Perovskite based photovoltaic cells

Abstract

Photovoltaic cell (or solar cell) based on perovskite ("Perovskite Solar Cell" - PSC) comprising at least one layer comprising at least one compound having general formula (I): (I) wherein: - n is 0 or 1; - X represents a hydrogen atom, or a hydroxyl group; 10 - R4 is selected from C1-C6, preferably C1-C4, linear or branched, saturated, alkylene groups, preferably it is methylene; - when n is 0 or 1 and X represents a hydrogen atom: - R1, R2 and R3, identical or different from each other, represent a hydrogen atom; or they are selected from C1-C12 alkyl groups, preferably C1-C8, linear or branched, saturated or unsaturated, aryl groups, cycloalkyl groups, said alkyl, aryl and cycloalkyl groups being optionally substituted with at least one group selected from alkyl groups, hydroxyl groups, ether groups, ester groups, carbonyl groups; provided that at least one of R1, R2 and R3 is different from hydrogen and that at least one of R1, R2 and R3 contains at least one hydroxyl group; - or, any two of R1, R2 and R3, can optionally be linked together so as to form, together with the other atoms to which they are linked, a heterocyclic group containing from 2 to 16 atoms, containing from 1 to 3 heteroatoms, preferably 2 heteroatoms, selected, for example, from oxygen, sulphur, nitrogen, silicon, phosphorus, selenium, preferably oxygen, nitrogen, said heterocyclic group being substituted with at least one hydroxyl group and optionally with at least one sulfonic group; - when n is 1 and X represents a hydroxyl group: - R1, R2 and R3, identical or different from each other, represent a hydrogen atom; or they are selected from C1-C12 alkyl groups, preferably C1-C8, linear or branched, saturated or unsaturated, aryl groups, cycloalkyl groups, said alkyl, aryl and cycloalkyl groups being optionally substituted with at least one group selected from alkyl groups, hydroxyl groups, ether groups, ester groups, carbonyl groups; - or, any two of R1, R2 and R3, can optionally be linked together so as to form, together with the other atoms to which they are linked, a heterocyclic group containing from 2 to 16 carbon atoms, containing from 1 to 3 heteroatoms, preferably 2 heteroatoms, selected, for example, from oxygen, sulphur, nitrogen, silicon, phosphorus, selenium, preferably oxygen, nitrogen, said heterocyclic group being optionally substituted with at least one hydroxyl group and / or with at least one sulfonic group. Said photovoltaic cell (or solar cell) based on perovskite ("Perovskite Solar Cells" - PSCs) can be part of a tandem perovskite / silicon photovoltaic cell (or solar cell). Said photovoltaic cell (or solar cell) based on perovskite ("Perovskite Solar Cells" - PSCs) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be advantageously used in various applications that require the generation of electricity by harnessing light energy, in particular the energy of solar radiation, such as: photovoltaic fields (or photovoltaic parks), residential use, commercial buildings. Said photovoltaic cell (or solar cell) based on perovskite ("Perovskite Solar Cells" - PSCs) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be used either in stand-alone mode or in modular systems.

Description

[0001] PEROVSKITE BASED PHOTOVOLTAIC CELLS

[0002] The present invention relates to photovoltaic cells (or solar cells) based on perovskite (“Perovskite Solar Cells” - PSCs).

[0003] More particularly, the present invention relates to a photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cells” - PSCs) comprising at least one layer comprising at least one compound having the specific general formula (I) below reported.

[0004] Said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cells” - PSCs) can be part of a tandem perovskite / silicon photovoltaic cell (or solar cell). Said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cells” - PSCs) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be advantageously used in various applications that require the generation of electricity by harnessing light energy, in particular the energy of solar radiation, such as: photovoltaic fields (or photovoltaic parks), residential use, commercial buildings. Said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cells” - PSCs) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be used either in stand-alone mode or in modular systems.

[0005] The present invention also relates to a tandem perovskite / silicon photovoltaic cell (or solar cell).

[0006] It is also a further object of the present invention to have a composition comprising at least one perovskite and at least one compound having the specific general formula (I) below reported.

[0007] Photovoltaic cells (or solar cells) are devices capable of converting the energy of a light radiation into electricity. At present, most photovoltaic cells (or solar cells) that can be used for practical applications exploit the chemical-physical properties of inorganic photoactive materials, particularly both crystalline and amorphous silicon, more particularly high-purity crystalline silicon.

[0008] Over the last decade, several new technologies related to photovoltaic cells (or solar cells) have attracted the attention of numerous research groups around the world with the aim of improving the characteristics of photovoltaic cells (or solar cells) based on silicon such as, for example, access to new fields ofapplication, improved efficiencies and possibly lower production costs.

[0009] In particular, photovoltaic cells (or solar cells) based on perovskite (" Perovskite Solar Cells" - PSCs) have rapidly become a promising alternative in recent years, as they combine a high power conversion efficiency [" Power Conversion Efficiency" - (PCE)], which has currently reached a certified value of over 26%, a series of characteristics typical of thin-film photovoltaic cells (or solar cells) based on organic polymers (" Organic Photovoltaics" - OPVs) such as, for example, lightness, flexibility and the simplicity of the manufacturing process which, starting from appropriate mixtures of the various precursors, can enable the production of photovoltaic cells (or solar cells) by means of well-known and established printing processes (including continuous printing) under mild conditions and at a sustainable costs. Furthermore, in recent years it has been demonstrated that particular photovoltaic cells (or solar cells) based on perovskite (" Perovskite Solar Cells" - PSCs) can exploit solar radiation not absorbed by photovoltaic cells (or solar cells) based on silicon and thus appropriately coupled with said photovoltaic cells (or solar cells) based on silicon, they result in so-called tandem photovoltaic cells (or solar cells) whose efficiency to date is close to 35%, thus achieving a significant improvement over all commercially available technologies.

