WO2014106694A1

WO2014106694A1 - Process for producing particles of chalcopyrite chosen from cu(inga)se2 and cu2znsns4 and pulverulent composition of particles thus obtained

Info

Publication number: WO2014106694A1
Application number: PCT/FR2013/000332
Authority: WO
Inventors: Aurélien AUGER
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives
Priority date: 2013-01-02
Filing date: 2013-12-11
Publication date: 2014-07-10
Also published as: FR3000486A1

Abstract

A process for producing particles of chalcopyrite chosen from CIGS and CZTS, comprising the following successive steps: providing a first solution containing metal ions, which are CIGS or CZTS precursors, adding a second solution to the first solution, wherein the second solution contains a reducing agent for reducing said metal ions so as to form CIGS or CZTS particles, and subjecting said particles in solution to microwave irradiation configured so as to crystallize the CIGS or CZTS particles.

Description

A process for producing chalcopite particles selected from Cu (InGa) Se ₂ and Cu ₂ ZnSnS ₄ and pulverulent composition of particles thus obtained.

Technical field of the invention

The invention relates to a process for producing chalcopyrite particles chosen from Cu (InGa) Se ₂ and Cu ₂ ZnSnS ₄ and also relates to a pulverulent composition of particles thus obtained.

State of the art

Quaternary semiconductor materials, such as Cu (lnGa) Se ₂ (CIGS) and Cu ₂ ZnSnS ₄ (CZTS), are increasingly used in the manufacture of high efficiency photovoltaic cells. Indeed, such semiconductor materials allow very good absorption of the incident light and has, moreover, excellent longevity. The use of crystalline thin films of CIGS or CZTS, as absorbing layers in photovoltaic devices, thus makes it possible to significantly improve the performance of these devices. And more particularly, the nanoparticles of CIGS or CZTS, present, today, an increasing interest for such applications. For example, the use of crystallized CIGS nanoparticles, in the form chalcopyrite Culn ₀ . ₈ Ga ₀ .2Se2, and of diameter less than 100 nm is particularly encouraging.

Jiang et al. (Inorganic Chemistry 2000, 39, 2964-2965) as well as Chun et al. (Thin Solid Films 2005, 480-481, 46-49) describe, respectively, the synthesis of nano-rods of CulnSe ₂ and nanoparticles CulnGaSe _2, by mixing the precursors in powder form in autoclaves presence of ethylene diamine and at temperatures between 180 ° C and 280 ° C. However, these temperature conditions, and especially pressure, require the use of special equipment and the process of elaboration is relatively long. In addition, the materials obtained are not in the ideal form Culn ₀ .8Ga ₀ . ₂ Se ₂ .

Benslim et al. (Journal of Alloys and Compounds 2010, 489, 437-440) discloses the synthesis of nanocrystalline powder of Culn ₀ .5Gao ₅ Se ₂ by mechanical grinding. Nevertheless, the CIGS particles thus obtained have an inhomogeneous distribution of the different elements.

Ahn et al. (Thin Solid Films 2000, 515, 4036-4040) synthesized nanoparticles Cuo.9lno.64Ga ₀ .23Se ₂ by colloidally from Cul, lnl ₃ Gal and ₃ in the presence of pyridine, methanol and Na ₂ Se at 0 ° C under an inert atmosphere. The particles have diameters of less than 100 nm but have an imperfect crystalline structure. In addition, the production process requires the use of toxic products.

Object of the invention

The aim of the invention is to overcome the drawbacks of the prior art and, in particular, to propose a method for producing chalcopyrite particles chosen from CIGS and CZTS which is simple and easy to implement, reproducible and allowing obtain crystalline particles of CIGS (Cu (InGa) Se ₂ ) or CZTS (Cu ₂ ZnSn (S, Se) ₄ ).

This object is approached by the appended claims. Brief description of the drawings

Other advantages and features will more clearly show the following description of particular embodiments of the invention given by way of nonlimiting example and represented in the accompanying drawings, in which:

FIG. 1 represents a nanoparticle image of CIGS obtained by transmission electron microscopy according to one embodiment of the invention,

FIG. 2 represents the diffraction diagram of the CIGS nanoparticles of FIG. 1 obtained by transmission electron microscopy,

FIG. 3 represents the elemental analysis, obtained by transmission electron microscopy, of the CIGS nanoparticles of FIG.

Description of a preferred embodiment of the invention

The process for producing chalcopyrite particles chosen from CIGS and CZTS comprises the following successive steps:

provide a first solution containing metal ions precursors of CIGS or CZTS,

adding a second solution to the first solution, the second solution containing a reducing agent for reducing said ions to form CIGS or CZTS particles,

subjecting said particles in solution to a microwave irradiation configured to crystallize CIGS or CZTS particles.

