Method for recovering lead from photoelectric conversion elements

Abstract

The objective is to provide a method for recovering lead from photoelectric conversion elements with a perovskite structure in an environmentally friendly manner, and a method for reusing electrode substrate materials. [Solution] A method for recovering lead from a photoelectric conversion element in which a photoelectric conversion layer made of a material having a perovskite structure containing lead and halogen elements as constituent components is supported on an electrode substrate, comprising a peeling step of peeling the photoelectric conversion layer from the electrode substrate in a processing solution and dissolving lead into the processing solution, and a recovery step of recovering the dissolved lead. The peeling step is characterized by processing the photoelectric conversion element in the processing solution with a peeling-promoting means added. The processing solution is preferably an aqueous solution with a pH of 0 or higher and a pH of 11 or lower, more preferably with a pH of 2 or higher and a pH of 11 or lower, and even more preferably with a pH of 2 or higher and a pH of 4 or lower. A preferred peeling-promoting means is ultrasonic treatment.

Description

[Technical Field]

[0001] This invention relates to a method for disassembling a photoelectric conversion element and recovering lead contained in the element. [Background technology]

[0002] In the manufacturing of photoelectric conversion elements, solar cells using organic-inorganic hybrid semiconductor materials containing metals such as lead and halogens such as iodine as the photoelectric layer are being developed as highly efficient thin-film solar cells. In particular, perovskite solar cells that use crystals with a perovskite structure or a perovskite-like structure as the photoelectric layer, and photoelectric conversion elements using perovskite quantum dots are being actively developed, and the manufacturing of large-area practical modules and solar panels using them is attracting attention. The thin film of perovskite crystal that makes up the photovoltaic layer of perovskite solar cells contains metals such as lead and tin. Lead, in particular, is a metal that is harmful to the environment, so the industry that manufactures and sells solar cells needs to safely recover and detoxify the lead from used solar cell modules.

[0003] In the manufacturing of solar cells, perovskite solar cells have the advantage of being able to be produced at a lower cost than conventional solar cells and having a relatively small environmental impact (CO2 emissions) during manufacturing. However, it is desirable to use environmentally friendly processing methods for used batteries as well. In particular, it is desirable to carry out the process of separating and recovering lead from lead-containing perovskite solar cells in an environmentally friendly manner. However, the recovery technologies for perovskite solar cells proposed so far have had safety problems, such as the use of highly toxic organic solvents, and have been associated with a high environmental impact.

[0004] Patent Document 1 discloses a method for recovering perovskite by immersing a perovskite solar cell substrate in a water-containing solution with a washing solvent such as alcohol, acetone, dimethylformamide, or γ-butyrolactone, or water with different pH values, for a certain period of time. In the step using water, the immersion time of the substrate is defined by a mathematical formula according to the pH value of the solution. However, according to this definition, when using water, it becomes necessary to immerse the substrate for a long period of time, ranging from 2 to 80 hours, as shown in the examples, which is extremely inefficient. Patent Document 2 describes a method for immersing and peeling a perovskite film made of MAPbI3 (where MA is methylammonium) using a halogenated solution as the solvent, and only examples using an aqueous solution of methylammonium iodide (MAI) as the halogenated substance are shown. However, methylammonium (MA) and the methylamine derived from MA are volatile and harmful substances. Patent Document 3 discloses a method for recovering lead iodide from a perovskite solar cell, which includes the steps of: pre-treating a recycled perovskite solar cell to obtain a perovskite; dissolving the perovskite in a solvent consisting of dimethyl sulfoxide or a dimethyl sulfoxide mixed solvent containing at least one of dimethylformamide, methylpyrrolidone, and γ-butyrolactone to obtain a lead iodide-containing solution; and mixing the lead iodide-containing solution with a solvent consisting of alcohol, ketone, ether, lipid, or hydrocarbon to precipitate lead iodide and collecting the lead iodide precipitate. However, a problem is that organic solvents such as dimethyl sulfoxide, dimethylformamide, methylpyrrolidone, and γ-butyrolactone are highly toxic and harmful to the environment.

[0005] Non-patent document 1 describes a method for eluting a perovskite semiconductor film composed of MAPbI3 (where MA is methylammonium) from a substrate using an organic solvent such as dimethylformamide (DMF), which is used for forming perovskite crystals. However, the problem is that organic solvents such as DMF are highly toxic and harmful to the environment. Non-Patent Document 2 describes that a perovskite semiconductor film composed of FA 0.83 Cs 0.17 PbI3 (where FA is formamidinium) on a glass substrate can be peeled off from the glass by a method of finely cutting the glass substrate and immersing it in warm water at 50°C. However, this method not only requires mechanical processes such as cutting the substrate, but also has the drawback that by breaking the substrate, an expensive electrode substrate coated with a transparent conductive film such as indium tin oxide cannot be reused. Non-Patent Document 3 is a review on the life cycle of the production of perovskite solar cells. Table 6 of Non-Patent Document 3 lists the perovskite recovery methods reported so far, and most of the recovery methods use organic solvents harmful to the environment such as DMF and alcohol.

[0006] As described above, in the process of recovering lead from perovskite materials containing lead used in solar cells and photoelectric conversion elements, the treatment process has problems such as the use of toxic and environmentally harmful organic solvents or the need for long-term immersion when using an aqueous solvent system, making the treatment process inefficient. Also, in the recovery process, as a member constituting the solar cell, it is preferable to recover a high-cost substrate material such as a transparent electrode of an indium tin oxide conductive film in a reusable form, or to use a process of separating and recovering it from lead.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Documents

[0008]

Non-Patent Document 1

[0009] To safely, quickly, and efficiently recover hazardous substances such as lead from used solar cell and photoelectric conversion element modules with high yield, a recovery method using environmentally friendly and safe solvents and processing steps is required. The present invention provides a method for recovering lead from perovskite solar cell and photoelectric conversion element modules using safe materials in an environmentally friendly manner, and further provides a recovery process that enables the reuse of substrate materials constituting the solar cell. [Means for solving the problem]

[0010] In view of the above problems, the present inventors have conducted extensive research and have found a method for recovering lead from photoelectric devices that use lead-containing perovskite and semiconductors having a perovskite-like structure as a photoelectric conversion layer. This method involves using an environmentally friendly aqueous solution as the processing solution to recover lead quickly and in high yield, thereby solving the above problems. Specifically, the problem can be solved in the following ways.

