Patent Application
20230088203
The present invention relates to a solar cell module comprising a toxic material, wherein said module is provided with an adsorbent material. The invention also relates to the use of the adsorbent materials for preventing and/or reducing the leakage of toxic materials from solar cells comprising such toxic materials. The invention also relates to methods for producing solar cells and in particular modules comprising such solar cells.
The efficiency of perovskite solar cells has dramatically increased from 3.2% in 20091 to >25% ten years later,2 however, perovskite solar cells are inherently unstable to oxygen and moisture,3 which makes the potential end-of-life environmental impact of installing perovskite solar modules at large scale a serious concern.4 Several recent life cycle assessments have concluded that even with the health concerns,5-7 Pb containing PV poses much less risk to the environment than coal power plants.4,8-10 Nevertheless, waste regulations in the EU and China deem producers liable for downstream environmental and health effects, which should signal to the community that developing a “Safe-by-Design” (SbD) approach is not only legally useful, but ethically responsible.11 In recent years, a number of publications have detailed the recycling and/or reuse of perovskite solar cells components,4,12-14 or the protection of the perovskite layer from water,15,16 but so far none have detailed the adsorption of Pb that results from degraded devices.
It is an objective of the invention to provide solutions for reducing the risk of leakage of toxic metals from perovskite solar cells and/or from modules comprising such solar cells, for example due to breakage of the module and/or the solar cells. Leakage may occur also for other reasons, for example wear, tear and/or leakage occurring with time, due to exposure to environmental conditions for a prolonged time. Leakage may occur, for example, if the materials of the solar cell and/or the module comprising the solar cells to lose their properties with time, such as sealants getting brittle and the like.
WO 2019/038645 discloses similar and further polymer-metal-organic framework (MOF) composite material, which were shown to be useful for extracting metals from water. For example, the polymer-MOFs, such as Fe-BTC/PpPDA (BTC=1,3,5-benzenetricarboxylate; PpPDA=poly-para-phenylenediamine), was found useful for recovering gold from sea water. Similarly, D. Sun et al, “Rapid, Selective Heavy Metal Removal from Water by a Metal-Organic Framework/Polydopamine Composite” ACS Cent. Sci. 2018, 4, 3, 349-356, reported a polymer-metal-organic framework (MOF) composite materials.17
Remarkably, the present inventors provide solutions with respect to preventing leakage of toxic metals comprised in certain optoelectronic devices, such as perovskite solar cells.
In an aspect, the invention provides a solar cell module comprising one or more solar cells comprising a toxic material, wherein said module is provided with an adsorbent material.
In an aspect, the invention provides a solar cell panel comprising a casing, one or more solar cells provided in said casing, and an adsorbent material. Preferably, said adsorbent material is also comprised in said casing.
In an aspect, the invention provides a solar cell module comprising one or more solar cells organic-lead perovskite solar cells, wherein said module is provided with a Metal Organic Framework (MOF)/polymer composite material, wherein said composite material is preferably provided so as to trap or capture lead in case of damage of the solar cell and/or in case of leakiness of said module with respect to the environment.
In an aspect, the invention provides a method for producing a solar cell module comprising one or more solar cells comprising a toxic material, wherein said method comprises providing an adsorbent material when assembling said solar cell module.
In an aspect, the invention provides the use of an adsorbent material, in particular a MOF/polymer composite material, for preventing and/or reducing leakage of toxic materials from solar cells comprising such toxic materials.
In an aspect, the invention provides the use of an adsorbent material, for example a MOF/polymer composite material, for capturing toxic materials, such as metals, from solar cells comprised of such toxic materials in case of damage to such cells, damage to panels and/or modules comprising such cells, and/or in case of leakiness of devices comprising such solar cells.
Further aspects and preferred embodiments of the invention are defined herein below and in the appended claims. Further features and advantages of the invention will become apparent to the skilled person from the description of the preferred embodiments given below.
Hereinafter, preferred embodiments of the device of the invention are described, in order to illustrate the invention, without any intention to limit the scope of the present invention.
The present invention relates to optoelectronic and/or photoelectronic devices comprising toxic materials and to the prevention or reduction of leakage from such toxic materials from the devices. In a preferred embodiment, the optoelectronic device is a solar cell, preferably a perovskite solar cell. The solar cell is preferably an organic-inorganic perovskite solar cell. In an embodiment, the perovskite solar cell comprises lead.
Methods for producing organic-inorganic perovskites and solar cells containing such perovskites are widely described in the state of the art.
In perovskite solar cells, the perovskite generally fulfils the purpose of the generation of an exited electron upon light absorption, wherein the electron will be transported to the front and/or rear contact of the solar cell and thus contributes to the generation of the photovoltage by the solar cell.
