TWI495114B - Fabrication method for light absorbing layers precursor solution - Google Patents

Description

Preparation method of light absorbing layer and precursor solution

This invention relates to light absorbing layers, and more particularly to a light absorbing layer of a CIGS solar cell.

In recent years, due to global climate change, environmental pollution problems and the shortage of resources, the solar photovoltaic industry has been booming under the warning of high environmental awareness and energy crisis. Among various solar cells, since Cu (In,Ga)Se ₂ , CIGS has high conversion efficiency, good stability, low material cost, and can be made into a film, it has received great attention. .

The CIGS compound belongs to the chalcopyrite structure, which is mainly composed of IB-IIIA-VIA compound, which is a direct bandgap semiconductor material, which can change the energy gap of the semiconductor by regulating the composition of the material. It is currently the main material for the light absorbing layer.

At present, the method for fabricating the CIGS absorber layer is mainly divided into a vacuum and a non-vacuum process, and the vacuum process includes a co-evaporation process, a sputtering process, and the like, and the non-vacuum process includes electrodeposition (electrodeposition) and electrodeless plating. (electroless), coating process or chemical spray pyrolysis, in which the vacuum process develops earlier and the technology is more mature, but because the process cost and equipment are expensive, many companies are headed Development of non-vacuum technology.

U.S. Patent No. 5,871,630 discloses a method of electrodeposition of a CIGS light absorbing layer by electrochemically obtaining a film containing copper, indium, gallium and selenium, followed by physical vapor deposition to make gallium/(indium +) in the film. The ratio of gallium is about 0.39.

International Solar Electronic Technology Inc. has proposed an ink process that uniformly coats copper, indium, and gallium nano-oxides onto a substrate and then selenization. A CIGS film was obtained.

UniSun Corporation of the United States has proposed a spray pyrolysis method, which first obtains metal oxide powder by ultrasonic spray oxidation, then grinds and disperses the powder to obtain a slurry, and then sprays the slurry onto the substrate by spraying. Finally, a CIGS film is obtained through a selenization step.

Among the above-mentioned methods, most of them need to synthesize a metal thin film, and then obtain a CIGS thin film through a selenization step, which is complicated in the process. Electrodeposition and electroless plating do not require a selenization process, but they require a complex redox reaction, so the plating solution is difficult to prepare and the electrode selection is limited.

In summary, if a method for easily fabricating a CIGS light absorbing layer can be provided, the future has great industrial application value.

The present invention provides a method for preparing a light absorbing layer, comprising: mixing a compound including Group IB, Group IIIA, and Group IVA in a solvent to obtain a precursor solution; coating the precursor solution on a substrate The substrate is placed in an atmosphere for heat treatment to form a light absorbing layer on the substrate.

The present invention further provides a light absorbing layer comprising a compound of the group IB-IIIA-IVA, which is obtained by the method for preparing the above light absorbing layer.

The invention also provides a precursor solution comprising a Group IB compound, a Group IIIA compound, a Group VIA compound and a solvent.

The present invention further provides a solar cell comprising: a back electrode formed on the substrate; a light absorbing layer formed on the back electrode, wherein the light absorbing layer comprises IB-IIIA-VIA The compound is prepared by the method for preparing the light absorbing layer described in claim 1; a buffer layer is formed on the light absorbing layer; and a transparent conducting oxide (transparent conducting oxide, TCO); and a front electrode formed on the transparent conductive layer.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