[0011] (Aspect 1) A method for recovering lead from a photoelectric element, wherein a photoelectric conversion layer made of a material having a perovskite structure containing lead and halogen elements as constituent components is supported on an electrode substrate, the method comprising a peeling step of peeling the photoelectric conversion layer from the electrode substrate in a processing solution and dissolving lead into the processing solution, and a recovery step of recovering the lead dissolved in the peeling step, wherein the peeling step is characterized by processing the photoelectric element in the processing solution with a peeling promoting means.

[0012] (Aspect 2) A method for recovering lead from a photoelectric element, wherein a photoelectric conversion layer made of a material having a perovskite structure containing lead and halogen elements as constituent components is supported on an electrode substrate, the method comprising a peeling step of peeling the photoelectric conversion layer from the electrode substrate in a processing solution and dissolving lead into the processing solution, and a recovery step of recovering the lead dissolved in the peeling step, wherein the peeling step is characterized by applying ultrasonic treatment to the photoelectric element in the processing solution as a means for promoting peeling.

[0013] (Aspect 3) A method for recovering lead from a photoelectric conversion element in which a photoelectric conversion layer made of a material having a perovskite structure containing lead and halogen elements as constituent components is supported on an electrode substrate, the method comprising a peeling step of peeling the photoelectric conversion layer from the electrode substrate in a processing solution and dissolving lead into the processing solution, and a recovery step of recovering the lead dissolved in the peeling step, wherein the peeling step is characterized by applying ultrasonic treatment as a means for promoting peeling in the processing solution, wherein the irradiation energy of the ultrasonic waves is 5 J / mL to 100 J / mL per unit volume of the processing solution in which the photoelectric conversion element is immersed.

[0014] (Aspect 4) The peeling step is a method for recovering lead from a photoelectric conversion element according to any one of aspects 1 to 3, characterized in that the processing liquid is an aqueous solution with a pH of 0 or higher and a pH of 11 or lower.

[0015] (Aspect 5) The peeling step is a method for recovering lead from a photoelectric conversion element according to any one of aspects 1 to 3, characterized in that the processing liquid is an aqueous solution with a pH of 2 or higher and a pH of 11 or lower.

[0016] (Aspect 6) The peeling step is a method for recovering lead from a photoelectric conversion element according to any one of aspects 1 to 3, characterized in that the processing liquid is an aqueous solution with a pH of 2 or higher and a pH of 4 or lower. [Effects of the Invention]

[0017] According to the present invention, lead can be recovered from photoelectric conversion elements using lead-containing semiconductors, such as perovskite solar cells, with high yield, in a short processing time, and without using environmentally harmful materials. This makes the recovery of materials from used photoelectric conversion elements more efficient and significantly reduces the environmental burden of the recovery process. Furthermore, after recovery, the substrate material used in the photoelectric conversion element can be reused in the manufacture of new photoelectric conversion elements. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic diagram showing a typical configuration of a perovskite photoelectric conversion element. [Figure 2] This is a schematic diagram showing the basic configuration types of perovskite photoelectric conversion elements. [Figure 3] This flowchart shows one embodiment of the method for recovering lead from a photoelectric conversion element according to the present invention. [Modes for carrying out the invention]

[0019] Embodiments for carrying out the present invention are described below. However, the invention is not limited to the embodiments described.

[0020] The present invention relates to a method for recovering lead from a photoelectric conversion element in which a photoelectric conversion layer containing lead and halogen elements as constituent components is supported on an electrode substrate. Specifically, the method comprises a peeling step in which the photoelectric conversion layer is peeled from the electrode substrate in a processing solution by adding a peeling-promoting means and the lead is dissolved into the processing solution, and a recovery step in which the lead dissolved in the peeling step is recovered. The following describes, in order, the structure of a photoelectric conversion element in which a photoelectric conversion layer containing lead and halogen elements as constituent components is supported on an electrode substrate, the peeling process in which the photoelectric conversion layer is peeled off from the electrode substrate by adding a peeling-promoting means in a processing solution and lead is dissolved into the processing solution, and the recovery process in which the lead dissolved in the peeling process is recovered.

[0021] 1. Photoelectric conversion element In this invention, the target of lead recovery treatment is a photoelectric conversion element capable of converting light input into electricity. In particular, the element is characterized in that the active material used in its structure, such as semiconductors or light-absorbing materials, contains lead as an element. Examples of such elements targeted by this invention include solar cells for outdoor installation that generate electricity using sunlight, photoelectric conversion elements that generate electricity using light sources other than sunlight, such as indoor lighting, photodetectors and light sensors manufactured for purposes other than power generation, and lighting equipment, light-emitting elements, and displays that convert electrical signals into light.

[0022] The photoelectric conversion elements targeted by the lead recovery treatment of this invention include lead-containing perovskite photoelectric conversion elements and their integrated modules. Perovskite photoelectric conversion elements and their integrated modules are used not only for outdoor power generation but also for power generation using indoor lighting. Their area is 1 cm². 2 From small sizes to 1m 2 They come in a wide range of sizes, from large to large, and their shapes vary from flat to curved and cylindrical. Figure 1 is a schematic diagram showing the general configuration of a perovskite photoelectric conversion element targeted for lead recovery in the present invention. It is a multilayer, flat element consisting of a transparent substrate, a transparent conductive film, a charge transport layer I, a perovskite semiconductor layer, a charge transport layer II, and a counter electrode, from the light incident side. The perovskite semiconductor layer plays the role of a photoelectric conversion layer responsible for light absorption and photoelectric generation. The perovskite semiconductor layer is usually a thin film with a thickness of about 1 μm and is colored dark to strongly absorb sunlight. Lead is included as one of the elements constituting the perovskite semiconductor in order to increase the photoelectric conversion efficiency. In addition, a gas barrier layer, a sealing material layer, and a laminate material that encloses the entire multilayer structure are added.