[0010] However, photovoltaic cells (or solar cells) based on perovskite (“Perovskite Solar Cells” - PSCs) can also have certain structural drawbacks which can also influence the macroscopic behaviour of said photovoltaic cells (or solar cells) based on perovskite (“Perovskite Solar Cells” - PSCs), such as, for example, a relatively high density of defects (for example, crystallinity defects, ion vacancies, etc.) both within the photoactive layer of perovskite ("bulk") and at the edges of the crystalline grains, and on the surface of said photoactive layer of perovskite. Indeed, interfaces between materials represent an area of discontinuity in the photovoltaic cell (or solar cell) based on perovskite ('Perovskite Solar Cells' -PSCs), and are the cause of the greatest gap between the theoretical performance of photovoltaic cells (or solar cells) based on perovskite (“Perovskite Solar Cells” - PSCs) (without any loss due to corollary phenomena) and the actual performance due to the high electron-lacuna recombination rate at the interface. More precisely,said defects reduce the overall efficiency of the photovoltaic cells (or solar cells) based on perovskite (“Perovskite Solar Cells” - PSCs) and also facilitate the initiation of degradation phenomena.

[0011] To bridge the aforementioned gap, research is focusing on the use of agents capable of passivating defects commonly present both on the surface (via surface treatment) and within the photoactive layer of perovskite (via bulk treatment). In particular, as reported, for example, by M. M. Byranvand and M. Saliba, " Defect Passivation of Perovskite Films for Highly Efficient and Stable Solar Cells", " Solar RRL" (2021), Vol. 5, 2100295; or by Abd. Rashid bin Mohd Yusoff et al, “Passivation and process engineering approaches of halide perovskite films for high efficiency and stability perovskite solar cells”, “Energy Environment Science” (2021), Vol. 14, p. 2906-2953, various compounds containing various functional groups capable of interacting via bonds, more or less strong, with the perovskite surface have been used as passivating agents. Common passivating agents include, for example, certain fullerene derivatives, transition metal salts, alkaline earth metal salts and lanthanide salts, urea, propylene carbonate, hexafluoroisopropanol, nitrogen-doped reduced graphene oxide, tris(pentafluorophenyl)phosphine, trioctylphosphinoxide, tribenzyl-phosphinoxide, acetic acid, conjugated molecules with a π–acceptor donor-bridge structure, conjugated molecules with rhodanine groups, thiophene, pyridine, mercaptopyridine, benzylamine, lead sulphate, pentaerythritol tetrakis(3-mercaptopropionate), butanediol, phenylethylammonium iodide, phenylethylammonium chloride, butylammonium iodide, octylammonium iodide, octyldiammonium iodide, benzylammonium iodide, 1,1,1-trifluoroethylammonium iodide 4-(aminomethyl)piperidinium iodide, 2-thiophenylmethylammonium iodide, 4-vinylbenzylammonium bromide, hexyltrimethylammonium bromide, azetidinium bromide, tetrakisammonium(zinc phthalocyanine) iodide, thiazoloammonium iodide, pentafluorophenylammonium iodide, 2-(4-fluorophenyl)ethylammonium iodide.

[0012] Chinese patent application CN 111777522 relates to a passivating agent comprising an alkyl segment, the alkyl segment containing a functional group (A), a functional group (B) and at least one functional group (C), the functional group(A) being an amine group, the functional group (B) being a carboxyl group and the functional group (C) being at least one group selected from: an amine group, a thiol group, a hydroxyl group, an imidazole group, a lipid group, an amide group, a nitro group, an aldehydic group, an aromatic group, a cyano group and a sulphonate group. The aforementioned passivating agent is said to be able to act as an electron donor or acceptor compound, interact with the electronic structural defects of the perovskite layer, and have a good passivating effect both at the edges of the crystalline grains and on the surface of said perovskite layer.

[0013] However, many of the compounds used as passivating agents can have critical aspects. For example, among those reported above, hexafluoroisopropanol, acetic acid, thiophene, pyridine, benzylamine, butantiol, are compounds with a high vapour pressure and a relatively low boiling point (well below 200°C). Since during the manufacturing process of photovoltaic cells (or solar cells) based on perovskite (“Perovskite Solar Cells” - PSCs), prolonged heat treatments are used at significant temperatures, which can reach, or in some cases even exceed, 150°C-180°C, said passivating agents can be removed to an uncontrollable extent, making the manufacturing process not very reproducible. Therefore, it would be preferable to have non-volatile compounds or compounds with a boiling or sublimation temperature significantly higher than that to which photovoltaic cells (or solar cells) based on perovskite (“Perovskite Solar Cells” - PSCs) are subjected during their manufacture. Furthermore, the use of ammonium iodides, which are very commonly used passivating agents, could be particularly inconvenient, as compounds of this type can be subject to undesirable decomposition reactions, especially when heated.

[0014] From what has been said above, it is clear that it is important to find other compounds that can be used as passivating agents both within the perovskite photoactive layer (via bulk treatment) and on its surface (via surface treatment), which will allow for photovoltaic cells (or solar cells) based on perovskite (“Perovskite Solar Cells” - PSC) that are capable of having a good power conversion efficiency [" Power Conversion Efficiency" - (PCE)].

[0015] The Applicant therefore set itself the problem of finding a photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) capable ofhaving a good power conversion efficiency [" Power Conversion Efficiency" -(PCE)].

[0016] The Applicant has now found a photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) comprising at least one layer comprising at least one compound having the specific general formula (I) below reported, capable of having a good power conversion efficiency [" Power Conversion Efficiency" - (PCE)] (i.e. PCE > 16%). In addition, said photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) has low hysteresis index (“Hysteresis Index” -HI) values (i.e. values less than or equal to 1.5%). In addition, said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) is able to maintain good photovoltaic properties, i.e. good values of FF (" Fill Factor"), Voc (" Open Circuit Voltage"), Jsc ("short-circuit photocurrent density"). Said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) can be part of a tandem perovskite / silicon photovoltaic cell (or solar cell). Said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be advantageously used in various applications that require the generation of electricity by harnessing light energy, in particular the energy of solar radiation, such as: photovoltaic fields (or photovoltaic parks), residential use, commercial buildings. Said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be used either in stand-alone mode or in modular systems.