The inorganic component of such perovskites is generally a metal, such as lead (Pb), tin (Sb), copper (Cu), bismuth (Bi), antimony (Sb), palladium (Pd), or any other alkali metal, metal, metalloid, or semi-metal with a positive or doubly positive charge, with Pb being used more widely. Lead is a heavy metal known to be toxic, acting, for example as a neurotoxin that accumulates in soft tissues and bones, interferes with the function of enzymes and may cause neurological disorders. In an embodiment, said toxic material is a toxic metal. In an embodiment, the toxic material is selected from lead and tin, but may also encompass other toxic metals. In a preferred embodiment, said toxic material is a toxic metal ion, in particular a lead-ion.
In an embodiment, the invention relates to a module comprising one or more solar cells. The module may, for example, comprise one or more solar cells as components of the overall module. The solar cell module may be provided in the form of a solar cell panel.
Preferably, the components of the solar cell, in particular the components comprising toxic materials, such as the lead-organic-perovskite, and optionally other components, such as hole transport materials, additives and the like, are sealed in the inside of the solar cell or inside the module. The solar cell or the module thus preferably comprises components forming a substrate of the solar cell. For example, transparent conductive glass or plastic may be provided on one side of the solar cells, forming a current collector and at the same time a substrate and/or delimitation on one side of the solar cell. Transparent conductive glass or plastic may be coated with transparent metal oxide conductive materials, such as indium doped tin oxide (ITO), fluorine doped tin oxide (FTO), ZnO—Ga2O3, ZnO—Al2O3, tin oxide, antimony doped tin oxide (ATO), SrGeO3 and zinc oxide, or combinations thereof. Any kind of panel, glass, plastic and the like may be provided to close the solar cell or module on the other side. In some instances, a cathode material directly forms the closure of the cell on the other side, generally the rear contact. Generally, the components of the solar cell or solar cell module, in particular the toxic material, is air and/or water tightly enclosed and/or sealed inside the solar cell. Therefore, in normal circumstances, there is only little risk of leakage of the lead or of other components to the outside of the solar cell.
Leakage of toxic materials may occur, for example, in case of damage to the solar cell and/or module and/or to the casing comprising the solar cell. Damage may occur due to impacts and/or due to material abrasion, material failure, production faults, or simply due to loss of the functionality of the components of the solar cell with time, for example due to continued exposure to oxygen, environmental conditions, such as rain, temperature fluctuations and the like, for example. In any event, damage of the solar cell or the module containing the cell cannot be excluded totally.
In order to reduce the amount of leaked toxic material and in particular of lead especially into the environment, the module and/or solar cell of the invention is preferably provided with an adsorbent material. The adsorbent material is preferably comprised in or in vicinity of the module comprising the solar cell.
In a preferred embodiment, said adsorbent material is provided for capturing said toxic material in case of leakage of components of the solar cell out of said module and/or solar cell.
In a preferred embodiment, solar cell module of any one of the preceding claims, wherein said one or more solar cells are provided in said casing. Preferably, said adsorbent material is also provided in said casing.
In an embodiment, the invention provides a solar cell panel comprising a casing, one or more solar cells provided in said casing, and said adsorbent material, wherein said adsorbent material is preferably also comprised in said casing.
Preferably, said solar cell and/or said adsorbent material are provided within said casing.
For example, the adsorbent material may be provided in one or more bags or any kind of water-permeable containers, which water-permeable containers are disposed in said casing.
In an embodiment, the module and said adsorbent material are sealed within said case or casing.
In an embodiment, the casing comprises one or more transparent glass or plastic covers or panels. Preferably, the casing may comprise a sealant, such that the solar cell module and the adsorbent material are sealed between two transparent panels or between a transparent (e.g. glass or plastic) panel and a non-transparent panel.
In an embodiment, the adsorbent material is directly integrated in or applied on said module. In this case, a separate casing may be absent. For example, the adsorbent material may be disposed on one or more surfaces of the module, e.g. coated on one or more surfaces of the module.
In an embodiment, the adsorbent material is provided within said casing and/or with respect to the solar cell module at a position which is likely to suffer damage and/or which may serve as a potential leaking point in case of damage to the module.
In an embodiment, the solar cell module and/or the casing containing the module may comprise one or more predetermined breaking points. The one or more predetermined breaking point may be engineered in such a manner that when the casing and/or module is exposed to mechanical stress or impact, a breakage and/or leakage is likely to occur at a predetermined position of the casing and/or module. In this case, the adsorbent materials is preferably disposed in spacial proximity to said predetermined breaking point, for example inside permeable containers such as bags, as a loosely disposed powder or structured pellets or beads, as a coating, or as a combination of two or more of the aforementioned.
In the embodiments shown in
In a solar cell module that is intended for horizontal or near to horizontal orientation when in use, for example, at an angle of up to 0° to 45° with respect to horizontal, the adsorbent material may advantageously be placed below the module, preferably on the rear side of the module, that is opposite the light impact side.
