WO2019138154A1

WO2019138154A1 - Method for refurbishing of carbon based perovskite solar cells (cpscs) and modules via recycling of active materials

Info

Publication number: WO2019138154A1
Application number: PCT/FI2018/050983
Authority: WO
Inventors: Ghufran Syed HASHMI; Teemu MYLLYMÄKI; David MARTINEAU
Original assignee: Aalto-Korkeakoulusäätiö Sr; Solaronix S.A.
Priority date: 2018-01-09
Filing date: 2018-12-28
Publication date: 2019-07-18

Abstract

The present invention relates to a process for the separation and recycling of the materials of a carbon based perovskite solar cell, by separation of the layers and the selective removal of active components,the process including the steps of removal of layers of silver nanoparticles using mechanical means, immersion into a polar aprotic solvent to dissolve the perovskite layer, removal of the carbon electrode using water, extraction of remaining active perovskite components, MAI and AVAI, by immersion into water, re-immersion of the remaining structure into a polar aprotic solvent, or into acetonitrile, followed by warming, to cause the remaining perovskite component PbI₂ to dissolve, and sonicating the remaining FTO-glass electrode, containing an insulator layer and TiO₂ layers, in a polar solvent.

Description

METHOD FOR REFURBISHING OF CARBON BASED PEROVSKITE SOLAR CELLS (CPSCS) AND MODULES VIA RECYCLING OF ACTIVE MATERIALS

Refurbished CPSCs with selective removal of halide perovskite, Pbl₂, Methylammonium iodide + 5-Ammonium valeric acid iodide i.e. MAI+5-AVAI and carbon back contact electrode from the carbon-based printed perovskite solar cells device structure: Processing steps towards low cost and recyclable photovoltaic technology.

Core of the invention

The application discloses a method of the selective removal of the active components (Pbl₂, MAI, 5-AVAI and carbon electrode) of a carbon based perovskite solar cell device geometry. These active components can be recycled and can be reused to produce refurbished carbon perovskite solar cells.

Problem it solves

An increase in the volume of degraded carbon based printed perovskite lab sized solar cell and large area carbon based printed perovskite PV panels combined with strict environmental laws generates a grand challenge to speedily develop a facile process through which, these degraded PV modules could be efficiently recycled or refurbished at viable cost.

Typical perovskite solar cells contain hazardous materials that cause problems in safe recycling. Among others, the lead content of typical perovskites can be challenging. Unique device structure of carbon based perovskite solar cells and large area carbon based printed perovskite solar modules and detail composition of perovskite precursor solution which is highly compatible for this device structure

In this document, we are strictly restricted to a unique device structure of carbon based printed perovskite solar cells and large area carbon based printed perovskite solar modules which has been reported in our previous work [1-3] or by others [4] or described in our previous patent application [5] as well as described in the following sections. Details of the fabrication and the device structure of carbon based perovskite solar cells

The details of device fabrication of carbon based printed perovskite solar cells is given below as well as in our previous work [1-3] including in our previous international patent application [5] as well as in Figure 1. The details of the carbon based perovskite solar cell device structure is more described in our previous work [1-3] including in our previous international patent application [5] as well as in Figure 2.

Perovskite solar cells for this work were fabricated as follows:

Fluorine doped tin oxide (FTO) coated glass substrates (10x10 cm2, RSH = 7 W/Sq, Product code: TC022-7, Solaronix) were first etched with an automated fiber laser, and cleaned by sequential sonications in Hellmanex 1% aqueous solution, acetone, and isopropanol (15 min each). Then a compact layer of Ti0₂ (30-40 nm) was deposited by spray pyrolysis over the etched glass substrates placed on a hot-plate set to 550 °C, of a diluted solution of titanium diisopropoxide bis(acetylacetonate) (75% in isopropanol, Sigma- Aldrich) in absolute ethanol (1 :80) using oxygen as a carrier gas. Areas of the substrate had been masked with glass strips to prevent the coating in the subsequent contact (silver) areas. After cooling down to room temperature, a silver paste (Sun Chemical CRSN2442) was screen-printed and dried at 150 °C for 15 min to obtain silver contacts for anode and cathode. The 500 nm thick mesoporous Ti0₂ layer was obtained by screen-printing (diluted Ti-Nanoxide T/SP in terpineol, Solaronix) on the compact Ti0₂ layer followed by drying at 150 °C for 5 min, and sintering at 500 °C for 15 min. The substrates were cooled down to room temperature. Similarly, the insulating mesoporous Zr0₂ layer was also obtained by screen-printing (Zr Nanoxide ZT/SP, Solaronix) on the aforementioned Ti0₂ layer followed by drying at l50°C for 5 min, and sintering at 500°C for 30 min. The substrates were again cooled down to room temperature. The thickness of the Zr0₂ was tuned by stacking 1-4 prints before sintering. The conductive porous carbon electrode was fabricated by screen-printing a carbon paste (Elcocarb B/SP, Solaronix), drying at 150 °C for 5 min, and firing at 400 °C for 30 minutes. The substrates were again cooled down to room temperature before the infiltration of perovskite precursor solution in the porous stack. Details of the perovskite precursor ink formulation of this work

The perovskite precursor ink for this experiment was prepared by mixing 0.53 g of Pbl₂ (TCI-Chemicals), 0.19 g of methyl ammonium iodide (MAI, Dyesol) and 0.0176 g of 5- ammonium valeric acid iodide (5-AVAI, Dyesol) in 1 ml of gamma-butyro lactone (Sigma Aldrich) in a glass vial under a laboratory fume hood. The glass vial was sealed and placed for stirring for 30 min on a preheated (70 °C) hot-plate. The ingredients were completely dissolved and a clear yellow solution was obtained that was allowed to cool down to room temperature. The perovskite precursor ink remained stable both in glass vial and in the printer cartridge for more than 2 weeks and no precipitation or precipitation of the solutes was observed.

Nevertheless, the composition of perovskite precursor solution is not restricted with the aforementioned ink- formulation but is further explained in the following:

In the perovskite precursor solution/ink, said perovskite is an organic-inorganic perovskite, which can also be composed of one organic or one inorganic cation ((for example: methyl- ammonium CFTNFT , ethyl-ammonium CFFCFFNFF , formamidinium NFl₂CF[=NF[₂ ⁺ or cesium Cs), a metal cation of carbon family (for example: Ge²⁺, Sn²⁺, Pb²⁺) and a halogen anion (preferrably: F , Cf, Br , T)) and is further comprised of a solvent (for example:

GBL, DMSO or DMF) for dissolving the components of the perovskite as well as a compound or component that is suitable to inhibit, slow down, reduce and/or prevent one or more selected from: nucleation rate, crystal growth and precipitation of perovskite, perovskite crystals and/or a perovskite intermediate phase. Said compound may be referred to as "precipitation retarding compound" or more shortly "retarding compound".

This compound may be any compound suitable to prevent or slow down precipitation of perovskite or perovskite intermediates in the precursor solution, while enabling and/or not preventing such precipitation upon deposition of the precursor solution. In an embodiment, the compound may allow crystallization and/or precipitation upon an additional process step, for example following heating. In an embodiment, the method of the invention comprises heating the deposited perovskite precursor solution, so as to as remove solvent and/or initiate and/or accelerate one or more selected from precipitation and perovskite crystal growth. The "precipitation retarding compound" may be part of the perovskite to be formed or may not be part of the perovskite to be formed. In some embodiments, the "precipitation retarding compound" is preferably associated with or comprised in said organic inorganic perovskite. In the perovskite precursor solution/ink, said perovskite precursor solution is stable when stored for 1 day or more at room temperature (RT, 25°C) in a glass vial and/or printer cartridge, wherein stable refers to the absence of crystal growth and/or precipitation of solutes during said 1 day (24 hours). In another embodiment, the perovskite precursor solution is stable for at least 12 hours following preparation. Preferably, however, said perovskite precursor solution is stable when stored for 2 days or more, more preferably for 5 days, even more preferably 1 week, and most preferably 2 weeks or more, at room temperature (RT). In some embodiments, the perovskite precursor solution is stable for up to 3 months and possibly more. Storing may take place in a glass or suitable plastic recipient. A printer cartridge is generally made from plastic material, and the precursor solution is preferably stable for the indicated time in a printer cartridge.

Precipitates resulting from said precipitation are preferably visible by eye, such that absence of precipitation refers to absence of precipitation that can be recognized by the eye, and in particular absence of precipitation that would result in clogging of the printer nozzle. In an embodiment, the "precipitation retarding compound" is an organic or an organometallic compound and/or preferably comprises one or more carbon atoms.