[0017] The present invention therefore relates to a photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) comprising at least one layer comprising at least one compound having general formula (I):

[0018]

[0019] wherein:

[0020] n is 0 or 1;X represents a hydrogen atom, or a hydroxyl group;

[0021] R4 is selected from Ci-Ce, preferably C1-C4, linear or branched, saturated, alkylene groups, preferably it is methylene;

[0022] when n is 0 or 1 and X represents a hydrogen atom:

[0023] Ri, R2 and R3, identical or different from each other, represent a hydrogen atom; or they are selected from C1-C12 alkyl groups, preferably C1-C8, linear or branched, saturated or unsaturated, aryl groups, cycloalkyl groups, said alkyl, aryl and cycloalkyl groups being optionally substituted with at least one group selected from alkyl groups, hydroxyl groups, ether groups, ester groups, carbonyl groups; provided that at least one of Ri, R2 and R3 is different from hydrogen and that at least one of Ri, R2 and R3 contains at least one hydroxyl group;

[0024] or, any two of Ri, R2 and R3, can optionally be linked together so as to form, together with the other atoms to which they are linked, a heterocyclic group containing from 2 to 16 atoms, containing from 1 to 3 heteroatoms, preferably 2 heteroatoms, selected, for example, from oxygen, sulphur, nitrogen, silicon, phosphorus, selenium, preferably oxygen, nitrogen, said heterocyclic group being substituted with at least one hydroxyl group and optionally with at least one sulfonic group;

[0025] when n is 1 and X represents a hydroxyl group:

[0026] Ri, R2 and R3, identical or different from each other, represent a hydrogen atom; or they are selected from C1-C12 alkyl groups, preferably C1-C8, linear or branched, saturated or unsaturated, aryl groups, cycloalkyl groups, said alkyl, aryl and cycloalkyl groups being optionally substituted with at least one group selected from alkyl groups, hydroxyl groups, ether groups, ester groups, carbonyl groups; or, any two of Ri, R2 and R3, can optionally be linked together so as to form, together with the other atoms to which they are linked, a heterocyclic group containing from 2 to 16 carbon atoms, containing from 1 to 3 heteroatoms, preferably 2 heteroatoms, selected, forexample, from oxygen, sulphur, nitrogen, silicon, phosphorus, selenium, preferably oxygen, nitrogen, said heterocyclic group being optionally substituted with at least one hydroxyl group and / or with at least one sulfonic group.

[0027] For the purpose of the present description and of the following claims, the definitions of the numeric ranges always include the extremes unless specified otherwise.

[0028] For the purpose of the present description and of the following claims, the term “comprising” also includes the terms “which essentially consists of’ or “which consists of’.

[0029] It should be noted that in the event that at least one of Ri, R2 and R3 represents a hydrogen atom, the above general formula (I) is in equilibrium and coexists with the following general formula (la) wherein R3 represents a hydrogen atom:

[0030]

[0031] wherein Ri, R2, R4, X and n, have the same meanings as described above. Cases wherein Ri or R2 represent a hydrogen atom are easily deduced from said general formula (la).

[0032] In accordance with a preferred embodiment of the present invention, said at least one layer is the perovskite photoactive layer.

[0033] In accordance with a further preferred embodiment of the present invention, said at least one layer is a layer positioned above and / or below the perovskite photoactive layer, preferably it is a layer positioned above the perovskite photoactive layer.

[0034] In accordance with a further preferred embodiment of the present invention, said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) comprises:

[0035] at least one layer positioned above and / or below the perovskite photoactive layer, preferably a layer positioned above the perovskite photoactive layer,comprising at least one compound having general formula (I); and a perovskite photoactive layer comprising at least one compound having general formula (I).

[0036] In accordance with a preferred embodiment of the present invention, said perovskite can be selected, for example, from organometallic trihalides having general formula ABX3 wherein:

[0037] A represents a monovalent organic cation such as, for example, methylammonium (CH3NH3+), formamidinium [CH(NH2)2+], n- butylammonium (C4H9NH3+), tetra-butylammonium (C16H36N+), guanidinium [NH2(NH2)2+], or combinations thereof; or A represents a monovalent inorganic cation such as, for example, caesium (Cs+), rubidium (Rb+), potassium (K+), lithium (Li+), sodium (Na+), copper (Cu+), silver (Ag+), or combinations thereof; or combinations of at least one monovalent organic cation and at least one monovalent inorganic cation;

[0038] B represents a divalent metallic cation such as for example lead (Pb2+), tin (Sn2+), or combinations thereof;

[0039] X represents a halide anion such as, for example, iodide (I ), chloride (Cl ), bromide (Br ), or combinations thereof.

