Method for forming a perovskite layer

Abstract

The present invention relates to a method for forming a perovskite layer on a silicon layer, comprising: depositing a perovskite inorganic layer on the silicon layer by a vapor deposition process; and coating a perovskite organic layer on the inorganic layer by a solution process; wherein the inorganic layer is formed by sequentially or simultaneously depositing three or more inorganic halogen compounds each containing a different halogen element.

Description

[Technical Field]

[0001] The present invention relates to a method for forming a photosensitive layer of a perovskite material included in a tandem solar cell. [Background technology]

[0002] Solar cells are aggregates that convert solar energy into electricity, and have been attracting attention as a next-generation energy source and have been the subject of long-term research, with high photovoltaic efficiency reported based on various materials such as silicon, CIGS, and perovskite. Currently, the most widely used commercial solar cells are silicon-based solar cells, accounting for over 90% of the solar cell market.

[0003] Silicon solar cells include crystalline silicon solar cells and amorphous silicon solar cells, and while crystalline solar cells have the disadvantage of high manufacturing costs, they are widely commercialized due to their high energy efficiency. In contrast, amorphous solar cells have difficult process technology, are highly dependent on equipment, and, above all, are less efficient, so development is currently stagnant. If silicon solar cells are classified as a first generation, then perovskite solar cells are a representative of the third generation solar cells that are currently being actively researched worldwide as a promising environmentally friendly product.

[0004] Perovskite solar cells utilize materials that combine inorganic and organic materials to form the perovskite crystalline structure. Perovskite has a very special structure that allows it to exhibit superconductivity as well as insulator, semiconductor, and conductor properties.

[0005] The perovskite light-absorbing layer used in perovskite solar cells consists of a perovskite material with an ABX3 structure (where A is a monovalent organic ammonium cation or metal cation, B is a divalent metal cation, and X is a halogen anion).

[0006] The A is methylammonium (CH3NH3 +) or ethylammonium (CH3CH2NH3 + ), B represents Pb or Sn, and X represents I, Br, or Cl.

[0007] Perovskite compounds include, for example, CH3NH3PbI3, CH3NH3PbI x Cl 3-x , MAPbI3, CH3NH3PbI x Br 3-x , CH3NH3PbCl x Br 3-x , HC(NH2)2PbI3, HC(NH2)2PbI x Cl 3-x , HC(NH2)2PbI x Br 3-x , HC(NH2)2PbCl x Br 3-x , (CH3NH3)(HC(NH2)2) 1-y PbI3, (CH3NH3)(HC(NH2)2) 1-y PbI x Cl 3-x , (CH3NH3)(HC(NH2)2) 1-y PbI x Br 3-x , (CH3NH3)(HC(NH2)2) 1-y PbCl x Br 3-x etc. can be used (0≦x, y≦1).

[0008] Perovskites are known to increase conversion efficiency due to their strong solar absorption, low non-radiative carrier recombination rate, high carrier mobility, and the fact that defects that induce non-radiative carrier recombination are not formed within the band gap or in deep levels.

[0009] These organic-inorganic hybrid perovskite solar cells are currently attracting attention as next-generation thin-film solar cells due to their low manufacturing costs and the ability to fabricate thin films using a solution process. Perovskite solar cells have been increasing in efficiency at a rapid rate for the first time in the 10 years since research began, and high photoelectric efficiency has been reported.

[0010] Techniques such as slot die, inkjet printing, and vacuum thermal evaporation are being developed to move beyond solution-based spin-coating thin film fabrication for commercialization.

[0011] To overcome the shortcomings of single-junction perovskite solar cells, research is ongoing into multi-junction tandem solar cells. In multi-junction tandem solar cells, the upper cell with a large bandgap absorbs solar energy in the low wavelength band, and the lower cell with a low bandgap absorbs solar energy in the high wavelength band, reducing losses and enabling the use of solar energy over a wide wavelength band, while achieving high efficiencies of over 30%, which are not possible with single-junction solar cells.

[0012] In particular, perovskite-silicon tandem solar cells have small and large bandgaps, respectively, which are advantageous for light management and are the subject of active research.