[0023] Excluding the transparent substrate, the total thickness of the layers from the transparent conductive film, charge transport layer I, perovskite semiconductor layer, charge transport layer II, to the counter electrode is usually several micrometers. The transparent substrate is the thickest, ranging from 0.1 to several millimeters. Furthermore, when using a general-purpose carbon material (such as graphite) for the counter electrode, the thickness can reach several tens of micrometers. Transparent conductive films are optically transparent conductive films coated onto a substrate, and fluorine-doped tin oxide (FTO) or indium tin oxide (ITO) are commonly used as inorganic oxides. In addition, conductive polymers (such as PEDOT:PSS) and nanocarbon films (such as carbon nanotubes and fullerenes) are also used. Charge transport layers I and II can be configured as either an electron transport layer (ETL) or a hole transport layer (HTL) (forward structure), or as the reverse configuration where they are both hole transport layers (HTL) and electron transport layers (ETL) (reverse structure). Furthermore, there are device structures that lack either or both of the hole transport layers (HTL) and electron transport layers (ETL). Perovskite photoelectric conversion elements come in various layer configurations with different thicknesses, but the perovskite crystal layer supported on the substrate (hereinafter referred to as the "perovskite semiconductor layer") weighs approximately 1 m 2 The amount is approximately 0.8g to 5.0g per unit. Furthermore, if the perovskite composition is a lead halide, the amount of lead supported on the substrate is approximately 1m³ in weight. 2 The amount per serving is approximately in the range of 0.2g to 1.3g.

[0024] Figure 2 is a schematic diagram showing the basic configuration types of perovskite photoelectric devices. (a) is a mesoporous structure in which a perovskite layer is supported on a mesoporous metal oxide (TiO2, SnO2, etc.). (b) and (c) are flat planar structures in which the perovskite layer is not supported on a mesoporous metal oxide. (b) is the forward structure and (c) is the reverse structure, respectively. Also, (d) is a structure without an electron transport layer and (e) is a structure without a hole transport layer. In Figure 2, a metal electrode made of gold or silver is shown as an example for the uppermost counter electrode, but other materials, as described later in section (2-5) Counter Electrodes, can also be used.

[0025] 2. Configuration of a perovskite photoelectric conversion element The following briefly describes the transparent electrode substrate, electron transport layer, perovskite semiconductor layer, hole transport layer, and counter electrode of a mesoporous perovskite semiconductor photoelectric conversion element.

[0026] (2-1) Transparent electrode substrate A transparent electrode substrate is a transparent substrate on which a transparent conductive layer is formed.

[0027] (2-1-1) Transparent substrate Glass and plastic substrates are preferred for the transparent substrate. Examples of glass substrate materials include inorganic substrates made of white glass, soda-lime glass, borosilicate glass, and the like. As the plastic substrate material, a material that is uncolored, highly transparent, has high heat resistance, excellent chemical resistance and gas barrier properties, and is low cost is preferred. Suitable materials include, for example, polyesters (polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc.), polystyrenes (syndiotactic polystyrene (SPS), etc.), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PAr), polysulfone (PSF), polyester sulfone (PES), polyetherimide (PEI), transparent polyimide (PI), cycloolefin copolymer (trade name Arton, etc.), and alicyclic polyolefin (trade name Zeonor, etc.). Among these, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and alicyclic polyolefin are particularly preferred in terms of chemical stability and cost. The structure and composition of these plastic substrates are not particularly limited, and any material suitable for constituting the solid-state junction type photoelectric conversion element of the present invention can be used. Furthermore, the glass substrate material does not necessarily have to be one with a visible light transmittance exceeding 80%, but rather an inorganic substrate made of, for example, white glass, soda glass, or borosilicate glass.

[0028] (2-1-2) Transparent conductive film For transparent conductive films used in photoelectric devices, fluorine-doped tin oxide (FTO) and indium tin oxide (ITO) are commonly used due to their high light transmittance and conductivity. The former is commonly used on glass substrates, while the latter is used on both glass and plastic substrates. These transparent conductive films must have low sheet resistance and high conductivity, with a sheet resistance of typically 30 Ω / sq. or less, preferably 10-20 Ω / sq. The thickness of a transparent conductive film that meets this requirement is several hundred nm, and ITO has a density of approximately 7 g / cm³. 3 ) In the case of 1m 2 The amount is approximately 1g to 3g per unit. Since ITO contains indium, it is expensive, and therefore, it is preferable to reuse the ITO electrode substrate when the photoelectric conversion element reaches the end of its lifespan and is recovered.

[0029] (2-2)Electron transport layer The electron transport layer has functions similar to those of an n-type semiconductor, and any material capable of selectively extracting electrons from the photoelectric conversion layer can be used. Examples of such materials include metal oxide semiconductors (TiO2, SnO2, ZnO, Nb2O3, etc.), conductive polymers with n-type properties, and nanocarbon materials such as fullerenes. A mesoporous perovskite semiconductor device is constructed by coating a perovskite semiconductor layer onto the surface of a porous microparticle layer made of n-type semiconductor metal oxides formed on a transparent electrode substrate.

[0030] (2-2-1) Porous fine particle layer The porous microparticle layer consists of a so-called mesoporous layer in which nano-sized pores are formed in a network-like structure. Semiconductors and insulators such as metal oxides and metal chalcogenides are used for the microparticles. Generally, n-type metal oxide semiconductors are used as semiconductors, and metal oxides such as alumina, silica, and zirconia are used as insulators. The metal elements that make up these metal oxides include, for example, titanium, tin, zinc, iron, copper, tungsten, strontium, niobium, indium, cerium, vanadium, tantalum, lead, antimony, and bismuth for semiconductors, and zirconium, aluminum, and silicon for insulators. The elements that make up metal chalcogenides include cadmium, sulfur, selenium, molybdenum, titanium, vanadium, chromium, cobalt, copper, nickel, and manganese.