In the perovskite precursor solution/ink, the "precipitation retarding compound" comprises an anchoring group, suitable to anchor the compound to the surface of a metal oxide material. Preferably, the anchoring is represented by the letter "A" as defined elsewhere in this specification. Indeed, in a preferred embodiment, the present invention relates to perovskite solar cells comprising metal oxide materials, for example metal oxide semiconductor materials suitable to transport electrons that have been photo-exited in the perovskite. Preferably, the perovskite is deposited such that it gets in contact with said metal oxide semiconductor.

Anchoring groups (A) may be selected from the group consisting of: -COOH, -CONH₂, - PO₃H₂, -PO₂H₂R², -PO₄H₂, -SO₃H₂, -CONHOH, combinations thereof, salts thereof, deprotonated forms thereof, and other derivatives thereof, for example. R² may be selected from organic substituent comprising from 1-20 carbon atoms and 0-10 heteroatoms, preferably from 1-10 carbon atoms and 0-8 heteroatoms, 1-5 carbon atoms and 0-3 heteroatoms, for example. In the perovskite precursor solution/ink, said R² also carries an anchoring group. Alternatively, R² is a hydrocarbon. In the perovskite precursor solution/ink, R² also is totally or partially halogenated, independently of said heteroatoms. Preferably, said heteroatoms are selected from O, S, Se, Te, N, B, P, for example.

In the perovskite precursor solution/ink, the "precipitation retarding compound" comprises a positively charged group. In an embodiment, said positively charged group may be any stable, positively charged group of an organic or organometallic compound.

In the perovskite precursor solution/ink, the "precipitation retarding compound" comprises a group comprising a nitrogen atom, preferably a nitrogen atom present in a positively charged state. Preferably, the nitrogen containing group is represented by the letter "W", for example as defined elsewhere in this specification. Exemplary groups may be selected from -NFT , -NHC(NH3⁺)=NH, and -N=CH-NH3⁺. The compound preferably comprises an ammonium group.

In the perovskite precursor solution/ink, said "precipitation retarding compound" comprises a linker or spaceholder moiety (R¹), connecting said anchoring group and said preferably positively charged group, for example said positively charged nitrogen atom.

In the perovskite precursor solution/ink, said linker moiety is preferably an organic moiety comprising 1-20 carbons and 0-10 heteroatoms, preferably 2-12 carbons and 0-7 heteroatoms, more preferably 3-10 carbons and 0-5 heteroatoms, and most preferably 4-8 carbons and 0 heteroatoms. Said organic moiety may be totally or partially halogenated, in addition to said heteroatoms.

In the perovskite precursor solution/ink, said linker moiety is preferably a C1-C20 hydrocarbon, preferably a C2-C15 hydrocarbon, more preferably a C3-C12 hydrocarbon, and most preferably a C4-C8 hydrocarbon.

In the perovskite precursor solution/ink, said linker moiety is preferably selected from the group consisting of a C1-C20 alkanediyl, C2-C20 alkynediyl, C2-C20 alkynediyl, C4-C20 heteroaryldiyl, and C6-C20 aryldiyl, preferably C2-C 15 alkanediyl, C2-C15 alkynediyl, C2-C15 alkynediyl, C4-C15 heteroaryldiyl, and C6-C15 aryldiyl, more preferably C3-C12 alkanediyl, C3-C12 alkynediyl, C3-C20 alkynediyl, C4-C12 heteroaryldiyl, and C6-C12 aryldiyl, most preferably C4-C8 alkanediyl, C4-C8 alkynediyl, C4-C8 alkynediyl, C4-C8 heteroaryldiyl, and C6-C8 aryldiyl.

In the perovskite precursor solution/ink, said linker moiety is preferably -(CH₂)-_n, with n being an integer of 1-20, preferably 2-15, more preferably 3-12 and most preferably 4-8, for example 2-7.

In the perovskite precursor solution/ink, said "precipitation retarding compound" is a cation of formula (I):

A-R'-W+ (I), wherein A is said anchoring group as defined in this specification, R¹ is said linker or spaceholder moiety, and W+ is said positively charged group. A, R¹ and W+ are preferably as defined above.

In the perovskite precursor solution/ink, A is selected from -COOH, -CONH₂, -R0₃H₂, - P0₂H₂R², - P0₄H₂, -S0₃H₂, -CONHOH, and salts thereof, R² is an organic substituent comprising from 1-20 carbon atoms and 0-10 heteroatoms, W is a positively charged moiety comprising a positively charged nitrogen atom; R¹ is an optionally substituted organic moiety comprising 1-20 carbons and 0-10 heteroatoms, wherein R¹ and R² may be, independently, totally or partially halogenated.

In the perovskite precursor solution/ink, said positively charged nitrogen atom is selected from the group consisting of: -NH₃ ⁺, -NH-C(NH₃ ⁺)=NH, and -N=CH-NH₃ ⁺.

In the perovskite precursor solution/ink, R² is as defined elsewhere in this specification. Preferably, R² is -(CH₂)-n, with n being an integer of 1-10, preferably 2-8, most preferably 3-7. In an embodiment, said "precipitation retarding compound" is a cation selected from the cations of formulae (l)-(3):

and salts of said cations (l)-(3), wherein n is an integer of 1-10, preferably 2-7, most preferably 3-6. In the perovskite precursor solution/ink, said "precipitation retarding compound" is selected from ammonium carboxylic acid halides with variable alkyl chains or moieties, for example separating the ammonium from the carboxylic acid group. For example, the alkyl chain may be as n defined with respect to formulae (l)-(3).

In the perovskite precursor solution/ink, the "precipitation retarding compound" is selected from 5-ammoniumvaleric acid (5-AVA), 5-aminopentanamide (5-APAC), 4- aminobutylphosphonic acid (4-ABPAC).

In some embodiments, said "precipitation retarding compound" is selected from an aminoacid, an amino acid hydrohalide, a formamidinium halide, and an imidazolium halide.

In an embodiment, the perovskite precursor solution comprises components in addition to said "precipitation retarding compound". In the event that the retarding compound is added in the form of a cation, this cation may also be referred to as a first organic cation. As indicated, the perovskite precursor solution preferably comprises at least a further or second organic cation, which is required for perovskite formation. Preferably, said second organic cation is comprised in said organic inorganic perovskite and/or said first organic cation is preferably associated with or comprised in said organic inorganic perovskite.

It is noted that said "second organic cation" may and preferably is present in higher amounts compared to said "first organic cation". Preferably, the "second organic cation" is present in higher amounts and thus preferably a more important constituent of the organic- inorganic perovskite to be deposited. Without wishing to be bound by theory, the inventors believe that the "first organic cation", on the other hand, may be located at the interfaces between the perovskite and other materials, for example with the n-type semiconductor or possibly said porous insulating or spaceholder layer as described elsewhere in this specification.

In the event that the "precipitation retarding compound" is not added in the form of a cation in said precursor solution, but as an uncharged molecule or as an anion, said "second organic cation" may be considered to be the only and thus first organic cation.

It has been indicated above that the perovskite precursor solution preferably comprises all components that are required to provide said perovskite, which is preferably an organic- inorganic perovskite. Accordingly, the perovskite is preferably deposited in a one-step deposition process, where all components of the perovskite are contained in a single solution that is deposited during said step of depositing a perovskite precursor solution. In a preferred embodiment, the invention does not encompass and/or excludes the deposition of the perovskite in a two-step deposition process, wherein the metal halide and organic cation halide are contained in different solutions, which are deposited sequentially.

However, in other embodiments, the invention also encompasses printing the perovskite by sequential deposition. Deposition in a single-step deposition of a solution containing all components of the perovskite is preferred. In an embodiment of the invention, the perovskite precursor solution is also an ink solution, as it can be deposited by printing techniques such as inkjet printing [1, 2 and 5]

Manual, Semi- Automated and Inkjet infiltration of the perovskite precursor ink

Perovskite precursor ink prepared either with fresh or recycled materials was infiltrated (□ 6-9 micro litres) either manually at room temperature (from a commonly available rubber based dropper) or by using a programmable multi-channel pipetting robot (home-made, Solaronix) or with a drop-on-demand Dimatix materials inkjet printer (DM P-2831.

Dimatix-Fujifilm Inc., USA as used in Reference 1 and 2 of this document) on carbon electrode from room temperature to 30 °C printing temperature with 15 pm drop spacing and by applying a customized waveform with 18V amplitude and 1-8 kHz frequency. The platen was kept at room temperature whereas the relative humidity inside the printer hood was ~ 32%. The non-active area of the samples was masked with adhesive polyimide cut out shapes (Impregnation Masks, Solaronix) prior dispensing to avoid the presence of perovskite anywhere else than the active area. The wet substrates were allowed to dwell for several minutes in order to let the liquid sip into the porous structures. After that, the carbon based perovskite solar cells were kept in the closed plastic box and were placed in a preheated oven at 50 °C for 30 minutes. After that the lid of the plastic box was removed and the carbon based perovskite solar cells were further heated for 1 -2 hours at 50 °C in the oven to ensure the complete growth perovskite absorber layer containing Pbl₂, MAI and 5-AVAI and were then removed from it and were kept in vacuum prior measurements.