[0013] However, stacking perovskite and silicon to create an effective tandem structure is not easy: silicon surfaces consist of a series of pyramidal structures that trap light and prevent it from reflecting, but these pyramidal surfaces of silicon make it difficult to coat a uniform film of perovskite.

[0014] When perovskite is coated in liquid form, it typically accumulates in the valleys between pyramidal structures on the silicon surface, exposing the peaks, which creates a problem of the perovskite not coating accurately.

[0015] To solve this problem, perovskite can be coated on flat silicon without pyramids. However, to maximize the efficiency gain from light reflection, a more recent method of manufacturing tandem solar cells involves first completely covering the pyramid structure on the silicon surface with an inorganic-based layer of perovskite using a vapor deposition method such as vacuum thermal evaporation, and then coating an organic layer on top of the inorganic-based layer using a solution deposition technique such as spin-coating.

[0016] However, when PbI2 240nm + CsBr 80nm was deposited as the inorganic base layer of perovskite using this latest technology, the phase of the inorganic base layer gradually changed over time under conditions of a temperature of less than 20°C, humidity of less than 20%, and light blocking, as shown in Figure 1, as observed through changes in absorbance.

[0017] As such, if the perovskite inorganic-based layer changes over time, the phase of the inorganic-based layer becomes unstable, making it unclear what state the organic layer will be coated in, ultimately resulting in an unstable and non-uniform perovskite layer formed on top of the silicon layer. In particular, when manufacturing large-area tandem solar cells, the time it takes for the inorganic layer to be formed may vary between portions / batch within the same perovskite inorganic layer, which can cause the properties of the final perovskite layer to vary between portions / batch after the organic layer is coated, which can pose an even greater problem in terms of yield when introducing mass production technology. Summary of the Invention [Problem to be solved by the invention]

[0018] The present invention has been devised to solve the above-mentioned problems, and aims to provide an apparatus and method for forming a perovskite layer that can prevent the phase of an inorganic halide-based layer, which is a precursor of the perovskite layer in a tandem solar cell, from changing over time, and that can produce a large-area perovskite light-absorbing layer with high uniformity. [Means for solving the problem]

[0019] As a means for solving the above-mentioned problems, the present invention provides a method for forming a perovskite layer on a silicon layer, comprising: depositing a perovskite inorganic layer on the silicon layer by a vapor deposition process; and coating a perovskite organic layer on the inorganic layer by a solution process; wherein the inorganic layer is formed by sequentially or simultaneously depositing three or more inorganic halogen compounds each containing a different halogen element.

[0020] The method may further include, after the coating step, waiting for a predetermined time to allow the inorganic material layer and the organic material layer to react with each other to form an organic-inorganic perovskite thin film; and, after the waiting step, heat-treating the organic-inorganic perovskite thin film at a predetermined temperature for a predetermined time.

[0021] The inorganic layer is characterized by containing at least one divalent metal cation and three or more halogen anions, and further containing at least one monovalent metal cation.

[0022] The monovalent metal cation is Li + , Na + , K. + , Rb + , and Cs + The alkali metal ions are selected from one or more of the alkali metal ions listed below.

[0023] The inorganic layer is composed of at least a first inorganic halogen compound, a second inorganic halogen compound, and a third inorganic halogen compound, and the first inorganic halogen compound and the second inorganic halogen compound have a chemical formula structure of BX2 and are different compounds from each other, and the B is lead (Pb 2+ ), tin (Sn 2+ ), tungsten (W 2+ ), copper (Cu 2 +), zinc (Zn 2+ ), Gallium (Ga 2+ ), germanium (Ge 2+ ), arsenic (As 2+ ), selenium (Se 2+ ), rhodium (Rh 2+ ), palladium (Pd 2+ ), silver (Ag 2+ ), cadmium (Cd 2+ ), indium (In 2+ ), antimony (Sb 2+ ), osmium (Os 2+ ), Iridium (Ir 2+ ), platinum (Pt 2+ ), gold (Au 2+ ), mercury (Hg 2+ ), thallium (Tl 2+ ), Bismuth (Bi 2+ ), polonium (Po 2+ ) and X is chlorine (Cl - ), Brom (Br - ), iodine (I - ) the anion of the third inorganic halide compound is any one of the following: + , Na + , K. + , Rb + , and Cs + and the halogen anion is chlorine (Cl - ), Brom (Br - ), iodine (I - ) is characterized in that it is composed of any one anion selected from the following.