Chalcopyrite particles are particles of semiconductor material having a chalcopyrite structure.

CIGS particles are CIGS particles whose general formula is defined by Culn _x Ga _y Se _z with 0.7 x x 0,8 0.8; 0.1 ≤ y ≤ 0.2 and 1.5 ≤ z ≤ 2. CZTS particles are understood to mean CZTS particles whose general formula is defined by Cu _to Zn _p Sn, (S _a Se _b ) 4 with 0.7≤ α / (β + γ) ≤ 1.2; 0.7 β / γ ≤ 1.5; a + b = 1; and a or b may be zero.

Preferably, the first solution contains water, a first alkane and a first surfactant to form inverse micelles. By micelle is meant an aggregate of molecules having a hydrophilic end directed towards water and a hydrophobic end directed towards a solvent. Reverse micelle means that the water is present inside the micelle and that the micelle is surrounded by solvent: the hydrophilic end is directed towards the inside of the micelle while the hydrophobic end is directed to the outside of the micelle, ie to the solvent.

The first solution forms an emulsion. Emulsion means that the first solution contains at least two elements in the liquid state and immiscible with each other. And more particularly, it is a reverse microemulsion. Reverse microemulsion means that it is a suspension of microdroplets of a polar liquid, water in an apolar liquid, the alkane.

According to a preferred embodiment, to form CIGS particles, the metal ions of the first solution are copper, indium, gallium and selenium ions. To obtain these metal ions, ionic precursor salts of CIGS, that is to say ionic salts based on copper, indium, gallium and selenium, are dissolved in the water of the first solution. Preferably, the ionic salts are salts of CuCl ₂ , InCl ₃ , GaCl ₃ and H ₂ SeO ₃ . Even more preferentially, the molar ratios between the various CuCl ₂ , InCl ₃ , GaCl ₃ and H ₂ SeO ₃ salts are, on introduction into the aqueous phase, of the order of 1: 0.8: 0.2: 2 respectively.

According to another preferred embodiment, to form CZTS particles, the metal ions of the first solution are copper, zinc and tin. The first solution additionally comprises sulfur and / or selenium ions. To obtain these metal ions, ionic precursor salts of CZTS, that is to say ionic salts based on copper, zinc and tin as well as ionic salts based on sulfur and / or selenium, are dissolved in the water of the first solution. Preferably, the precursor ionic salts of CZTS are salts of CuCl ₂ , ZnCl ₂ , SnCl ₄ and Na ₂ S.

The metal salts, being dissolved in the water of the first solution, are therefore located inside the reverse micelles.

Preferably, the second solution contains water, a second alkane and a second surfactant in order to form inverse micelles. The second solution also forms an inverse microemulsion.

The reducing agent is dissolved in water and is therefore inside the reverse micelle.

According to a preferred embodiment, the reducing agent is hydrazine monohydrate. Advantageously, the hydrazine monohydrate makes it possible to reduce the copper, indium, gallium and selenium ions relatively rapidly and forms, after reduction of the ions, mainly nitrogen and water. By relatively fast, we hear of the order of a few minutes, e.g. less than 10 minutes, or instantaneous.

Alternatively, the η, η-diethylhydroxylamine may be used as a reducing agent.

The reducing agent may also be N- (methyl) mercaptoacetamide, triethylsilane, sodium borohydride, aluminum hydride and lithium or lithium diisopropylamide. Advantageously, the presence of a surfactant makes it possible to stabilize the reverse micelles, by interacting on the one hand with the solvent by its hydrophobic end and on the other hand with water by its hydrophilic end.

Preferably, the surfactant is nonionic, that is to say it has no net charge and therefore does not ionize in water. It may be an ester-linked surfactant, ether or amide. For example, it may be a sorbitan ester, such as the polyoxyethylene sorbitan ester also called Tween. Preferably, it is an ether-linked surfactant.

Even more preferably, at least one of the first or second surfactant is Triton X-100 or igepal C0520.

Advantageously, Triton X-100 is compatible with other anionic, cationic and nonionic surfactants. Triton X-100 is an excellent surfactant: it significantly modifies the surface tension, which facilitates the formation of reverse micelles.

Even more preferably, the first surfactant and the second surfactant are Triton X-100. This facilitates the fusion of the inverse micelles of the first solution with those of the second solution.

Preferably, at least one of the first or second alkane is cyclohexane. Cyclohexane is, advantageously, chemically inert and insoluble in water. Even more preferably, the first alkane and the second alkane are cyclohexane to facilitate the miscibility of the first and second solutions.

According to a preferred embodiment, the water is deionized water so as not to bring pollutant into the solution.

