METHOD FOR PRODUCING HIGH-PURITY CESIUM HALIDE, AND PEROVSKITE COMPOSITE MATERIAL

Abstract

The present invention relates to a method for producing a cesium halide, and more particularly, to a novel method for producing a cesium halide with high purity; and perovskites produced using same.

Claims

1. A method of producing a cesium halide (CsX), comprising: preparing an aqueous Cs.sub.2CO.sub.3 solution (Step 1); adding an aqueous hydrogen halide (HX) solution dropwise to the aqueous Cs.sub.2CO.sub.3 solution while stirring to allow a reaction (Step 2); preparing a mixture by inputting and washing the reaction solution obtained in Step 2 in a washing solvent (Step 3); and obtaining a CsX powder by filtering and drying the mixed solution of Step 3 (Step 4).

2. The method of claim 1, wherein the aqueous Cs.sub.2CO.sub.3 solution of Step 1 includes 40 to 50 wt % of Cs.sub.2CO.sub.3 and the remainder of water.

3. The method of claim 1, wherein the aqueous HX solution of Step 2 includes 46 to 50 wt % of HX and the remainder of water, and the dropwise addition in Step 2 is carried out so that the aqueous Cs.sub.2CO.sub.3 solution and the aqueous HX solution are mixed in a volume ratio of 1:0.87 to 1.

4. The method of claim 1, wherein the washing solvent of Step 3 has a polarity of 4 to 6, a dipole moment of 1.60 to 4.00 (debye, D), and a dielectric constant of 13 to 37.

5. The method of claim 1, wherein the mixed solution of Step 3 includes the reaction solution and the washing solvent in a volume ratio of 1:5 or more.

6. The method of claim 1, wherein the CsX powder obtained in Step 4 has a yield of 83 to 99% and a purity of 97 to 99.9%.

7. A perovskite composite material using the cesium halide (CsX) of claim 1, which is a compound represented by Chemical Formula 1 below:
Cs.sub.aA.sub.(3a)MX.sub.bX.sub.(3b) [Chemical Formula 1] where, in Chemical Formula 1, A is a monovalent cation, such as an amine, ammonium, a Group 1 metal, a Group 2 metal, and/or another cation, or a cation-like compound, where M is a divalent cation, including one or two selected from Fe, Co, Ni, Cu, Sn, Pb, Bi, Ge, Ti, Eu, and Zr, X and X are independently Cl, Br, or I (however, X and X are halogen atoms different from each other), a is an integer such that 0<a1, and b is an integer such that 0<a3.

8. A perovskite solar cell comprising the perovskite composite material of claim 7 as a light absorbing layer.

Description

DESCRIPTION OF DRAWINGS

[0037] FIG. 1 is a graph showing the results of measuring the photoelectric conversion efficiency (PCE, %) of perovskite (CsPbBr.sub.3) solar cells manufactured in Preparation Example 1 and Comparative Preparation Example 1.

MODES OF THE INVENTION

[0038] Hereinafter, the present invention will be described in further detail.

[0039] The present invention relates to a method of producing a cesium halide (CsX, where X is Cl, Br, or I), which is used in the production of a perovskite composite material, with a high yield and high purity.

[0040] The perovskite composite material is a perovskite composite material represented by Chemical Formula 1.

Cs.sub.aA.sub.(3a)MX.sub.bX.sub.(3b) [Chemical Formula 1]

[0041] In Chemical Formula 1, A is a monovalent cation, such as an amine, ammonium, a Group 1 metal, a Group 2 metal, and/or another cation, or a cation-like compound, and preferably, formamidinium (FA), methylammonium (MA), FAMA, or N(R).sub.4.sup.+ (where R may be the same group or different groups, and R may be a C1 to C5 linear alkyl group, a C3 to C5 branched alkyl group, a phenyl group, an alkylphenyl group, an alkoxyphenyl group, or an alkyl halide).

[0042] In addition, in Chemical Formula 1, M may be a divalent cation, including one or two selected from Fe, Co, Ni, Cu, Sn, Pb, Bi, Ge, Ti, Eu, and Zr, preferably, one or two selected from Cu, Sn, and Pb, and more preferably, Pb.

[0043] In addition, in Chemical Formula 1, X and X are independently Cl, Br, or I. However, X and X are halogen atoms that are different from each other. In addition, a is an integer such that 0<a1, and b is an integer such that 0<a3.

