Method for preparing light absorption layer of copper-indium-gallium-sulfur-selenium thin film solar cells

Abstract

A preparation method of the light absorption layer of a copper-indium-gallium-sulfur-selenium film solar cell is provided. The method employs a non-vacuum liquid-phase chemical technique, which comprises following steps: forming source solution containing copper, indium, gallium, sulfur and selenium; using the solution to form a precursor film on a substrate by a non-vacuum liquid-phase process; drying and annealing the precursor film. Thus, a compound film of copper-indium-gallium-sulfur-selenium is gained.

Claims

1. A method for preparing a light absorption layer of copper-indium-gallium-sulfur-selenium (CIGSS) thin film solar cell, through a non-vacuum liquid phase process, the method comprising the steps of: (1) forming stable clear source solutions of Cu, In, Ga, S, and Se, including (a) forming stable clear source solutions of Cu by dissolving halides of Cu into a solvent selected from the group consisting of at least one of liquid ammonia, ethanolamine, diethanolamine, triethanolamine, isopropanolamine, formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, dimethylsulfoxide, tetrahydrothiophene-1,1-dioxide, pyrrolidone, and a mixture thereof, and adding a solution conditioner therein, wherein said solution conditioner is selected from the group consisting of at least one of chalcogenide of alkali metal and chalcogenide of alkali earth metal; (b) forming stable clear source solutions of In and Ga by dissolving halides of In and Ga into a solvent selected from the group consisting of at least one of methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, pentanol, 2-methyl-1-butanol, isopentanol, sec-pentanol, tert-pentanol, 3-methyl-2-butanol, and a mixture thereof; and (c) forming stable clear source solutions of S and Se by dissolving ingredients of sulfur and selenium into a solvent selected from the group consisting of at least one of ethanolamine, diethanolamine, triethanolamine, isopropanolamine, formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and a mixture thereof, wherein said ingredients of sulfur and selenium are selected from the group consisting of at least one of elemental S and Se, amine salts or hydrazine salts of S and Se; (2) producing a mixed clear solution of Cu, In, Ga, S, and Se by mixing said stable clear source solutions obtained from (1) according to the stoichiometry ratios of Cu, In, and Ga in formula Cu.sub.1-xIn.sub.1-yGa.sub.ySe.sub.2-zS.sub.z of the light absorption layer of said CIGSS thin film solar cell, and excess sulfur and/or selenium, wherein 0≦x≦0.3, 0≦y≦1, 0≦z≦2, and the excess degree of S or Se is 0%-800%; (3) using said mixed clear solution of (2) to form a precursor thin film on a substrate through a non-vacuum liquid phase process; and (4) drying and annealing said precursor thin film of (3) to produce a CIGSS compound thin film.

2. The method of claim 1, wherein said halide of Cu of (1) is represented by the formula MX, wherein M is Cu, and X is one or more halogens selected from Cl, Br and I; or said halide of Cu of (1) is represented by the formula MX.sub.2, wherein M is Cu, and X is one or more halogens selected from Cl, Br and I; or said halide of In, Ga of (1) is represented by the formula M′X.sub.3, wherein M′ is In and/or Ga, and X is one or more halogens selected from Cl, Br and I; or said halide of Cu, In, Ga of (1) is represented by the formula MM′X.sub.4, wherein M is Cu, M′ is In and/or Ga, and X is one or more halogens selected from Cl, Br and I.

3. The method of claim 1, wherein a) said amine salts of S and Se of (1) are the salts formed by H.sub.2S and H.sub.2Se with N—R.sub.1R.sub.2R.sub.3, wherein R.sub.1, R.sub.2 and R.sub.3 is independently selected from aryl, hydrogen, methyl, ethyl or C.sub.3-C.sub.6 alkyl; or b) said hydrazine salts of S and Se of step (1) are the salts formed by H.sub.2S and H.sub.2Se with R.sub.4R.sub.5N—NR.sub.6R.sub.7, wherein R.sub.4, R.sub.5, R.sub.6 and R.sub.7 is independently selected from aryl, hydrogen, methyl, ethyl or C.sub.3-C.sub.6 alkyl.

4. The method of claim 1, wherein said chalcogenide of alkali metal is A.sub.2Q, wherein A is selected from the group consisting of Li, Na, K, Rb, Cs and a combination thereof, and Q is selected from the group consisting of S, Se, Te and a combination thereof; and said chalcogenide of alkali earth metal is BQ, wherein B is selected from the group consisting of Mg, Ca, Sr, Ba and a combination thereof, and Q is selected from the group consisting of S, Se, Te and a combination thereof.

5. The method of claim 1, wherein said excess degree of S or Se is 100%-400%.

6. The method of claim 1, wherein, a mole ratio of a total amount of S and Se to a total amount of Cu, In and Ga ranges from 1.75 to 5 in said mixed clear solution of Cu, In, Ga, S and Se of step (2), and a mole ratio of a total amount of S to a total amount of S and Se ranges from 0 to 0.4 in said mixed clear solution of Cu, In, Ga, S and Se of step (2).

7. The method of claim 1, wherein said light absorption layer of CIGSS thin film solar cell of (2) has a formula Cu.sub.1-xIn.sub.1-yGa.sub.ySe.sub.2-zS.sub.z, wherein 0≦x≦0.3, 0.2≦y≦0.4, 0≦z≦0.2.

8. The method of claim 1, wherein said non-vacuum liquid phase process, which is used in step (3) for preparing said precursor thin film, is selected from the group consisting of spin-coating, tape-casting, spray-deposition, dip-coating, screen-printing, ink-jet printing, drop-casting, roller-coating, slot die coating, Meiyerbar coating, capillary coating, Comma-coating or gravure-coating; or said substrate of (3) is selected from any of the group consisting of polyimide, Si wafer, amorphous hydrogenated silicon wafer, silicon carbide, silica, quartz, sapphire, glass, metal, diamond-like carbon, hydrogenated diamond-like carbon, gallium nitride, gallium arsenide, germanium, Si—Ge alloys, ITO, boron carbide, silicon nitride, alumina, ceria, tin oxide, zinc titanate and plastic.