More details of the device structure of carbon-based perovskite solar cells The basic individual components of the carbon based perovskite solar cells and their fabrication is detailed in previous sections as well as in Figure 1. However, the

combinations of materials are not restricted to these basic materials but: The individual components presented in Figure 1 are re-drawn in Figure 2 in which 2 comprises a conducting current collector layer. 3 and 5. are n-type semiconductor layer, 8 is a light harvester or sensitizer layer and 4 is printed silver layer to serve as contacts which can also be produced from printing gold for carbon based perovskite solar cells. Layer 6 is an insulating layer such as Zr0₂ but can also be produced from AI2O3.

In some embodiments, the current collector comprises a material selected from indium doped tin oxide (ITO), fluorine doped tin oxide (FTO), Zn0-Ga₂0₃, Zn0-Al₂0₃, tin oxide, antimony doped tin oxide (ATO), SrGeCL and zinc oxide, or combinations thereof.

The method preferably further comprises the step of depositing at least one n-type semiconductor layer. Suitable semiconductor materials are known to the skilled person. They may be selected, for example, from metal oxides having the appropriate electronic properties. In an embodiment, the n-type semiconductor layers 3 and 5 is deposited from a material selected from the group consisting of: Si, Si0₂ , Ti0₂ , Al₂0₃ , Zr0₂ , Hf0₂ ,

Sn0₂, Fe₂0₃, ZnO, WO₃, Nb₂Os, In₂0₃, Bi₂0₃, Y₂C>₃, Pr₂0₃, Ce0₂ and other rare earth metal oxides, CdS, ZnS, PbS, Bi₂S₃, CdSe, CdTe, MgTiCL, SrTiCL, BaTiCL, Al₂Ti0₅, BfrThO ₁₂ and other titanates, CaSnCL, SrSnCL, BaSnCL, Bi₂Sn₃0₉, Zn₂Sn0₄, ZnSnCL and other stannates, CaZrCL, SrZrCL, BaZrCL, B Zr^On and other zirconates, combinations of two or more of the aforementioned and other multi-element oxides containing at least two of alkaline metal, alkaline earth metal elements, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, Sc, Y,

La or any other lanthanide, Ti, Zr, Hf, Nb, Ta, Mo, W, Ni or Cu.

In an embodiment, the solar cell of the invention comprises a surface-increasing structure. In some embodiments, the semiconductor layer or part thereof has a surface increasing structure. The surface-increasing structure may be formed by nanoparticles that are applied on the current collector or on an optional underlayer, such as a dense or compact

(preferably n-type) semiconductor layer. If present, the dense underlayer is preferably deposited onto the conductive transparent substrate, and the surface increasing structure is then deposited on top of the dense underlayer.

The dense (or compact) underlayer (layer 3) may be deposited, for example, by slot coating, screen-printing, sol-gel deposition, spray pyrolysis or inkjet printing, as illustrated in Fig. 1. The underlayer and the surface increasing, nanoporous structure preferably comprises the same n-type semiconductor material. The expression "nanoparticles" encompasses particles or particulate elements, which may have any form, in particular also so-called nanosheets, nanocolumns and/or nanotubes, for example. Nanosheets made from anatase Ti0₂ have been reported by Etgar et al, Adv. Mater. 2012, 24, 2202-2206, for example. Preferably, the nanoparticles comprise or consist essentially of said semiconductor material. The surface increasing structure may also be prepared by screen printing, inkjet printing or spin coating, for example as is conventional for the preparation of porous semiconductor (e.g. Ti0₂) surfaces in heterojunction solar cells, see for example, Noh et al., Nano Lett. 2013, 7, 486-491 or Etgar et al, Adv. Mater. 2012, 24, 2202-2206. Nanoporous semiconductor structures and surfaces have been disclosed, for example, in EP 0333641 and EP 0606453.

According to an embodiment of the invention, said surface-increasing structure comprises and/or is prepared from nanoparticles, in particular nanosheets, nanocolumns and/or nanotubes, which nanoparticles are preferably further annealed.

According to an embodiment, the surface-increasing structure and/or said n-type semiconductor is nanostructured and/or nanoporous. In an embodiment, said

semiconductor material is mesoporous and/or mesoscopic. According to an embodiment, the surface increasing structure and/or said semiconductor material is nanocrystalline.

Preferably, said surface-increasing structure is provided by said n-type semiconductor material. In some embodiments, the surface increasing structure is not an n-type semiconductor material, but may be, for example, an insulating material. In this case, there is generally the compact underlayer made from n-type semiconductor material, and the surface-increasing structure does not cover the underlayer entirely, such that the perovskite layer can get in contact with the underlayer.

Layer 7 is comprised of carbon nanoparticles and works as back contact. The material of this layer may be a catalytically active material. This back contact electrode may, for example, comprise one or more materials selected from (the group consisting of) Pt, Au, Ni, Cu, Ag, In, Ru, Pd, Rh, Ir, Os, C, including carbon, graphene and graphene oxide, conductive polymer, single walled carbon nanotubes (SWCNT), multiwalled carbon nanotubes (MWCNT) and a combination of two or more of the aforementioned, for example. Conductive polymers may be selected from polymers comprising polyaniline, polypyrrole, polythiophene, polybenzene, polyethylenedioxythiophene, polypropylenedioxy-thiophene, polyacetylene, and combinations of two or more of the aforementioned, for example.

The Layer 7 may be applied as is conventional, for example by thermal or electron beam evaporation, sputtering or a printing (which includes screen printing and inkjet printing) or spraying process, optionally dispersed or dissolved in a water or solvent-based carrier medium, for example. In some embodiments discussed above, the back contact (layer 7) is made from a porous material, such as a porous carbon material.

The solar cell of the invention may comprise more layers and/or materials as appropriate.

10 Many different types and/or structures of perovskite solar cells have been reported, including cells where the nanoporous, surface increasing structure is made from an insulating material, and a perovskite material is in contact with a semiconductor under layer, such as a dense or compact n-type semiconductor underlayer.

In a preferred embodiment, the method of the invention concerns the manufacturing of a perovskite solar cell in which a porous carbon back contact electrode is deposited before deposition of the perovskite precursor solution, and the precursor solution is deposited onto the porous carbon back contact electrode so as to infiltrate the latter and to get in contact with the surface increasing structure, preferably filling the pores of the latter.

In an embodiment, such cells comprise a subassembly or sub-entity comprising at preferably at least a porous n-type semiconductor layer, a porous insulating or space layer, a porous carbon back contact electrode and a perovskite deposited to be in contact with said porous n-type semiconductor layer. Such a configuration has been disclosed, for example, at the example of the TiCL/ZrCL/C configuration disclosed in reference 6 (Z. Ku et al, 2013) and reference 4 (A. Mei et al, 2014).

The particularity with cells comprising such a subassembly is that the carbon back contact electrode is porous and is deposited before the deposition of the perovskite. Without wishing to be bound by theory, it is speculated that the above is possible because a space layer has been provided, for example comprising and/or consisting of an insulating material, such as Zr0₂, on top of the n-type semiconductor layer. For the purpose of the present invention, an insulating material is a material through which electrons will not flow by electronic motion during operation of the device under normal circumstances. In an embodiment of the method of the invention, said perovskite precursor solution is deposited per printing/manually infiltrated or infiltrated via programmable multi-channel pipetting robot the precursor solution on a porous carbon back contact layer so as to infiltrate said porous carbon back contact layer. For example, said porous carbon back contact is a porous carbon electrode. The carbon electrode may be deposited by screen printing, for example.

The porous carbon back contact electrode, which may be made, for example, from porous carbon, is deposited on top of the space layer. The space layer prevents the carbon back contact electrode to be in direct contact with the n-type semiconductor layer (Layers 3 and 5).

Preferably, the space layer (Layer 6) is porous, so as to allow access of the perovskite to the semiconductor layer during the perovskite deposition. Preferably, the space layer is meso and/or nanoporous. In space layer may be deposited by screen printing, for example. Preferably, the space layer is also made from nanoparticles as defined herein, but said nanoparticles have preferably larger dimensions compared to the dimensions of the n-type semiconductor nanoparticles. The dimension of the space layer particles are preferably selected such as not to fill up the pores provided by the porous n-type semiconductor layer.

Without wishing to be bound by theory, it is believed that the perovskite is in contact with said porous n-type semiconductor, and it is also expected that the perovskite be in contact with said insulting layer and said carbon back contact electrode. The perovskite is thus preferably integrated in the porous n-type semiconductor layer and, if present, said insulating layer, and possibly in part of said porous carbon back contact electrode. In such embodiments, an entire layer consisting exclusively of perovskite may be absent.