The predetermined breaking point, if present, is preferably designed with respect to the intended orientation (vertical or horizontal, for example) of the solar cell panel or module.
In an embodiment, said adsorbent material is porous.
In an embodiment, said adsorbent material is selected from a particulate material, a powdered material, and a film, for example a thin film.
In an embodiment, said adsorbent material is selected from the group consisting of: metal organic frameworks (MOFs), MOF/polymer composites, covalent organic frameworks (COFs), carbon, porous polymers, and combinations comprising one or more of the aforementioned.
Examples of porous polymers of cyclodextrin, cellulose, and tannins. Pourous-β-cyclodextrin polymer is disclosed, for example, in Alsbaiee et al, “Rapid removal of organic micropollutants from water by a porous β-cyclodextrin polymer”, Nature, volume 529, pages 190-194 (2016).
Said carbon may be an activated carbon material.
MOFs are also known as porous coordination polymers (PCPs), organic porous materials (MOPMs), porous coordination networks (PCNs), or metal organic materials (MOMs), are a class of crystalline materials having generally infinite network structures built with multitopic organic ligands and metal ions.
In an embodiment, said adsorbent material comprises a Metal Organic Framework/polymer (MOF/polymer) composite material. The MOF/polymer composite material may also be referred to as polymer-MOF in this specification. In this specification, the expressions “composite material” and “composites” are generally meant to refer to said MOF/polymer composites (or composite material).
In an embodiment, wherein the polymer of said MOF/polymer, as applicable, is selected from the group consisting of: redox active polymers, peptides, biopolymer including polypeptides and polysaccharides, epoxy-based polymer, fluoropolymer, acrylics, dedrimers, rubbers, inorganic polymers, organic polymers, and two or more of the aforementioned.
For the purpose of the present specification, the term “polymer” preferably encompasses the situation where two or more, preferably three or more, and most preferably four or more monomeric units are covalently connected. In a preferred embodiment, 5, 6, 7, 8 and 10 or more monomeric units are connected so as to form a polymer. For the purpose of the present specification, polymer encompasses oligomers and reference to polymer encompasses a reference to a corresponding oligomer.
In a preferred embodiment, the polymer of said MOF/polymer are organic polymers.
In an embodiment, said polymer of said composite material comprises one or more of the following chemical functions: alcohol/hydroxyl, catechol, and/or primary, secondary or tertiary amine, amide, nitrile, pyridine, pyrrole, thiol, thiolether, thiophene, thiadiazole, phenol, pyragallol, carboxylic acid, ester, acyl, crown ether, phosphate, phosphoryl, epoxide, halogen, haloalkane.
In a preferred embodiment, said polymer said composite material comprises one or more of the following chemical functions: alcohol/hydroxyl, catechol and primary amine.
In an embodiment of the solar cell module of the invention, the polymer of said MOF/polymer comprises and/or is formed from one or more moieties, which are independently selected from moieties of formula (I):
wherein,
the dotted lines in formula (I) represent the two single bonds by which the moiety of formula (I) is connected to a neighbouring moiety of the polymer; R1, R2, R3 and R3 are independently selected from H, —OH, —NH2, —NO2, —COH, —COOH, —CN, from substituents of formula (V) and (VI):
and from organic substituents comprising from 1 to 20 carbons and 0 to 20 heteroatoms selected from O, N, S, P and halogen;
wherein two or three of R1, R2, R3 and R3 may be connected with each other so as to form a ring or ring system fused to the benzene ring of formula (I), said ring or ring system comprising from 2-30 carbons and 0 to 30 heteroatoms;
with the proviso that one or more selected from R1, R2, R3 and R3 are independently selected from substituents of formula (II):
wherein:
the dotted lines in formulae (II), (V) and (VI) represent the single bond by which the respective substituent of formula (II), (V) and/or (VI) is connected to the benzene ring of formula (I),
A is independently selected from —OH, —NH2, and —SH,
n is 0 or an integer of 1-10.
Preferably, n is 0 or an integer of 1-5, more preferably 1-3.
Preferably, A is independently selected from —OH and —NH2.
In an embodiment, said organic substituents are selected from C1-C20 alkyl, C2-C20 alkenyls, C2-C20 alkynyls, C1-C20 alkoxyl, C1-C20 thioalkyl, C6-C20 aryls and/or C4-C20 heteroaryls, optionally further substituted with one or more further substituents selected independently from the group consisting of: —OH, ═O, —COOH, —NH2, —SH, amidoximyl, C1-C10 alkyl, C1-C10 alkoxyl, and C1-C10 thioalkyl.
The carbons and heteroatoms of said further substituents are included in the number of 1-20 carbons and 0-20 heteroatoms indicated with respect to said organic substituent.