9. The method of claim 8, wherein said precursor thin film is annealed at a temperature of 250-650° C.

10. The method of claim 1, wherein said precursor thin film is annealed at a temperature of 50-850° C.

11. The method of claim 10, wherein said precursor thin film is annealed in Se atmosphere at a temperature of 450-600° C. for 10 to 60 minutes, and in S atmosphere at a temperature of 350-550° C. for 10 to 60 minutes.

12. The method of claim 1, wherein a thickness of said CIGSS compound thin film of step (4) is 5-5000 nm.

13. The method of claim 1, wherein said adding said solution conditioner thereby stabilizes said clear stable source solutions.

Description

SUMMARY OF DRAWINGS

(1) FIG. 1 is a process flow diagram for the preparation of the precursor solution of CIGSS thin films;

(2) FIG. 2 is the X-ray diffraction pattern of CIGSS powder prepared by drying the precursor solution of CIGSS thin film at 160° C.;

(3) FIG. 3 is the X-ray diffraction pattern of CIGSS thin film formed on a quartz substrate;

(4) FIG. 4 is the UV-Vis transmittance spectrum of CIGSS thin film formed on a quartz substrate;

(5) FIG. 5 is a front view and cross-sectional view scanning electron microscopy (SEM) image of the CIGSS thin film formed on a quartz substrate;

(6) FIG. 6 is a high resolution transmission electron microscopy (HRTEM) image of CIGSS thin film;

(7) FIG. 7 is a schematic diagram showing the structure of CIGSS thin film solar cell.

(8) FIG. 8 is a schematic diagram showing the efficiency of the present CIGSS thin film solar cell.

(9) FIG. 9 is a schematic diagram showing the SEM image of the present CIGSS thin film solar cell.

BEST MODE FOR CARRYING OUT THE INVENTION

(10) A great deal of experiments and investigations were conducted by inventors, and advantages can be seen apparently when employing the novel non-vacuum solution chemical method, which can be summarized as follows: simple in process, low cost, low capital investment, high utilization rate of raw materials, excellent controllability, high reproductivity, facile production of large-area and high-quality thin film as well as being favorable for large-scale production. The present invention is thus completed.

(11) As used in the disclosure, the term “aryl” includes monocyclic aryls comprising six carbon atoms, bicyclic aryls containing ten carbon atoms and tricyclic aryls containing fourteen carbon atoms, wherein each cycle may comprise 1 to 4 substituting groups. For example, the aryls include but are not limited to phenyl, naphthyl and anthracyl.

(12) Step 1

(13) In Step 1 of the present invention, stable source solutions of copper, indium, gallium, sulfur and selenium are formed by dissolving chalcogenides or halides of copper, indium, gallium as well as ingredients of sulfur and selenium into solvents containing strong coordinating groups, and adding a solution conditioner therein; wherein said ingredients of sulfur and selenium are selected from elemental sulfur and selenium, amine salts or hydrazine salts of sulfur and selenium, wherein

(14) said chalcogenides of step 1 can be depicted as M.sub.2Q, wherein M is copper (Cu), and Q is one or more chalcogens selected from sulfur (S), selenium (Se), tellurium (Te). For example, the representative chalcogenides include but are not limited to Cu.sub.2S, Cu.sub.2Se, and Cu.sub.2(S, Se), etc.;

(15) said chalcogenides of step 1 can also be depicted as MQ, wherein M is copper (Cu), and Q is one or more chalcogens selected from sulfur (S), selenium (Se), tellurium (Te). For example, the representative chalcogenides include but are not limited to CuS, CuSe, and Cu(S, Se), etc.;

(16) said chalcogenides of step 1 can also be depicted as M′.sub.2Q.sub.3, wherein M′ is indium (In) and/or gallium (Ga), and Q is one or more chalcogens selected from sulfur (S), selenium (Se), tellurium (Te). For example, the representative chalcogenides include but are not limited to In.sub.2Se.sub.3, Ga.sub.2Se.sub.3, (In, Ga).sub.2Se.sub.3 and (In, Ga).sub.2(S, Se).sub.3, etc.;

(17) said chalcogenides of step 1 can also be depicted as MM′Q.sub.2, wherein M is Cu, M′ is In and/or Ga, and Q is one or more chalcogens selected from S, Se, Te. For example, the representative chalcogenides include but are not limited to CuInS.sub.2, Cu(In, Ga)Se.sub.2 and Cu(In, Ga)(S, Se).sub.2, etc.;

(18) said halides of step 1 can be depicted as MX, wherein M is Cu, and X is one or more halogens selected from Cl, Br, I. For example, the representative halides include but are not limited to CuI, CuBr, and Cu(Br, I), etc.;

(19) said halides of step 1 can also be depicted as MX.sub.2, wherein M is Cu, and X is one or more halogens selected from Cl, Br, I. For example, the representative halides include but are not limited to CuI.sub.2, CuBr.sub.2, and Cu(Br, I).sub.2, etc.;

(20) said halides of step 1 can also be depicted as M′X.sub.3, wherein M′ is In and/or Ga, and X is one or more halogens selected from Cl, Br, I. For example, the representative halides include but are not limited to InI.sub.3, GaI.sub.3, (In, Ga)I.sub.3, and (In, Ga)(I, Br).sub.3, etc.;

(21) said halides of step 1 can also be depicted as MM′X.sub.4, wherein M is Cu, M′ is In and/or Ga, and X is one or more halogens selected from Cl, Br, I. For example, the representative halides include but are not limited to CuInI.sub.4, Cu(In, Ga)I.sub.4, and Cu(In, Ga)(I, Br).sub.4, etc.

(22) In Step 1, said chalcogenides and halides of copper, indium and gallium can be used separately or in combination.