In some embodiment, the method of the invention comprises the step of exposing the perovskite, after it has been deposited, to heat, for example one or more heat treatments. Preferably, the perovskite is exposed to 30-80 °C for 5-120 minutes, preferably 35-70 °C for 10-90 minutes, most preferably 40-60 °C for 15-60 minutes.

In some embodiments, one, two or more heating steps are applied, with or without letting the deposited perovskite cool down, for example to room temperature (25°C) or lower, or to a 10 temperature below the heating temperature, between heating steps. The heating is preferably provided to remove solvent and thereby ensure complete growth of the perovskite crystal. In an embodiment, the deposited perovskite, for example in the completely or partially assembled solar cell, is heated while being in a closed contained, and in a subsequent heating step, the perovskite is heated outside said closed container, allowing for solvent evaporation. In some embodiments, solar cells prepared in accordance with the invention are stored in the dark, for example for 1 day to 8 weeks, more preferably 2 days to 6 weeks, most preferably 1 week to 5 weeks. Preferably, the cells are stored in vacuum or in an inert atmosphere, that is an atmosphere with reduced or absent moisture (H₂0 and oxygen (0₂) during this time. In some embodiments, the storage takes place in a reduced moisture environment, for example an environment which is protected from external moisture.

As shown in Figure 1, thanks to depositing perovskite efficiently by inkjet printing, the entire solar cell may be deposited by scalable techniques, including in particular scalable printing techniques, allowing industrial production of the solar cells on a large scale.

The sealant materials can be a thermoplastic such as Surlyn or Bynel thermoplastics or a double sided common scotch tape or a double sided pressure sensitive tape Scotch TM or a screen printable epoxy. The back cover to protect the whole active materials can be a thin glass cover, any metal cover or a plastic cover which can be sealed/fused with

aforementioned thermoplastics or a double sided common scotch tape or a double sided pressure sensitive tape Scotch TM or a screen printable epoxy. Measurements

The J-V curves of CPSCs were recorded under 1000 W/m2 light intensity equivalent to 1 Sun with a reference solar cell (PV measurements Inc) in the Xenon lamp based solar simulator (Peccell Technologies, PEC-L01, Japan). The scan rate of the measured J-V curves was 4.2 mVs-l whereas the aperture area was 0.16 cm2 which was defined by the black tape mask. The XRD data was measured using a Rigaku Smartlab diffractometer with Cu anode and Ge (220) double bounce monochromator. Fourier-transformed infrared (FTIR) spectroscopy was used to determine the purity of the recycled gamma- butyrolactone (GBF) and was compared with the purity of fresh GBF solvent. Benefits the invention provides

A potentially low cost and facile process through which the degraded carbon based perovskite solar cells having degraded materials can be safely re-used with the same performance as achieved with the fresh materials.

Another important aspect to the best of our own experience and knowledge is that this ink formulation (Pbl₂, MAI and AVAI in GBL) is highly compatible and works efficiently for this unique carbon-based perovskite solar cells device structure as described in details for this work in which the separation of Pbl₂ is fairly easy compared to the perovskite precursor ink for the traditional device structure having Spiro-OMeTAD as a holes transporting material [7] where a mixed cation ink has now frequently used for very high efficiency (> 20%) perovskite solar cells such as presented in this reference [8] where it has not been demonstrated yet that how someone will separate all the four components i.e. FAI, Pbl₂, MABr, and PbBr₂ (where FA stands for formamidinium cations and MA stands for methylammonium cations).

Only proof of concept of recycling the basic recipe [7] of perovskite ink in traditional perovskite solar cells (PSCs) is demonstrated in Dl, D2, D3 which is not significantly relevant to protect this work since now it is proven that this ink cannot produce the traditional high efficiency perovskite solar cells (> 20%) so no one is going to employ this basic ink recipe except for mixed cation ink as we discussed above.

Known prior-art and how this invention is different and unique:

Document Dl discloses a process for the recovery and recycling of active materials in a perovskite solar cell. The active components are selectively removed by immersion in DMF, DMSO, chlorobenzene and water. The obtained substrate is there after reused to make a new perovskite solar cell. The dissolved metal electrode materials and lead halide components can be filtered, purified and reused.

Document D2 discloses a method for recycling the perovskite solar cell substrate by removal of the active components by immersion in GBL, DMSO and DMF. The obtained substrate is thereafter reused to make a new perovskite solar cell with fresh components.

Document D3 discloses a method for recycling a perovskite solar cell by removing the metal electrode and hole transport material and decomposing the perovskite layer with thermal treatment. The lead halide component remains on the substrate and is used in the synthesis of a new perovskite layer when spin-coating additional methyl ammonium halide solution on the substrate.

Document D4 discloses a method to fabricate perovskite solar cells using lead iodide recovered from car batteries. Pb0₂ is extracted from car batteries, purified and converted to Pbl₂, which is thereafter used for the synthesis of perovskite layers.

The selective removal of the active components by immersion in different solvents and reuse of the substrate are disclosed in documents D1-D3. The recycling of lead halides to make new perovskite layer is disclosed in documents Dl and D3. The perovskite solar cell structures disclosed in the documents D1-D4 are different from the one disclosed in this application. None of the documents disclose the use of carbon electrode nor the use of recycled GBL or MAI+AVAI for the perovskite synthesis.

Dl CN 106876597 A (UNIV NANKAI) 20 June 2017 (20.06.2017)

D2 WO 2017073974 Al (GLOBAL FRONTIER CENTER FOR MULTISCALE

ENERGY SYSTEMS [KR]) 04 May 2017 (04.05.2017)

D3 CN 106410048 A (UNIV NINGBO) 15 February 2017 (15.02.2017)

D4 US 2016043449 Al (BELCHER ANGELA M [US] et al.) 11 February 2016

(11.02.2016)

What is different and unique in this work compared to prior art

1. The perovskite precursor ink composition which is mentioned in D 1 , D2 and D3 is different and cannot be used in carbon based perovskite solar cells as described in this work without 5 -AVAL As without 5-AVAI, the liquid precursor containing only MAI and Pbl₂ in the mentioned solvents i.e. DMF or DMSO or even in GBL quickly transforms into the crystals of perovskite hence cannot be successfully infiltrate in the thicker (12-15 pm) stack of carbon based perovskite solar cells compared to the traditional perovskite solar cells as prepared and mentioned in Reference 7 and in Reference 8.

2. Another important aspect is that Dl, D2, D3 and D4 do not claim that the same procedures can also be applied for every configuration of perovskite solar cells. It is not specified that the same method can also be used to recycle the carbon based printed perovskite solar cells.

3. The composition of ink demonstrated in Dl, D2, D3 and D4 is very different from the composition of the ink we use in carbon based printed perovskite solar cells. 4. D4 is also irrelevant since we are not claiming in this document that we purified the Pbl₂ from some other source but we are claiming that we can recycle the Pbl₂ from this different perovskite precursor ink (containing Pbl₂, MAI, 5-AVAI in GBL) after infiltration in the carbon based perovskite solar cells.

The following is a brief description of the drawings used to illustrate the invention

Drawings

Figure 1. Fabrication step and basic device structure of carbon-based perovskite solar cell and large area modules fabricated for this work. Only scalable processes are highlighted here. The sintering steps consecutive to screen-printing are not represented for better clarity.

Figure 2. Details of the device structure of carbon based perovskite solar cells presented in Figure 1 and fabricated for this work.

Figure 3. Complete process for refurbishing of carbon based perovskite solar cells and modules and recycling/recovery of some of the degraded active materials. The drying of electrodes after Step 4 will be performed either by placing the electrodes on hotplate in between 40 °C to 120 °C or by hand dryer to dry any possible remaining of water in the porous stack.

Figure 4: Process flow for sequential removal of silver nano-particles based layer and perovskite light absorbing layer from the device stack and extraction scheme to separate the solvents and other active components of the ink i.e. PbI2+MAI+5-AVAI.

Figure 5: XRD plots of a carbon based perovskite solar cell before and after the removal of perovskite light absorbing layer from the carbon based perovskite solar cells. XRD plot indicates successful removal of perovskite light absorbing layer as the peak of perovskite at 14.1° was completely disappeared from the electrode.

Figure 6: CPSC was infiltrated after perovskite extraction with fresh perovskite precursor ink suggesting that the Ti02 layers working efficiently as similar JSC values achieved as typically obtain in the fresh devices. Nevertheless, the device exhibits low voltage, low fill factor and high cell resistance, which indicate that the carbon layer does not remain efficient due to wet process for dissolving perovskite crystals in water.