In a preferred embodiment, said organic substituents comprise from 1 to 10 carbons and 0 to 10 heteroatoms, preferably 1 to 5 carbons and 0 to 4 heteroatoms selected from O, N, S, P and halogen. In a preferred embodiment, said organic substituents are selected from C1-C10 alkyl, alkenyls, alkynyls, C1-C10 alkoxyl, C1-C10 thioalkyl, C6-C10 aryls and/or C4-C10 heteroaryls, optionally substituted with one or more selected independently form —OH, —NH2, —SH, C1-C6 alkyl, C1-C6 alkoxyl and C1-C6 thioalkyl.
In an embodiment, said ring or ring system fused to the benzene ring of formula (I), comprises from 2-15 carbons and 0 to 10 heteroatoms, including ring heteroatoms selected from O, N and S. In a preferred embodiment, said ring or ring system comprises 2-10 carbons and 0-5 heteroatoms, more preferably 2-6 carbons and 0-3 heteroatoms.
Said ring or ring system may comprise further substituents preferably selected from —OH, —NH2, —SH, halogen, C1-C10 alkyl, C1-C10 alkoxyl, and C1-C10 thioalkyl, wherein carbons and heteroatoms of said further substituents are included in the number of carbons and heteroatoms indicated above with respect to the ring or ring system.
In an embodiment, the polymer of said MOF/polymer comprises one or more moieties, which are independently selected from moieties of formula (III):
wherein: said dotted lines, R1 and R2 are independently defined as above, including the embodiments of formula (II) and preferred embodiments thereof.
In an embodiment, the polymer of said MOF/polymer comprises one or more moieties, which are independently selected from moieties of formula (IV):
wherein: said dotted lines, R1 and R2 are independently defined as above, including the embodiments of formula (II) and preferred embodiments thereof.
In an embodiment, the polymer comprises and/or is formed from one or more of the following monomeric moieties: dopamine (DA), serotonin (S), 2-aminophenol (oAP), 3-aminophenol (mAP), 4-aminophenol (pAP), p-phenylenediamine (pPDA), o-phenylenediamine (oPDA), 3,4-dihydroxybenzoic acid (3,4-DHBA), 3,4-dihydroxyphenylacetic acid (3,4-DHPAA), 3,4-dihydroxyhydrocinnamic acid (3,4-DHHCA), 3,4-dihydroxybenzonitrile (3,4-DHBN), 4-nitrocatechol (3-NC), 3,4-dihydroxybenzaldehyde(3,4-DHB AH), 2,3,5-trihydrixybenzaldehyde (2,3,5-THBA), 217 3,4-dihydroxybenzylamine (3,4-DHBAM), 3,4-dihydroxybenzamidoxime (3,4-DHBAMX), (+)epinephrine (Adrenaline), Tetracyanoquinodimethane (TCNQ), viologens, Tetrathiafulvalene (TTF), quinone (Q), hydroquinone (HQ), tyramine (TA), vinylferrocene (VF or VFc), perfluorinated Sulfonic acids (Nafion®), styrene sulfonate (SS), 4-vinylpyridine (VP), aniline (ANI), aniline derivatives, 1-aminoanthracene, o-toluidine, 1,8-diaminonaphthalene (DAN), aniline-co-N-propanesulfonic acid-aniline, diphenylamine (DPA), 2-aminodiphenylamine (2ADPA), luminol (L), pyrrole (P) and P derivatives, indole and derivatives, melatonin (M), indoline, carbazole (Cz), thiophene (T) and T derivatives, azines, 1-Hydroxyphenazine (PhOH), acridine red (AR), phenosafranin (PhS), flavin (FI), new Fuchsin (nF), fluorene (F), 9-Fluorenone (FO), 9,10-dihydrophenanthrene, p-phenylene (PP), phenylenevinylene (PPV), triphenylamine (TPA), 4-vinyl-triphenylamine (VTPA), polyrhodanine (Rh), Eriochrome Black T, 5-amino-1,4-naphthoquinone (ANQ), 5-amino-1-naphthol, 4-ferrocenylmethylidene-4H-cyclopenta-[2,1-b;3,4-b °]-dithiophene, fullerene-functionalized terthiophene (TTh-BB), tetra-substituted porphyrins, phtalocyanines, tetra-substituted-phtalocyanines,)4,4° (5°-bis(3,4-ethylenedioxy)thien-2-yl, tetrathiafulvalene (EDOT-TTF), {3-[7-Oxa-8-(4-tetrathiafulvalenyl) octyl]-2,2°-bithiophene} (T-TTF), aniline-co-diaminodiphenyl sulfone, aniline-co-2,3-amino or 2,5-diamino benzenesulfonic acid, aniline-co-o-aminophenol, m-toluidine-co-o-phenylenediamine, luminol-aniline, and 2,5-dihydroxy-1,4-benzenediacetic acid (DHAA).