(23) In addition, it should be pointed out that said source solutions of copper, indium and gallium can be prepared separately or together. When source solutions of different elements are separately prepared, multiple separately-prepared source solutions can be blended such as, according to certain stoichiometry ratio. For example, precursor solutions of copper-indium and gallium can be separately prepared, followed by mixing the two precursor solutions to form a CIGSS thin film precursor solution when necessary.

(24) In Step 1, the mixing ratio between said chalcogenides or halides of Cu, In, Ga and ingredients of sulfur and selenium can be adjusted according to the targeted product, that is to say, the ratio was determined according to the stoichiometry ratio of Cu, In and Ga in the light absorption layer of CIGSS thin film solar cells, Cu.sub.1-xIn.sub.1-yGa.sub.ySe.sub.2-zS.sub.z (0≦x≦0.3, 0≦y≦1, 0≦z≦2), wherein the ingredients of sulfur and selenium are selected from elemental sulfur and selenium, amine salts or hydrazine salts of sulfur and selenium.

(25) In Step 1, said solvent containing strong coordinating groups include: water (H.sub.2O), liquid ammonia (NH.sub.3), hydrazine compounds (R.sub.4R.sub.5N—NR.sub.6R.sub.7), lower alcohol, ethanolamine, diethanolamine, triethanolamine, isopropanolamine, formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, dimethylsulfoxide, tetrahydrothiophene-1,1-dioxide, pyrrolidone, or a mixture thereof. Preferably, the solvent having strong coordinating groups is selected from the group consisting of: liquid ammonia, hydrazine compounds (R.sub.4R.sub.5N—NR.sub.6R.sub.7), diethanolamine, triethanolamine and a mixture thereof. The hydrazine compounds is represented by the formula of R.sub.4R.sub.5N—NR.sub.6R.sub.7, wherein each of R.sub.4, R.sub.5, R.sub.6 and R.sub.7 is independently selected from aryl, hydrogen, methyl, ethyl, C.sub.3-C.sub.6 alkyl. The lower alcohol includes: methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, pentanol, optically reactive pentanol (2-methyl-1-butanol), isopentanol, sec-pentanol, tert-pentanol and 3-methyl-2-butanol or a mixture thereof. As used in this invention, said alkyl can be linear branched alkyl. Said alkyl can also be a cyclic alkyl.

(26) As known those skilled in the art, the solution can be stabilized by introducing solution conditioner. The solution conditioner of step 1 includes: (1) chalcogens, (2) transition elements, (3) chalcogenides of alkali metals, (4) chalcogenides of alkali earth metals, (5) amine salts of chalcogens, (6) alkali metals, (7) alkali earth metals. The chalcogens are selected from the group consisting of S, Se, Te and a combination thereof; the transition elements are selected from the groups consisting of: nickel (Ni), palladium (Pd), platinum (Pt), rhodium (Rh), iridium (Ir), ruthenium (Ru) and a combination thereof; the chalcogenides of alkali metals include A.sub.2Q, wherein A is selected from the group consisting of: Li, Na, K, Rb, Cs and a combination thereof, and Q is selected from the group consisting of: S, Se, Te and a combination thereof; the chalcogenides of alkali earth metals includes BQ, wherein B is selected from the group consisting of: Mg, Ca, Sr, Ba and a combination thereof, and Q is selected from the group consisting of: S, Se, Te and a combination thereof; the amine salts of chalcogens include one or a mixture of the salts formed by hydrogen sulfide (H.sub.2S), hydrogen selenide (H.sub.2Se) or hydrogen telluride (H.sub.2Te) with N—R.sub.1R.sub.2R.sub.3 (R.sub.1, R.sub.2, R.sub.3 is independently selected from aryl, hydrogen, methyl, ethyl, C.sub.3-C.sub.6 alkyl), the alkali metals are selected from the group consisting of: elemental Li, Na, K, Rb and Cs, and alloys or mixtures thereof; the alkali earth metals are selected from the group consisting of elemental Mg, Ca, Sr and Ba, and alloys or mixtures thereof.

(27) It should be noted that the solution conditioner may be unnecessary if the source solution is adequately stable, and the amount of the solution conditioner added to the solution is variable as long as the stability of the solution is ensured. This is well known to those skilled in the art.

(28) The solution conditioner can be separated from the solution. For example, the solution conditioner can be separated from the solution by filtration. It should be understood that some remaining solution conditioners will not exert any influence on the performance of the targeted products, which excludes the necessity of separation.

(29) Step 2

(30) In Step 2, the source solutions prepared in Step 1 are mixed according to the stoichiometry ratio of copper, indium, gallium of the light absorption layer of CIGSS thin film solar cell, Cu.sub.1-xIn.sub.1-yGa.sub.ySe.sub.2-zS.sub.z (0≦x≦0.3, 0≦y≦1, 0≦z≦2), with excess sulfur and/or selenium to produce a mixed solution of copper, indium, gallium, sulfur and selenium.

(31) Preferably, in the formula of Cu.sub.1-xIn.sub.1-yGa.sub.ySe.sub.2-zS.sub.z, 0≦x≦0.3, 0.2≦y≦0.4, 0≦z≦0.2.

(32) With regard to step 2, the excess degree of sulfur and/or selenium is 0%-800%, preferably 100%-400%. The degree of excess depends on the targeted CIGSS thin film. In another word, the relation of the source elements in the mixed solution of the Cu, In, Ga, S and Se, may be illustrated as in the following formula:
1≦(S+Se)/M≦9, preferably, 1≦(S+Se)/M≦5,

(33) wherein the (S+Se)/M refers to the mole ratio of the total amount of the S and Se to the total amount of the Cu, In and Ga, i.e. the (S+Se)/M equal to 1 when the elements of the CIGSS thin film solar cell has a stoichiometry mole ration.

(34) The mole ratio of the total amount of S to the total amount of S and Se in the mixed solution of Cu, In, Ga, S and Se ranges from 0 to 1,i.e. 0≦S/(S+Se)≦1, preferably, 0≦S/(S+Se)≦0.4, more preferably, 0≦S/(S+Se)≦0.3.