[0040] In accordance with a further preferred embodiment of the present invention, said perovskite can be selected, for example, from: methylammonium lead iodide [CH3NH3PbI3], formamidinium lead iodide [CH(NH2)2PbI3], caesium lead iodide [CsPbI3], methylammonium formamidinium lead iodide [(CH3NH3)x(CH(NH2)2)1-xPbI3], caesium methylammonium lead iodide [Csx(CH3NH3)1-xPbI3], caesium formamidinium lead iodide [Csx(CH(NH2)2)1-xPbI3], caesium methylammonium formamidinium lead iodide [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbI3], methylammonium lead bromide [CH3NH3PbBr3], formamidinium lead bromide [CH(NH2)2PbBr3], caesium lead bromide [CsPbBr3], methylammonium formamidinium lead bromide [(CH3NH3)x(CH(NH2)2)1-xPbBr3], caesium methylammonium lead bromide [Csx(CH3NH3)1-xPbBr3], caesium formamidinium lead bromide [Csx(CH(NH2)2)1-xPbBr3], caesium methylammonium formamidinium lead bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbBr3], methylammonium lead chloride[CH3NH3PbCl3], formamidinium lead chloride [CH(NH2)2PbCl3], caesium lead chloride [CsPbCl3], methylammonium formamidinium lead chloride [(CH3NH3)x(CH(NH2)2)1-xPbCl3], caesium methylammonium lead chloride [Csx(CH3NH3)1-xPbCl3], caesium formamidinium lead chloride [Csx(CH(NH2)2)1-xPbCl3], caesium methylammonium formamidinium lead chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbCl3], methylammonium lead iodide bromide [CH3NH3PbI3-wBrw], formamidinium lead iodide bromide [CH(NH2)2Pbl3-wBrw], caesium lead iodide bromide [CsPbI3-wBrw], methylammonium formamidinium lead iodide bromide [(CH3NH3)x(CH(NH2)2)1-xPbI3-wBrw], caesium methylammonium lead iodide bromide [Csx(CH3NH3)1-xPbI3-wBrw], caesium formamidinium lead iodide bromide [Csx(CH(NH2)2)1-xPbI3-wBrw], caesium methylammonium formamidinium lead iodide bromide [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbI3-wBrw], methylammonium lead iodide chloride [CH3NH3PbI3-wClw], formamidinium lead iodide chloride [CH(NH2)2Pbl3-wClw], caesium lead iodide chloride [CsPbI3-wClw], methylammonium formamidinium lead iodide chloride [(CH3NH3)x(CH(NH2)2)1-xPbI3-wClw], caesium methylammonium lead iodide chloride [Csx(CH3NH3)1-xPbI3-wClw], caesium formamidinium lead iodide chloride [Csx(CH(NH2)2)1-xPbI3-wClw], caesium methylammonium formamidinium lead iodide chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbI3-wClw], methylammonium lead bromide chloride [CH3NH3PbBr3-wClw], formamidinium lead bromide chloride [CH(NH2)2PbBr3-wClw], caesium lead bromide chloride [CsPbBr3-wClw], methylammonium formamidinium lead bromide chloride [(CH3NH3)x(CH(NH2)2)1-xPbBr3-wClw], caesium methylammonium lead bromide chloride [Csx(CH3NH3)1-xPbBr3-wClw], caesium formamidinium lead bromide chloride [Csx(CH(NH2)2)1-xPbBr3-wClw], caesium methylammonium formamidinium lead bromide chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbBr3-wClw], methylammonium lead iodide bromide chloride [CH3NH3PbI3-w-vBrwClv], formamidinium lead iodide bromide chloride [CH(NH2)2Pbl3-w-vBrwClv], caesium lead iodide bromide chloride [CsPbI3-w-vBrwClv], methylammonium formamidinium lead iodide bromide chloride [(CH3NH3)x(CH(NH2)2)1-xPbI3-w-vBrwClv], caesium methylammonium lead iodide bromide chloride [Csx(CH3NH3)1-xPbI3-w-vBrwClv], caesium formamidinium lead iodide bromidechloride [Csx(CH(NH2)2)1-xPbI3-w-vBrwClv], caesium methylammonium formamidinium lead iodide bromide chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbI3-w-vBrwClv], methylammonium tin iodide [CH3NH3SnI3], formamidinium tin iodide [CH(NH2)2SnI3], caesium tin iodide [CsSnI3], methylammonium formamidinium tin iodide [(CH3NH3)x(CH(NH2)2)1-xSnI3], caesium methylammonium tin iodide [Csx(CH3NH3)1-xSnI3], caesium formamidinium tin iodide [Csx(CH(NH2)2)1-xSnI3], caesium methylammonium formamidinium tin iodide [(CsxCH3NH3)y(CH(NH2)2)1-x-ySnI3], methylammonium tin bromide [CH3NH3SnBr3], formamidinium tin bromide [CH(NH2)2SnBr3], caesium tin bromide [CsSnBr3], methylammonium formamidinium tin bromide [(CH3NH3)x(CH(NH2)2)1-xSnBr3], caesium methylammonium tin bromide [Csx(CH3NH3)i-xSnBr3], caesium formamidinium tin bromide [Csx(CH(NH2)2)1-xSnBr3], caesium methylammonium formamidinium tin bromide [(CsxCH3NH3)y(CH(NH2)2)1-x-ySnBr3], methylammonium tin chloride [CH3NH3SnCl3], formamidinium tin chloride [CH(NH2)2SnCl3], caesium tin chloride [CsSnCl3], methylammonium formamidinium tin chloride [(CH3NH3)x(CH(NH2)2)1-xSnCl3], caesium methylammonium tin chloride [Csx(CH3NH3)1-xSnCl3], caesium formamidinium tin chloride [Csx(CH(NH2)2)1-xSnCl3], caesium methylammonium formamidinium tin chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-ySnCl3], methylammonium tin iodide bromide [CH3NH3SnI3-wBrw], formamidinium tin iodide bromide [CH(NH2)2Snl3-wBrw], caesium tin iodide bromide [CsSnl3-wBrw], methylammonium formamidinium tin iodide bromide [(CH3NH3)x(CH(NH2)2)1-xSnI3-wBrw], caesium methylammonium tin iodide bromide [Csx(CH3NH3)1-xSnI3-wBrw], caesium formamidinium tin iodide bromide [Csx(CH(NH2)2)1-xSnI3-wBrw], caesium methylammonium formamidinium tin iodide bromide [(CsxCH3NH3)y(CH(NH2)2)1-x-ySnI3-wBrw], methylammonium tin iodide chloride [CH3NH3SnI3-wClw], formamidinium tin iodide chloride [CH(NH2)2Snl3-wClw], caesium tin iodide chloride [CsSnl3-wClw], methylammonium formamidinium tin iodide chloride [(CH3NH3)x(CH(NH2)2)1-xSnI3-wClw], caesium methylammonium tin iodide chloride [Csx(CH3NH3)1-xSnI3-wClw], caesium formamidinium tin iodide chloride [Csx(CH(NH2)2)1-xSnI3-wClw], caesium methylammonium formamidinium tin iodide chloride[(CsxCH3NH3)y(CH(NH2)2)i-x-ySnl3-wClw], methylammonium tin bromide chloride [CHsNHsSnBrs-wClw], formamidinium tin bromide chloride [CH(NH2)2SnBr3-wClw], caesium tin bromide chloride [CsSnBn-wClw], methylammonium formamidinium tin bromide chloride [(CH3NH3)X(CH(NH2)2)I- SnBrs-wClw], caesium methylammonium tin bromide chloride [CSX(CH3NH3)I-xSnBrs-wClw], caesium formamidinium tin bromide chloride [Csx(CH(NH2)2)i- SnBrs-wClw], caesium methylammonium formamidinium tin bromide chloride [(CsxCH3NH3)y(CH(NH2)2)i- -ySnBr3-wClw], methylammonium tin iodide bromide chloride [CHsNHsSnls-w-vBrwClv], formamidinium tin iodide bromide chloride [CH(NH2)2Snl3-w-vBrwClv], caesium tin iodide bromide chloride [CsSnI3-w-vBrwClv], methylammonium formamidinium tin iodide bromide chloride [(CH3NH3)x(CH(NH2)2)i- Snl3-w-vBrwClv], caesium methylammonium tin iodide bromide chloride [Csx(CH3NH3)i- Snl3-w-vBrwClv], caesium formamidinium tin iodide bromide chloride [Csx(CH(NH2)2)i- Snl3-w-vBrwClv], caesium methylammonium formamidinium tin iodide bromide chloride [(CsxCH3NH3)y(CH(NH2)2)i- -ySnl3-w-vBrwClv], wherein in the case where only the index x is present, x is comprised between 0.01 and 0.99, in the case where the indices x and y are present, the sum of x+y is comprised between 0.01 and 0.99 with x and y different from 0, in case where only index w is present, w is comprised between 0.01 and 2.99, in case where the indices w and v are present, the sum of w+v is comprised between 0.01 and 2.99 with w and v different from 0. Preferably, said perovskite can be selected, for example, from: methylammonium lead iodide [CHsNHsPbl,], formamidinium lead iodide [CH(NH2)2PbI3], caesium lead iodide [CsPbls], methylammonium formamidinium lead iodide [(CH3NH3)x(CH(NH2)2)1-xPbI3], caesium methylammonium lead iodide [CsxlCH NH Ji-xPbl ], caesium formamidinium lead iodide [Csx(CH(NH2)2)i- Pbl3], caesium methylammonium formamidinium lead iodide [(CsxCH3NH3)y(CH(NH2)2)i- -yPbl3], methylammonium lead iodide bromide [CHsNHsPbls-wBrw], formamidinium lead iodide bromide [CH(NH2)2Pbl3-wBrw], caesium lead iodide bromide [CsPbI3-wBrw], methylammonium formamidinium lead iodide bromide [(CHsNHs (CH(NH2)2)i-xPbl3-wBrw], caesium methylammonium lead iodide bromide [CSX(CH3NH3)I-xPbl3-wBrw], caesium formamidinium lead iodide bromide [Csx(CH(NH2)2)i-xPbl3-wBrw], caesium methylammonium formamidinium lead iodide bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-wBrw]; even more preferably between: caesium methylammonium lead iodide bromide [Csx(CH3NH3)i-xPbl3-wBrw], caesium formamidinium lead iodide bromide [Csx(CH(NH2)2)1-xPbI3-wBrw], caesium methylammonium formamidinium lead iodide bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-wBrw].