The invention provides a method for manufacturing a light absorbing layer, comprising: first preparing a precursor solution obtained by mixing a compound of a group IB, a group IIIA and a group VIA compound in a solvent, wherein the group IB comprises copper (Cu) ), silver (Ag), gold (Au) or a combination thereof, and the group IB compound includes an oxide, a nitride, a hydroxide, a halide, a nitrate, an acetate, a sulfate, a carbonate, Chloric acid, phosphoric acid, selenate, oxalic acid, phosphide, such as copper oxide (CuO), copper nitride (Cu(N ₃ ) ₂ ), copper hydroxide (Cu(OH) ₂ ), copper chloride (CuCl ₂ ), silver nitrate (AgNO ₃ ), copper nitrate (Cu(NO ₃ ) ₂ ), copper sulfate (CuSO ₄ ), copper acetate (Cu(CH ₃ COO) ₂ ), silver acetate (CH ₃ COOAg), carbonic acid Copper (Cu ₂ CO ₃ ), copper oxalate (CuC ₂ O ₄ ), copper chlorate (Cu(ClO ₄ ) ₂ ), copper phosphate (Cu ₃ (PO ₄ ) ₂ ), copper selenate (CuSeO ₄ ) or phosphorus Copper (Cu ₃ P). Group IIIA includes aluminum (Al), indium (In), gallium (Ga), or a combination thereof, and the Group IIIA compound includes an oxide, a nitride, a hydroxide, a halide, a nitrate, an acetate, and a group IIIA. Sulfate, carbonate, chlorate, phosphate, selenate, oxalate or phosphide, such as indium oxide (In ₂ O ₃ ), gallium oxide (Ga ₂ O ₃ ), indium nitride (InN), nitrogen Gallium (GaN), indium (Indium) (In(OH) ₃ ), gallium hydroxide (Ga(OH) ₃ ), aluminum chloride (AlCl ₃ ), indium chloride (InCl ₃ ), gallium chloride (GaCl _{3 )} ), aluminum nitrate (Al(NO ₃ ) ₃ ), indium nitrate (In(NO ₃ ) ₃ ), gallium nitrate (Ga(NO ₃ ) ₃ ), indium acetate (In(CH ₃ COO) ₃ ), aluminum acetate ( Al(CH ₃ COO) ₃ ), aluminum carbonate (Al ₂ (CO ₃ ) ₃ ), aluminum oxalate (Al ₂ (C ₂ O ₄ ) ₃ ), gallium acetate (Ga(CH ₃ COO) ₃ ), indium sulfate ( In ₂ (SO ₄ ) ₃ ), aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), gallium sulfate (Ga ₂ (SO ₄ ) ₃ ), indium chlorate (In(ClO ₄ ) ₃ ), gallium chlorate (Ga (ClO ₄ ) ₃ ), indium phosphate (InPO ₄ ), gallium phosphate (GaPO ₄ ), indium selenate (In ₂ (SeO ₄ ) ₃ ), gallium selenate (Ga ₂ (SeO ₄ ) ₃ ), indium phosphide (InP) or gallium phosphide (GaP). Group VIA includes sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, and Group VIA compounds include oxides, halides, oxyhalides, sulfides, selenides, amines of Group VIA, Urea, selenate, sulphate or sulphuric acid, such as selenium oxide (SeO ₂ ), strontium oxide (TeO ₂ ), sulfuric acid (H ₂ SO ₄ ), selenate (H ₂ SeO ₄ ), citric acid (H) ₂ TeO ₄ ), sulfurous acid (H ₂ SO ₃ ), selenite (H ₂ SeO ₃ ), telluric acid (H ₂ TeO ₃ ), thiourea (CS(NH ₂ ) ₂ ), selenium urea ( _{seenourea, CSe (NH 2) 2} ), selenium dichloride (SeCl _2), selenium tetrachloride (SeCl _4), tellurium dichloride (TeCl _2), four tellurium chloride (TeCl _4), selenium dibromide (SeBr ₂ ), selenium tetrabromide (SeBr ₄ ), cesium dibromide (TeBr ₂ ), cesium tetrabromide (TeBr ₄ ), selenium oxychloride (SeOCl ₂ ) or selenium sulfide (SeS ₂ ).

In the above precursor solution, the molar ratio of the group IB, IIIA, and VIA compounds is about (0.7~.3): (0.7~.3): (.5~20), preferably about (0.8). ~1.2): (0.8~1.2): (1.7~16), the best is about (0.8~1.2): (0.8~1.2): (1.8~15).

The selection of the above compounds is not limited to the above-mentioned compounds, and may be any compound which can contain Group IB, Group IIIA, and Group VIA. The solvent includes water, an acid, a base, an alcohol, a ketone, an ether, an amine or other organic solvent, and the solvent is a non-toxic general solvent, wherein the acid includes nitric acid, hydrochloric acid, sulfuric acid, acetic acid or pyruvic acid; The class includes sodium hydroxide solution or citric acid solution, ammonia water; alcohols include methanol, ethanol, propanol, isopropanol, n-butanol, isoamyl alcohol or ethylene glycol; ketones include acetone, methyl ethyl ketone, methyl iso Butanone; ethers include methyl ether, diethyl ether, methyl ethyl ether, diphenyl ether, ethylene glycol methyl ether, ethylene glycol butyl ether or ethylene glycol ethyl ether; amines include ethylene diamine, dimethylformamide, Triethanolamine or diethanolamine. However, the choice of the solvent is not limited to the above-mentioned alcohol, ether or ketone solvent, as long as it is a single or mixed solvent capable of dissolving the above compound.