[0044] In the present invention, CsX (where X is Cl, Br, or I) may be synthesized by preparing an aqueous Cs.sub.2CO.sub.3 solution (Step 1); adding an aqueous HX solution dropwise to the aqueous Cs.sub.2CO.sub.3 solution while stirring to allow a reaction (Step 2); preparing a mixture by inputting and washing the reaction solution obtained in Step 2 in a washing solvent (Step 3); and obtaining CsX powder by filtering and drying the mixed solution of Step 3 (Step 4).

[0045] The aqueous Cs.sub.2CO.sub.3 solution of Step 1 may include 40 to 50 wt % of Cs.sub.2CO.sub.3 and the remainder of water, preferably, 45 to 50 wt % of Cs.sub.2CO.sub.3 and the remainder of water, and more preferably, 48 to 50 wt % of Cs.sub.2CO.sub.3 and the remainder of water. Here, in the aqueous Cs.sub.2CO.sub.3 solution, when the content of Cs.sub.2CO.sub.3 is less than 40 wt %, the amount of CsX, which is the reaction product, is too small, and when the content of Cs.sub.2CO.sub.3 is more than 50 wt %, the purity of CsX obtained by unreacted Cs.sub.2CO.sub.3 is lowered. Therefore, it is preferable that the CsX be included within the above range.

[0046] In addition, the aqueous HX solution of Step 2 (where X is Cl, Br, or I) may include 46 to 50 wt % of HX (where X is Cl, Br, or I) and the remainder of water, preferably, 46.5 to 49.0 wt % of HX and the remainder of water, and more preferably, 47.0 to 48.0 wt % of HX and the remainder of water. Here, in the aqueous HX solution, when the content of HX is less than 46 wt %, the amount of CsX, which is the reaction product, is too small, and when the content of HX is more than 50 wt %, the purity of CsX obtained by unreacted HX may be lowered. Therefore, it is preferable that the CsX be included within the above range.

[0047] In addition, the dropwise addition and reaction in Step 2 may be performed at 20 to 40 C., preferably 30 to 40 C., and more preferably 35 to 37 C. Here, when this process is performed at less than 20 C., the reaction rate between Cs.sub.2CO.sub.3 and HX may be too slow, making the process in Step 2 too long and reducing the productivity of CsX. Since it is uneconomical to perform this process at a temperature exceeding 40 C., there is no further increase in CsX yield. Therefore, it is preferable to perform this process at the above temperature condition.

[0048] In addition, the dropwise addition and reaction in Step 2 may be performed under the stirring condition of 500 to 1500 rpm, preferably, 700 to 1,000 rpm, and more preferably, 700 to 800 rpm. Here, when the stirring rate is less than 500 rpm, the reaction ate between Cs.sub.2CO.sub.3 and HX is too slow, and the process of Step 2 takes too long, reducing the mass productivity of CsX, and when the reaction rate exceeds 1500 rpm, there may be difficulty in uniform stirring, so it is preferable to perform stirring under the above conditions.

[0049] In addition, it is appropriate to carry out the reaction in Step 2 for approximately 40 to 120 minutes, and preferably, approximately 40 to 90 minutes, under the above temperature and stirring conditions.

[0050] In addition, the dropwise addition of the aqueous HX solution in Step 2 may be performed to mix the aqueous Cs.sub.2CO.sub.3 solution and the aqueous HX solution in a volume ratio of 1:0.87 to 1.00, preferably, 1:0.87 to 0.95, and more preferably, 1:0.87 to 0.88 and react them. When the volume ratio is outside of the above range, the CsX yield may decrease, and the purity of CsX may be lowered due to the remaining unreacted materials, so it is preferable to mix and react them within a range satisfying the above volume ratio.

[0051] When the process of Step 2 is completed, by the reaction between Cs.sub.2CO.sub.3 and HX, the reaction products, such as CsX (aqueous), CO.sub.2 and H.sub.2O, are generated, and CO.sub.2 is evaporated and removed from the reaction solution, leaving CsX (aqueous), H.sub.2O, and unreacted residues in the reaction solution.

[0052] Subsequently, Step 3 is a process of solidifying and precipitating CsX dissolved in a reaction solution and separating and removing the unreacted residues from CsX. Here, the reaction solution which has undergone Step 2 is added to the washing solvent of 4 to 10 C., preferably, 4 to 8 C., and then the solidified CsX is precipitated.