[0041] In accordance with a further preferred embodiment of the present invention, said perovskite can be selected, for example, from perovskites having a band gap value comprised between 1.60 eV and 1.78 eV, preferably comprised between 1.65 eV and 1.72 eV.

[0042] For the purpose of the present description and of the following claims, the term “Ci-Ce alkylene groups” means alkylene groups having from 1 to 6 carbon atoms, linear or branched, saturated. Specific examples of Ci-Ce alkylene groups are: methylene, ethylene, n-propylcnc, / '.so-propylcnc, n-butylene, / '.so-butylcnc, tert-butylene, pentylene, hexylene.

[0043] For the purpose of the present description and of the following claims, the term “C1-C12 alkyl groups” means alkyl groups having from 1 to 12 carbon atoms, linear or branched, saturated or unsaturated. Said alkyl groups can optionally be substituted with one or more groups, identical or different from each other, selected from: alkyl groups; hydroxyl groups; ether groups; ester groups; carbonyl groups. Specific examples of C1-C162 alkyl groups are: methyl, ethyl, n-propyl, / '.so-propyl, n-butyl, zso-butyl, tert-butyl, pentyl, 2-ethyl-hexyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl.

[0044] For the purpose of the present description and of the following claims, the term “aryl groups” indicates aromatic carbocyclic groups containing from 6 to 14 carbon atoms. Said aryl groups can optionally be substituted with one or more groups, identical or different from each other, selected from: alkyl groups; hydroxyl groups; ether groups; ester groups; carbonyl groups. Specific examples of aryl groups are: phenyl, methylphenyl, dimethylphenyl, trimethylphenyl, methoxyphenyl, hydroxyphenyl, phenyloxyphenyl, naphthyl, phenylnaphthyl, phenanthryl, anthracenyl.For the purpose of the present description and of the following claims, the term “cycloalkyl groups” indicates cycloalkyl groups having from 5 to 12 carbon atoms. Said cycloalkyl groups can optionally be substituted with one or more groups, identical or different from each other, selected from: alkyl groups; hydroxyl groups; ether groups; ester groups; carbonyl groups. Specific examples of cycloalkyl groups are: cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, methylcyclohexyl, phenylcyclohexyl, decalin, norbornyl, abietyl.