Preferably, at least one of the first or second solution contains an alcohol. Advantageously, the alcohol makes it possible to facilitate the formation of inverse micelles by increasing the flexibility of the interfacial layer. According to an even more preferred embodiment, the first solution and the second solution contain an alcohol. Advantageously, the first and second solutions contain the same alcohol. Thus, the surface tensions of the reverse micelles of the first and second solutions are identical and the coalescence of the micelles is facilitated.

In a preferred embodiment, the alcohol is 1-hexanol, also called n-hexanol. Advantageously, 1-hexanol has a good affinity with the surfactant and a good miscibility.

When the second solution is added to the first solution, there is collision of the inverse micelles of the first solution with the inverse micelles of the second solution and thus coalescence of the reverse micelles, resulting in a mixing of the aqueous phases of the first and second solution and therefore reduction of metal ions by the reducing agent.

The reduction of the metal ions makes it possible to form either CIGS particles or CZTS particles.

Advantageously, since the reaction is carried out inside the inverse micelles, the particles created are confined inside the reverse micelles and protected from aggregation with the particles of the other inverse micelles by the surfactant film. Inverse micelles act as microreactors.

The CIGS or CZTS particles in solution, thus obtained, are subjected to a hydrothermal treatment initiated by microwave irradiation. By hydrothermal treatment is meant a heat treatment in an aqueous medium. After irradiation, the solution is at a temperature below 100 ° C, of the order of 80 ° C-90 ° C.

Microwave irradiation makes it possible to crystallize CIGS or CZTS particles.

Preferably, the microwave irradiation is carried out at a power P of between 500W and 2000W, which makes it possible to obtain particles that are well crystallized while having relatively short irradiation times. With a power P between 500W and 2000W we mean that 500W≤ P≤ 2000W.

Advantageously, the irradiation does not destroy the micelles.

The duration of the microwave treatment is between 10 seconds and 2 minutes, and advantageously between 30 seconds and 1 minute 30 seconds.

After microwave irradiation, a membrane separation step is performed to purify the solution containing the crystallized particles of CIGS. Preferably, the membrane separation is performed by dialysis.

According to a preferred embodiment, after the microwave irradiation step, and before the membrane separation step, the solution containing the particles is destabilized. Destabilization means that the reverse micelles are destroyed.

The destabilization of the reverse micelles advantageously makes it possible to release the crystallized particles which were in the aqueous core from the reverse micelles.

Preferably, the destabilization is carried out by adding ethanol to the solution containing the crystallized particles. The volume of ethanol added to destabilize the solution containing the particles is at least equal to the volume of the solution containing the particles,

Example

In the CIGS particle synthesis method, CIGS particles were produced according to the protocol described below.

Step 1: Prepare the first solution and the second solution

A first solution S1 is prepared by mixing Triton X-100 (8.4 mL), 1-hexanol (8.2 mL) and cyclohexane (38 mL), and then adding a aqueous solution containing CuCl ₂ (54 mg, 134.45 gmol ^-1 (0.5 M), 1nCl ₃ (71 mg, 221.18 gmol ^-1 or 0.4 M), GaCl ₃ (14 mg, 176.08 gmol ^-1 or 0.1 M) , H ₂ SeO ₃ (103 mg, 128.97 gmol ^-1 , 1 M) and deionized water (0.8 mL). The solution S1 is then left stirring until stabilization at room temperature.

A second solution S2 is prepared by mixing Triton X-100 (8.4 mL), 1-hexanol (8.2 mL), cyclohexane (38 mL) and hydrazine monohydrate (0.8 mL to 12 M in water). The solution S2 is then left stirring until stabilization at room temperature.

Step 2: reduction of cuiyre, gallium, indium and selenium ions

The second solution S2 is added dropwise to the first solution S1. Preferentially, the solution S1 is stirred during the dropwise addition of the solution S2. The dropwise addition makes it possible to introduce the second solution homogeneously into the first solution.

A third solution S3 is then obtained. Solution S3 is stirred vigorously at room temperature for 5 minutes in order to reduce all the ions present in solution. Preferably, the reducing agent is introduced in excess relative to the ions present in solution. By ambient temperature is meant a temperature of between 18 ° C and 25 ° C. The copper, gallium, indium and selenium ions are therefore reduced, forming particles of Cu (lnGa) Se2. The formation of CIGS particles is characterized by a blackening of the solution.

Step 3: microwave irradiation

The third solution containing the Cu (InGa) Se ₂ particles is then subjected to microwave irradiation for one minute. Different powers were used: 500 W, 1000 W, 1500 W and 2000 W so as to obtain four different samples of CIGS particles, respectively called A, B, C and D. The microwave irradiation causing a heating of the third solution, the third solution is allowed to stand until it is at room temperature.