(35) For example, if a solution of Cu, In, Ga, S and Se contains 1 mmol S, 2 mmol Se, 1 mmol Cu, 0.7 mmol In, 0.3 mmol Ga, it means that (S+Se)/M=1.5, S/(S+Se)=0.33, i.e., if the (S+Se)/M=1.5, it means the total amount of the S and Se is in an excess of 50%.

(36) The present invention further provides a preferred embodiment as follows:

(37) providing a mixed solution of Cu, In, Ga, S and Se, wherein the mole ratio of the total amount of S and Se to the total amount of Cu, In and Ga ranges from 1.75 to 5, and the mole ratio of the total amount of S to the total amount of S and Se ranges from 0 to 0.4, preferably 0 to 0.3. After continuing research, the inventor found that when the contents of the mixed solution of Cu, In, Ga, S and Se are refined to a certain range, the CIGSS thin film solar cell achieved more satisfactory performance.

(38) Step 3

(39) In Step 3, the mixed solution prepared in Step 2 is applied onto a substrate through a non-vacuum liquid phase process to produce the precursor thin films.

(40) Wherein said non-vacuum processes used for step 3 include: (1) spin-coating, (2) tape-casting, (3) spray-deposition, (4) dip-coating, (5) screen-printing, (6) ink-jet printing, (7) drop-casting, (8) roller-coating, (9) slot die coating, (10) Meiyerbar coating, (11) capillary coating, (12) Comma-coating, (13) gravure-coating, etc.

(41) The substrates used for step 3 include: polyimide, Si wafer, amorphous hydrogenated silicon wafer, silicon carbide, silica, quartz, sapphire, glass, metal, diamond-like carbon, hydrogenated diamond-like carbon, gallium nitride (GaN), gallium arsenide, germanium, Si—Ge alloys, ITO, boron carbide, silicon nitride, alumina, ceria, tin oxide, zinc titanate, plastic and so on.

(42) Step 4

(43) In Step 4, the precursor thin films prepared in Step 3 are dried and annealed to produce the targeted CIGSS thin films.

(44) In step 4, the procedure of drying is carried out at a temperature of room temperature to 80° C., though other temperature can also be adopted as long as it is sufficient to achieve the final target.

(45) The annealing is carried out at a temperature of 50° C. to 850° C., preferably at a temperature of 250° C. to 650° C.

(46) The composition of the targeted CIGSS thin film is Cu.sub.1-xIn.sub.1-yGa.sub.ySe.sub.2-zS.sub.z, wherein 0≦x≦0.3, 0≦y≦1 and 0≦z≦2.

(47) The thickness of the targeted CIGSS thin film can be adjusted as required. For example, the thickness can be 5-5000 nm, and preferably, 100-3000 nm.

(48) The present invention further provides a preferred embodiment as follows:

(49) the precursor thin film was annealed in Se atmosphere at a temperature of 450-600° C. for 10 to 60 minutes, and in S atmosphere at a temperature of 350-550° C. for 10 to 60 minutes.

(50) After continuing research, the inventor found that when precursor thin film is treated by particular annealing atmosphere, as a result, the CIGSS thin film solar cell achieved more satisfactory performance.

ADVANTAGES

(51) The non-vacuum liquid phase chemical process for preparing light absorption layers of CIGSS thin film solar cells provided by the present invention exhibits the following advantages over those conventional high-vacuum vapor phase methods: simple in process, low cost, favorable controllability, high reproductivity, production of large-area and high-quality thin film and favorable for large-scale production, low capital investment and high utilization rate of raw materials, which leading to substantial decrease in production cost of CIGSS thin film solar cells, and will boosting the rapid development of CIGSS thin film solar cell industrialization.

(52) Moreover, as compared with the non-vacuum liquid phase methods of the prior art, the process provided by the present invention will not be hindered by the following shortcomings: incomplete selenization of the precursor thin film occurred in the oxide-based non-vacuum liquid method, the complexity in the controlling of the coated nano-particles encountered in the non-oxide-based non-vacuum liquid phase process as developed by Nanosolar, the difficulties in the stoichiometry-control of the thin film in electrochemical deposition methods, or the highly-concentrated impurities in the thin film prepared by spray pyrolysis.

(53) Accurate control and continuous adjustment of the stoichiometry of the targeted CIGSS thin film at atomic scale can be readily reached by the method provided in this invention, and the distribution of elements can also be facilely achieved through fabricating multi-layer thin films and adjusting the chemical composition in each layer.

(54) The method provided by this invention is characterized by: low annealing temperature, inhomogeneous composition in the resulted thin film, high surface smoothness, high crystallinity, favorable orientation degree, low concentration of impurities, applicable to various substrates (including polyimide and other organic flexible substrates) and facile to control the stoichiometry and element distribution in the film, which facilitates the fabrication of large-area and high-quality CIGSS thin films. Furthermore, the utilization rate of the raw materials of Cu, In, Ga, S and Se, etc. can be up to 100%.

(55) Other technological aspects of this invention will be apparent to those skilled in the art after reviewing the disclosure of the present invention.

(56) Hereinafter, further description of the present invention will be provided through specific embodiments. It should be noted that these embodiments are merely used for explaining rather than restricting the range of the present invention. The experiment processes without indication of specific operational parameters in the following embodiments are carried out under regular conditions, or follow the conditions recommended by the manufacturer. All terms of the portion and percentage used in this invention are in weight unless otherwise specified.

(57) All the technical terms used in this invention are in the same meanings with those familiar to those skilled in the relevant art unless otherwise specified. In addition, any similar or equivalent methods or materials can be applied in present invention.

Example 1

(58) 1. Preparation of the precursor solution of CIGSS thin film

(59) (a) Preparation of the solution comprising Cu and In

(60) 1 mmol Cu.sub.2(S,Se), 0.5 mmol In.sub.2Se.sub.3, 0.2 mmol InI.sub.3, 0˜8 mmol S and 0˜8 mmol Se were added into 2˜16 ml mixed solvents composed of methyl hydrazine, ethanolamine and dimethyl sulfoxide, wherein the volume ratio was methyl hydrazine:ethanolamine:dimethyl sulfoxide=1˜3:1˜6:1˜8. The mixture was agitated to produce a clear solution.