[0045] For the purpose of the present description and of the following claims, the term “heterocyclic groups” indicates rings having from 2 to 16 carbon atoms, saturated or unsaturated, containing at least one heteroatom selected from oxygen, sulphur, nitrogen, silicon, phosphorus, selenium. Said heterocyclic groups can optionally be substituted with at least one hydroxyl group and / or with at least one sulfonic group. Specific examples of heterocyclic groups are those derived from pyrrolidine, piperidine, piperazine, morpholine, thiazine, indoline, pyridine, pyrrole, tetrahydrofuran, furan, dioxane, propylene oxide, cyclohexene oxide, thiophene.

[0046] The above compounds having general formula (I) are known in the art and commercially available.

[0047] Specific examples of compounds having general formula (I) that are advantageously usable for the purpose of the present invention are reported in Table 1.

[0048] Table 1

[0049] O OH r OH H3C H?H°k, OH

[0050] XS. hk / -X' HO.

[0051] HO OH O CH3

[0052] DIPSO AMPSO

[0053] M n01H 0v 0i-f f N SO3H A Js

[0054] \\

[0055] OH o MOPSO CAPSO

[0056]

[0057]

[0058] For the purpose of the present invention, said compound having general formula (I) can be dissolved in a solvent.

[0059] Specific examples of solvents that are advantageously usable for the purpose of the present invention are: water; aromatic hydrocarbons such as, for example, toluene, benzene, o-xylene, p-xylene, m-xylene, or mixtures thereof; linear esters such as, for example, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, butyl propionate, ethyl butyrate, propyl butyrate, butyl butyrate; cyclic esters such as, for example, y-butyrolactone, 8-valerolactone, or mixtures thereof; ethers such as, for example, diethyl ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethoxyethane, or mixtures thereof; amides such as, for example, N,N-dimethylformamide, N-methylpyrrolidone, dimethylacetamide, or mixtures thereof; sulfoxides such as, for example, dimethyl sulfoxide, diethyl sulfoxide, or mixtures thereof; nitrilessuch as, for example, acetonitrile, propionitrile, butyronitrile, benzonitrile, or mixtures thereof; alcohols such as, for example, methanol, ethanol, n-propanol, Ao-propanoL n-butanol, or mixtures thereof; ketones such as, for example, acetone, methyl ethyl ketone, cyclohexanone, or mixtures thereof; chlorinated solvents such as, for example, chloroform, methylene chloride, dichloroethane, tetrachloroethane, chlorobenzene, or mixtures thereof; or mixtures of said solvents.

[0060] At the end of the above-mentioned procedure:

[0061] in the case wherein the solvent used in the aforementioned process is selected from among solvents defined as antisolvents of perovskite such as, for example, aromatic solvents, chlorinated solvents, linear esters, ethers, ketones, nitriles, alcohols, said solvents being selected from among those reported above, the aforementioned solution containing the compound having general formula (I) can be directly used for surface treatment of the perovskite photoactive layer (surface treatment) wherein a layer of the resulting solution is deposited above and / or below the perovskite photoactive layer, preferably above; or

[0062] in the case wherein the solvent used in the above process is selected from among solvents capable of dissolving perovskite such as, for example, sulfoxides, amides, cyclic esters, said solvents being selected from among those reported above, the aforementioned solution containing the compound having general formula (I) can be directly used in a mixture with the perovskite precursors with subsequent formation of the perovskite photoactive layer (bulk treatment); or

[0063] the compound having general formula (I) can be isolated and purified from the abovemetioned solution by evaporation of the solvent and subsequently dissolved in a suitable solvent selected from those reported above, depending on whether it is used in surface treatment or bulk treatment; in particular:

[0064] the purified compound having general formula (I) can be dissolved in a solvent selected from among the solvents defined as antisolvents of perovskite reported above, resulting in a solution containing thecompound having general formula (I) that can be directly used for surface treatment of the perovskite photoactive layer (surface treatment) wherein a layer of the resulting solution is deposited above of and / or below the perovskite photoactive layer, preferably above; or the purified compound having general formula (I) can be dissolved in a solvent selected from those capable of dissolving the perovskite reported above in a mixture with the perovskite precursors with subsequent formation of the perovskite photoactive layer (bulk treatment).

[0065] More information on antisolvents used in photovoltaic cells (or solar cells) based on perovskite is reported, for example, by Ghosh S. et al. in " Advanced. Materials Interfaces" (2020), Vol. 7, 200950, DOI: 10.1002 / admi.202000950.

[0066] In accordance with a preferred embodiment of the present invention, said at least one compound having general formula (I) can be present in the perovskite photoactive layer in an amount comprised between 0.01 millimoles and 5 millimoles, preferably comprised between 0.02 millimoles and 2 millimoles, with respect to the millimoles of lead.

[0067] In accordance with a preferred embodiment of the present invention, said at least one compound having general formula (I) can be present in the solution used in the surface treatment in order to obtain the layer positioned above and / or below the perovskite photoactive layer, in concentration comprised between 0.01 millimoles / litre and 100 millimoles / litre, preferably comprised between 0.1 millimoles / litre and 20 millimoles / litre.

[0068] In accordance with a preferred embodiment of the present invention, said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” -PSC) comprises:

[0069] a glass substrate covered with at least one layer of transparent and conductive oxide (" Transparent Conductive Oxide" - TCO), said oxide being preferably selected from fluorine doped tin oxide (SnO2: F) (" Fluorinedoped Tin Oxide" - FTO), indium tin oxide (" Indium Tin Oxide" - ITO), aluminium zinc oxide (AZO), indium zinc oxide (" Indium Zinc Oxide" IZO), hydrogenated indium oxide (" Hydrogenated Indium Oxide - IO: H),which constitutes the anode;

[0070] at least one layer based on a hole transport material (" Hole Transport Layer" - HTL), said material being preferably selected from (2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl phosphonic acid (MeO-2PACz)], 2-(9H-carbazol-9-yl)ethyl phosphonic acid (2PACz), nickel oxide (NiOx), copper sulfocyanide (CuSCN), copper iodide (Cui), copper oxide (CuOx), copper sulphide (CuS), or a combination of layers of the aforementioned materials; optionally at least one layer based on a material useful for improving wettability, preferably a layer of nanoparticles of aluminium oxide (n-AI2O3);