In addition, the above precursor solution may be further added with other ions to improve the characteristics of the solar cell. For example, a group IA compound may be added to increase the photoelectric conversion efficiency of the battery, wherein the selected group IA includes lithium (Li), sodium (Na), potassium (K) or a combination thereof, and the group IA compound includes a group IA halide. , nitrate, acetic acid, sulfuric acid, carbonate or chloric acid, such as lithium chloride (LiCl), sodium chloride (NaCl), potassium chloride (KCl), lithium nitrate (LiNO ₃ ), sodium nitrate (NaNO ₃ ), potassium nitrate (KNO ₃ ), lithium acetate (CH ₃ COOLi), sodium acetate (CH ₃ COONa), potassium acetate (CH ₃ COOK), lithium sulfate (Li ₂ SO ₄ ), sodium sulfate (Na ₂ SO _{4 )} ), potassium sulfate (K ₂ SO ₄ ), lithium carbonate (Li ₂ CO ₃ ), sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), lithium chlorate (LiClO ₃ ), sodium chlorate ( NaClO ₃ ) or potassium chlorate (KClO ₃ ). The molar ratio of the precursor solution to the doped Group IA is about (10 to 2000): 1, preferably about (20 to 1000): 1.

In a preferred embodiment, copper chloride (CuCl ₂ ), indium chloride (InCl ₃ ), gallium nitrate (Ga(NO ₃ ) ₃ ), and selenous acid (H ₂ SeO ₃ ) are mixed in an ethanol solution. The precursor solution of the present invention can be obtained.

It should be noted here that the preparation process of the above precursor solution is carried out under normal room temperature and atmospheric environment, and no additional control of the atmosphere, temperature, humidity and pressure of the process is required.

In addition, a thickener may be added to the precursor solution to adjust the viscosity and adhesion of the precursor solution to facilitate the subsequent coating process, and the thickener is, for example, methyl cellulose or ethyl. Cellulose derivatives such as cellulose and carboxymethyl cellulose, starch derivatives, casein, sodium polyacrylate, polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, low molecular polyethylene wax, polypropylene decylamine, citric acid /ethylene glycol or a combination of the above.

Next, the precursor solution is coated on a substrate having a thickness of about 0.1 to 20 μm, preferably 0.2 to 15 μm, and an optimum thickness of 0.5 to 10 μm, and the selected coating method includes solution coating. Cloth method, such as spin coating, bar coating, dip coating, roll coating, spray coating, gravure coating ( Gravure coating), ink jet printing, slot coating or blade coating.

The substrate mentioned above includes glass, a polymer substrate, a metal substrate, a transparent conducting oxide (TCO) or a combination thereof, wherein the polymer substrate is, for example, polyimide (PI) or polyparaphenylene. Ethylene terephthalate (PET), poly carbonate (PC), poly(methyl methacrylate, PMMA) or a combination thereof, and the transparent conductive layer ( The TCO) includes, for example, zinc oxide: aluminum (ZnO: Al), indium oxide: tin (In ₂ O ₃ :Sn), tin dioxide: fluorine (SnO ₂ :F), or a combination thereof.

In addition, a back electrode is further included on the glass, the polymer substrate or the metal substrate, wherein the back electrode comprises a molybdenum (Mo) electrode, a titanium (Ti) electrode, a tungsten (W) electrode, a tantalum (Ta) electrode, and a niobium (Nb). Electrode or a combination of the above. In addition, a buffer layer is further included on the transparent conducting layer, wherein the buffer layer comprises cadmium sulfide (CdS), zinc hydroxide (Zn(OH) ₂ ), and zinc oxide. (ZnO), zinc sulfide (ZnS), indium selenide (In ₂ Se ₃ ), indium sulfide (In ₂ S ₃ ), or a combination thereof.

In addition, the precursor solution may be repeatedly applied to the substrate to increase the thickness of the film and then heat treated by an atmosphere. Alternatively, after the heat treatment, the coating and heat treatment steps are repeated to control the thickness and characteristics of the film, and when the coating step is repeated, the composition of the precursor solution can be adjusted.

It should be noted here that the substrate selected above depends on the process steps. When the solar cell is first fabricated from the back contact, for example, glass is selected as the substrate, and then the back electrode is fabricated and then coated. Absorbing layer. Further, when the solar cell is first produced from the front contact, for example, zinc oxide: aluminum (ZnO: Al) is selected as the substrate, and then a buffer layer is formed, and then the light absorbing layer is applied. Therefore, the selection of the substrate is not limited to the above-mentioned substrate, and as the solar cell process technology is developed, the selection of the substrate may also vary with the process steps.