Figure 7: The weak carbon back contact layer can be easily removed of by immersing the electrode (as described in Figure 4) into water followed by its sonication for 2-10 seconds which does not damage any other layer (i.e. FTO, compact Ti02, mesoporous Ti02 and insulating Zr02) of the remaining stack These dispersed graphite and carbon black nano- particles in water can be easily recovered by evaporating water via rotary evaporator.

These recovered carbon nanoparticles can be reprocessed to produce the printable pastes to print again the carbon electrode over insulating Zr02 or A1203 layers in the carbon based perovskite solar cell device structure followed by re-infiltration of the perovskite precursor ink in the refurbished carbon-based printed perovskite solar cells device structure.

Figure 8: Process flow of removal of MAI+5-AVAI from the device structure followed by their extraction from the solvents.

Figure 9: XRD plots of a carbon based perovskite solar cell before and after the removal of MAI+5-AVAI from the device structure.

Figure 10: comparison of extracted MAI+5-AVAI after water evaporation with fresh MAI+5-AVAI as well as individual fresh MAI and 5 -AVAL The XRD plots confirms that no change occurred in the chemical structure of the recycled MAI+5-AVAI. (Note: AVAI in the figure stands for 5-AVAI). Figure 11 : Process flow of removal of PbI2 from the device structure followed by its extraction from the solvents. The recycled PbI2 can be reused with GBL, MAI and 5- AVAI to produce again the perovskite precursor solution for carbon based perovskite solar cells fabricated for this work.

Figure 12: XRD plots of a carbon based perovskite solar cell before and after the removal of PbI2 from the device structure. Figure 13: Process flow for recycling of FTO-Glass which can be re-used to produce carbon-based perovskite solar cells.

Figure 14: Process flow for the recycling of fresh perovskite precursor ink and its remaking to be infiltrated in carbon-based printed perovskite solar cells. Figure 15: XRD spectra of recycled PbI2, Perovskite crystals formed after vacuum distillation of GBL and fresh PbI2 powder for comparison.

Figure 16: XRD spectra of recycled MAI+5-AVAI recovered after rotary evaporation of water and fresh MAI+ 5-AVAI for comparison.

Figure 17: FTIR spectra of fresh and recycled GBL. Figure 18: J-V curves of carbon-based printed perovskite solar cells infiltrated with Ink 1 and Ink 2. The values presented here are the average of forward and reverse scans.

Figure 19: J-V curves of carbon-based printed perovskite solar cells after 300 hours stored in vacuum and dark conditions. The values presented here are the average of forward and reverse scans.

Object of the present invention

An object of the present invention is to provide a carbon based perovskite solar cell, which is based on fully recyclable materials, with material layers that can be separated and reused, and with active compounds that can be separated by selective dissolution.

Details of the invention

A degraded carbon based perovskite solar cell may be efficiently refurbished via executing some facile steps, which can make this emerging PV Technology highly economical. In short, the degraded materials (i.e. Pbl₂, MAI, AVAI and carbon back contact comprised of carbon nano-particles) in a degraded carbon based perovskite solar cell can be recovered very safely which can be reused into the refurbished CPSCs without performance compromise. The process flow of the refurbishing or recycling of carbon based perovskite solar cells and modules is depicted in Figure 3.

Following is the description about the selective removal of some of the components of the carbon based perovskite solar cell.

A. Removal of silver layer based contacts from the carbon based perovskite solar cell

In the beginning, the silver nanoparticles based layers can be easily removed off from the non-active areas of the carbon based perovskite solar cells (CPSCs) and large area carbon based perovskite solar modules by either manual or automated scrapping blades. These silver nanoparticles can be reused in making a screen printable paste.

B. Removal of Perovskite light absorbing layer from the carbon based perovskite solar cell

The perovskite light absorbing layer is highly soluble in a polar aprotic solvent such as gamma butyrolactone (GBL) or DMF and can be efficiently removed from the stack of a CPSC without damaging active layers. The details of the process to remove the perovskite light absorbing layer containing Pbl₂, MAI and 5-AVAI from the device stack is summarized in Figure 4 which is a direct immersion of the carbon based perovskite solar cells in polar aprotic solvents such as gamma-butyro lactone (GBL) Dimethylformamide (DMF), Acetone or DMSO after removing the silver contact layer, removing the back cover and removing the thermoplastic or double sided tape. Other possible solvent can be Acetonitrile. The perovskite light absorbing layer dissolves upon immersion in above mentioned solvents and completely leaves off from the cell structure. The complete removal of the perovskite layer from the device structure was also confirmed from the XRD measurements. The results are presented in Figure 5. From the solution containing solvent and PbI₂+MAI+5-AVAI, the further separation of solvents (DMF, GBL and DMSO) can be performed with vacuum distillation or rotary evaporation in case of using Acetonitrile or Acetone. Then the separated solvents and extracted PbI2, MAI+5-AVAI can be re-mixed to prepare the fresh ink and can be re infiltrate in the porous stack of carbon-based printed perovskite solar cells. C. Removal of carbon electrode from the structure and recycling of carbon

nanoparticles

After that the wet processed electrodes upon re-infiltration with a fresh perovskite precursor ink exhibit very promising high short circuit current densities (JSC, Figure 6) values that is typically obtained with the fresh CPSCs which suggest no chemical change or damage occurs in the electron transport layer (Ti0₂) or insulating layer (Zr0₂) during the dissolution of perovskite layer in GBL. However, the lower VOC, lower FF and high RCELL (Figure 6) obtained from these wet-processed CPSCs indicate that the carbon back contact layer may becomes weak and cannot withstand with a wet process and

consequently affect the overall photovoltaic performance. Nevertheless, this weak carbon back contact layer which is composed of graphite and carbon black nano-particles can also be removed from the stack via sonicating the electrode in water for few (~ 2-10) seconds. These carbon nano-particles can then be easily collected by evaporating the water via rotary evaporation and can be reprocessed to produce the screen printable carbon paste. The process flow for recycling of carbon electrode is shown in Figure 7.

D. Removal of MAI+5-AVAI from the device structure and it’s extraction

In the ideal case, the performance of a CPSC compromises due to the degradation in perovskite absorber layer, which converts back to Pbl₂ into the pores of the stack along with the MAI and AVAI, which may also be efficiently extracted from the degraded CPSCs. Figure 8 represents a process flow for the extraction of MAI+AVAI from a degraded CPSCs which can be realized by simply immersing the degraded CPSC electrode into water. Upon immersion, the traces of perovskite crystals rapidly remove off from the device and the MAI+AVAI completely dissolves in water and consequently leave only Pbl₂ in the pores of the stacked layers of CPSCs electrodes as verified via XRD

measurements. The MAI+AVAI can also be safely collected by evaporating again the water via rotary evaporation and can be reused to produce perovskite precursor ink. Figure 9 represents the systematic XRD spectra of the device stack before and after the removal of MAI+5-AVAI from the device structure when immersed in water whereas Figure 10 represents the XRD spectra for the comparison of extracted MAI+5-AVAI after water evaporation with fresh MAI+5-AVAI as well as individual fresh MAI and fresh 5 -AVAI. E. Removal of Pbl₂ from the device structure and it’s extraction

Similarly, the remaining Pbl₂ after the removal of MAI+5-AVAI from the device structure can also be removed off from the device stack by again immersing the electrodes in DMF, GBL or DMSO followed by warming the solvent containing electrodes at 50-70°C from 1 hour to 1 day. The Pbl₂, upon warming, slowly dissolve in aforementioned solvents and comes off from the stacked layers of a carbon based perovskite solar cells and modules. After that, the Pbl₂ can then be safely extracted via vacuum distillation/evaporation of GBL, DMF or DMSO. The other possible solvents which can be used to dissolute Pbl₂ could be the acetonitrile or acetone. The process flow regarding removal and extraction of Pbl₂ is summarized in Figure 11. The confirmation of removal of Pbl₂ from the device stack was also confirmed via XRD measurements which is presented in Figure 12.

F. Recovery of FTO Glass via removing compact TK)₂, mesoporous Ti0₂ and

insulating Zr0₂ or insulating A1₂0₃ layers

In addition to that, the FTO glass used to produce the carbon based perovskite perovskite solar cells for this work can also be recovered (recycled) after the removal of carbon electrode as presented in section C (i.e. Removal of carbon electrode from the structure and recycling of carbon nano-particles). The recycling of FTO-glass can be achieved by simply sonicating the FTO-Glass electrode (containing i nsulator layer such as Zr0₂ or Al₂0₃, mesoporous Ti0₂ layer and compact Ti0₂ layer) in an ultra-sonicator bath by using solvents such as ethanol, acetone or water. The further cleaning of the FTO-Glass can be done via sonicating again the recycled FTO-Glass in water based detergent solution followed by recleaning in ethanol, acetone and iso-proponal (10 minutes each). This recycled FTO glass can be re-used to reproduce carbon based perovskite solar cells by performing the same fabrication steps as described in the fabrication section of these carbon based perovskite solar cells in this document.