(61) (b) Preparation of the solution containing Ga

(62) 0.6 mmol Ga.sub.2Se.sub.3, 0.3 mmol GaBr.sub.3, 0.1 mmol GaI.sub.3, 0˜8 mmol Se and a trace of Ru powders were added into a 1˜8 ml mixed solvents composed of methyl hydrazine, ethanolamine and dimethyl sulfoxide, wherein the volume ratio was methyl hydrazine:ethanolamine:dimethyl sulfoxide=1˜3:1˜6:1˜8. The mixture was sufficiently agitated and filtrated through a 0.2 μm filter to produce a clear solution comprising Ga.

(63) (c) Preparation of the precursor solution of CIGSS thin film

(64) Above solutions comprising Cu/In and Ga are metered and blended at a volume ratio according to the stoichiometry ratios of Cu, In and Ga in the targeted CIGSS thin film to produce the precursor solution of CIGSS thin film.

(65) 2. Preparation of CIGSS thin film

(66) Above precursor solution of CIGSS thin film is applied onto a substrate through a non-vacuum film-forming process (selected from spin-coating, tape-casting, stamping and printing, etc) to fabricate a precursor CIGSS thin film. After drying under low temperature (room temperature˜80° C.), the precursor CIGSS thin film was rapidly annealed under high temperature (250° C.˜650° C.) to form CIGSS thin film.

(67) 3. Characterization of CIGSS thin film

(68) (a) Phase characterization

(69) The CIGSS precursor solution was dried at 120° C.˜200° C. under flow of dried inert gas to form black powders, which was characterized by X-ray diffraction (XRD) (as shown in FIG. 2). The result showed that the powder was CIGSS. The CIGSS thin film formed on quartz substrate was also characterized by XRD (as shown in FIG. 3), the XRD pattern showed that the thin film was CIGSS will a relatively strong (112) orientation.

(70) (b) Electrical properties

(71) The electrical properties of the thin film were measured by a four-electrode method on Accent HL5500 Hall System. The results (as shown in Table 1) illustrated that the as-prepared CIGSS thin film fulfilled the criterion of CIGSS thin film solar cell device.

(72) TABLE-US-00001 TABLE 1 Carrier concentration Carrier mobility Sample (cm.sup.−3) (cm.sup.−2 V.sup.−1 s.sup.−1) CIGSS 1.5 × 10.sup.17 1.12

(73) (c) Optical properties

(74) The UV-Vis transmittance spectrum of the CIGSS thin film formed on quartz substrate was measured. The results (as shown in FIG. 4) showed that the band gap of the CIGS thin film could meet the requirement of CIGS solar cell devices.

(75) (d) Characterization of the microstructure

(76) The microstructure of the as-formed CIGSS thin film was characterized. The left part of FIG. 5 was a front-view SEM image, and the right part was a cross-sectional SEM image of the CIGSS thin film. The as-prepared CIGSS thin film is characterized by excellent surface smoothness, homogeneous composition and high crystallinity, as shown in FIG. 5. FIG. 6 was a high resolution transmission electron microscopy (HRTEM) image of CIGSS thin film, which further illustrated that CIGSS thin film was well crystallized, and the lattice plane spacing is 0.331 nm, which is consistent with the spacing between the (112) lattice planes of CIGSS crystal structure.

(77) 4. Fabrication of CIGSS thin film solar cell

(78) The CIGSS thin film solar cell, which had a device structure as shown in FIG. 7, was prepared by a serial of steps as follows: firstly, a buffer layer was deposited onto the CIGSS thin film to a thickness of about 50 nm; then the window layer and interdigital electrode were prepared; finally, an anti-reflective film was deposited. A photoelectric conversion efficiency of 13% could be achieved with the as-fabricated CIGSS thin film solar cell having an aperture area of 1.5 cm.sup.2 after optimization.

Example 2

(79) 1. Preparation of the precursor solution of CIGSS thin film

(80) (a) Preparation of the solution containing Cu

(81) 1 mmol CuI was added into 2˜16 ml ethylene glycol. The mixture was sufficiently agitated to produce a clear solution.

(82) (b) Preparation of the solution containing In

(83) 1 mmol indium iodide and 0˜8 mmol Se were added into 1˜8 ml mixed solvents composed of methyl hydrazine and n-butanol, wherein the volume ratio was methyl hydrazine:n-butanol=1˜3:1˜8. The mixture was sufficiently agitated and filtrated through a 0.2 μm filter to produce a clear solution containing In.

(84) (c) Preparation of the solution containing Ga

(85) 1 mmol GaI.sub.3 and 4˜8 mmol Se were added into 1˜8 ml mixed solvents composed of methyl hydrazine and n-butanol, wherein the volume ratio was methyl hydrazinem-butanol=1˜3:1˜8. The mixture was sufficiently agitated and filtrated through a 0.2 μm filter to produce a clear solution containing Ga.

(86) (d) Preparation of the precursor solution of CIGSS thin film

(87) Above solutions comprising Cu, In and Ga are metered and blended at a volume ratio according to the stoichiometry ratios of Cu, In and Ga in the targeted CIGSS thin film to produce the precursor solution of CIGSS thin film.

(88) 2. Preparation of CIGSS thin film

(89) Above precursor solution of CIGSS thin film is applied onto a substrate through a non-vacuum film-forming process (for example, spin-coating, tape-casting, stamping and printing, etc) to fabricate a precursor CIGSS thin film. After drying under low temperature (room temperature˜80° C.), the precursor CIGSS thin film was rapidly annealed under high temperature (250° C.˜650° C.) to form CIGSS thin film.

(90) 3. Characterization of CIGSS thin film

(91) (a) Phase characterization was carried out by following the procedures of example 1 and the results were similar with that of example 1.

(92) (b) Electric properties were characterized by following the procedures of example 1 and the results were similar with that of example 1.