[0024] The inorganic layer is formed by depositing PbI2 to a thickness of 240 nm, PbBr2 to a thickness of 80 nm, and CsCl to a thickness of 20 nm.

[0025] The organic halogen compound forming the organic layer is any one of methylammonium (MA=CHNH) selected from the group consisting of MACl, MABr, and MAI. 3+ ) compound or any one formamidinium (FA = HC(NH2)) compound selected from the group consisting of FACl, FABr, and FAI. 2+ ) compound. [Effects of the Invention]

[0026] According to the method for forming a perovskite layer according to an embodiment of the present invention, it is possible to prevent the phase of the inorganic halide-based layer, which is the precursor of the perovskite layer in a tandem solar cell, from changing over time, and to manufacture a large-area perovskite light-absorbing layer with high uniformity. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a graph showing the change in absorbance over time of an inorganic-based layer of perovskite produced according to the prior art; [Figure 2] 1 is a flowchart of a method of forming a perovskite layer according to one embodiment of the present invention. [Figure 3] 1 is a graph showing the change in absorbance over time of a perovskite inorganic-based layer produced according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, various modifications may be made to the embodiments, and the scope of the patent application is not limited or restricted by such embodiments. It should be understood that all modifications, equivalents, and alternatives to the embodiments are included in the scope of the patent application.

[0029] The terms used in the embodiments are merely for the purpose of description and should not be construed as limiting. A singular expression includes a plural expression unless otherwise clearly indicated. In this specification, the terms "comprise," "include," "comprise," "have," and the like are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should be understood not to preclude the presence or possibility of addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0030] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the embodiments pertain. Terms as defined in commonly used dictionaries should be understood to have a meaning consistent with the meaning they have in the relevant art, and should not be understood as idealized or overly formal unless expressly defined in this application.

[0031] When an element or layer is referred to as being "on," "on top of," "connected to," or "coupled to" another element or layer, it should be understood that this may be directly on the other element or layer, connected to, or coupled to, or that there may be intervening elements and layers.

[0032] The apparatus and method for forming a perovskite layer of the present invention will be specifically described below with reference to embodiments and drawings, but the present invention is not limited to such embodiments and drawings.

[0033] FIG. 2 is a flowchart of a method of forming a perovskite layer according to one embodiment of the present invention, and FIG. 3 is a graph showing the change in absorbance over time of an inorganic-based layer of perovskite produced according to one embodiment of the present invention.

[0034] As shown in FIG. 2, a method for forming a perovskite layer according to an embodiment of the present invention may include a step of vapor-depositing an inorganic perovskite layer (S10), a step of solution-coating an organic perovskite layer (S20), a step of waiting for a predetermined time (S30), and a step of heat-treating (S40).

[0035] The step of vapor-depositing the inorganic perovskite layer (S10) is a step of depositing an inorganic halide compound on the silicon layer constituting the tandem solar cell by a vapor-deposition process. In one or more embodiments, the vapor-deposition process may be a vacuum thermal evaporation process.

[0036] The vacuum thermal evaporation process may be performed using, for example, a chamber maintained under ultra-high vacuum and an evaporator installed inside the chamber. A holder to which a silicon layer can be fixed may be installed on the ceiling of the chamber, and an evaporator may be installed at the bottom of the chamber to evaporate an inorganic halide compound and deposit the inorganic halide compound to a predetermined thickness on the silicon layer fixed to the holder. For precise deposition, a residual gas analyzer, a QCM (quartz crystal microbalance) sensor, etc. may be installed in the chamber.

[0037] According to an embodiment of the present invention, the perovskite inorganic layer deposited on the silicon layer in the vapor deposition step (S10) includes three or more different halogen elements.

[0038] According to an embodiment of the present invention, three or more inorganic halogen compounds containing different halogen elements may be deposited sequentially or simultaneously to form the inorganic perovskite layer of the present invention.