Next, the substrate is placed in an atmosphere including a heat treatment to form a light absorbing layer thereon, wherein the light absorbing layer comprises a IB-IIIA-VIA compound. The atmosphere includes vacuum or non-vacuum, and the non-vacuum gas includes oxygen (O ₂ ), nitrogen (N ₂ ), hydrogen (H ₂ ), argon (Ar), or a combination thereof. The heat treatment temperature is about 350 ° C to 650 ° C, preferably about 400 ° C to 600 ° C, and the heat treatment time is about 0.1 to 8 hours, preferably about 0.3 to 6 hours, preferably 0.5 hours. After 4 hours, the light absorbing layer of the present invention can be obtained after heat treatment, which can be applied to a CIGS solar cell. In order to promote the reaction, the above non-vacuum gas still includes a gas of Group VIA, such as hydrogen selenide (H ₂ Se), hydrogen sulfide (H ₂ S), selenium (Se) vapor, sulfur (S) vapor, hydrazine ( Te) Vapor or a combination of the above.

In addition, in order to obtain a light absorbing layer of better characteristics, a pre-treatment step may be performed before the heat treatment step, and the pretreatment temperature is about 70 ° C to 500 ° C, preferably about 150 ° C to 400 °C, and the pretreatment time is about 1 minute to 4 hours, preferably about 10 minutes to 2 hours, to exclude organic matter that is not desired to remain. The atmosphere of the pretreatment may be air or a gas containing oxygen. After the above steps, the thickness of the light absorbing layer is finally obtained to be about 0.08 μm to 18 μm, preferably 0.1 μm to 12 μm.

In order to better understand the composition of the light absorbing layer, the present invention analyzes the IB-IIIA-VIA compound by X-ray diffraction pattern, and the experimental results show that it has (112), (211), (204)/(220) and (312). ) / (116) four main diffraction fronts, (204) and (220) are the same position of the diffraction front, (312) and (116) are also the same position of the diffraction front, the analysis results in line with the ICDD card number 35-1102 map, so the compound is a crystal structure of chalcopyrite, wherein the chemical formula of the IB-IIIA-VIA compound is expressed as IB _x IIIA _y VIA _(x+3y)/2 , where x=0.7~1.3, y=0.7~1.3. In addition, other elements may be doped in the compound.

In one embodiment, the resulting compound is CuIn _0.3 Ga _0.7 Se ₂ . In a preferred embodiment, the resulting compound is CuIn _0.7 Ga _0.3 Se ₂ .

In summary, the preparation method of the light absorbing layer of the present invention is characterized in that a compound of the VIA group is directly added to the precursor solution to obtain a compound of the IB-IIIA-VIA group, and in the prior art, it is required to pass the VIA group. The heat treatment of the gas (for example, the selenization step) or the complicated oxidation-reduction reaction (for example, electrodeposition and electroless plating) can be carried out to obtain the IB-IIIA-VIA compound. Therefore, the production method of the present invention is relatively simple. Can save production costs.

Further, the light absorbing layer of the present invention was observed by an atomic force microscope (AFM), and the experimental results showed that the surface type of the light absorbing layer was dense and uniform. Furthermore, the roughness of the light absorbing layer of the present invention is about 60 to 75 nm, and the surface roughness of the light absorbing layer of the present invention is rougher than the conventional vacuum selenization process (roughness is about 80 to 100 nm). It is lower, which is beneficial to the coating of other layers of materials. Furthermore, there is a literature (Solar Energy Materials & Solar Cells, 93 (2009) 114-118; Solar Energy, 77, (2004) 685-695) that, in CIGS solar cells, a light absorbing layer and a buffer layer are required. A PN junction is formed between the electrons and the hole. If the surface roughness of the light absorbing layer is too high, the buffer layer cannot completely cover the light absorbing layer, which will result in the light absorbing layer and the electrode. Direct contact, resulting in an unwanted shunt current, thereby reducing the photoelectric conversion efficiency of the solar cell. Therefore, the light absorbing layer obtained by the preparation method of the present invention has a low surface roughness. The shunt current can be avoided, thereby improving the photoelectric conversion efficiency of the solar cell.

The present invention further provides a light absorbing layer comprising the IB-IIIA-VIA compound obtained by the above-mentioned method for preparing a light absorbing layer.