(93) (c) Optical properties were characterized by following the procedures of example 1 and the results were similar with that of example 1.

(94) (d) Microstructure was characterized by following the procedures of example 1 and the results were similar with that of example 1.

(95) 4. The CIGSS thin film solar cell was fabricated by following the procedures of example 1 and the measured results were similar with that of example 1.

Example 3

(96) 1. Preparation of the precursor solution of CIGSS thin film

(97) (a) Preparation of the solution containing Cu and Se

(98) 1 mmol CuCl was added into 2˜16 ml mixed solvents composed of ethylene diamine, dodecyl mercaptan and N,N-dimethyl formamide, wherein volume ratio was ethylene diamine:dodecyl mercaptan:N,N-dimethyl formamide=1˜8:1˜3:1˜6. The mixture was sufficiently agitated to produce a clear solution containing copper. Then 2-6 mmol Se was added into 4-16 ml ethylene diamine, and the mixture was sufficiently agitated and refluxed under 80° C. to produce a clear solution of selenium in ethylene diamine. The ethylene diamine solution of selenium was added in above solution containing Cu under agitation to produce the solution containing Cu and Se.

(99) (b) Preparation of the solution containing In

(100) 1 mmol indium iodide InI.sub.3 was added into 2˜16 ml mixed solvents composed of ethanol and isopropanol, wherein the volume ratio was ethanol isopropanol=1˜3:1˜6. The mixture was sufficiently agitated to produce a clear solution containing In.

(101) (c) Preparation of the solution containing Ga

(102) 1 mmol GaI.sub.3 was added into 2˜16 ml mixed solvents composed of ethanol and isopropanol, wherein the volume ratio was ethanol:isopropanol=1˜3:1˜6. The mixture was sufficiently agitated to produce a clear solution containing Ga.

(103) (d) Preparation of the precursor solution of CIGSS thin film

(104) The precursor solution of CIGSS thin film was formulated by following the procedures of example 1.

(105) 2. Preparation of CIGSS thin film

(106) The CIGSS thin film was prepared by following the procedures of example 1.

(107) 3. Characterization of CIGSS thin film

(108) (a) Phase characterization was carried out by following the procedures of example 1 and the results were similar with that of example 1.

(109) (b) Electric properties were characterized by following the procedures of example 1 and the results were similar with that of example 1.

(110) (c) Optical properties were characterized by following the procedures of example 1 and the results were similar with that of example 1.

(111) (d) Microstructure was characterized by following the procedures of example 1 and the results were similar with that of example 1.

(112) 4. The CIGSS thin film solar cell device was fabricated by following the procedures of example 1 and the measured results were similar with that of example 1.

Example 4

(113) 1. Preparation of the precursor solution of CIGSS thin film

(114) (a) Preparation of the solution containing Cu

(115) 1 mmol CuCl was added into 2˜16 ml mixed solvents composed of ethylene diamine, dodecyl mercaptan and N,N-dimethyl formamide, wherein volume ratio was ethylene diamine:dodecyl mercaptan:N,N-dimethyl formamide=1˜8:1˜3:1˜6. The mixture was sufficiently agitated to produce a clear solution containing copper. Then 2-6 mmol Se was added into 4-16 ml dimethyl hydrazine, and the mixture was sufficiently agitated to produce a clear solution of selenium in dimethyl hydrazine. The dimethyl hydrazine solution of selenium was added in above solution containing Cu under agitation to produce the solution containing Cu and Se.

(116) (b) Preparation of the solution containing In and Ga

(117) 1 mmol (In, Ga)I.sub.3 was added into 2˜16 ml mixed solvents composed of ethanol and isopropanol, wherein the volume ratio was ethanol:isopropanol=1˜3:1˜6. The mixture was sufficiently agitated to produce a clear solution containing In and Ga.

(118) (c) Preparation of the precursor solution of CIGSS thin film

(119) The precursor solution of CIGSS thin film was formulated by following the procedures of example 1.

(120) 2. Preparation of CIGSS thin film

(121) The CIGSS thin film was prepared by following the procedures of example 1.

(122) 3. Characterization of CIGSS thin film

(123) (a) Phase characterization was carried out by following the procedures of example 1 and the results were similar with that of example 1.

(124) (b) Electric properties were characterized by following the procedures of example 1 and the results were similar with that of example 1.

(125) (c) Optical properties were characterized by following the procedures of example 1 and the results were similar with that of example 1.

(126) (d) Microstructure was characterized by following the procedures of example 1 and the results were similar with that of example 1.

(127) 4. The CIGSS thin film solar cell device was fabricated by following the procedures of example 1 and the measured results were similar with that of example 1.

Example 5

(128) 1. Preparation of the precursor solution of CIGSS thin film

(129) (a) Preparation of the solution containing Cu

(130) 1 mmol CuS and 2 mmol (NH.sub.4).sub.2S were added into 2˜16 ml mixed solvents composed of triethanolamine, hydrazine hydrate and dimethyl sulfoxide, wherein volume ratio was triethanolamine:hydrazine hydrate:dimethyl sulfoxide=1˜8:1˜3:1˜6. The mixture was sufficiently agitated to produce a clear solution containing copper. Then 2-6 mmol Se was added into 4-16 ml hydrazine hydrate, and the mixture was sufficiently agitated and refluxed under 80° C. to produce a clear solution of selenium in hydrazine hydrate. The hydrazine hydrate solution of selenium was added in above solution containing Cu under agitation to produce the solution containing Cu and Se.

(131) (b) Preparation of the solution containing In and Ga

(132) 1 mmol (In, Ga)I.sub.3 was added into 2˜16 ml mixed solvents composed of ethanol and isopropanol, wherein the volume ratio was ethanol:isopropanol=1˜3:1˜6. The mixture was sufficiently agitated to produce a clear solution containing In and Ga.

(133) (c) Preparation of the precursor solution of CIGSS thin film

(134) The precursor solution of CIGSS thin film was formulated by following the procedures of example 1.