Step 4: washing

The third solution is destabilized by addition of ethanol (250 ml).

The particles are then washed several times with ethanol and once with water, each washing being followed by centrifugal sedimentation for 15 minutes at 6000 rpm (also denoted 6000 rpm). After the washing step, the purification of the CIGS particles is completed by dialysis (nominal MCWO 3500 Daltons) in degassed water (5 L) and with magnetic stirring for 3 days in order not to observe the natural phenomenon of oxidation.

Finally, a pulverulent composition of Cu (lnGa) Se ₂ particles is obtained for each power used.

The four powder compositions of CIGS particles are then characterized by transmission electron microscopy (TEM) analysis so as to obtain, for each sample:

- images to determine the particle diameter,

- diffraction patterns to determine if the particles are in crystalline form,

- and elementary analyzes to determine the composition of the particles.

The results obtained are listed in Table I. Table I

All the particles thus obtained have a diameter of less than 100 nm and, more particularly, a diameter of between 20 nm and 40 nm. FIG. 1 represents, for example, CIGS particles having a diameter of between 30 and 40 nm. The scale corresponds to 20nm.

Advantageously, the inverse microemulsion method makes it possible to obtain particles whose size distribution is monodisperse. By monodisperse, we mean that the particles, for the same conditions of elaboration, have almost all the same diameter, within a few nanometers. For example, the particles of samples A and B have a diameter of 25 nm ± 5 nm and the particles of samples C and D have a diameter of 35 nm ± 5 nm.

In addition, the diffraction patterns of the CIGS particles thus obtained, such as that of FIG. 2, show that the particles are crystallized.

As shown in FIG. 3, the crystallized particles contain copper, indium, gallium and selenium, confirming the reduction of the ions initially present in solution. The presence of nickel, silicon and carbon comes from the grid, having a carbon film, on which are deposited the particles to be observed under the transmission electron microscope. The particles obtained have the general formula Culn _x Ga _y Se ₂ with x = 0.75 ±

0.04, y = 0.165 ± 0.035 and z = 1.73 ± 0.13.

The method is also readily applicable to the preparation of CIGS particles having compositions different from Cu1 lno.8Gao.2Se ₂ chalcopyrite. For example, it is possible to modify the proportions of the reactants introduced,

1. e. the molar ratios between the copper, indium, gallium and selenium ions initially present in solution.

Advantageously, the process is devoid of selenization step and is applicable industrially.

This production method is not limited to the production of CIGS or CZTS particles, it can also be used for the elaboration of other semiconductor materials having a chalcopyrite structure. The process applies to both binary and ternary or even quaternary materials. The development of more complex materials can also be considered.

The materials thus obtained can be used for high efficiency solar cells.

Claims

claims

A method for producing chalcopyrite particles selected from CIGS and CZTS comprising the following successive steps:

provide a first solution containing metal ions precursors of CIGS or CZTS,

adding a second solution to the first solution, the second solution containing a reducing agent for reducing said metal ions to form CIGS or CZTS particles,

2. Method according to claim 1, characterized in that the metal ions are copper, indium, gallium and selenium ions in order to form CIGS particles.

3. Process according to claim 1, characterized in that the metal ions are copper, zinc and tin ions and sulfur and / or selenium ions in order to form CZTS particles.

4. Method according to one of claims 1 to 3, characterized in that the first solution comprises water, a first alkane and a first surfactant to form inverse micelles.

5. Method according to one of claims 1 to 4, characterized in that the second solution comprises water, a second alkane and a second surfactant to form inverse micelles.

6. Method according to any one of claims 4 to 5, characterized in that at least one of the first or second alkane is cyclohexane.

7. Method according to one of claims 1 to 6, characterized in that at least one of the first or second solution contains an alcohol.

8. Process according to claim 7, characterized in that the alcohol is 1-hexanol.

9. Process according to any one of claims 1 to 8, characterized in that the reducing agent is hydrazine monohydrate.

10. Method according to any one of claims 1 to 9, characterized in that the microwave irradiation is carried out at a power between 500W and 2000W.

11. A method according to any one of claims 1 to 10, characterized in that, after microwave irradiation, a membrane separation step is performed to purify the solution containing the particles, said membrane separation being performed by dialysis.

12. Pulverulent composition of CIGS particles obtained according to any one of claims 1 to 1 1, characterized in that the particles have the general formula Culn _x Ga _y Se _z with x = 0.75 ± 0.04, y = 0.165 ± 0.035 and z = 1.73 ± 0.13.

13. powdery composition of CIGS particles according to claim 12, characterized in that the crystalline particles have a diameter between 20nm and 40nm.