The polymers obtained in said MOF/polymer using the above monomers may be directly derived from the monomers. For example, the polymer obtained using dopamine is polydopamine (PDA), the polymer of serotonin is polyserotonin (PS), and so forth.
In an embodiment, the polymer of said MOF/polymer is selected from the polymers mentioned above, which comprise a primary amino group.
In an embodiment, the polymer of said MOF/polymer is selected from the group consisting of: polydopamine (PDA), polyquinone (PQ), polyhydroquinone (PHQ), polytyramine (PTA), poly(o-aminophenol) (PoAP), polymelatonin (PM), polyhydroxyphenazine (PPhOH), poly(aniline-co-o-aminophenol), polymer of 2,5-dihydroxy-1,4-benzenediacetic acid (PDHAA), poly-para-phenylenediamine (PpPDA). The aforementioned polymers preferably comprise one or more free hydroxy groups.
In an embodiment, the polymer of said adsorbent material is selected from the group consisting of: polydopamine (PDA), polytyramine (PTA), poly(o-Aminophenol) (POAP), poly(aniline-co-o-aminophenol), polymer of 2,5-dihydroxy-1,4-benzenediacetic acid (PDHAA), poly-para-phenylenediamine (PpPDA,), preferably among polydopamine (PDA) and polytyramine (PTA). The aforementioned polymers preferably comprise one or more free hydroxy and one or more primary amino groups.
In an embodiment, the polymer of said composite material is selected from the group consisting of: PDA, PS, PpAP, PoAP, PmAP, PpPDA, P-3,4-DHBA, P-3,4-DHPAA, P-3,4-DHHCA, P-3,4,-DHBN, P-4-NC, P-3,4-DHBAH, P-2,3,5-THBA, P-3,4-DHBAM, P-3,4-DHBAMX, P-Adrenaline.
In a preferred embodiment, said polymer is polydopamine (PDA).
In a preferred embodiment, said metal organic frameworks (MOFs) comprises Fe-BTC (BTC=1,3,5-benzenetricarboxylate), Cu-BTC, Cu-TDPAT (TPDAT=2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine, or Al-BDC-NH2 (BDC=2-amino-1,4-benzenedicarboxylate), preferably Fe-BTC or Cu-BTC.
In a preferred embodiment, said polymer-porous template composite material is selected from the group consisting of: Fe-BTC/PS, Fe-BTC/PpAP, Fe-BTC/PoAP, Fe-BTC/PmAP, Zr-BDPC/PpPDA, Al-BDC-NH2/PpPDA, Cu-TDPAT/PpPDA, Zr-(tetrakis(4-carboxyphenyl)porphyrin (H2TCPP) and [M-5,10,15,20-tetrakis(4-carboxyphenyl)porphyrinato] (where M=a transition metal)PpPDA, Fe-3,3,′5,5′-azobenzenetetracarboxylate)PpPDA, Fe-BTC/P-3,4-DHBA, mFe-BTC/P-3,4-DHPAA, Fe-BTC/P-3,4-DHHCA, Fe-BTC/P-3,4-DHBN, Fe-BTC/P-4-NC, Fe-BTC/P-3,4-DHBAH, Fe-BTC/P-2,3,5-THBA, Fe-BTC/P-3,4-DHBAM, Fe-BTC/P-3,4-DHBAMX, and Fe-BTC/P-Adrenaline.
In a preferred embodiment, said polymer-porous template composite material comprises Fe-BTC/PDA.
Methods for producing polymer-porous template composite materials such as those disclosed herein above are disclosed, for example in WO 2019/038645 and in D. Sun et al, 2018, cited above.
The synthesis of MOFs has been disclosed previously. The following literature references are cited in an exemplary, non-limitative manner for the purpose of illustration only:
A reference disclosing M2(NDISA)-PDA MOFs is Li et al 2019, J. Am. Chem. Soc. 2019, 141, 12397-12405.
A reference disclosing NH2-MIL-53(Al) is J Serra-Crespo et al. Am. Chem. Soc. 2012, 134, 8314-8317.