(135) 2. Preparation of CIGSS thin film

(136) The CIGSS thin film was prepared by following the procedures of example 1.

(137) 3. Characterization of CIGSS thin film

(138) (a) Phase characterization was carried out by following the procedures of example 1 and the results were similar with that of example 1.

(139) (b) Electric properties were characterized by following the procedures of example 1 and the results were similar with that of example 1.

(140) (c) Optical properties were characterized by following the procedures of example 1 and the results were similar with that of example 1.

(141) (d) Microstructure was characterized by following the procedures of example 1 and the results were similar with that of example 1.

(142) 4. The CIGSS thin film solar cell device was fabricated by following the procedures of example 1 and the measured results were similar with that of example 1.

Example 6

(143) 1. Preparation of the precursor solution of CIGSS thin film

(144) (a) Preparation of the solution containing Cu

(145) 1 mmol CuInSe.sub.2 and 2 mmol (NH.sub.4).sub.2S were added into 2˜16 ml mixed solvents composed of ethylene diamine, anhydrous hydrazine and dimethyl sulfoxide, wherein volume ratio was ethylene diamine:anhydrous hydrazine:dimethyl sulfoxide=1˜3:1˜8:1˜6. The mixture was sufficiently agitated under low temperature and filtered with a 0.2 μm filtrate to produce a clear solution containing copper.

(146) (b) Preparation of the solution containing In and Ga

(147) 1 mmol (In, Ga).sub.2Se.sub.3 was added into 2˜16 ml mixed solvents composed of ethylene diamine and anhydrous hydrazine, wherein the volume ratio was ethylene diamine:anhydrous hydrazine=1˜3:1˜6. The mixture was sufficiently agitated to produce a clear solution containing In and Ga.

(148) (c) Preparation of the precursor solution of CIGSS thin film

(149) The precursor solution of CIGSS thin film was formulated by following the procedures of example 1.

(150) 2. Preparation of CIGSS thin film

(151) The CIGSS thin film was prepared by following the procedures of example 1.

(152) 3. Characterization of CIGSS thin film

(153) (a) Phase characterization was carried out by following the procedures of example 1 and the results were similar with that of example 1.

(154) (b) Electric properties were characterized by following the procedures of example 1 and the results were similar with that of example 1.

(155) (c) Optical properties were characterized by following the procedures of example 1 and the results were similar with that of example 1.

(156) (d) Microstructure was characterized by following the procedures of example 1 and the results were similar with that of example 1.

(157) 4. The CIGSS thin film solar cell device was fabricated by following the procedures of example 1 and the measured results were similar with that of example 1.

Example 7

(158) 1. Preparation of the precursor solution of CIGSS thin film

(159) (a) Preparation of the solution containing Cu

(160) 1 mmol CuI was added into 4 ml ethanediamine, and was sufficiently agitated under low temperature to produce a clear solution containing Cu.

(161) (b) Preparation of the solution containing In

(162) 1 mmol InI.sub.3 was added into 4 ml methanol, and was sufficiently agitated to produce a clear solution containing In.

(163) (c) Preparation of the solution containing Ga

(164) 1 mmol GaI.sub.3 was added into 4 ml methanol, and was sufficiently agitated to produce a clear solution containing In.

(165) (d) Preparation of the solution containing S

(166) 8 mmol S was added into 8 ml ethanediamine, and was sufficiently agitated under low temperature to produce a clear solution containing S.

(167) (e) Preparation of the solution containing Se

(168) 8 mmol Se was added into 16 ml ethanediamine, and was sufficiently agitated under low temperature to produce a clear solution containing Se.

(169) (f) Preparation of the precursor solution of CIGSS thin film

(170) 3.6 ml solution containing Cu, 2.8 ml solution containing In, 1.2 ml solution containing Ga, 3 ml solution containing S and 0 ml solution containing Se are metered and blended under a temperature of 10° C. to produce the precursor solution of CIGSS thin film.

(171) 2. Preparation of CIGSS thin film

(172) Firstly, drop the above precursor solution of CIGSS thin film onto a Mo-coated glass and spin it at a high speed of 3000 rpm for 45 s after a pre-spin of 6 s at a low speed of 1000 rpm to produce a precursor CIGSS thin film. Anneal the precursor CIGSS thin film at 300° C. for 5 min and cool it down to room temperature, thus a layer of CIGSS thin film was gotten. Repeat the above procedure for another 9 times, and a 1.4 μm thick CIGSS thin film was fabricated. Anneal the gotten 1.4 μm thick CIGSS thin film at 550° C. for 25 min under high pure nitrogen gas (N.sub.2), a device-quality CIGSS thin film was prepared, which can be served as the light absorption layer of CIGSS thin film solar cell.

(173) 3. The CIGSS thin film solar cell was fabricated by following the procedures of example 1 and a photoelectric conversion efficiency of 4.97% was achieved.

Example 8

(174) The steps of (a), (b), (c), (d), (e) in the preparation of the precursor solution of CIGSS thin film were the same with example 7, and the step of (f) was: 3.6 ml solution containing Cu, 2.8 ml solution containing In, 1.2 ml solution containing Ga, 1.5 ml solution containing S and 3 ml solution containing Se are metered and blended under a temperature of 10° C. to produce the precursor solution of CIGSS thin film.

(175) Other steps of the process were the same with example 7.

(176) The as-fabricated CIGSS thin film solar cell has a photoelectric conversion efficiency of 7.52%.

Example 9

(177) The steps of (a), (b), (c), (d), (e) in the preparation of the precursor solution of CIGSS thin film were the same with example 7, and the step of (f) was: 3.6 ml solution containing Cu, 2.8 ml solution containing In, 1.2 ml solution containing Ga, 0.6 ml solution containing S and 4.8 ml solution containing Se are metered and blended under a temperature of 10° C. to produce the precursor solution of CIGSS thin film.

(178) Other steps of the process were the same with example 7.

(179) The as-fabricated CIGSS thin film solar cell has a photoelectric conversion efficiency of 9.4%.