[0071] optionally, at least one layer comprising at least one compound having general formula (I);

[0072] a photoactive layer comprising at least one perovskite preferably selected from caesium methylammonium lead iodide bromide [Cs0,05(CH3NH3)0,95PbI2,55Br0,45], caesium formamidinium lead iodide bromide [Cs0.17FA0.83PbI2.79Br0.3], more preferably caesium methylammonium lead iodide bromide [Cs0,05(CH3NH3)0,95PbI2,55Br0,45], and, optionally, at least one compound having general formula (I); optionally, at least one layer comprising at least one compound having general formula (I);

[0073] at least one layer based on an electron transport material (" Electron Transport Layer" - ETL), said material being preferably selected from methyl ester of the [6,6]-phenyl-C61-butyric acid (PC61BM), fullerene (C60), tin oxide (SnOx), polyethyleneimine (PEI), ethoxylated polyethyleneimine (PEIE), or a combination of layers of the aforementioned materials; optionally, at least one layer based on a hole blocking material (" Hole Blocking Layer" - HBL), preferably 2, 9-dimethyl-4, 7 -diphenyl- 1,10-phenanthroline (Batocuproine - BCP);

[0074] a cathode consisting of:

[0075] a metal contact known as back contact preferably a layer of gold, silver, or metallic aluminium; or,

[0076] a layer of transparent and conductive oxide (" Transparent ConductiveOxide" - TCO) and metal grids.

[0077] It should be noted, in fact, that in the case of tandem perovskite / silicon photovoltaic cells (or solar cells), in the photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) the aforementioned metal contact known as back contact will be substituted by a layer of transparent and conductive oxide (“Transparent Conductive Oxide”-TCO) and metal grids forming the cathode.

[0078] In accordance with a preferred embodiment of the present invention, the electric energy generated by said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) can be transported using a wiring system which is connected with said photovoltaic cell (or solar cell) based on perovskite.

[0079] Said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) can be prepared in accordance with processes known in the art.

[0080] For example, said photovoltaic cell (or solar cell) based on perovskite (“'Perovskite Solar Cell” - PSC) can be prepared by a process comprising the following stages:

[0081] (a) preparing a glass substrate covered with a layer of transparent and conductive oxide (TCO) (anode);

[0082] (b) depositing at least one layer based on hole transport material (" Hole Transport Layer" - HTL) on the substrate obtained in said stage (a);

[0083] (c) optionally, depositing on the layer based on a hole transport material (" Hole Transport Layer" - HTL) obtained in said stage (b) at least one layer based on a material for improving wettability;

[0084] (d) optionally depositing on the layer based on a hole transport material (" Hole Transport Layer" - HTL) obtained in said stage (b), or on the layer based on a material for improving wettability obtained in said stage (c), at least one layer comprising at least one compound having general formula (I);

[0085] (e) preparing a mixture comprising perovskite precursors and, optionally, at least one compound having general formula (I);

[0086] (f) depositing, in the presence or absence of air, the mixture obtained in said stage (e) on the layer based on a hole transport material (" Hole TransportLayer" - HTL) obtained in said stage (b), or on the layer based on a material for improving wettability obtained in said stage (c), or on the layer comprising at least one compound having general formula (I) obtained in said stage (d), obtaining a photoactive layer;

[0087] (g) optionally, depositing on the photoactive layer obtained in said stage (f) at least one layer comprising at least one compound having general formula (i);

[0088] (h) depositing at least one layer based on an electron transport material (" Electron Transport Layer" - ETL), on the photoactive layer obtained in said stage (f) or on the layer comprising at least one compound having general formula (I) obtained in said stage (g);

[0089] (i) optionally, depositing on the layer based on an electron transport material (" Electron Transport Layer" - ETL) obtained in said stage (h), a layer based on a hole blocking material (" Hole Blocking Layer" - HBL);

[0090] (1) depositing a cathode comprising a metal contact known as a back contact preferably a gold, silver or metallic aluminium layer, or, a cathode consisting of a transparent conductive oxide (" Transparent Conductive Oxide" - TCO) layer and metal grids on the layer based on an electron transport material (" Electron Transport Layer" - ETL) obtained in said stage (h), or on the layer based on a hole blocking material (" Hole Blocking Layer" - HBL) obtained in said stage (i).

[0091] It should be noted, in fact, that in the case of tandem perovskite / silicon photovoltaic cells (or solar cells) in said stage (1), on the layer based on an electron transport material (“Electron Transport Layer” - ETL) obtained in said stage (h) or on the layer based on a hole blocking material (" Hole Blocking Layer” - HBL) obtained in said step (i), a layer of transparent and conductive oxide (" Transparent Conductive Oxide" - TCO) and metal grids forming the cathode will be deposited.

[0092] For the purpose of the aforementioned process, said transparent conductive oxide (“Transparent Conductive Oxide” - TCO), said layer based on a hole transport material (“Hole Transport Layer” - HTL), said layer based on an electron transport material (“Electron Transport Layer” - ETL), said layer based on a material for improving wettability, said layer based on a hole blocking material(“Hole Blocking Layer” - HBL) and said metallic contact known as back contact are selected from those reported above.

[0093] For the purpose of the aforementioned process, said mixture comprising perovskite precursors and, optionally at least one compound having general formula (I), comprises:

[0094] at least one halide selected from among the halides of the monovalent organic cations or monovalent inorganic cations reported above, preferably iodides, chlorides, bromides, more preferably iodides and bromides, and at least one halide selected from among the halides of the bivalent metal cations reported above, preferably iodides, chlorides, bromides, more preferably iodides and bromides [for example, caesium iodide (CsI), lead iodide (PbI2), lead bromide (PbBr2)] as perovskite precursors;

[0095] - optionally at least one compound having general formula (I).