The present invention also provides a precursor solution comprising a Group IB compound, a Group IIIA compound and a Group VIA compound and a solvent, wherein the molar ratio of the Group IB, Group IIIA, and Group VIA compounds is about (0.7 to 1.3): 0.7~1.3): (1.5~20), preferably about (0.8~1.2): (0.8~1.2): (1.7~16), the best is about (0.8~1.2): (0.8~1.2):( 1.8~15), and the selection of the IB group, the IIIA group, the VIA group compound and the solvent is the same as described above, and will not be described herein. In addition, the above precursor solution may be further added with other ions to improve the characteristics of the solar cell. For example, a group IA compound may be added to improve the photoelectric conversion efficiency of the battery, and the selection of the group IA compound is the same as described above, and details are not described herein again.

The present invention further provides a solar cell, see Fig. 1, which includes a substrate 10, wherein the substrate 10 comprises glass, a polymer substrate, a metal substrate, or a combination thereof. a back electrode 20 formed on the substrate 10, wherein the back electrode comprises a molybdenum (Mo) electrode, a titanium (Ti) electrode, a tungsten (W) electrode, a tantalum (Ta) electrode, a niobium (Nb) electrode, or a combination thereof The thickness of the back electrode is about 0.1 μm to 2 μm. A light absorbing layer 30 is formed on the back electrode 20, and the light absorbing layer 30 comprises a compound of IB-IIIA-VIA, which can be prepared by a solution coating method, and the composition and thickness of the compound and the preparation method thereof As mentioned above, it will not be described here. A buffer layer 40 is formed on the light absorbing layer 30, wherein the buffer layer 40 comprises cadmium sulfide (CdS), zinc hydroxide (Zn(OH) ₂ ), zinc oxide (ZnO), and zinc sulfide (ZnS). Indium selenide (In ₂ Se ₃ ), indium sulfide (In ₂ S ₃ ), or a combination thereof, which functions to bond with the light absorbing layer 30 to form a suitable heterojunction, which can increase the absorption efficiency of short-wavelength light. Its thickness is about 0.01 μm to 0.5 μm. A transparent conducting oxide (TCO) 50 is formed over the buffer layer 40 and includes zinc oxide: aluminum (ZnO: Al), indium oxide: tin (In ₂ O ₃ :Sn), tin dioxide: Fluorine (SnO ₂ :F) or a combination thereof, having a thickness of about 0.1 μm to 1 μm. And a front electrode 60 formed on the transparent conductive layer 50, wherein the front electrode 60 comprises aluminum, copper, nickel or a combination thereof, and has a thickness of about 0.1 μm to 2 μm. In addition, an anti-reflective layer 62 can be formed on the front electrode 60. The anti-reflective layer 62 is, for example, magnesium fluoride (MgF ₂ ) or other anti-reflective material, which serves to reduce the loss of light 70 during incident. Further, in addition to the above structure, a zinc oxide (ZnO) layer may be formed between the buffer layer 40 and the transparent conductive layer 50 for suppressing the loss of current, and the structure may be provided as needed.

The CIGS solar cell of the invention comprises the IB-IIIA-VIA compound in the light absorbing layer, which is prepared by directly containing the VIA compound precursor solution, without complicated selenization treatment or redox reaction. Simplify process steps and save costs. Moreover, the surface roughness of the obtained light absorbing layer is small, which helps to reduce the generation of the shunt current, thereby improving the photoelectric conversion efficiency of the solar cell.

[Examples] Example 1

The starting materials CuCl ₂ , InCl ₃ , Ga(NO ₃ ) ₃ and H ₂ SeO ₃ were dissolved in an ethanol solution in a molar ratio of 1:0.7:0.3:10, in which H ₂ SeO _{3 was} excessively added. Further, ethyl cellulose is added as a thickener, and after mixing, it becomes a precursor solution, and the precursor solution is applied to a glass substrate by spin coating to obtain high-purity nitrogen and hydrogen. The desired light absorbing layer CuIn _0.7 Ga _0.3 Se ₂ was obtained by heating at 350 ° C for 30 minutes in a mixed gas atmosphere.

Fig. 2 shows an X-ray diffraction pattern of the light absorbing layer, and the results show that the light absorbing layer has four main windings of (112), (211), (204)/(220), and (312)/(116). Shooting, where (204) and (220) are the same position of the diffraction front, (312) and (116) are also the same position of the diffraction front, in line with ICDD card number 35-1102 map, this is chalcopyrite crystal structure.

Further, the light absorbing layer was analyzed by an atomic force microscope (AFM), and as shown in Fig. 3, the surface roughness was 69.7 nm.