[0031] For the deposition of these metal oxide and metal chalcogenide nanoparticles, either chemical solution coating, physical vacuum deposition, or both are used. Solution coating methods include, for example, slot die coating, bar coating, drop casting, spin coating, inkjet printing, screen printing, air spraying, and air spraying using a spraying device. Vacuum deposition methods, including chemical deposition, are used for the deposition of various thin-film solar cells.

[0032] (2-2-2) Other electron transport layers In addition to the porous inorganic materials mentioned above, organic compounds are also used as materials for the electron transport layer. Examples of these include, at the low molecular weight level, carbon-based materials such as fullerene compounds, vasocuproin (BCP), and vasophenanthrene (Bphen), as well as phosphine compounds having double bonds with Group 16 elements of the periodic table, such as (8-hydroxyquinolinato)aluminum (Alq3), boron compounds, oxadiazole compounds, benzimidazole compounds, naphthalenetetracarboxylic anhydride (NTCDA), perylenetetracarboxylic anhydride (PTCDA), phosphine oxide compounds, and phosphine sulfide compounds. As polymer compounds, for example, n-type conductive polymers such as polyalylene, polyacetylene, polyphenylenevinylene, and polyphenanthroline are used.

[0033] (2-3) Perovskite semiconductor layer Perovskite semiconductors are crystals with a perovskite structure, and polycrystalline aggregates of these nanocrystals form thin films that constitute the photoelectric conversion layer (perovskite semiconductor layer) of photoelectric conversion elements. The basic structure of a perovskite crystal is the ABX3 structure, which has a three-dimensional network of BX6 octahedra sharing vertices. X is a halogen, and perovskites are characterized by being halogen compounds. The B component of the ABX3 structure is a divalent metal cation in which a monovalent X anion can take octahedral coordination, and the A cation is an inorganic or organic cation located in the 12 coordination pores between the BX6 octahedra. By using an organic cation for A, a perovskite crystal with an organic-inorganic hybrid structure, so-called organic-inorganic hybrid perovskite, can be obtained.

[0034] The photoelectric conversion element targeted by the lead recovery method of the present invention is a photoelectric conversion element in which a photoelectric conversion layer made of a semiconductor containing lead and a halogen element as constituent components is supported on an electrode substrate, and the semiconductor containing lead and a halogen element as constituent components is composed of a halide perovskite compound represented by the following general formula (1) alone or in a mixture of two or more. ([A 1 [B])a[X]3(1) Here, [A 1 is a monovalent organic cation or an inorganic cation. As the organic cation, methylammonium (CH3NH3 + ), formamidinium (CH(NH2)2 + ) is preferably used, and in addition, an organic cation represented by R 1 NH3 + is used. Here, examples of R 1 include an alkyl group, alkenyl group, aralkyl group, aryl group, heterocyclic group, and aromatic heterocyclic group having 2 or more carbon atoms. As the inorganic cation, Cs + , Rb + , K + , Na + , Cu + , Pd + , Pt + , Ag + , Au + , Rh + , Ru + are selected and one or more monovalent cations are used, and particularly Cs + is preferably used. [B] is a metal ion from which a perovskite crystal can be obtained, and generally, a divalent metal ion selected from Pb 2+ , Sn 2+ etc. is used. For the purpose of the present invention, it is essential to contain at least Pb 2+ . [X] is a halide anion selected from F - , Cl - , Br - , I - , and particularly, I - as well as I -and Br - A mixture of these is commonly used. The value of 'a' is between 0.7 and 1.3, with 0.8 to 1.2 being the most common.

[0035] Furthermore, the semiconductor constituting the photoelectric conversion layer may also be a compound represented by the following general formula (2) or general formula (3). [A 2 ]2[B][X]4(2) [A 3 ][B][X]4(3) Here, [A 2 ] is R 1 NH3 + or R 2 H + It is a monovalent organic cation represented by [A 3 ] is R 2 H2 2+ or R 3 (NH3)2 2+ This is a divalent organic cation represented by R. 1 As with the case of general formula (1), examples include alkyl groups, alkenyl groups, aralkyl groups, aryl groups, heterocyclic groups, and aromatic heterocyclic groups having 2 or more carbon atoms. 2 Examples include heterocyclic groups and aromatic heterocyclic groups. 3 Examples include alkylene groups, alkenylene groups, aralkylene groups, arylene groups, heterocyclic groups, and aromatic heterocyclic groups. The definitions of [B] and [X] are the same as in the general formula (1) above. The photoelectric conversion layer can be appropriately mixed with compounds represented by general formulas (1), (2), and (3). Furthermore, the compounds represented by general formulas (2) and (3) can be used as so-called two-dimensional perovskites, not only in the photoelectric conversion layer but also for purposes such as charge transport and interface stabilization.

[0036] The lead- and halogen-containing perovskite materials targeted for lead recovery in this invention include organic-inorganic hybrid perovskites and inorganic perovskites, which include those described in "Essential Points of Chemistry Series 48, Perovskite Solar Cells" by Tsutomu Miyasaka, 2024, Kyoritsu Shuppan, and "Perovskite photovoltaics and Optoelectronics" edited by Tsutomu Miyasaka, 2022, Wiley-VCH Publishing.

[0037] (2-4) Hole transport layer The hole transport layer has functions similar to those of a p-type semiconductor, and any inorganic or organic material with the ability to selectively extract holes from the photoelectric conversion layer can be used.

[0038] Examples of inorganic materials for the hole transport layer include metal oxides such as copper oxide, nickel oxide, manganese oxide, iron oxide, molybdenum oxide, vanadium oxide, and tungsten oxide. For hole transport layers, spiro-OMeTAD, a derivative of spirobifluorene, and its analogues are widely used as organic materials at the low molecular weight level. At the polymer level, triarylamine derivatives are widely used. For example, polymers of many thiophene derivatives, including PTAA (poly(triarylamine)) and PEDOT (poly(3,4-ethylenedioxythiophene)), as well as polypyrrole, polyacetylene, triphenylenediamine, and polyaniline, which have n-type conductivity due to doping, are also used. The hole transport layer thickness is thick in spiro-OMeTAD, ranging from 100nm to 500nm, but in many polymer materials, it is extremely thin, typically less than 50nm.