[0053] In addition, after adding the reaction solution to the washing solvent, the washing reaction in Step 3 may be performed under a stirring condition of 800 to 1,500 rpm, preferably, 800 to 1,300 rpm, and more preferably, 800 to 1,000 rpm. Here, when the stirring rate is less than 800 rpm, the purity is reduced because the rate at which unreacted materials are washed is too slow, and when the reaction rate exceeds 1500 rpm, there may be difficulty in uniform stirring. Therefore, it is preferable to perform stirring under the above condition.

[0054] In addition, the reaction in Step 3 may be performed for approximately 40 to 120 minutes, and preferably, approximately 40 to 90 minutes under the temperature and stirring conditions.

[0055] Step 3 is a process of precipitating CsX using solubility caused by the polarity difference between the reaction product and unreacted materials in the reaction solution, and the washing solvent. Here, due to the low solubility in the washing solvent, CsX is precipitated, and the unreacted residues (Cs.sub.2CO.sub.3, HX, etc.) exhibit low solubility and thus are dissolved in the washing solvent.

[0056] The washing solvent is a polar solvent which mixes well with water, preferably satisfying a polarity of 4 to 6, a dipole moment of 1.6 to 4.0 (debye, D), and a dielectric constant of 13 to 37, preferably, a polarity of 4.2 to 5.7, a dipole moment of 1.6 to 3.5 (debye, D), and a dielectric constant of 13 to 28, more preferably, a polarity of 4.5 to 5.5, a dipole moment of 2.5 to 3 (debye, D), and a dielectric constant of 18.0 to 22.0. When the polarity, dipole moment, and/or dielectric constant are not satisfied, the yield and/or purity of CsX may decrease.

[0057] As a preferable example of a solvent from which a washing solvent satisfying the purity, dipole moment, and dielectric constant can be prepared, a washing solvent obtained by mixing one or two or more selected from acetone, methanol, ethyl alcohol, acetonitrile, tetrahydrofuran (THF), pyridine, methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK), and preferably, one or two or more selected from acetone, methanol, and ethyl alcohol, may be used.

[0058] In addition, the mixing ratio of the washing solvent and the reaction solution in Step 3 may be 1:5 or more, preferably, 1:5 to 20, more preferably, 1:8 to 15, and even more preferably, 1:8 to 12.

[0059] Next, Step 4 is a process of separating and obtaining the CsX precipitated from Step 3 from the mixed solution, by a CsX powder can be obtained by filtering the mixed solution of Step 3 by a method generally used in the art and drying the filtering residue.

[0060] The yield and purity of the CsX (where X is Cl, Br, or I) prepared as described above may respectively be 83 to 99% and 97.0 to 99.9%, preferably, 85.0 to 99.0% and 98.0to 99.9%, more preferably, 86.0 to 99.0% and 99.0 to 99.9%, and even more preferably, 90.0 to 99.0% and 99.0 to 99.9%.

[0061] A perovskite composite material having higher economic feasibility than that of the conventional perovskite composite material may be provided by synthesizing the perovskite composite material represented by Chemical Formula 1 using the CsX prepared in the above manner.

[0062] In addition, the perovskite composite material may be used in various technical fields, including solar cells, displays, and laser sensors.

[0063] As a preferable example, the perovskite composite material may be applied as a material for a light absorbing layer (or light activating layer) of a solar cell. Such a perovskite solar cell may be a p-i-n perovskite solar cell, an inverted perovskite solar cell, a tandem-type perovskite solar cell, or a tandem silicon/perovskite heterojunction solar cell.

[0064] As an exemplary embodiment of the perovskite solar cell, a solar cell, which includes a laminate having a structure in which a hole transport layer (HTL), a perovskite light absorbing layer, an electron transport layer (ETL), a passivation layer, and a source electrode are sequentially stacked, is provided.

[0065] In addition, when the solar cell of the present invention is an inverted perovskite solar cell, the laminate may be disposed on a drain electrode.

[0066] In addition, the inverted perovskite solar cell may be manufactured by forming a set consisting of a conductive substrate, a drain electrode, a hole transport layer, a light absorbing layer, an electron transport layer, and a source electrode in that order, and stacking the set in one or multiple layers.