The mixed nanoparticles i.e. Ti0₂+Zr0₂ or Ti0₂+Al₂0₃ containing solution having possible solvents i.e. ethanol, acetone or water can be further processed and all these solvents can be once again evaporated using rotary evaporation method. The further separation of collected mixed Ti0₂+Zr0₂ or Ti0₂+Al₂0₃ nanoparticles is not possible. Nevertheless, a screen printable paste may be produce for a composite of Ti0₂+Zr0₂ nano- particles after recovery of these nano-particles by evaporating the solvent after the aforementioned sonication step for some other possible applications. The process flow for recycling of FTO-Glass is summarized in Figure 13.

Hence, refurbished carbon based perovskite solar cells and modules can be produced at low cost without investing same amount of energy which is required to produce the fresh solar cells and modules with similar photovoltaic performance as achieved with the freshly produce carbon based perovskite solar cells and modules. We proved here that effective recycling of some of the active components of the carbon-based printed perovskite solar cells (CPSCs) is possible via facile steps as shown in this work. This scheme will greatly help to eliminate the rising problem to remove the degraded lead based solar panels from the planet and thus contributes to the circular economy policy of Finland as well as European Union and United Nations.

Section 2:

A recyclable perovskite precursor solution/ink for carbon-based printed perovskite solar cells and large area carbon-based printed perovskite solar modules.

A perovskite precursor solution/ink containing lead iodide (Pbl₂), Methyl ammonium- iodide (MAI) and 5-Ammonium valeric acid iodide (5-AVAI) in GBL is proven in this work as a recyclable ink which is highly compatible for the carbon-based printed perovskite solar cells as well as for the large area carbon based perovskite solar modules and gives similar photovoltaic performance as achieved with the fresh perovskite precursor solution.

Core of the invention

The application discloses a proof of concept for the recycling of a unique perovskite precursor solution which can be effectively recycled via selective removal of the solvent (GBL), selective removal of Pbl₂ alone and selective removal of MAI+5-AVAI together. These recycled materials can be reused to produce a refurbished perovskite precursor ink which can be infiltrated in carbon perovskite solar cells and gives similar photovoltaic performance in these carbon based printed perovskite solar cells as achieved with the fresh perovskite precursor solution. Problem it solves

An increase in the volume of degraded carbon based printed perovskite lab sized solar cell and large area carbon based printed perovskite PV panels combined with strict

environmental laws generates a grand challenge to speedily develop a facile process through which, these degraded PV modules could be efficiently recycled or refurbished at viable cost. The recycling steps presented here for this unique perovskite precursor ink can also be adopted during the refurbishing and recycling of carbon-based printed perovskite solar cells and large area carbon-based printed perovskite solar modules.

Unique device structure of carbon based perovskite solar cells and detail composition of perovskite precursor solution which is highly compatible for this device structure

In this document, we are strictly restricted to a unique device structure of carbon based printed perovskite solar cells and large area carbon based printed perovskite solar modules which has been reported in our previous work [1-3] or by others [4] or described in our previous patent application [5] as well as described in the following sections. Experimental section

Details of the fabrication and the device structure of carbon based perovskite solar cells

The details of manufacturing this device structure is given below as well as in our previous work [1-3] including in our previous international patent application [5] as well as in Figure 1. The details of the carbon based perovskite solar cell device structure is described in our previous work [1-3] including in our previous international patent application [5] as well as in Figure 2.

Perovskite solar cells for this work were fabricated as follows:

Fluorine doped tin oxide (FTO) coated glass substrates (10x10 cm2, RSH = 7 W/Sq, Product code: TC022-7, Solaronix) were first etched with an automated fiber laser, and cleaned by sequential sonications in Hellmanex 1% aqueous solution, acetone, and isopropanol (15 min each). Then a compact layer of Ti0₂ (30-40 nm) was deposited by spray pyrolysis over the etched glass substrates placed on a hot-plate set to 550 °C, of a diluted solution of titanium diisopropoxide bis(acetylacetonate) (75% in isopropanol, Sigma- Aldrich) in absolute ethanol (1 :80) using oxygen as a carrier gas. Areas of the substrate had been masked with glass strips to prevent the coating in the subsequent silver areas. After cooling down to room temperature, a silver paste (Sun Chemical CRSN2442) was screen-printed and dried at 150 °C for 15 min to obtain silver contacts for anode and cathode. The 500 nm thick mesoporous Ti0₂ layer was obtained by screen-printing (diluted Ti-Nanoxide T/SP in terpineol, Solaronix) on the compact Ti0₂ layer followed by drying at 150 °C for 5 min, and sintering at 500 °C for 15 min. Similarly, the insulating mesoporous Zr0₂ layer was also obtained by screen-printing (Zr Nanoxide ZT/SP, Solaronix) on the aforementioned Ti0₂ layer, drying at l50°C for 5 min, and sintering at 500°C for 30 min. The thickness of the Zr0₂ was tuned by stacking 1-4 prints before sintering. The conductive porous carbon electrode was fabricated by screen-printing a carbon paste (Elcocarb B/SP, Solaronix), drying at 150 °C for 5 min, and firing at 400 °C for 30 minutes.

Details of the perovskite precursor ink formulation of this work

The fresh perovskite precursor ink (Ink 1) for this experiment was prepared by mixing all the fresh materials i.e. 0.53 g of Pbl₂ (99.99%, TCI Chemicals), 0.19 g of methyl ammonium iodide (MAI, Solaronix) and 0.0176 g of 5- ammonium valeric acid iodide (5- AVAI, Dyesol) in 1 ml of distilled gamma-butyro lactone (Sigma Aldrich) in a glass vial under a laboratory fume hood.

The ink for recycling experiment was prepared in large volume (10 ml) by mixing 5.3 g of Pbl ₍99%, Sigma Aldrich). 1.9 g of MAI (Dyesol) and 0.176 g of 5-AVAI (Dyesol) in 10 ml of GBL (Sigma Aldrich)

The re-fabricated recycled perovskite precursor ink (Ink 2) to demonstrate its working was also prepared by mixing all recycled materials i.e. recycled Pbl₂ (0.53 g, Sigma Aldrich 99% purity) and recycled MAI+5-AVAI (0.2076 g, Dyesol) in the distilled GBL (Sigma Aldrich) in a glass vial under a laboratory fume hood.

During each ink preparation, the glass vial was further sealed and placed for stirring for 30 min on a preheated (at 70 °C) hot-plate. The ingredients were completely dissolved and a clear yellow solution was obtained that was allowed to cool down to room temperature. The perovskite precursor ink remained stable both in glass vial and in the printer cartridge for more than 2 weeks and no precipitation or precipitation of the solutes was observed. Nevertheless, the composition of perovskite precursor solution is not restricted with the aforementioned ink- formulation but is already explained in details in the first section disclosing the“details of the perovskite precursor ink formulation of this work” (from Page 2 to Page 5 of the priority document).

Manual, Semi- Automated and Inkjet infiltration of the perovskite precursor ink

Perovskite precursor ink prepared either with fresh or recycled materials was infiltrated (□ 6-9 mΐ) either manually at room temperature (from a commonly available rubber based dropper) or by using a programmable multi-channel pipetting robot (home-made,

Solaronix) or with a drop-on-demand Dimatix materials inkjet printer (DM P-2831.

Dimatix-Fujifilm Inc., USA as used in Reference 1 and 2 of this document) on carbon electrode from room temperature to 30 °C printing temperature with 15 pm drop spacing and by applying a customized waveform with 18V amplitude and 1-8 kHz frequency. The platen was kept at room temperature whereas the relative humidity inside the printer hood was ~ 32%. The non-active area of the samples was masked with adhesive polyimide cut out shapes (Impregnation Masks, Solaronix) prior dispensing to avoid the presence of perovskite anywhere else than the active area. The wet substrates were allowed to dwell for several minutes in order to let the liquid sip into the porous structures. After that, the carbon based perovskite solar cells were kept in the closed plastic box and were placed in a preheated oven at 50 °C for 30 minutes. After that the lid of the plastic box was removed and the carbon based perovskite solar cells were further heated for 1-2 hours at 50 °C in the oven to ensure the complete growth perovskite absorber layer containing Pbl₂, MAI and 5-AVAI and were then removed from it and were kept in vacuum prior measurements.