[0039] Instead of a hole transport layer, a method of forming a self-assembled molecular film of organic molecules at the interface between the perovskite and the electrode is also used in photoelectric devices as a structure that does not use hole transport materials. For example, phosphate derivatives of carbazole, such as [2-(9H-carbazole-9-yl)ethyl]phosphonic acid, are used for this self-assembled molecular film. These self-assembled molecular films are used by coating the surface of oxides such as ITO and FTO of the electrode substrate.

[0040] (2-5) Counter electrode The counter electrode is made of various conductive materials. For example, metal electrodes such as Al, Au, Mg-Ag alloy, or Au-Sb alloy are preferably used, but materials other than metal electrodes, such as conductive oxides, conductive resins, and carbon materials, may also be used as needed. These counter electrodes are formed by vacuum deposition methods such as vapor deposition or sputtering, or by wet coating methods such as applying ink containing nanoparticles or precursors. The thickness is usually around 0.2 to 50 μm.

[0041] (2-6) Outer packaging and barrier packaging Perovskite semiconductor devices may experience output degradation under harsh environmental conditions, and providing durability is particularly important under high temperature and high humidity conditions. For this reason, the devices are often enclosed in barrier-type outer materials or packaging.

[0042] 3. Method for recovering lead from photoelectric conversion elements Figure 3 is a flowchart illustrating one embodiment of the lead recovery method from photoelectric conversion elements according to the present invention. In the lead recovery method from photoelectric conversion elements according to the present invention, as a preliminary step, the laminate material is mechanically peeled off and removed from the photoelectric conversion elements recovered from the market, and a pre-treatment is performed to extract the photoelectric conversion elements to be used for lead recovery. The present invention provides a method for recovering lead from a photoelectric conversion element, comprising: a peeling step in which a photoelectric conversion element having a photoelectric conversion layer made of a material having a perovskite structure containing lead and halogen elements as constituent components is supported on an electrode substrate, is immersed in a processing solution, and a peeling accelerating means is added to peel off the photoelectric conversion layer made of a material having a perovskite structure containing lead and halogen elements as constituent components from the electrode substrate and dissolve the lead into the processing solution; and a recovery step in which the peeled electrode substrate is reused and lead is recovered from the processing solution.

[0043] (3-1) Peeling process The peeling step in the lead recovery method from a photoelectric conversion element of the present invention involves immersing a photoelectric conversion element, in which a photoelectric conversion layer made of a material having a perovskite structure containing lead and halogen elements as constituent components is supported on an electrode substrate, in a processing solution, and adding a peeling accelerating means to peel off the photoelectric conversion layer and other layers constituting the photoelectric conversion element (electron transport layer, hole transport layer, electrode layer, etc.) from the electrode substrate and dissolve lead into the processing solution. The following describes the processing solution and the means for promoting peeling.

[0044] (3-1-1) Treatment solution The processing solution used in the stripping step of the lead recovery method from photoelectric conversion elements of the present invention is preferably an aqueous solution with a pH of 0 or higher and a pH of 11 or lower, more preferably an aqueous solution with a pH of 2 or higher and a pH of 11 or lower, and even more preferably an aqueous solution with a pH of 2 or higher and a pH of 4 or lower. Since pH changes with water temperature, the pH in the present invention refers to the pH measured at an aqueous solution temperature of 25°C, and the pH value includes a range of rounding.

[0045] Considering the safety of the processing solution, it is preferable to avoid strong acids and strong alkalis. However, since strong acids are effective in quickly dissolving lead, pH levels down to around 0 should be acceptable. However, if the pH drops below 2, valuable indium, mainly contained in the transparent conductive film, will also dissolve. While it is possible to dissolve and recover the indium, it is preferable to leave it in the substrate so that it can be reused as a transparent electrode substrate. It is also effective to leave it in the substrate and recover it using a method other than that used for lead.

[0046] Even in pH ranges where lead can hardly be dissolved even after prolonged periods of standing, stirring, or penetration, lead can be dissolved relatively quickly by using peel-accelerating methods such as ultrasound. In other words, lead can be dissolved relatively quickly even when the pH of the treatment solution is 2 or higher, making it effective for retaining indium on the substrate. However, simply increasing the pH will not increase the amount of elution or shorten the elution time, and using a strong alkali also carries risks. Therefore, for safety reasons, it is preferable to work in a neutral or weakly alkaline solution, and a pH lower than approximately 11 is preferable. The processing solution of the present invention can be pure water, as well as tap water or industrial water, which does not contain any solutes such as acids or bases. Using water as a safe and easy-to-handle processing solution and using a peeling-promoting means such as ultrasound to dissolve lead is one of the preferred embodiments of the present invention.

[0047] Acids, bases, and salts can be used as appropriate to adjust the pH. Examples of inorganic acids used to adjust the pH of the treatment solution of the present invention include sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid. Chloride ions and nitrate ions (NO3) contained in hydrochloric acid and nitric acid - While sulfuric acid has a large solubility product with lead and is therefore less likely to form precipitates, sulfuric acid is more likely to form lead sulfate precipitates. Whether or not to allow precipitate formation should be chosen depending on the method used in the recovery process following the stripping process. In other words, if ion exchange or adsorption methods described later are used, it is preferable that no precipitate is formed, but if the precipitate is to be recovered, it is rather preferable for a precipitate to form at this stage. Examples of organic acids include formic acid, acetic acid, propionic acid, citric acid, tartaric acid, glycolic acid, malic acid, succinic acid, acetic acid, ascorbic acid, etc., with acetic acid and citric acid being preferred. Many organic acids tend to form precipitates with lead, but acetate ions have a high solubility product with lead ions, making them less likely to form precipitates. Examples of bases include potassium hydroxide and sodium hydroxide. Various salts can also be used to adjust the pH. To adjust to a weakly alkaline solution, sodium carbonate, sodium bicarbonate, potassium carbonate, sodium acetate, and sodium phosphate can be used. To adjust to a weakly acidic solution, ammonium sulfate, ammonium bisulfate, ammonium nitrate, and ammonium chloride can be used. The acid, base, and salt of the treated aqueous solution are not particularly limited, as long as they maintain the pH value described above.