[0067] As a still another exemplary embodiment, when the solar cell of the present invention is a tandem silicon/perovskite heterojunction solar cell, it may be manufactured by stacking a drain electrode, a silicon solar cell, a recombination layer, and the laminate sequentially.

[0068] The present invention will be described in detail by describing a method of forming the above-mentioned laminate constituting the perovskite solar cell of the present invention, and the laminate may be formed by a process including: forming an electron transport layer by coating a perovskite light absorbing layer of the laminate including a hole transport layer and the perovskite light absorbing layer with a coating agent for forming an electron transport layer (Step 1); forming a passivation layer on the electron transport layer through a deposition process (Step 2); and forming a source electrode on the passivation layer (Step 3).

[0069] The hole transport layer (HTL) may include an inorganic and/or organic hole transport material. The inorganic hole transport material may include one or more selected from nickel oxide (NiO.sup.x), CuSCN, CuCrO.sub.2, and CuI.

[0070] The organic hole transport material may include a carbazole derivative, a polyarylalkane derivative, a phenylenediamine derivative, an arylamine derivative, an amino-substituted chalcone derivative, a styrylanthracene derivative, a fluorene derivative, a hydrazone derivative, a stilbene derivative, a silazane derivative, an aromatic tertiary amine compound, a styrylamine compound, an aromatic dimethylidine-based compound, a porphyrin-based compound, a phthalocyanine-based compound, a polythiophene derivative, a polypyrrole derivative, a polyparaphenylenevinylene derivative, pentacene, coumarin 6, 3-(2-benzothiazolyl)-7-(diethylamino)coumarin), zinc phthalocyanine (ZnPC), copper phthalocyanine (CuPC), titanium oxide phthalocyanine (TiOPC), 2,2,7,7-tetrakis(N,N-p-dimethoxyphenylamino)-9,9-spirobifluorene (spiro-MeOTAD), copper(II) 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H,31H-phthalocyanine (F16CuPC), boron subphthalocyanine chloride (SubPc), cis-di(thiocyanato)-bis(2,2-bipyridyl-4,4-dicarboxylic acid)-ruthenium(II) (N3), poly[3-hexylthiophene] (P3HT), poly[2-methoxy-5-(3,7-dimethyloctyloxyl)]-1,4-phenylene vinylene (MDMO-PPV), poly[2-methoxy-5-(2-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV), poly(3-octyl thiophene) (P3OT), poly(octyl thiophene) (POT), poly(3-decyl thiophene) (P3DT), poly(3-dodecyl thiophene) (P3DDT), poly(p-phenylene vinylene) (PPV), poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenyl amine) (TFB), polyaniline, spiro-MeOTAD ([2,22,7,77-tetrkis(N,N-di-pmethoxyphenyl amine)-9,9,9-spirobifluorine]), CuSCN, CuI, poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl-4H-cyclopenta[2,1-b:3,4-b]dithiophene-2,6-diyl]] (PCPDTBT), poly[(4,4-bis(2-ethylhexyl)dithieno[3,2-b:2,3-d]silole)-2,6-diyl-alt-(2,1,3- benzothiadiazole)-4,7-diyl]) (Si-PCPDTBT), poly(4,8-diethylhexyloxyl) (PBDTTPD), poly[2,7-(9-(2-ethylhexyl)-9-hexyl-fluorene)-alt-5,5-(4,7,-di-2-thienyl-2,1,3-benzothiadiazole)] (PFDTBT), poly[2,7-9,9-(dioctyl-fluorene)-alt-5,5-(4,7-di- 2-.thienyl-2,1,3-benzothiadiazole)] (PFO-DBT), poly[(2,7-dioctylsilafluorene)-2,7-diyl-alt-(4,7-bis(2-thienyl)-2,1,3-benzothiadiazole)-5,5-diyl] (PSiFDTBT), poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT), poly(9,9-dioctylfluorene-co-bis(N,N-(4,butylphenyl))bis(N,N-phenyl-1,4-phenylene)diamine (PFB), poly(9,9-dioctylfluorene-cobenzothiadiazole) (F8BT), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), poly(triarylamine) (PTAA), 2-PACz, and/or MeO-2PACz.

[0071] In addition, as methods of forming the hole transport layer, coating and vacuum deposition may be used, and for coating, gravure coating, bar coating, printing, spraying, spin coating, dipping, and die coating may be used.

[0072] Afterwards, the light absorbing layer may include the perovskite composite material represented by Chemical Formula 1 described above.