A general, exemplary way of producing MOF/polymer is provided as follows for the purpose of illustration only:
Initially, MOF/Polymer composites may be constructed under air free conditions to reduce variables that could affect the performance of the resulting material. First, MOFs were activated under vacuum in a 2-neck round bottom flask connected to a schlenk line and a rough oil pump at a temperature higher than the boiling point of water or solvent. This increases monomer diffusion into the porous networks and removes any solvent or water bound to open metal sites so that they may be used to facilitate the in-situ polymerization of the monomers. After activation, usually overnight, the reaction vessel is filled with an inert gas like argon or nitrogen. Next, in a dry box the monomer is mixed with anhydrous alcohol, stirred until dissolved and sealed. Using a steel canula and an inert gas, the solution is transferred to the reaction vessel containing the activated MOF and allowed to stir at room temperature under an inert atmosphere until the polymerization has finished again usually overnight. It should be noted that if the reaction mixture is exposed to air and temperatures are elevated then the polymer wt. percent will increase in the system. Likely, this is due to oxygen oxidizing and regenerating the catalytic open metal site to push the in-situ polymerization reaction forward. After reaction completion, the powder now a darker color is separated with centrifugation or vacuum filtration and washed with the solvent used in the reaction. The powder is loaded into a cellulose whatman thimble and undergoes soxhlet purification overnight with the solvent of choice. After purification, the powder is dried under vacuum and is activated at the desired temperature before standard characterization.
Double Solvent Method. This method can be utilized if MOFs do not have unsaturated open metal sites that facilitate the in-situ polymerization reaction, but also works with MOFs that do have open metal sites. First, a MOF is activated under vacuum in a two-neck round bottom flask using a schlenk line and rough oil pump to remove any polar solvent like water. After dosing an inert gas into the system, anhydrous non-polar hexane is added to the reaction mixture and allowed to stir until complete diffusion usually in less than 30 minutes. The monomer is then dissolved into the most minimal amount of water as possible. This aqueous solution is then syringed into the reaction mixture. Over time, the hydrophilic MOF will mix will the water and work its way to the bottom of the reaction vessel. Once this is achieved, the anhydrous hexane is then decanted out. Now a pH swing is conducted to facilitate the in-situ polymerization reaction. An alcohol solution containing a base like ammonia (NH3) is added to the reaction and allowed to stir until reaction completion usually overnight. The solids now a darker color is separated from the solvent either by centrifugation or vacuum filtration and is washed with fresh solvent that is used in the reaction. The powder is loaded into a cellulose whatman thimble and undergoes soxhlet purification overnight. After purification, the powder is dried and activated before standard characterization. A reference disclosing the double solvent method for producing MOF/polymer composites is “MOF/polymer composite synthesized using a double solvent method offers enhanced water and CO2 adsorption properties” L. Peng, S. Yang, D. T. Sun, M. Asgari, W. L. Queen, Chem. Commun. 2018, 54, 10602.
While certain of the preferred embodiments of the present invention have been described and specifically exemplified above, it is not intended that the invention be limited to such embodiments. Various modifications may be made thereto without departing from the scope and spirit of the present invention, as set forth in the following claims. Herein below, examples of the invention are disclosed. These examples are for illustration only and are not intended to limit the scope of the present invention.
To adequately simulate the propensity of the polymer-MOF composite to take up Pb from perovskite solar cells, we decided to use a work flow (
General Considerations: All commercial reagents and consumable items were used as received. ICP-OES measurements carried out using an Agilent 5110 ICP-OES. The porous polymer-MOF composite uptake material was synthesized as previously reported. For this example, the MOF/polymer was Fe-BTC/PDA, which was produced as disclosed in WO 2019/038649, pages 31-32. See also Sun et al 2018.
Thin Film Fabrication: FTO-coated glass (Nippon Sheet Glass) was patterned by chemical etching with zinc powder and HCl solution. The etched glass substrate was then sonically cleaned with Hellmanex solution, water, acetone, and 2-propanol. A 30 nm thick electron transporting layer was deposited by spray pyrolysis of titanium diisopropoxide bis(acetylacetonate) (Sigma-Aldrich) in 2-propanol (1:15 v/v) at 450° C. A 1.3M triple cation [(FAPbI3)0.87(MAPbBr3)0.13]0.92(CsPbI3)0.08 perovskite precursor with excess PbI2 (PbI2:FAI=1.05:1) was prepared by dissolving FAI (GreatCellSolar), MABr (GreatCellSolar), CsI (ABCR), PbI2 (TCI), and PbBr2 (TCI) in DMF and DMSO mixture (0.78:0.22 v/v). Perovskite film was deposited on the prepared substrate by spin-coating the precursor solution at 2000 rpm for 12 s and 5000 rpm for 30 s. Chlorobenzene as an anti-solvent was added 15 s before the end of spin-coating process. Finally, the film was annealed on a hot plate at 100° C. for 60 minutes.
Lead Uptake Experiments: Using Solutions of dissolved PbI2: Solutions of known PbI2 concentration were held at a certain temperature for at least twenty minutes before the addition of the porous uptake material. After waiting a set period of time with minimal agitation, the solution was filtered with a 0.45 μm filter and the resulting filtrate acidified to 2% HNO3 using concentrated HNO3.