[0039] In one or more embodiments, the perovskite inorganic layer may be formed by sequentially or simultaneously depositing a first inorganic halide compound 100, a second inorganic halide compound 200, and a third inorganic halide compound 300 on a silicon layer by a vacuum thermal evaporation process, and the halogen elements contained in the first inorganic halide compound 100, the second inorganic halide compound 200, and the third inorganic halide compound 300 are different from each other.

[0040] The first inorganic halide compound 100 may have a chemical structure of BX2, where B is a divalent metal cation and X is a halide anion. 2+ ), tin (Sn 2+ ), tungsten (W 2+ ), copper (Cu 2+ ), zinc (Zn 2+ ), Gallium (Ga 2+ ), germanium (Ge 2+ ), arsenic (As 2+ ), selenium (Se 2+ ), rhodium (Rh 2+ ), palladium (Pd 2+ ), silver (Ag 2+ ), cadmium (Cd 2+ ), indium (In 2+ ), antimony (Sb 2+ ), osmium (Os 2+ ), Iridium (Ir 2+ ), platinum (Pt 2+ ), gold (Au 2+ ), mercury (Hg 2+ ), thallium (Tl 2+), Bismuth (Bi 2+ ), polonium (Po 2+ ) and X is chlorine (Cl - ), Brom (Br - ), iodine (I - ) The anion may be any one of the following. For example, the metal halide compound may be PbCl2, PbBr2, PbI2, SnCl2, SnBr2, SnI2, etc.

[0041] As shown in FIG. 3, the first inorganic halide compound 100 used in one embodiment of the present invention may be PbI2.

[0042] The second inorganic halide compound 200 is different in type from the first inorganic halide compound 100, but like the first inorganic halide compound, it can have a chemical formula of BX2 (B is a divalent metal cation and X is a halogen anion). B is lead (Pb 2+ ), tin (Sn 2+ ), tungsten (W 2+ ), copper (Cu 2+ +), zinc (Zn 2+ ), Gallium (Ga 2+ ), germanium (Ge 2+ ), arsenic (As 2+ ), selenium (Se 2+ ), rhodium (Rh 2+ ), palladium (Pd 2+ ), silver (Ag 2+ ), cadmium (Cd 2+ ), indium (In 2+ ), antimony (Sb 2+ ), osmium (Os 2+ ), Iridium (Ir 2+ ), platinum (Pt 2+ ), gold (Au 2+ ), mercury (Hg 2+ ), thallium (Tl 2+ ), Bismuth (Bi 2+ ), polonium (Po 2+ ) and chlorine (Cl - ), Brom (Br- ), iodine (I - ) The anion may be any one of the following. For example, the metal halide compound may be PbCl2, PbBr2, PbI2, SnCl2, SnBr2, SnI2, etc.

[0043] As shown in FIG. 3, the second inorganic halide compound 200 used in one embodiment of the present invention may be PbBr2.

[0044] The third inorganic halide compound 300 has a cation of Li + , Na + , K. + , Rb + , and Cs + and the halogen anion may be a monovalent alkali metal ion selected from the group consisting of chlorine (Cl - ), Brom (Br - ), iodine (I - ) may be any one anion selected from the group consisting of

[0045] As shown in FIG. 3, the third inorganic halide compound 300 used in one embodiment of the present invention may be CsCl.

[0046] According to an embodiment of the present invention, a first inorganic halide compound 100 (PbI2) is deposited to a thickness of 240 nm, a second inorganic halide compound 200 (PbBr2) is deposited to a thickness of 80 nm, and a third inorganic halide compound 300 (CsCl) is deposited to a thickness of 20 nm by a vacuum thermal evaporation process, thereby forming a perovskite inorganic layer on top of a silicon layer.

[0047] The absorbance of the perovskite inorganic layer thus produced was measured at different times. As a result, as shown in Figure 3, it was found that the absorbance of the inorganic layer hardly changed from the absorbance at the time when the perovskite inorganic layer was first deposited on the silicon layer (as-deposited).

[0048] That is, the absorbance measurement shown in Figure 3 reveals that the phase of the inorganic layer 1 hour after the perovskite inorganic layer was deposited on the silicon layer and the phase of the inorganic layer 24 hours after the perovskite inorganic layer was deposited on the silicon layer (overnight) remain almost identical to the phase of the inorganic layer when the perovskite inorganic layer was initially deposited on the silicon layer (as-deposited).