[0073] Afterwards, the coating agent for forming an electron transport layer is a dispersion in which LiF nanoparticles are dispersed in an organic solvent, and includes 0.50 to 3.00 wt % of the LiF nanoparticles and the remainder of an organic solvent, preferably, 0.58 to 2.88 wt % of the LiF nanoparticles and the remainder of an organic solvent, and more preferably, 0.65 to 1.91 wt % of the LiF nanoparticles and the remainder of an organic solvent in the total weight.

[0074] In addition, the organic solvent may have a dielectric constant of 20 or less, and preferably, a dielectric constant of 5 to 15. As a specific example of the organic solvent, isopropyl alcohol, butyl alcohol, ethyl alcohol, and ethyl acetate may be used alone or in a combination thereof. When a solvent having a dielectric constant of more than 20 is used, the attraction between the LiF nanoparticles and a polar solvent may increase (decreased dispersibility and dispersion stability), causing the LiF nanoparticles to agglomerate, and the perovskite material, which is the light absorbing layer, may be dissolved in a polar solvent during the formation of a LiF thin film.

[0075] The coating agent for forming an electron transport layer may be used in a general solution coating method, such as spin coating, blade coating, bar coating, spray coating, gravure coating, or die coating. In one embodiment, after coating, the coated result may be heat-treated at 200 C. or less to form a super thin film with a thickness of 100 nm or less, preferably, 1 to 40 nm, and more preferably, 1 to 20 nm.

[0076] In the method of manufacturing a perovskite solar cell of the present invention, the laminate of Step 1 may be formed by forming a drain electrode on a conductive substrate, and then forming a hole transport layer, a perovskite light absorbing layer, and an electron transport layer, which have been described above, on the drain electrode sequentially.

[0077] Here, as the conductive substrate, a general conductive substrate used in the art may be used, and it may be a transparent plastic substrate made of, for example, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, aromatic polyester, or polyimide, a glass substrate, a quartz substrate, or a silicon substrate.

[0078] The drain electrode may be formed of a material including one or more selected from a conductive metal, an alloy of conductive metals, a metal oxide, and a conductive polymer. As preferable examples, these materials may include indium tin oxide (ITO), fluorine-doped tin oxide (FTO), Sb.sub.2O.sub.3-doped tin oxide (ATO), gallium-doped tin oxide (GTO), tin-doped zinc oxide (ZTO), gallium-doped ZTO (ZTO:Ga), indium gallium zinc oxide (IGZO, indium-doped zinc oxide (IZO), and/or aluminum-doped zinc oxide (AZO).

[0079] The electron transport layer formed in Step 1 is formed to have a thickness of 100 nm or less, preferably, 1 to 40 nm, and more preferably, 1 to 20 nm. Here, when the thickness of the electron transport layer exceeds 100 nm, the short-circuit current (Jsc) and open circuit voltage (Voc) of the solar cell may be reduced, and therefore the electron transport layer is preferably formed to a thickness within the above range.

[0080] The surface of the coating layer formed as described above, that is, the electron transport layer, may be formed to have a very low roughness, and the root mean square (RMS) and roughness may satisfy 25 nm or less, preferably, 17.0 to 25.0 nm, and more preferably, 17.5 to 24.0 nm.

[0081] Afterwards, in the method of manufacturing a perovskite solar cell of the present invention, Step 2 is a process of forming a passivation layer (or conductive barrier layer) on the electron transport layer through a deposition process. Here, the passivation layer may be a transparent thin film in which fullerene (C.sub.60), LiF, bathocuproine (BCP), indium tin oxide (ITO), fluorine-doped tin oxide (FTO), Sb.sub.2O.sub.3-doped tin oxide (ATO), gallium-doped tin oxide (GTO), tin-doped zinc oxide (ZTO), gallium-doped ZTO (ZTO:Ga), indium gallium zinc oxide (IGZO), indium-doped zinc oxide (IZO), or aluminum-doped zinc oxide (AZO) is deposited.

[0082] Here, the deposition may be performed in a general deposition process used in the art, and is preferably carried out through sputtering at a process temperature of 100 C. or less under the conditions including an RF power of 100 to 300 W, a process pressure of 1 to 3 mTorr, and an argon (Ar) flow of 10 to 40 sccm.