Using perovskite film: Following decomposition of the perovskite film at 50° C. for 1 h, the temperature was allowed to stabilize for at least 10 min and the porous uptake material was added. The submerged cell was then kept at the desired temperature with minimal agitation until the suspension was decanted from the substrate, filtered using a 0.45 μm filter, and the filtrate acidified to 2% HNO3 using concentrated HNO3.
The propensity for the polymer-MOF composite material to take up Pb from simulated perovskite solar cell extracts was tested to determine the optimal conditions for lead uptake (
Because perovskite absorber materials contain more materials than just PbI2, we tested whether it was these other materials that led to increased uptake in the thin film extract samples. In each perovskite film we used, there are methylammonium, formamidinium, and cesium cations as well as iodide and bromide anions. To simulate the conditions found in the dissolved thin film solution, we added methylammonium iodide, formamidinium iodide, and cesium iodide to the PbI2 solution in the same molar ratio as was found in the perovskite thin films and tested the effect on lead uptake (
Once we had established that the composite could take up Pb efficiently from thin film absorbers, we then moved to understanding the kinetics of Pb removal from degraded thin films. We performed time dependent lead uptake trials of aqueous PbI2 solutions at different temperatures using a single 5 mg treatment, from 4° C. to room temperature (rt, 22° C.) to 50° C.
(
After establishing the amount of time needed to reach equilibrium (at least four minutes), we further investigated how increasing mass and number of treatments affected Pb removal (
a Pb uptake study of aqueous PbI2 solutions with varying mass and
a Uptake measured after 5 min treatment at 295K. Each data point is the average of three experimental data points and each experimental data point is the average of three replicate measurements. Error bars are included for each plotted point and represent one standard deviation. ND = not determined,
bSolution resulted from digestion of 1.35 cm × 2.35 cm perovskite thin film degraded with 5 mL DI water at 323K for 1 h.
cSolution resulted from digestion of 1.35 cm × 2.35 cm perovskite solar cell degraded with 5 mL DI water at 323K for 1 h.
We were pleased to observe that double treatment of 10 mg led to greater uptake, and double treatment of 20 mg removed ˜99.5% of the initial Pb (0.182±0.045 ppm). Triple treatment of 10 mg led to >99.8% reduction, and triple treatment of 15 mg yielded a Pb concentration that was less than the EPA mandated 0.015 ppm value for safe drinking water (0.013±0.002 ppm, 30 ppm starting concentration and 5 mL sample volume, Table 2). Using 20 mg triple treatment also reduced the Pb concentration below the 0.015 ppm level (0.008±0.002). When using solutions obtained from perovskite thin film or complete solar cell degradation (3.17 cm2 substrate area, ˜600-700 nm absorber thickness), three treatments of 15 mg or 20 mg composite resulted in >99.8% Pb uptake (5 mL sample volume) to yield a Pb concentration that was below the EPA threshold of 0.015 ppm (0.010 ppm for thin films, 0.008 ppm for complete cells using 15 and 20 mg triple treatment). These data clearly indicate that this MOF/polymer material holds great potential for the sequestration of perovskite-derived Pb, and could render safe perovskite solar cells in the case of catastrophic device failure.
b Solutions filtered and acidified after 5 min at 295K and minimal solution agitation. Each data point is the average of three experimental data points and each experimental data point is the average of three replicate measurements.
After investigating the adsorption rate and optimized the treatment procedure, we investigated how pH could affect Pb uptake as well as the degree of desorption in neutral water. We observed that Pb uptake from stock solutions of PbI2 with one treatment of 10 mg was more efficient at pH values between 6-3 (<20% Pb remaining in each case, compared with 21.5% for pH=7,
After understanding the degree of Pb desorption from the material, we used accelerated aging to investigate how field conditions could affect Pb absorption (
Once we optimized the treatment conditions for small cells and films, we ventured to extend the treatments to module-sized substrates. Using degraded monolithic series cell modules with an area of 45.5 cm2, we compared Pb leaching under two types of conditions: total submersion with water and flow-through of water during extended heavy rain. The treatments were scaled linearly from three 15 mg treatments for 3.17 cm2 substrates to three 300 mg treatments for a 45.5 cm2 substrate. Because the nature of the device failure is different, the concentrations resulting from each failure are expected to be different.
Module-Scale Pb Uptake: Submersion: A 45.5 cm2 perovskite solar cell module was fixed to a 10 cm×10 cm glass sheet using two-sided scotch tape. Three sachets of 300 mg polymer-MOF composite were placed around the module and butylene rubber was added to each side. Separately, a second 10 cm×10 cm glass sheet with butylene rubber on three sides was warmed to 150° C. for 5 minutes. The warmed sheet was gently pressed against the other to make contact between the rubber sections and then the previously cool glass sheet was placed on a hot plate set to 150° C. for five minutes. Gentle pressing on the top of the partially encapsulated module ensured the butylene rubber was sealed well on all sides. After cooling to room temperature, DI water was added until the module and sachets were completely submerged. Each day, an aliquot was taken, acidified to 2% HNO3 using concentrated HNO3 and analyzed using ICP-OES.