Example 10

(180) The steps of (a), (b), (c), (d), (e) in the preparation of the precursor solution of CIGSS thin film were the same with example 7, and the step of (f) was: 3.6 ml solution containing Cu, 2.8 ml solution containing In, 1.2 ml solution containing Ga, 0 ml solution containing S and 6 ml solution containing Se are metered and blended under a temperature of 10° C. to produce the precursor solution of CIGSS thin film.

(181) Other steps of the process were the same with example 7.

(182) The as-fabricated CIGSS thin film solar cell has a photoelectric conversion efficiency of 9.1%.

Example 11

(183) The steps of (a), (b), (c), (d), (e) in the preparation of the precursor solution of CIGSS thin film were the same with example 7, and the step of (f) was: 3.6 ml solution containing Cu, 2.8 ml solution containing In, 1.2 ml solution containing Ga, 1.2 ml solution containing S and 9.6 ml solution containing Se are metered and blended under a temperature of 10° C. to produce the precursor solution of CIGSS thin film.

(184) Other steps of the process were the same with example 7.

(185) The as-fabricated CIGSS thin film solar cell has a photoelectric conversion efficiency of 13.2%.

Example 12

(186) The steps of (a), (b), (c), (d), (e) in the preparation of the precursor solution of CIGSS thin film were the same with example 7, and the step of (f) was: 3.6 ml solution containing Cu, 2.8 ml solution containing In, 1.2 ml solution containing Ga, 2 ml solution containing S and 16 ml solution containing Se are metered and blended under a temperature of 10° C. to produce the precursor solution of CIGSS thin film.

(187) Other steps of the process were the same with example 7.

(188) The as-fabricated CIGSS thin film solar cell has a photoelectric conversion efficiency of 10.6%.

Example 13

(189) The steps of (a), (b), (c), (d), (e) in the preparation of the precursor solution of CIGSS thin film were the same with example 7, and the step of (f) was: 3.6 ml solution containing Cu, 2.8 ml solution containing In, 1.2 ml solution containing Ga, 3.6 ml solution containing S and 28.8 ml solution containing Se are metered and blended under a temperature of 10° C. to produce the precursor solution of CIGSS thin film.

(190) Other steps of the process were the same with example 7.

(191) The as-fabricated CIGSS thin film solar cell has a photoelectric conversion efficiency of 7.4%.

Example 14

(192) 1. Preparation of the precursor solution of CIGSS thin film

(193) (a) Preparation of the solution containing Cu

(194) 0.5 mmol Cu.sub.2S and 1 mmol (NH.sub.4).sub.2S was added into 4 ml methyl hydrazine, and sufficient ammonia gas NH.sub.3 was introduced into the mixture, as well as 10 μmol Na.sub.2S was added as solution conditioner. After a sufficient stirring, a clear solution containing Cu was produced.

(195) The steps of (b), (c), (d), (e), (f) in the preparation of the precursor solution of CIGSS thin film were the same with example 11.

(196) 2. Preparation of CIGSS thin film

(197) Firstly, drop the above precursor solution of CIGSS thin film onto a Mo-coated glass and spin it at a high speed of 3000 rpm for 45 s after a pre-spin of 6 s at a low speed of 1000 rpm to produce a precursor CIGSS thin film. Anneal the precursor CIGSS thin film at 300° C. for 5 min and cool it down to room temperature, thus a layer of CIGSS thin film was gotten. Repeat the above procedure for another 9 times, and a 1.4 μm thick CIGSS thin film was fabricated.

(198) 3. Annealing of CIGSS thin film

(199) Annealing the gotten 1.4 μm thick CIGSS thin film at 550° C. for 15 min under a saturated Se atmosphere, a device-quality CIGSS thin film was prepared, which can be served as the light absorption layer of CIGSS thin film solar cell.

(200) 4. The CIGSS thin film solar cell was fabricated by following the procedures of example 1 and a photoelectric conversion efficiency of 14.0% was achieved.

Example 15

(201) 1. The precursor solution of CIGSS thin film and the CIGSS thin film were fabricated by following the procedures of example 14.

(202) 2. Annealing of CIGSS thin film

(203) Annealing the gotten 1.4 μm thick CIGSS thin film at 550° C. for 15 min under a saturated Se atmosphere, followed by a subsequent annealing at 475° C. for 25 min under a saturated S atmosphere, a device-quality CIGSS thin film was prepared, which can be served as the light absorption layer of CIGSS thin film solar cell.

(204) 3. The CIGSS thin film solar cell was fabricated by following the procedures of example 1 and a photoelectric conversion efficiency of 14.6% was achieved, as illustrated in FIG. 8.

(205) 4. As illustrated in FIG. 9 is the scanning electron microscopy image of the as-fabricated CIGSS thin film solar cell device.

Example 16

(206) The steps of (a) in the preparation of the precursor solution of CIGSS thin film was: 0.5 mmol Cu.sub.2S and 1 mmol (NH.sub.4).sub.2S was added into 4 ml methyl hydrazine, and sufficient ammonia gas NH.sub.3 was introduced into the mixture, as well as 10 μmol BaS was added as solution conditioner. After a sufficient stirring, a clear solution containing Cu was produced.

(207) The steps of (b), (c), (d), (e), (f) in the preparation of the precursor solution of CIGSS thin film were the same with example 14.

(208) Other steps of the process were the same with example 14.

(209) The as-fabricated CIGSS thin film solar cell has a photoelectric conversion efficiency of 13.8%.

Example 17

(210) 1. The precursor solution of CIGSS thin film and the CIGSS thin film were fabricated by following the procedures of example 14.

(211) 2. Annealing of CIGSS thin film

(212) Annealing the gotten 1.4 μm thick CIGSS thin film at 550° C. for 15 min under high pure nitrogen gas (N.sub.2), a device-quality CIGSS thin film was prepared, which can be served as the light absorption layer of CIGSS thin film solar cell.

(213) 3. The CIGSS thin film solar cell was fabricated by following the procedures of example 1 and a photoelectric conversion efficiency of 13.4% was achieved.