[0083] In addition, the surface of the passivation layer may satisfy an RMS roughness of 30 nm or less, preferably, 17.5 to 27.0 nm, and more preferably, 18.0 to 25.0 nm.

[0084] In addition, the passivation layer may have a low sheet resistance of 80 W/sq or less, preferably, 76 W/sq or less, and more preferably, 30.0 to 70.0 W/sq.

[0085] The passivation layer formed in Step 2 may have an average thickness of 50 to 110 nm, preferably, 55 to 105 nm, and more preferably, 60 to 100 nm. Here, when the average thickness of the passivation layer is less than 50 nm, the thickness is so thin that an effect of preventing the penetration and ion migration into electrodes, caused by the introduction of the passivation layer, is insufficient or absent, and the sheet resistance may increase, causing a problem of reduced device performance. In addition, when the average thickness of the passivation layer exceeds 110 nm, there is an advantage in operating a device because the charge migration becomes smoother due to the decrease in sheet resistance, but damage to the light absorbing layer may occur with an increase in processing time, and productivity may decrease. In the case of a tandem device, since the light receiving direction reaches the perovskite light activating layer via the passivation layer, unnecessary photocurrent loss may occur due to the thick passivation layer, so it is preferable that the passivation layer be formed by performing deposition to have an average thickness within the above range.

[0086] Bathocuproine (BCP), which has a large energy bandgap and a very low HOMO energy level, is a compound inserted between a C60 electron acceptor layer and an electrode to suppress the phenomenon in which excitons recombine with the electrode and are extinguished. In addition, for forming the BCP passivation layer, coating and vacuum deposition may be used, and as the coating, spin coating may be used.

[0087] Afterwards, Step 3 is a process of forming a source electrode on the conductive barrier layer (passivation layer) formed in Step 2, in which the source electrode may be formed by coating or depositing one or more materials selected from Pt, Au, Ni, Cu, Ag, In, Ru, Pd, Rh, Ir, Os, C, and a conductive polymer.

[0088] In addition, among the solar cell components, the source electrode may be formed by coating or depositing one or more materials selected from Pt, Au, Ni, Cu, Ag, In, Ru, Pd, Rh, Ir, Os, C, and a conductive polymer.

[0089] Hereinafter, the present invention will be described more specifically with reference to examples, but the following examples do not limit the scope of the present invention, and should be interpreted as helping to understand the present invention.

EXAMPLES

Example 1: Synthesis of CsBr

[0090] An aqueous Cs.sub.2CO.sub.3 solution including 50 wt % of Cs.sub.2CO.sub.3 and the remainder of water was prepared. Separately, an aqueous HBr solution including 48 wt % of hydrogen bromide (HBr) and the remainder of water was prepared.

[0091] After putting the aqueous Cs.sub.2CO.sub.3 solution into a reactor, the aqueous HBr solution was added dropwise while stirring at 800 rpm and 35 C., and after the dropwise addition was completed, the reaction was performed for 1 hour while stirring was maintained, thereby preparing a reaction solution containing the reaction product CsBr (aq).

[0092] Here, the aqueous HBr solution was added dropwise so that the volume ratio of the aqueous Cs.sub.2CO.sub.3 solution and the aqueous HX solution was 1:0.87.

[0093] Next, after the reaction was completed, the aqueous HBr solution was added to a washing solvent, acetone (5 to 6 C.), with a volume ratio 10 times that of the reaction solution, and when the reaction solution was added dropwise to the washing solvent under the condition where the temperature was maintained at 5 to 6 C., the moment the reaction solution was mixed with the washing solvent, the solubility constant changed rapidly, resulting in CsBr precipitation. Here, the acetone had a polarity of 5.1, a dipole moment of 2.72, and a dielectric constant of 20.7.

[0094] Afterwards, the solution from which CsBr was precipitated was filtered using a filtering device such as a filter paper and a funnel, and the filtering residue was dried for 24 hours in a 40 C. vacuum oven to obtain a CsBr powder.

[0095] The yield of the obtained CsBr powder was 98.4%, and the purity thereof was 99.9%.

Examples 2 to 6 and Comparative Examples 1 to 4

[0096] CsBr powders were prepared in the same manner as in Example 1, except that, as shown in Table 1 below, Examples 2 to 6 and Comparative Examples 1 to 4 were performed using methanol, ethyl alcohol, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), acetonitrile, hexane, ether, toluene, and benzene as a washing solvent instead of acetone. The yields and purity of the obtained CsBr powders are shown in Table 2 below.