Comparative example 1

The starting materials CuCl ₂ , InCl ₃ and Ga(NO ₃ ) ₃ were dissolved in an ethanol solution in accordance with a molar ratio of 1:0.7:0.3. Ethyl cellulose (ethyl cellulose) is added as a thickener, and after mixing, it becomes a precursor solution, and the precursor solution is applied to a glass substrate by a spin coating method in a high-purity nitrogen-hydrogen mixed gas environment. The desired light absorbing layer CuIn _0.7 Ga _0.3 Se ₂ was obtained by heating at 350 ° C for 30 minutes and introducing selenium vapor.

The absorption layer can be found by X-ray diffraction pattern with four main diffraction fronts of (112), (211), (204)/(220), and (312)/(116), in accordance with ICDD card number 35. -1102 map, the light absorbing layer is a crystal structure of chalcopyrite.

Further, the light absorbing layer was analyzed by an atomic force microscope (AFM). As a result, as shown in Fig. 4, the surface roughness was 80.7 nm. It can be seen from Table 1 that the addition of selenium to the solution can effectively reduce the surface roughness of the light absorbing layer.

Example 2

The starting materials CuCl ₂ , InCl ₃ , Ga(NO ₃ ) ₃ and H ₂ SeO ₃ were dissolved in an ethanol solution in a molar ratio of 1:0.3:0.7:10, in which H ₂ SeO _{3 was} excessively added. Ethyl cellulose (ethyl cellulose) is added as a thickener, and after mixing, it becomes a precursor solution, and the precursor solution is applied to a glass substrate by a spin coating method in a high-purity nitrogen-hydrogen mixed gas environment. The desired light absorbing layer CuIn _0.3 Ga _0.7 Se ₂ was obtained by heating at 500 ° C for 1 hour.

The light absorbing layer is analyzed by X-ray diffraction pattern and shows that it has four main diffraction fronts (112), (211), (204)/(220), and (312)/(116), which conforms to the ICDD card. No. 35-1102 map, this light absorbing layer is a chalcopyrite crystal structure.

Example 3

The starting materials CuCl ₂ , InCl ₃ , CS(NH ₂ ) ₂ and H ₂ SeO ₃ are dissolved in an ethanol solution according to a molar ratio of 1:1:2.5:2.5, wherein CS(NH ₂ ) ₂ and H are excessively added. ₂ SeO ₃ . Ethyl cellulose (ethyl cellulose) was added as a thickener, and after mixing, it became a precursor solution, and the precursor solution was applied by spin coating to a glass substrate of sputtered Mo for high purity nitrogen. Under the environment, heating at 450 ° C for 30 minutes, the desired light absorbing layer CuInSeS can be obtained.

The light absorbing layer is analyzed by X-ray diffraction pattern and shows that it has four main diffraction fronts (112), (211), (204)/(220), and (312)/(116), which conforms to the ICDD card. No. 36-1311 map, this light absorbing layer is a chalcopyrite crystal structure.

Example 4

The starting materials CuCl ₂ , InCl ₃ , Al(No ₃ ) ₃ and SeO ₂ are dissolved in an aqueous solution according to a molar ratio of 1.2:0.1:0.7:1.5, wherein the amount of SeO ₂ added is insufficient, and then the selenization reaction is supplemented. Insufficient amount. Further, ethyl cellulose is added as a thickener and NaCl is used as a modifier. The molar ratio of Cu _1.2 In _0.1 Al _0.7 Se _1.8 to NaCl is 20:1. After mixing, it becomes a precursor solution. The precursor solution is applied to a transparent conductive glass substrate on which CdS is deposited by a spin coating method, heated at 550 ° C for 30 minutes in a high-purity argon atmosphere, and selenized by a selenium vapor. A Cu _1.2 In _0.1 Al _0.7 Se _1.8 light absorbing layer film containing Na.

The light absorbing layer was analyzed by X-ray diffraction pattern and showed that it has four main diffraction fronts of (112), (211), (204)/(220), and (312)/(116). The layer is a chalcopyrite crystal structure.

Example 5

The starting materials CuCl ₂ , InCl ₃ , Ga(NO ₃ ) ₃ and SeO ₂ were dissolved in the acetone solution in a molar ratio of 0.8:0.5:0.5:1.8. Further, ethyl cellulose is added as a thickener and NaCl is used as a modifier. The molar ratio of Cu _0.8 In _0.5 Ga _0.5 Se _1.8 to NaCl is 10:1. After mixing, it becomes a precursor solution. The precursor solution is applied to a titanium substrate by a spin coating method, heated at 400 ° C for 30 minutes in a high-purity nitrogen atmosphere, and a selenium vapor is introduced to obtain a Na-containing Cu _0.8 In _0.5 Ga _0.5 Se. _1.8 light absorbing layer film.