[0048] The temperature of the processing solution is raised by vibration energy from the peeling-promoting means, but a temperature of 20°C to 60°C is preferred.

[0049] In the lead recovery method from photoelectric conversion elements of the present invention, the processing liquid used in the stripping step may contain organic solvents that are miscible with water, such as alcohols.

[0050] Examples of alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, n-hexanol, ethylene glycol, propylene glycol, diethylene glycol, diethylene glycol, and aliphatic alcohols such as glycerin. The mixing ratio of alcohols with water should preferably be kept to 0.1 or less by mass ratio to water.

[0051] (3-1-2) means for promoting peeling The present invention provides a method for promoting the peeling or dissolution of the perovskite layer by applying elastic vibrations to a photoelectric conversion element. It is preferable to use ultrasonic vibrations because they can be transmitted non-contact. A preferred embodiment is a processing method in which a processing tank is filled with a processing liquid, a photoelectric conversion element is immersed in the processing liquid, an ultrasonic application mechanism is inserted into the processing liquid, and ultrasonic waves are applied to the photoelectric conversion element.

[0052] The ultrasonic application mechanism comprises at least an ultrasonic transducer inserted into the processing tank and an oscillator that applies a driving voltage to the ultrasonic transducer (neither of which is shown in the figures). An example of an ultrasonic transducer is one comprising a piezoelectric material such as piezoelectric ceramics and a pair of electrodes provided on the piezoelectric material. A pair of electrodes are in contact with a piezoelectric element and are also electrically connected to an oscillator. When the oscillator outputs a drive voltage, such as a high-frequency voltage, to the ultrasonic transducer in response to an operation command from the control unit, the drive voltage is applied between the pair of electrodes, thereby applying the drive voltage to the piezoelectric element. The piezoelectric element, to which the drive voltage is applied, vibrates by repeatedly contracting and expanding alternately in response to the drive voltage from the oscillator. This allows ultrasonic waves to be applied to the processing liquid stored in the processing tank.

[0053] The ultrasonic treatment is preferably performed with 10 to 300 cycles of oscillation and stopping. The ultrasonic irradiation energy should be sufficient to peel off the photoelectric conversion layer and other layers constituting the photoelectric conversion element (electron transport layer, hole transport layer, electrode layer, etc.), which are made of a perovskite structure material containing lead and halogen elements as constituent components, from the electrode substrate and dissolve lead into the treatment solution. When calculated as irradiation energy per unit volume of treatment solution, it is preferably 5 J / mL to 100 J / mL, more preferably 10 J / mL to 60 J / mL. Higher irradiation energy is preferable for lead dissolution, but applying unnecessary energy can cause the temperature of the treatment solution to rise too high, which is dangerous. The treatment time is less than 30 minutes, preferably less than 10 minutes, more preferably less than 5 minutes.

[0054] As a means of promoting peeling according to the present invention, elastic wave vibration treatment can also be used, in which at least one of the photoelectric conversion elements is gripped by a vibration actuator and vibrated while the photoelectric conversion elements are immersed in a treatment liquid. The elastic wave vibration mechanism uses a piezoelectric actuator, which has a gripping means fixed to a base, to grip a photoelectric conversion element, and vibrates the gripping part vertically at a frequency of 100 to 2000 Hz. The piezoelectric actuator is an actuator that has a piezoelectric element, and expands and contracts when a voltage is applied to the piezoelectric element.

[0055] (3-2) Recovery process The recovery process is a solid-liquid separation process that separates the treatment liquid containing lead leached by the stripping process into solid components and a lead-containing solution. The lead leached into the treatment liquid can be recovered by known methods. Commonly used methods include precipitation, electrolysis, ion exchange, adsorption, and chemical reduction. [Examples]

[0056] The lead recovery method of the present invention will be described in detail below with reference to examples and comparative examples, but the present invention should not be construed as being limited to these examples. Table 1 summarizes examples and comparative examples of the peeling and recovery steps that constitute the lead recovery method of the present invention.

[0057] The evaluation of the examples and comparative examples is based on the following criteria. <Evaluation Criteria> A: High Pb elution rate (95% or more) and high In retention rate (90% or more) A1: Short processing time (less than 5 minutes). A2: Processing time will be slightly longer, but well within an acceptable range (5 minutes to less than 10 minutes). B: The elution rate of Pb is high (over 95%), but the residual rate of In is low (less than 10%). C: Low Pb elution rate (less than 95%) D: Even with a longer processing time (30 minutes or more), the lead leaching rate remains low (less than 95%).

[0058] [Table 1]

[0059] 1. Fabrication of perovskite photoelectric conversion elements (1-1) Preparation of coating solution for electron transport layer A 1.5% by weight aqueous tin oxide dispersion was prepared by adding ultrapure water to a 15% aqueous tin(IV) oxide dispersion (manufactured by Alfa Aesar), and this was used as the coating solution for the electron transport layer.

[0060] (1-2-1) Preparation of coating solution 1 for photoelectric conversion layer A 0.625 mL mixed solution of DMF / DMSO (volume ratio 3:1) was prepared with concentrations of 1 mol / L of methylammonium iodide (MAI) and 1 mol / L of lead iodide (PbI2), respectively, and this was used as photoelectric conversion layer coating solution 1.

[0061] (1-2-2) Preparation of coating solution 2 for photoelectric conversion layer A 1 mL DMF / DMSO (volume ratio 3:1) mixed solution was prepared with the following concentrations: formamidine hydroiodide (FAI) 0.94 mol / L, lead iodide (PbI2) 1.17 mol / L, lead bromide (PbBr2) 0.03 mol / L, methylamine hydrobromide (MABr) 0.2 mol / L, and cesium iodide (CsI) 0.06 mol / L, and this was used as coating solution 2 for the photoelectric conversion layer.