TABLE-US-00001 TABLE 1 Washing Dipole Dielectric Classification solvent Polarity moment constant Example 1 Acetone 5.1 2.72 20.7 Example 2 Methanol 5.1 1.69 24 Example 3 Ethyl alcohol 5.2 1.66 25.3 Example 4 MEK 4.7 2.76 18.9 Example 5 MIBK 4.2 2.80 13.1 Example 6 Acetonitrile 5.8 3.92 37 Comparative Hexane 0.1 0.08 1.9 Example 1 Comparative Ether 0.1 1.15 4.3 Example 2 Comparative Toluene 2.4 0.36 2.3 Example 3 Comparative Benzene 2.7 0.00 2.4 Example 4

TABLE-US-00002 TABLE 2 Washing Yield (%)/ Classification solvent Purity (%) Example 1 Acetone 98.4/99.9 Example 2 Methanol 87.2/99.2 Example 3 Ethyl alcohol 86.5/99.2 Example 4 MEK 85.1/99.0 Example 5 MIBK 84.2/98.6 Example 6 Acetonitrile 83.0/98.0 Comparative Example 1 Hexene 71.4/83.2 Comparative Example 2 Ether 68.5/83.0 Comparative Example 3 Toluene 70.2/81.3 Comparative Example 4 Benzene 62.1/78.4

Preparation Example 1: Preparation of Perovskite Composite Material

[0097] A precursor solution was prepared by dissolving CsBr and PbBr.sub.2, which were prepared in Example 1, in dimethyl sulfoxide (DMSO).

[0098] Next, hydrobromic acid was added dropwise to the precursor solution, thereby forming an orange precipitate.

[0099] The filtrate was removed and separated using a centrifuge, and the precipitate (CsPbBr.sub.3) was purified by washing it with ethanol.

[0100] Subsequently, a CsPbBr.sub.3 perovskite composite material was prepared by drying the purified CsPbBr.sub.3 in a vacuum oven for 24 hours.

Comparative Preparation Example 1

[0101] A CsPbBr.sub.3 perovskite composite material was prepared in the same manner as in Preparation Example 1, except that commercially available CsBr (TCI product) was used instead of the CsBr prepared in Example 1. Here, the CsBr (TCI product) was prepared by a conventional method of removing impurities through a high-temperature heating process.

Preparation Examples 2 to 6 and Comparative Preparation Examples 2 to 5

[0102] CsPbBr.sub.3 perovskite composite materials were prepared in the same manner as in Preparation Example 1, except that CsBrs prepared in Examples 2 to 6 and Comparative Examples 1 to 4 were used instead of the CsBr prepared in Example 1 (see Table 3).

TABLE-US-00003 TABLE 3 Classification CsBr precursor Preparation Example 1 Example 1 Preparation Example 2 Example 2 Preparation Example 3 Example 3 Preparation Example 4 Example 4 Preparation Example 5 Example 5 Preparation Example 6 Example 6 Comparative Preparation CsBr Example 1 (TCI product) Comparative Preparation Comparative Example 2 Example 1 Comparative Preparation Comparative Example 3 Example 2 Comparative Preparation Comparative Example 4 Example 3 Comparative Preparation Comparative Example 5 Example 4

Preparation Example 7: Manufacture of Perovskite Solar Cell

[0103] As a drain electrode (source electrode), an organic substrate (thickness: 1.1 mm, 15.0 /sq) coated with indium tin oxide (ITO) to a thickness of approximately 110 nm was washed sequentially with acetone and isopropyl alcohol (IPA) every hour using a sonicator.

[0104] Subsequently, a 30 nm-thick hole transport layer (NiO.sub.x) was formed on the ITO substrate under conditions for E-beam vacuum deposition.

[0105] Subsequently, the hole transport layer (NiO.sub.x) was spin-coated with a solution in which 2PACz was dissolved in ethanol at a concentration of 2 mM, and thermally treated at 100 C. for 10 minutes, thereby forming a 2PACz hole transport layer to a thickness of 15 to 20 nm.