More details of the device structure of carbon-based perovskite solar cells

The basic individual components of the carbon-based perovskite solar cells (CPSCs) and their fabrication is detailed in earlier sections of this document as well as in Figure 1 and Figure 2. However, the combinations of materials are not restricted to these basic materials but also extended to the embodiments which are already explained in the first section describing“More details of the device structure of carbon-based perovskite solar cells” (from Page 6 to Page 10 of the priority document) by keeping Figure 2 as a reference structure. In some embodiments, the current collector comprises a material selected from indium doped tin oxide (ITO), fluorine doped tin oxide (FTO), Zn0-Ga₂0₃, Zn0-Al₂0₃, tin oxide, antimony doped tin oxide (ATO), SrGeCh and zinc oxide, or combinations thereof.

Measurements

The J-V curves of CPSCs were recorded under 1000 W/m2 light intensity equivalent to 1 Sun with a reference solar cell (PV measurements Inc) in the Xenon lamp based solar simulator (Peccell Technologies, PEC-L01, Japan). The scan rate of the measured J-V curves was 4.2 mVs-l whereas the aperture area was 0.16 cm2 which was defined by the black tape mask. The XRD data was measured using a Rigaku Smartlab diffractometer with Cu anode and Ge (220) double bounce monochromator. Fourier-transformed infrared (FTIR) spectroscopy was used to determine the purity of the recycled gamma- butyrolactone (GBF) and was compared with the purity of fresh GBF solvent.

Benefits the invention provides

The proof of concept for efficient recycling of perovskite precursor ink used for this work can be efficiently adopted for a low cost and facile process through which the degraded carbon based perovskite solar cells having degraded materials can be safely removed and can be re-used with the same photovoltaic performance as achieved with the fresh materials.

Another important aspect to the best of our own experience and knowledge is that this ink formulation (Pbl₂, MAI and AVAI in GBF) is highly compatible and works efficiently for this unique carbon-based perovskite solar cells device structure as described in details for this work in which the separation of Pbl₂ is fairly easy compared to the perovskite precursor ink for the traditional device structure having Spiro-OMeTAD as a holes transporting material [7] where a mixed cation ink has now frequently used for very high efficiency (> 20%) perovskite solar cells such as presented in this reference [8] where it has not been demonstrated yet that how someone will separate all the four components i.e. FAI, Pbl₂, MABr, and PbBr₂ (where FA stands for formamidinium cations and MA stands for methylammonium cations).

Only proof of concept of recycling the basic recipe [7] of perovskite ink in traditional perovskite solar cells (PSCs) is demonstrated in Dl, D2, D3 which is not significantly relevant to protect this work since now it is proven that this traditional perovskite ink cannot produce the traditional high efficiency perovskite solar cells (> 20%) so it will not be practical to employ this basic ink recipe except for mixed cation ink as we discussed above [8]

Known prior-art and how this invention is different and unique: Document Dl discloses a process for the recovery and recycling of active materials in a perovskite solar cell. The active components are selectively removed by immersion in DMF, DMSO, chlorobenzene and water. The obtained substrate is there after reused to make a new perovskite solar cell. The dissolved metal electrode materials and lead halide components can be filtered, purified and reused. Document D2 discloses a method for recycling the perovskite solar cell substrate by removal of the active components by immersion in GBL, DMSO and DMF. The obtained substrate is thereafter reused to make a new perovskite solar cell with fresh components.

Dl CN 106876597 A (UNIV NANKAI) 20 June 2017 (20.06.2017)

D2 WO 2017073974 Al (GLOBAL FRONTIER CENTER FOR MULTISCALE

ENERGY SYSTEMS [KR]) 04 May 2017 (04.05.2017) D3 CN 106410048 A (UNIV NINGBO) 15 February 2017 (15.02.2017)

D4 US 2016043449 Al (BELCHER ANGELA M [US] et al.) 11 February 2016

(11.02.2016)

What is different and unique in this work compared to prior art

1. The perovskite precursor ink composition which mentioned in D 1 , D2 and D3 is different and cannot be used in carbon based perovskite solar cells as described in this work without 5-AVAI, as without 5-AVAI, the liquid precursor containing only MAI and Pbl₂ in the mentioned solvents i.e. DMF or DMSO or even in GBL quickly transforms into the crystals of perovskite hence cannot be successfully infiltrate in the thicker (12-15 pm) stack of carbon based perovskite solar cells compared to the thinner traditional perovskite solar cells (□ 1 pm) as prepared and mentioned in References 7 and 8.

3. The composition of ink demonstrated in Dl, D2, D3 and D4 is very different from the composition of the ink we use in carbon based printed perovskite solar cells.

4. D4 is also irrelevant since we are not claiming in this document that we purified the Pbl₂ from some other source but we are claiming that we can recycle the Pbl₂ from this different perovskite precursor ink (containing Pbl₂, MAI, 5-AVAI in GBL) after infiltration in the carbon based perovskite solar cells.

5. No one before this work has proven that this unique perovskite precursor ink (containing Pbl₂, MAI, 5-AVAI in GBL) is a recyclable ink and can give similar

photovoltaic performance as anyone can achieve with a fresh ink when infiltrated in carbon based printed perovskite solar cells. Details of the invention

The perovskite precursor solution containing Pbl₂, MAI and 5-AVAI in solvent GBL is a unique perovskite precursor ink which has been to date found the best compatible ink for the unique carbon-based printed perovskite solar cell structure [1-5]. However, it has never been shown to date that this unique perovskite precursor solution is actually a recyclable perovskite precursor solution and can greatly contribute in recycling or refurbishing of carbon-based printed perovskite solar cells [1-5] and also the refurbishing of large area carbon-based printed solar modules [5, 9]

To prove this unique perovskite precursor solution a recyclable ink, an experiment is simulated which replicates some of the fabrication steps to produce carbon-based printed perovskite solar cells as detailed in the experimental section.

The recycling experiment for the perovskite precursor solution containing Pbl₂, MAI and 5-AVAI in solvent GBL is described in Figure 14.

In detail, the fresh perovskite precursor ink was fabricated in the beginning (Step 1). After that, the GBL from this freshly prepared ink was removed off via vacuum distillation (Step

2) which is one of a similar steps during the fabrication of carbon-based printed perovskite solar cells where the perovskite precursor ink is infiltrated and after that the GBL was evaporated from the device structure by heating the CPSC at 50°C for 30 minutes.

Additionally, as a result of GBL evaporation, the perovskite crystals formation occur within the carbon-based printed perovskite solar cell’s stack as described in experimental section as well as in Figure 1. Therefore similarly, the crystals of perovskite are formed as a result of GBL removal via vacuum distillation (Step 3). Small amount of these perovskite crystals was stored in a separate glass vial for XRD measurements. The XRD results of these perovskite crystal are summarized in Figure 4 which gives strong peak at 14.1° which is associated with perovskite crystals and has also been observed in our previous work [1-

3]

After that, the water was added into the flask containing perovskite crystals (Step 4) to decompose these perovskite crystals into Pbl₂, MAI and 5-AVAI which resembles the proposed method of extraction of MAI+5-AVAI (Figure 8) from a degraded carbon-based printed perovskite solar cell in which the degraded light absorbing perovskite layer containing carbon based printed perovskite solar cells can be first immersed into water which dissolves the MAI+5-AVAI and removes them from the device stack and leaves behind only the Pbl₂ in the device stack. The dark brown color of perovskite crystals was immediately transformed into yellow color indicating the formation of Pbl₂ in the solution containing water. The Pbl₂ was then separated via filtering water containing MAI+5-AVAI (Step 5). The collected Pbl₂ was examined via XRD and was compared with fresh Pbl₂ powder. The XRD results are summarized in Figure 15 which revealed no significant chemical change for recycled Pbl₂ in comparison with the fresh Pbl₂ (Figure 15). The peaks of both the recycled Pbl₂ powder (lst plot from the top in Figure 15) and fresh Pbl₂ (third plot from the top in Figure 15) overlapping (such as at 12.4° which is well known peak for Pbl₂) and confirms that no sign of chemical change occurred during GBL distillation (Step 2) as well as the perovskite and Pbl₂ formation.

After that, the solution of water containing MAI +5-AVAI was subjected to rotary evaporation to remove the water from the MAI+5-AVAI particles (Step 6-7). After extraction of MAI+5-AVAI, the XRD measurements were performed to compare the extracted MAI+5-AVAI which exhibited similar characteristic peaks as obtained from the fresh MAI+5-AVAI powder confirming no chemical change occurred during the extraction (Figure 16).

Moreover, the purity of distilled GBL was also checked with FTIR spectroscopy measurements and was compared with the purity of fresh GBL. Figure 17 represents the results of FTIR spectra of both the fresh and distilled GBL which suggested no change in the property of distilled GBL occurred during the vacuum distillation.

