performed in the presence of SnS.   The method according to claim 7, wherein the baking step is a step of baking the CZTS compound at a temperature of 500 ° C. or more and 670 ° C. or less.   The said baking process is a method in any one of Claims 7-10 which is a process of baking the said CZTS type compound at the temperature of 500 to 570 degreeC.   The method according to any one of claims 7 to 11, wherein the firing step is a step of firing the CZTS compound at a temperature of 550 ° C or higher and 570 ° C or lower. A CZTS photoelectric conversion device comprising a CZTS compound semiconductor layer mainly composed of Cu, Zn, Sn and S,
An electrode layer;
A CZTS compound semiconductor material in which the CZTS compound semiconductor material according to any one of claims 1 to 6 is integrated with the electrode layer by firing;
An apparatus comprising:   The apparatus of claim 13, wherein the electrode layer comprises Mo. A method of manufacturing a CZT-based photoelectric conversion device including a CZTS-based compound semiconductor layer containing Cu, Zn, Sn, and S as main components,
Supplying the CZTS compound semiconductor material according to any one of claims 1 to 6 to an electrode layer to form a CZTS compound semiconductor material layer;
Firing the electrode layer and the CZTS-based compound semiconductor material layer at a temperature of 500 ° C. or higher and 670 ° C. or lower;
A method comprising: A sintering aid for CZTS compounds,
A sintering aid containing either or both of simple Sn and simple Zn.   The sintering aid according to claim 16, further comprising SnS.

Images