Flow-Through: A 45.5 cm2 perovskite solar cell module was fixed to a 7 cm×10 cm glass sheet using butylene rubber. Three sachets of 300 mg polymer-MOF composite were placed beneath the module and butylene rubber was added to the longer sides of the module. Separately, a second 7 cm×10 cm glass sheet with butylene rubber on the longer sides was warmed to 150° C. for 5 minutes. The warmed sheet was gently pressed against the other to make contact between the rubber sections and then the previously cool glass sheet was placed on a hot plate set to 150° C. for five minutes. Gentle pressing on the top of the partially encapsulated module ensured the butylene rubber was sealed well on all sides. After cooling to room temperature, DI water was through the module from the top (side without sachets) at a rate of 37 mL/hr and fractions taken every 12 minutes. During the treatment, the substrate was stationary and fixed at a 60° angle and the droplet placement was randomized. Each droplet flowed through the module was observed to be in contact with the solar cell for approximately 5 s, and in contact with the MOF underneath the solar cell for ˜25 s before dropping into the collection vial. The fractions were then acidified to 2% HNO3 using concentrated HNO3 and analyzed using ICP-OES.
In the first type of failure, submersion, a hole in the top front panel causes water to enter, become trapped, and eventually submerge the module inside its case. To test Pb leaching resulting from submersion, we encapsulated a module on three sides with 300 mg of polymer-MOF composite in a water-permeable paper sachet on each closed side. DI water was added to submerge the module and aliquots were taken each day. Within seconds, the black portion of the perovskite absorber in contact with the water turned yellow (
In the second type of failure, leakage, water not only enters the cell, but a hole in the bottom allows water to exit the cell, ostensibly after extracting some of the perovskite absorber layer. While there could be many versions of this failure with varying degrees of severity, we chose to construct the worst-case scenario, where the top and bottom of the encapsulating box is completely open, allowing water maximum contact time with the perovskite module and unimpeded flow-through (
During the hour-long simulated rainfall, the amount of Pb present in each fraction (6-8 mL) was low, with each 12 min fraction containing less than 0.4% of the theoretical maximum value. Concentrations increased from 1.78 ppm for the first twelve-minute fraction to a maximum of 2.66 ppm for the 24-36 min fraction and then decreased to 2.38 ppm in the 48-60 min fraction. After this treatment, four days were allowed to pass to simulate drying between rainfall events, and another simulated rainfall treatment performed on the fifth day. During this treatment, much lower Pb concentrations were observed in each of the twelve-minute fractions, and each successive fraction (from 0.55 ppm for 0-12 min to 0.07 ppm for 48-60 min) contained less Pb than the last. While these values are higher than the EPA limit, the amount of Pb leached at this scale (45.5 cm2 substrate, <0.4% % for the first day and <0.1% for the fifth day, three treatments of 300 mg) was similar to small scale experiments (3.17 cm2 substrate, <0.1% for three treatments of 15 and 20 mg).
Finally, we performed X-ray Photoelectron Spectroscopy (XPS) on powder samples of composite material with and without adsorbed Lead in an effort to identify which moieties in the poly(dopamine) material were responsible for adsorption. Dopamine oxidation produces oligomers with a random distribution of several functional groups and linkages between units.21,2223 Representative spectra of the O 1s, N 1s, and Pb 4f regions were obtained and shown in
Before Pb adsorption, no Pb was detected in the Pb 4f region of either material (
We have investigated the propensity for a polymer-MOF composite to act as a Pb uptake material specifically for hybrid organic-inorganic Pb halide perovskite materials. We studied the kinetics of Pb uptake and found that the cations other than Pb present in the perovskite film increased uptake, while the Br anions decreased Pb uptake. We optimized the treatments required to lower the Pb concentration resulting from a fully dissolved 3.17 cm2 perovskite absorber layer to below the EPA limit for safe drinking water and successfully scaled up the optimized treatment protocol to a 45.5 cm2 monolithic series cell. We also investigated Pb desorption from the composite and found very little Pb leached back into solution once adsorbed in a range of temperatures. We found that acid rain (rain pH<5.6) and light soaking at 60° C. did not appreciably lower uptake activity, and proposed an adsorption mechanism where catechol and amine functional groups were mainly responsible for Pb chelation in the polymeric material. After demonstrating the efficacy of this material for perovskite-originating Pb, we believe it could be used in field-wide application as a “Safe-by-Design” strategy for mitigating any detrimental environment impact that could be foreseen from industrialization of perovskite solar cells.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19217049.6 | Dec 2019 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/086581 | 12/16/2020 | WO |