The light absorbing layer was analyzed by X-ray diffraction pattern and showed that it has four main diffraction fronts of (112), (211), (204)/(220), and (312)/(116). The layer is a chalcopyrite crystal structure.

Example 6

The starting materials AgNO ₃ , InCl ₃ , GaLNO ₃ ) ₃ and SeO ₂ were dissolved in an isopropanol solution in a molar ratio of 1:0.9:0.3:15, in which SeO _{2 was} excessively added. Ethyl cellulose (ethyl cellulose) is added as a thickener and KC1 is used as a modifier. AgIn _0.9 Ga _0.3 Se _2.3 and KCl molar ratio is 10:1. After mixing, it becomes a precursor solution and is rotated. The coating method was applied to a stainless steel substrate by a coating method, and heated at 400 ° C for 2 hours in a high-purity nitrogen-hydrogen mixed gas atmosphere to obtain a K-containing AgIn _0.9 Ga _0.3 Se _2.3 light absorbing layer film.

The light absorbing layer was analyzed by X-ray diffraction pattern and showed that it has four main diffraction fronts of (112), (211), (204)/(220), and (312)/(116). The layer is a chalcopyrite crystal structure.

While the invention has been described above in terms of several preferred embodiments, it is not intended to limit the scope of the present invention, and any one of ordinary skill in the art can make any changes without departing from the spirit and scope of the invention. And the scope of the present invention is defined by the scope of the appended claims.

10. . . Substrate

20. . . Back electrode

30. . . Light absorbing layer

40. . . The buffer layer

50. . . Transparent conductive layer

60. . . Front electrode

62. . . Antireflection layer

70. . . Light

1 is a cross-sectional view for explaining a solar cell according to an embodiment of the present invention.

Fig. 2 is an X-ray diffraction pattern for explaining the crystal structure of the light absorbing layer of an embodiment of the present invention.

Fig. 3 is an atomic force microscope image (AFM) for explaining the surface morphology of the light absorbing layer of an embodiment of the present invention.

Figure 4 is an atomic force microscope image (AFM) illustrating the surface morphology of a conventional light absorbing layer.

10. . . Substrate

20. . . Back electrode

30. . . Light absorbing layer

40. . . The buffer layer

50. . . Transparent conductive layer

60. . . Front electrode

62. . . Antireflection layer

70. . . Light

Claims (35)