In the similar fashion, the GBL which was used to extract the Pbl₂ from the device structure as descried under headline“E. Removal of Pbl₂ from the device structure and it’s extraction” (on Page 17 to Page 18 of the priority document) and in Figure 11 and Figure 12 can also be distilled in the similar fashion as described here and can be used to fabricate new perovskite precursor ink which can be infiltrated again either in fresh or recycled carbon-based printed perovskite solar cells.

Hence motivated by these promising aforementioned results, two different inks were prepared: Ink 1 was formulated by dissolving fresh materials (which includes high purity Pbl₂ 99.99% from TCI chemicals, very fresh MAI (Solaronix) and very fresh 5-AVAI from Dyesol) in the distilled GBL by stirring the solution on a preheated (70 °C) hot plate.

Ink 2 was prepared by dissolving all the recycled materials i.e. PbI2, MAI+5-AVAI in the distilled GBL by stirring the solution on a preheated (70 °C) hot plate.

Both Ink 1 and Ink 2 were infiltrated in the (3-5) carbon-based printed perovskite solar cells which were taken from the same plate i.e. l0xl0cm2 over which 18 individual cells were fabricated.

Figure 18 represents the J-V curves of the carbon based printed perovskite solar cells which were infiltrated with Ink 1 and Ink 2 which revealed comparable photovoltaic performance. The slight difference in efficiency for the device which is infiltrated with Ink 1 is an expected result which can be realized due to high purity of Pbl₂ (99.99%) whereas in Ink 2 (the recycled Pbl₂ was having 99% purity.

More importantly, the fabricated carbon based printed perovskite solar cells prepared with Ink 2 (i.e. recycled materials) also exhibited remarkable long term stability when stored for more than 300 hours in vacuum with dark conditions and showed impressive improvement (> 13%) in the conversion efficiency when re-measured in a solar simulator (Figure 19). Hence this work is unique in one more way which is: Although in documents Dland D2, the recycling of basic perovskite components was revealed, however in these document no long term stability of the recycled materials was shown whereas in our work we demonstrated that the ink materials can be efficienctly recycled with similar performance along with long term stability.

Hence these results strongly endorse the successful accomplishment of proof of concept for the highly important idea which can be taken as a model and as first step towards facile recycling of this emerging and low cost carbon based printed perovskite solar cells technology. Therefore, we proved in this work that the unique perovskite precursor solution containing PbI2, MAI and 5-AVAI in GBL is a recyclable ink which can be re- used to achieve the same high performance of carbon-based printed perovskite solar cells as can be achieved with the fresh and high purity materials. References

[1] S. G. Hashmi et al., Air processed inkjet infiltrated carbon based printed perovskite solar cells with high stability and reproducibility, Adv. Mater. Technology.

2016, 1600183, 1-6. [2] S. G. Hashmi et al., Long-term stability of air processed inkjet infiltrated carbon-based printed perovskite solar cells in ultra-violet light soaking, J. Mater. Chem. A,

2017, 5, 4797-4802.

[3] S. G. Hashmi et al., High performance carbon based printed perovskite solar cells with humidity assisted thermal treatment, J. Mater. Chem. A, 2017, 5, 12060-12067. [4] A. Mei, et al, A hole conductor free, fully printable mesoscopic perovskite solar cell with high stability, Science, 2014, 345, 295-298.

[5] Dr. Syed Ghuffan HASHMI, Ms. Merve OZKAN, Mr. David

MARTINEAU, Mr. Xiong LI, Mr. Shaik Mohammed ZAKEERUDDIN, Prof. Michael GRAETZEL, Method for Inkjet Printing an Organic-Inorganic Perovskite, International Patent Application, Application number: PCT/EP2017/069543.

[6] Z. Ku, Y. Rong, M. Xu, T. Liu, Hongwei Han, Full Printable Processed Mesoscopic CH3NH3PbI3/Ti02 Heterojunction Solar Cells with Carbon Counter

Electrode, Scientific Reports 3, Article number: 3132 (2013).

[7] J. Burschka et al., Sequential deposition as a route to high-performance perovskite sensitized solar cells, Nature 499, 316-319 (2013).

[8] D. Bi et al, Efficient luminescent solar cells based on tailored mixed-cation perovskites, Science Advances 01 Jan 2016: Vol. 2, no. 1, el50H70 DOI:

10.1 l26/sciadv.1501170.

[9] Y. Hu, S. Si, A. Mei, Y. Rong, H. Liu, X. Li, H. Han, Stable Large- Area (l0^x 10 cm2) Printable Mesoscopic Perovskite Module Exceeding 10% Efficiency, Solar

RRL, 2017.

Claims

1. A process for the recycling of a perovskite precursor solution containing lead iodide (Pbl₂), Methylammonium iodide (MAI) and 5-Ammonium valeric iodide (AVAI), characterized by the removal of the solvent, removal of Pbl₂ and removal of MAI and 5 -AVAI together.

2. The process according to claim 1, wherein the active perovskite components, MAI and AVAI, are extracted from the solar cell structure by immersion into water, whereby the traces of MAI and AVAI dissolve.

3. The process according to claim 1 or 2, wherein the solar cell structure is immersed into a polar aprotic solvent selected from gamma-butyro lactone (GBL),

Dimethylformamide (DMF), Acetone or DMSO, or into acetonitrile, followed by warming the solvent, to cause the lead iodide (Pbl₂), to dissolve.

4. The process according to any one of claims 1 - 3, comprising reusing the removed solvent, Pbl₂, MAI and 5-AVAI to produce a refurbished perovskite precursor ink, which is suitable for being infiltrated in carbon perovskite solar cells.

5. A process for the separation and recycling of the materials of a carbon based

perovskite solar cell, by separation of the layers and the selective removal of active components as described in any of claims 1 - 4, characterized by comprising the following steps:

A. removal of the layers of silver nanoparticles, which are in contact with the carbon electrode in the solar cell, using mechanical means,

B. immersion of the solar cell in a polar aprotic solvent to dissolve the perovskite layer,

C. removal of the carbon electrode, which is composed of graphite and carbon black nano-particles, using water,

D. extraction of remaining active perovskite components, Methylammonium

iodide (MAI) and 5-Ammonium valeric acid iodide (AVAI), from the remaining solar cell structure by immersion of the remaining structure into water, whereby the traces of MAI and AVAI dissolve, E. re-immersion of the remaining solar cell structure into a polar aprotic solvent, or into acetonitrile, followed by warming the solvent, to cause the remaining perovskite component, lead iodide (Pbl₂), to dissolve, and

F. sonicating the remaining FTO-glass electrode, containing an insulator layer, a mesoporous Ti0₂ layer and a compact Ti0₂ layer, in a polar solvent.

6. The process according to claim 5, wherein the removal of step A is performed using either manual or automated scrapping blades.

7. The process according to claim 5 or 6, wherein the polar aprotic solvent used in steps B and D is gamma-butyro lactone (GBF), Dimethylformamide (DMF), Acetone or DMSO.

8. The process according to any one of claims 5 - 7 preceding claim, wherein the polar aprotic solvent is further separated from the solution obtained in step B, containing solvent and active components Pbl₂, MAI and 5-AVAI, by vacuum distillation or rotary evaporation.

9. The process according to any one of claims 5 - 8, wherein step C is carried out by sonicating in water, and preferably continuing the sonication for 2-10 seconds, whereafter the carbon nanoparticles can be collected from the sonicated mixture, for example by evaporating the water via rotary evaporation.

10. The process according to any one of claims 5 - 9, wherein the perovskite components MAI and AVAI, extracted from the remaining solar cell structure in step D are collected by evaporating the water via rotary evaporation.

11. The process according to any one of claims 5 - 10, wherein the re-immersion of step E is followed by warming the solvent at 50-70°C from 1 hour to 1 day, whereby the Pbl₂ can be separated from the solvent, e.g. via vacuum distillation or evaporation.

12. The process according to any one of claims 5 - 11, wherein the polar solvent used in step F is selected from ethanol, acetone and water.

13. The process according to any one of claims 5 - 12, wherein the FTO-Glass obtained from step F is further purified by sonicating again in a water based detergent solution, followed by recleaning in ethanol, acetone and iso-proponal, preferably for 10 minutes in each.

14. The process according to any one of claims 5 - 13, wherein the silver nanoparticles obtained from step A are reused in making a screen printable silver paste.

15. The process according to any one of claims 5 - 14, wherein the carbon nanoparticles collected from the sonicated mixture obtained from step C are reprocessed to produce a screen printable carbon paste.

16. The process according to any one of claims 5 - 15, wherein the perovskite components MAI and AVAI, collected from the remaining solar cell structure after step D, as well as the Pbl₂ separated in the re-immersion of step E, are reused to produce perovskite precursor ink solution.

17. The process according to any one of claims 5 - 16, wherein the recycled FTO glass obtained from step F is re-used to reproduce carbon based perovskite solar cells.