[0049] Comparing this with the perovskite inorganic layer (PbI2+CsBr) formed by the conventional method shown in Figure 1, it can be seen that the perovskite inorganic layer (PbI2+CsBr) formed by the conventional method exhibits a significant decrease in absorbance over time in the wavelength range of 450nm to 650nm, whereas the perovskite inorganic layer (PbI2+PbBr2+CsCl) formed by the method of the present invention maintains almost the same absorbance over time across the entire wavelength range (450nm to 800nm) measured.

[0050] Therefore, according to the method for forming a perovskite according to an embodiment of the present invention, the phase of the inorganic perovskite layer is stably maintained over time, so that the organic perovskite layer can be coated on top of the inorganic layer while accurately determining the phase of the inorganic layer. Therefore, the organic-inorganic perovskite layer formed by the reaction between the organic layer and the inorganic layer can also be formed stably and uniformly.

[0051] In particular, when manufacturing a large-area tandem solar cell, even if the time taken to form the perovskite inorganic material layer varies depending on the part / batch, the state of the inorganic material layer in each part does not change over time, so the perovskite inorganic material layer can be formed uniformly over the entire area, resulting in the advantage that a large-area perovskite light-absorbing layer with high uniformity can be manufactured.

[0052] In the embodiment of the present invention, three inorganic halogen compounds having different halogen elements are deposited to form a perovskite inorganic layer. However, the present invention is not limited to this, and the inorganic layer can be formed through various combinations of three, four, five or more precursors, such as PbI2 + CsBr + PbCl2, PbI2 + CsBr + CsCl + PbBr2, etc.

[0053] Next, a step (S20) of coating a perovskite organic material layer on the thus formed inorganic perovskite layer by solution processing is performed. In one or more embodiments, a heat treatment process may be added before the step (S20) of coating the organic material layer.

[0054] There are various solution processing methods available (spin coating, doctor blade coating, drop casting, inkjet printing, electrospray, slot die coating, spray coating, etc.) The solution processing has the advantage of easily forming perovskite thin films with a consistent element ratio (stoichiometry).

[0055] In one or more embodiments, the solution process may be a spin-coating process, which involves dropping a precursor solution of a perovskite organic material layer onto a perovskite inorganic material layer formed on a substrate, and then rotating the substrate to remove excess perovskite organic material layer precursor solution by centrifugal force, thereby forming a uniform wetted film on the perovskite inorganic material layer.

[0056] The organic halogen compound forming the organic layer may have a chemical structure of AX (A is a monovalent organic ammonium cation or metal cation, and X is a halogen anion), where A is cesium (Cs + ), rubidium (Rb + ), potassium (K + ), an amide group, an amidino group, or an alkali group cation, and X is chlorine (Cl- ), Brom (Br - ), iodine (I - ), thiocyanate group (NCS - ), cyano group (CN - ), Oxycyanide (NCO - The organic halogen compound may be any one of the anions of methylammonium (MA=CH3NH 3+ ) compounds (e.g., MACl, MABr, MAI, etc.), formamidinium (FA = HC(NH2) 2+ ) compounds (e.g., FACl, FABr, FAI, etc.).

[0057] In one or many embodiments, the organic halogen compounds FAI and FABr can be dissolved in isopropyl alcohol (IPA) and then the solution can be spin-coated to form a perovskite organic layer.

[0058] Next, the inorganic perovskite layer is coated with the organic perovskite layer, and the process is left for a predetermined time, whereupon the inorganic perovskite layer and the organic perovskite layer react with each other to form a thin film made of an organic-inorganic perovskite compound (S30).

[0059] The waiting time for the organic-inorganic perovskite thin film to form is also known as the quenching time, and in one or more embodiments, the quenching time may be approximately 5 to 20 seconds, although this is not limited thereto and quenching may not be necessary depending on the penetration strength of the solvent used.