[0062] (1-3) Preparation of coating solution for hole transport layer 2,2',7,7'-tetrakis[N,N-di-4-methoxyphenylamino]-9,9'-spirobifluorene (Spiro-OMeTAD) was dissolved in chlorobenzene to a concentration of 36 mg / mL. A coating solution for the hole transport layer was prepared by adding 14.5 μL of acetonitrile solution of LiTFSI (520 mg / mL) and 8.5 μL of 4-tert-butylpyridine as dopants.

[0063] (1-4) Preparation of collected samples (1-4-1) Preparation of collected sample 1 A perovskite photoelectric conversion element was fabricated by laminating an electron transport layer (SnO2), a photoelectric conversion layer (perovskite crystal: MAPbI3, 350 nm thick), and a hole transport layer (spiro-OMeTAD) on a transparent conductive substrate (hereinafter referred to as "ITO-PET substrate") coated with indium tin oxide (ITO) on a PET film (thickness 125 μm) using the coating solutions prepared in (1-1), (1-2-1), and (1-3), and then sequentially laminating a counter electrode (gold vapor-deposited film). The surface of the gold electrode was laminated with a moisture-proof barrier film using a encapsulant and PET substrate, and this was used as the recovered sample 1. The total thickness was 250 μm.

[0064] (1-4-2) Preparation of the second collected sample On an ITO-PET substrate, the coating solution prepared in (1-1), (1-2-2), and (1-3) is used to create an electron transport layer (SnO2) and a photoelectric conversion layer [perovskite crystal: Cs 0.05 FA 0.783 MA 0.167 PbI 2.78 Br 0.22 A perovskite photoelectric conversion element was fabricated by laminating a hole transport layer (spiro-OMeTAD) with a thickness of 350 nm, followed by a counter electrode (gold vapor-deposited film). The surface of the gold electrode was laminated with a moisture-proof barrier film using a encapsulant and PET substrate, and this was collected as sample 2. The total thickness was 250 μm.

[0065] <Example 1> 1. Pre-treatment process To prepare the recovered sample (25mm x 15mm) prepared above for the peeling process, the laminate film covering the element was mechanically peeled off.

[0066] 2. Peeling process As shown in Table 1, a 0.0001M to 1M hydrochloric acid aqueous solution (pH 0 to 4) was used as the treatment solution. 80 mL of the treatment solution for lead elution was placed in a treatment container (100 mL beaker), and the recovered sample 1 was immersed in the treatment solution and submerged at the bottom of the treatment container. The horn of an ultrasonic homogenizer (Branson Sonifier SFX550) was immersed in the processing solution in which the recovered sample 1 was soaked, and the tip of the horn was positioned approximately 1 cm away from the recovered sample 1. Next, the ultrasonic oscillator was adjusted to a frequency of 20 kHz and an output of 40 W to 50 W. Ultrasonic treatment was performed by repeating a 1-second irradiation followed by a 4-second pause 30 times. The total treatment time was 150 seconds. Although the ultrasonic output fluctuated, the total energy was measured by this device and recorded as the irradiation energy. The results are shown in Table 1. Note that the temperature of the treatment solution rose from approximately 25°C to approximately 45°C during the ultrasonic treatment. This process visually confirmed the disappearance of the photoelectric conversion layer (brown) on the ITO-PET substrate.

[0067] The ultrasonic horn and recovered sample 1 were washed with 20 mL of the same processing solution used for elution to obtain 100 mL of processing solution for measurement. The recovered sample after peeling was washed with pure water and dried, and then used for measurement of residual substances.

[0068] 3. Measurement of lead leaching The treatment liquid from which lead and other materials were recovered during the stripping process contained residues and organic matter. The organic matter was completely decomposed with nitric acid and perchloric acid, and after drying, it was dissolved in nitric acid, adjusted to a fixed volume, and quantitative analysis was performed using ICP emission spectrometry (Shimadzu Corporation ICPS-8100). The amount of lead leached was calculated by comparing the obtained quantitative values ​​with the theoretical amount of Pb coating on the recovered samples. The results are shown in Table 1.

[0069] 4. Measurement of residual lead and indium The amount of metals remaining in the recovered samples after elution of lead and other metals was analyzed by X-ray fluorescence analysis (SEA6000VX HSFinder, SII). The signal intensity of each metal in the recovered samples before and after elution was compared to calculate the remaining percentage. Furthermore, the elution rate was calculated by subtracting the remaining percentage from 100%. The results are shown in Table 1.

[0070] 5. Evaluation of lead and indium leaching In all samples from Examples 1-1 to 1-4, it was found that nearly 100% of the lead was leached. Comparison with the results of the comparative examples described later shows that applying ultrasonic energy is effective in shortening the processing time. On the other hand, indium leaches out in processing solutions with a pH lower than 2, but not in processing solutions with a pH higher than 2. To reuse ITO substrates containing expensive indium as is, it is preferable to prevent indium from leaching out. Even if they are not reused as is, leaving the indium on the film side makes it possible to separate it from the lead and recover the indium. The lead dissolved in the treatment solution can be recovered in a subsequent recovery process using known methods. Commonly used methods include precipitation, electrolysis, ion exchange, adsorption, and chemical reduction.

[0071] <Example 2> Except for using an acid other than hydrochloric acid (1M nitric acid, 1M sulfuric acid, 1M acetic acid) as the treatment solution, the elution treatment of recovered sample 1 was performed under the treatment conditions shown in Table 1, in the same manner as in Example 1. Almost all of the lead could be eluted under all treatment conditions. On the other hand, indium hardly eluted at all in the case of 1M acetic acid, where the pH was 2 or higher, but almost all of it eluted in sulfuric acid and nitric acid at pH 0. Considering the results together with those of Example 1, it can be concluded that these results depend on the pH value of the treatment solution, rather than the type of acid. Furthermore, a comparison with the results of the comparative examples described later shows that applying ultrasonic energy is effective in shortening the processing time.