A method for preparing a light absorbing layer, comprising: mixing a compound comprising Group IB, Group III A, Group VI A in a solvent to obtain a precursor solution; coating the precursor solution on a substrate The substrate is placed in an atmosphere for heat treatment to form a light absorbing layer on the substrate. The method for producing a light absorbing layer according to claim 1, wherein the light absorbing layer comprises an I B-III A-VI A compound. The method for preparing a light absorbing layer according to claim 1, wherein the precursor solution further comprises a group I A. The method of producing a light absorbing layer according to claim 3, wherein the Group I A comprises lithium (Li), sodium (Na), potassium (K) or a combination thereof. The method for producing a light absorbing layer according to claim 1, wherein the Group I B includes copper (Cu), silver (Ag), gold (Au) or a combination thereof. The method for preparing a light absorbing layer according to claim 1, wherein the compound of the group IB comprises an oxide, a nitride, a hydroxide, a halide, a nitrate, an acetate, a sulfate, and a IB group. Carbonic acid, chlorate, phosphate, selenate, oxalic acid or phosphide. The method of producing a light absorbing layer according to claim 1, wherein the Group III A comprises aluminum (Al), indium (In), gallium (Ga) or a combination thereof. The method for preparing a light absorbing layer according to claim 1, wherein the compound of Group III A comprises an oxide, a nitride, a hydroxide, a halide, a nitrate, an acetate, a sulfate containing III A. Carbonic acid , chlorate, phosphate, selenate, oxalate or phosphide. The method for producing a light absorbing layer according to claim 1, wherein the group VIA comprises sulfur (S), selenium (Se), tellurium (Te) or a combination thereof. The method for preparing a light absorbing layer according to claim 1, wherein the group VIA compound comprises an oxide, a halide, an oxyhalide, a sulfide, a selenide, an amination, a urea, and a selenium containing a group VIA. Acid, sulphate or citrate. The method for preparing a light absorbing layer according to claim 1, wherein the molar ratio of the group IB compound, the group III A compound, and the VI A compound in the precursor solution is about (0.7 to 1.3): 0.7~1.3): (1.5~20). The method for producing a light absorbing layer according to claim 1, wherein the solvent comprises water, an acid, a base, an alcohol, a ketone, an ether, an amine or a combination thereof. The method for preparing a light absorbing layer according to claim 1, wherein a pre-treatment step is included before the heat treatment step. The method for producing a light absorbing layer according to claim 13, wherein the pre-treatment step has a temperature of about 70 ° C to 500 ° C. The method for preparing a light absorbing layer according to claim 13, wherein the pre-treatment step is performed for about 1 minute to 4 hours. The method for producing a light absorbing layer according to claim 1, wherein the method of coating the precursor solution comprises a solution coating method. Preparation of the light absorbing layer as described in claim 16 a method in which the solution coating method includes spin coating, bar coating, dip coating, roll coating, spray coating, Gravure coating, ink jet printing, slot coating or blade coating. The method for preparing a light absorbing layer according to claim 1, wherein the substrate comprises glass, a polymer substrate, a metal substrate, a transparent conducting oxide (TCO) or a combination thereof. The method for preparing a light absorbing layer according to claim 18, wherein the polymer substrate comprises polyimide (PI), polyethylene terephthalate (PET), and polyethylene terephthalate (PET). Polycarbonate (PC), poly(methyl methacrylate) (PMMA) or a combination thereof. The method for preparing a light absorbing layer according to claim 18, wherein the transparent conductive layer (TCO) comprises zinc oxide: aluminum (ZnO: Al), indium oxide: tin (In ₂ O ₃ : Sn), Tin oxide: fluorine (SnO ₂ : F) or a combination thereof. The method for preparing a light absorbing layer according to claim 18, wherein the glass, the polymer substrate or the metal substrate further comprises a back electrode. The method for preparing a light absorbing layer according to claim 21, wherein the back electrode comprises a molybdenum (Mo) electrode, a titanium (Ti) electrode, a tungsten (W) electrode, a tantalum (Ta) electrode, and a niobium (Nb). Electrode or a combination of the above. The method for preparing a light absorbing layer according to claim 18, wherein a buffer layer is further included on the transparent conducting layer. The method for preparing a light absorbing layer according to claim 23, wherein the buffer layer comprises cadmium sulfide (CdS), zinc hydroxide (Zn(OH) ₂ ), zinc oxide (ZnO), and vulcanization. Zinc (ZnS), indium selenide (In ₂ Se ₃ ), indium sulfide (In ₂ S ₃ ), or a combination thereof. The method of producing a light absorbing layer according to claim 1, wherein the atmosphere comprises vacuum or non-vacuum. The method for preparing a light absorbing layer according to claim 25, wherein the non-vacuum gas comprises oxygen (O ₂ ), nitrogen (N ₂ ), hydrogen (H ₂ ), argon (Ar) or a combination thereof. . The method for preparing a light absorbing layer according to claim 25, wherein the non-vacuum gas further comprises hydrogen selenide (H ₂ Se), hydrogen sulfide (H ₂ S), selenium (Se) vapor, sulfur (S). ) Vapor, cerium (Te) vapor or a combination thereof. The method for producing a light absorbing layer according to claim 1, wherein the heat treatment temperature is about 350 ° C to 650 ° C. The method for preparing a light absorbing layer according to claim 1, wherein the heat treatment time is about 0.1 to 8 hours. The method for producing a light absorbing layer according to claim 1, wherein the light absorbing layer has a coating thickness of about 0.1 to 20 μm. The method for producing a light absorbing layer according to claim 1, wherein the light absorbing layer is applied to a CIGS solar cell. A precursor solution comprising a Group I B compound, a Group III A compound, a Group IA and a Group VI A compound dissolved in a solvent. A precursor solution as described in claim 32, wherein the Group I B compound is a chloride or a nitrate, the Group III A compound is a chloride or a nitrate, and the Group VI A compound is a selenate or an oxide. The precursor solution as described in claim 32, wherein the group I B compound, the group III A compound, and the VI A in the precursor solution The molar ratio of the compound is about (0.7~1.3): (0.7~1.3): (1.5~20). The precursor solution as described in claim 32, wherein the solvent comprises water, an acid, a base, an alcohol, a ketone, an ether, an amine or a combination thereof.