[0106] Subsequently, a yellow light absorbing layer solution prepared by dissolving CsPbBr.sub.3 perovskite of Preparation Example 1, commercial FAI, and commercial PbI.sub.2 in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) was spin-coated on the hole transport layer, and thermally treated at 100 C. for 20 minutes, thereby forming a NiO.sub.x hole transport layer and a light absorbing layer ((FAPbI.sub.3).sub.0.8 (CsPbBr.sub.3).sub.0.2) having a perovskite crystal structure with a thickness of 450 to 500 nm.

[0107] Afterwards, an electron transport layer (LiF) with a thickness of 0.8 nm was formed on the perovskite light absorbing layer under thermal evaporation conditions.

[0108] Afterwards, a passivation layer (C.sub.60 fullerene) with a thickness of 13 nm was formed on the electron transport layer under thermal evaporation conditions.

[0109] Afterwards, a BCP electron transport layer with a thickness of 5 to 10 nm was formed on the passivation layer by spin-coating a solution prepared by dissolving BCP in ethanol.

[0110] Afterwards, an inverted perovskite solar cell was manufactured by forming a source electrode by depositing silver on the BCP layer to a thickness of 150 nm under a pressure of 110.sup.8 torr.

Preparation Examples 8 to 12 and Comparative Preparation Examples 6 to 10

[0111] Inverted perovskite solar cells were manufactured in the same manner as in Preparation Example 1, except that the perovskites of Preparation Examples 2 to 6 and Comparative Preparation Examples 1 to 5 were used instead of the perovskite of Preparation Example 1 (see Table 4).

TABLE-US-00004 TABLE 4 Solar cell Perovskite CsBr precursor Preparation Example 7 Preparation Example 1 Example 1 Preparation Example 8 Preparation Example 2 Example 2 Preparation Example 9 Preparation Example 3 Example 3 Preparation Example 10 Preparation Example 4 Example 4 Preparation Example 11 Preparation Example 5 Example 5 Preparation Example 12 Preparation Example 6 Example 6 Comparative Preparation Comparative Preparation CsBr (TCI product) Example 6 Example 1 Comparative Preparation Comparative Preparation Comparative Example 7 Example 2 Example 1 Comparative Preparation Comparative Preparation Comparative Example 8 Example 3 Example 2 Comparative Preparation Comparative Preparation Comparative Example 9 Example 4 Example 3 Comparative Preparation Comparative Preparation Comparative Example 10 Example 5 Example 4

Experimental Example 1: Measurement of Solar Cell Performance

[0112] The current-voltage characteristics and efficiency of the solar cells manufactured in Preparation Example 1 were measured, and the results are shown in Table 5 below. In addition, the results of measuring the photoelectric conversion efficiency (PCE, %) for Preparation Example 7 and Comparative Preparation Example 6 are shown in FIG. 1.

TABLE-US-00005 TABLE 5 Open Short Photoelectric circuit circuit current Fill conversion voltage density factor efficiency Classification (V.sub.oc, V) (J.sub.sc, mA/cm.sup.2) (FF) (%) Preparation 1.148 21.31 75.96 18.59 Example 7 Preparation 1.145 21.24 75.87 18.50 Example 8 Preparation 1.144 21.21 75.84 18.49 Example 9 Preparation 1.140 21.13 75.53 18.22 Example 10 Preparation 1.139 21.04 75.47 18.11 Example 11 Preparation 1.138 20.93 75.39 17.97 Example 12 Comparative 1.137 20.87 75.36 17.89 Preparation Example 6 Comparative 1.089 19.25 74.43 17.35 Preparation Example 7 Comparative 1.072 19.07 74.04 17.32 Preparation Example 8 Comparative 1.024 18.82 73.18 16.24 Preparation Example 9 Comparative 0.989 17.79 71.27 15.76 Preparation Example 10

[0113] From the photoelectric conversion efficiency of Table 5 and FIG. 1, it was confirmed that the solar cells using the perovskites prepared using CsBr prepared by the preparation method of the present invention (Preparation Examples 7 to 12) as the material for the light absorbing layer exhibit relatively higher photoelectric conversion efficiency than that using the perovskite prepared from commercial CsBr (Comparative Preparation Example 6). In contrast, the solar cells of Comparative Preparation Examples 7 to 10 showed lower solar cell performance than that of Comparative Preparation Example 6.

[0114] According to Examples and Experimental Examples, it was able to be confirmed that the CsX production method of the present invention can be used to prepare a high-yield and high-purity CsX, and that the purity of the device used in the production of a perovskite (light activating layer) is a major factor affecting the performance of a solar cell.