[0072] <Example 3> Except for using pure water and 0.001 MKOH as the processing solution, the elution treatment of recovered sample 1 was performed under the processing conditions shown in Table 1, in the same manner as in Example 1. Furthermore, a comparison with the results of the comparative examples described later shows that lead can be eluted even under neutral to weakly alkaline conditions by applying ultrasonic energy. Moreover, the fact that nearly 100% of the lead can be eluted in a relatively short treatment time is a remarkable effect. Furthermore, in neutral to alkaline treatment solutions, indium hardly dissolves. Therefore, under these conditions, it is possible to reuse ITO, which uses expensive indium, as is, or to recover indium by separating it from lead.

[0073] <Example 4> As shown in Table 1, the elution treatment of recovered sample 2 was performed in the same manner as in Example 1, except that a small amount of ethanol was added to an acidic aqueous solution as the treatment solution, and recovered sample 1 was used as recovered sample 2. Comparing the values ​​of Example 4-1 with Example 1-2, and Example 4-2 with Example 2-3, there were no significant differences, indicating that the lead recovery treatment from the photoelectric conversion element of the present invention can be achieved even with the addition of a small amount of ethanol. Furthermore, the results obtained were generally similar even when the composition of the recovered sample or the perovskite layer was changed.

[0074] <Example 5> Except for using 1M acetic acid as the treatment solution, the elution treatment of recovered sample 1 was performed under the treatment conditions shown in Table 1, in the same manner as in Example 1. Here, the effect was observed by changing the number of ultrasonic irradiations, i.e., the total amount of irradiation energy. With 5 irradiation cycles, lead leaching was insufficient, with the leaching rate being less than 90%. With 10 cycles, over 95% leaching occurred. Higher irradiation energy is preferable for lead leaching, but care must be taken as applying unnecessary energy can cause the temperature of the treatment solution to rise too high, posing a danger.

[0075] <Example 6> In the peeling process of Example 1, the recovered sample 1 was attached to the tip of a plate-shaped piezoelectric actuator and immersed in the processing solution. Instead of using an ultrasonic homogenizer, the recovered sample was vibrated by vibrating a piezoelectric element at 1 kHz to attempt to dissolve lead and indium. The contents of the treatment solution and the treatment time are shown in Table 1. The elution treatment was performed in a cycle of 5 seconds of vibration followed by a 5-second pause, and the total time shown is the total time. After treatment, measurements were performed in the same manner as in Example 1, and the remaining amounts of lead and indium and the amount eluted are shown in Table 1. As can be seen from these results, it was confirmed that applying elastic waves in the form of vibration to the recovered sample 1 accelerates lead recovery. Based on this, the recovered sample was processed. It can be seen that directly applying elastic waves in the form of vibration to the recovered sample is a means of accelerating delamination.

[0076] <Comparative Example 1> In the stripping process of Example 1, 1M hydrochloric acid, 1M acetic acid, pure water, and 0.001 MKOH were used as the treatment solution. Instead of using an ultrasonic homogenizer, the beaker containing the treatment solution and recovered sample 1 was placed on a linear shaker and shaken at approximately 1 Hz to attempt to dissolve lead and indium. After treatment, measurements were performed in the same manner as in Example 1, and the remaining amounts of lead and indium and the amount dissolved were measured. The results are shown in Table 1. By continuing the shaking treatment for one hour, more than 90% of the lead was leached out in 1M hydrochloric acid with a low pH (Comparative Example 1-1), but the amount of lead leached out in the treatment solution with a pH of 2 or higher (Comparative Example 1-2) was less than 90%. Furthermore, when the pH increased to neutral to weakly alkaline (Comparative Examples 1-3 and 1-4), almost no lead was leached out. [Industrial applicability]

[0077] This invention can be used in the field of recovering and recycling metal resources from photoelectric conversion elements.

Claims

1. A method for recovering lead from a photoelectric element in which a photoelectric conversion layer made of a material having a perovskite structure containing lead and halogen elements as constituent components is supported on an electrode substrate, The lead recovery method includes a peeling step of peeling the photoelectric conversion layer from the electrode substrate in a processing solution and dissolving lead into the processing solution, This process consists of a recovery step for recovering the lead dissolved in the aforementioned peeling step, The method for recovering lead from a photoelectric conversion element is characterized in that the peeling step involves processing the photoelectric conversion element in a processing liquid with a peeling promoting means added.

2. A method for recovering lead from a photoelectric element in which a photoelectric conversion layer made of a material having a perovskite structure containing lead and halogen elements as constituent components is supported on an electrode substrate, The lead recovery method includes a peeling step of peeling the photoelectric conversion layer from the electrode substrate in a processing solution and dissolving lead into the processing solution, This process consists of a recovery step for recovering the lead dissolved in the aforementioned peeling step, The method for recovering lead from a photoelectric conversion element is characterized in that the peeling step involves treating the photoelectric conversion element in a processing liquid with ultrasonic treatment as a means for promoting peeling.

3. A method for recovering lead from a photoelectric element in which a photoelectric conversion layer made of a material having a perovskite structure containing lead and halogen elements as constituent components is supported on an electrode substrate, The lead recovery method includes a peeling step of peeling the photoelectric conversion layer from the electrode substrate in a processing solution and dissolving lead into the processing solution, This process consists of a recovery step for recovering the lead dissolved in the aforementioned peeling step, The peeling step is characterized by treating the photoelectric conversion element in a processing solution with ultrasonic treatment, where the irradiation energy of the ultrasonic waves is 5 J / mL to 100 J / mL per unit volume of the processing solution in which the photoelectric conversion element is immersed, as a means for promoting peeling.

4. The method for recovering lead from a photoelectric conversion element according to any one of claims 1 to 3, characterized in that the peeling step is an aqueous solution with a pH of 0 or higher and a pH of 11 or lower.

5. The method for recovering lead from a photoelectric conversion element according to any one of claims 1 to 3, characterized in that the peeling step is an aqueous solution with a pH of 2 or higher and a pH of 11 or lower.

6. The method for recovering lead from a photoelectric conversion element according to any one of claims 1 to 3, characterized in that the stripping step is an aqueous solution with a pH of 2 or higher and a pH of 4 or lower.

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