[0060] Next, the organic-inorganic perovskite thin film is heat-treated at a predetermined temperature for a predetermined time to harden the organic-inorganic perovskite thin film, thereby forming an organic-inorganic perovskite layer (S40). In one or many embodiments, the organic-inorganic perovskite thin film can be heat-treated at a temperature of 100 to 150°C for 10 to 30 minutes.

[0061] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the technical spirit of the present invention may be easily modified into other specific forms without changing the essential features. Therefore, the above-described embodiments should be understood to be illustrative in all respects and not restrictive. For example, components described as single may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner. The scope of the present invention is defined by the following claims, and all modifications and variations derived from the meaning and scope of the claims and their equivalents should be construed as being within the scope of the present invention. [Industrial Applicability]

[0062] The present invention can be used in the field of solar cell manufacturing.

Claims

1. 1. A method for forming a perovskite layer on top of a silicon layer, comprising: depositing an inorganic layer on top of the silicon layer by a vapor deposition process; and coating an organic layer on top of the inorganic layer by a solution process; The inorganic layer is formed by sequentially or simultaneously depositing three or more inorganic halogen compounds containing different halogen elements, the inorganic layer is composed of at least a first inorganic halogen compound, a second inorganic halogen compound, and a third inorganic halogen compound; The first inorganic halide compound and the second inorganic halide compound have a chemical formula structure of BX 2 and are different compounds, and B is selected from lead (Pb 2+ ), tin (Sn 2+ ), tungsten (W 2+ ), copper (Cu 2+ ), zinc (Zn 2+ ), gallium (Ga 2+ ), germanium (Ge 2+ ), arsenic (As 2+ ), selenium (Se 2+ ), rhodium (Rh 2+ ), palladium (Pd 2+ ), silver (Ag 2+ ), cadmium (Cd 2+ ), indium (In 2+ ), antimony (Sb 2+ ), osmium (Os 2+ ), iridium (Ir 2+ ), platinum (Pt 2+ ), gold (Au 2+ ), mercury (Hg 2+ ), thallium (Tl 2+ ), a method for forming a perovskite layer, characterized in that X is a cation selected from the group consisting of bismuth (Bi 2+ ), polonium (Po 2+ ), and X is an anion selected from the group consisting of chlorine (Cl − ), bromine (Br − ), and iodine (I − ); and the third inorganic halide compound has a cation selected from the group consisting of a monovalent alkali metal ion selected from the group consisting of Li + , Na + , K + , Rb + , and Cs + , and a halogen anion selected from the group consisting of chlorine (Cl − ), bromine (Br − ), and iodine (I − ).

2. 2. The method for forming a perovskite layer according to claim 1, further comprising: after the coating step, waiting a predetermined time to allow the inorganic layer and the organic layer to react to form an organic-inorganic perovskite thin film; and after the waiting step, heat-treating the organic-inorganic perovskite thin film at a predetermined temperature for a predetermined time.

3. 2. The method for forming a perovskite layer according to claim 1, wherein the inorganic layer comprises at least one or more divalent metal cations and three or more halogen anions.

4. 4. The method for forming a perovskite layer according to claim 3, wherein the inorganic layer further comprises at least one monovalent metal cation.

5. The monovalent metal cation is Li ＋ , Na ＋ , K. ＋ , Rb ＋ , and Cs ＋ 5. The method for forming a perovskite layer according to claim 4, wherein one or more alkali metal ions are selected from the group consisting of:

6. The first inorganic halide compound is PbI 2 ; the second inorganic halide compound is PbBr 2 ; The third inorganic halide compound is CsCl.

2. A method for forming a perovskite layer according to claim 1.

7. The inorganic layer is PbI ２ was evaporated to a thickness of 240 nm, and PbBr ２ 7. The method for forming a perovskite layer according to claim 6, wherein the perovskite layer is formed by depositing CsCl to a thickness of 20 nm and then depositing CsCl to a thickness of 80 nm.

8. The organic halogen compound forming the organic layer is any one of methylammonium (MA=CH) selected from the group consisting of MACl, MABr, and MAI. ３ NH ３＋ ) compound or any one formamidinium compound selected from the group consisting of FACl, FABr, and FAI (FA=HC(NH ２ ) ２＋ 2. The method for forming a perovskite layer according to claim 1, wherein the compound is a ZnO-based perovskite compound.

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