[0096] For the purpose of the aforementioned process, said steps (b), (c), (d), (e), (f), (g), (h) and (i) can be carried out according to depositing techniques known in the art such as, for example, spin coating, spray-coating, ink-jet printing, slot die coating, gravure printing, Physical Vapor Deposition (PVD), Radio Frequency Sputtering (“RF-sputtering”), Direct Current sputtering (“DC-sputtering”), Magnetron sputtering, Thermal evaporation, Electron Beam Evaporation (EBE), Chemical Vapor Deposition (CVD), Pulsed Laser Deposition (PLD), Atomic Layer Deposition (ALD): the technique used will vary depending on the layer considered.

[0097] For the purpose of the aforementioned process, said stage (1) can be carried out according to techniques known in the art such as, for example, evaporation, cathodic sputtering, electron beam assisted deposition, Physical Vapor Deposition (PVD), Radio Frequency Sputtering (“RF-sputtering”), Direct Current sputtering (“DC-sputtering”).

[0098] As mentioned above, said photovoltaic cell (or solar cell) based on perovskite ('Perovskite Solar Cell' - PSC) can be part of a tandem perovskite / silicon photovoltaic cell (or solar cell).

[0099] Accordingly, it is a further object of the present invention to provide a tandem perovskite / silicon photovoltaic cell (or solar cell) comprising:a silicon photovoltaic cell (or solar cell);

[0100] a photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) comprising at least one layer comprising at least one compound having general formula (I), disposed above said silicon photovoltaic cell (or solar cell).

[0101] In accordance with a preferred embodiment of the present invention, the electric energy generated by said tandem perov ski te / silicon photovoltaic cell (or solar cell) can be transported using a wiring system which is connected with said tandem perov skite / silicon photovoltaic cell (or solar cell).

[0102] As mentioned above, said photovoltaic cell (or solar cell) based on perovskite ('Perovskite Solar Cell' - PSC) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be advantageously used in various applications that require the generation of electricity by harnessing light energy, in particular the energy of solar radiation, such as: photovoltaic fields (or photovoltaic parks), residential use, commercial buildings. Said photovoltaic cell (or solar cell) based on perovskite ('Perovskite Solar Cell' - PSC) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be used either in stand-alone mode or in modular systems.

[0103] Accordingly, a further object of the present invention is the use of said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” -PSC) or said tandem perovskite / silicon photovoltaic cell (or solar cell) in: photovoltaic fields (or photovoltaic parks), residential use, commercial buildings.

[0104] As mentioned above, it is also a further object of the present invention to have a composition comprising at least one perovskite and at least one compound having general formula (I).

[0105] Accordingly, it is also a further object of the present invention to have a composition comprising at least one perovskite and at least one compound having general formula (I).

[0106] Said at least one perovskite can be selected from among those reported above.

[0107] The present invention will now be illustrated in greater detail through an embodiment with reference to Figure 1 reported below.In particular, Figure 1 depicts a cross-sectional view of a photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) (1) comprising the following layers: a glass substrate (7) covered with layer of transparent and conductive oxide (“Transparent Conductive Oxide” - TCO) (anode) [e.g, indium tin oxide (" Indium Tin Oxide" - ITO)] (2); a layer based on a hole transport material (" Hole Transport Layer" - HTL) [e.g, (2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl phosphonic acid (MeO-2PACz)] (3); optionally, a layer based on a material useful for improving wettability, (not shown in Figure 1); optionally, a layer comprising at least one compound having general formula (I) (not shown in Figure 1); a photoactive layer comprising at least one perovskite [e.g, caesium methylammonium lead iodide bromide [Cso,o5(CH3NH3)o,95Pbl2,55Bro,4s)] and optionally at least one compound having general formula (I), preferably TAPS, TAPSO, BES (4); optionally a layer comprising at least one compound having general formula (I) (not shown in Figure 1); a layer based on an electron transport material [" Electron Transport Layer" (ETL)] [e.g., methyl ester of [6,6]-phenyl-Cei-butyric acid (PCeiBM)] (5a); a layer based on a hole blocking material ("Hole Blocking Layer" (HBL)) [e.g, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (Batocuproin - BCP)] (5b); a metal contact known as back contact that forms the cathode [e.g., a layer of silver] (6).

[0108] In order to better understand the present invention and to put it into practice, some illustrative and non-limiting examples thereof are reported below.

[0109] In the following examples, for the sake of simplicity, the term "solar cell" is used, which is to be intended to have the same meaning as "photovoltaic cell". EXAMPLE 1 (comparative)

[0110] Preparation of a perovskite-based solar cell (“Perovskite Solar Cell” - PSC)

[0111] For this purpose, a perovskite-based solar cell (“Perovskite Solar Cell” -PSC) was prepared on a glass substrate coated with ITO (“Indium Tin Oxide”) (Kintec KT 18086-1) and patterned (dimensions 15x15x1 mm; “sheet resistance” equal to 12 Ω / cm2) previously subjected to a cleaning process consisting of manual cleaning by wiping with a lint-free cloth soaked in a detergent diluted with deionized water. The substrate was then rinsed with deionized water. Subsequently, the substrate was thoroughly cleaned using the following methodsin sequence: ultrasonic baths in (i) deionized water plus detergent (followed by manual drying with a lint-free cloth); (ii) distilled water [followed by manual drying with a lint-free cloth]; (iii) acetone (Merck) and (iv) iso-propanol (Merck) in sequence. In particular, the substrate was placed in a beaker containing the solvent, placed in an ultrasonic bath, kept at 40°C, for a treatment of 10 minutes. After treatments (iii) and (iv), the substrate was dried with a compressed nitrogen flow.

[0112] Subsequently, the glass / ITO was further cleaned by treatment in an ozone device (UV Ozone Cleaning System EXPO3 - Astel), immediately before proceeding to the next step.

[0113] The substrate thus treated was ready for the deposition of the layer based on a hole transport material (“Hole Transport Layer” - HTL). For this purpose, a solution of (2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl phosphonic acid (MeO-2PACz) (Merck) in anhydrous ethanol (max. 0.003% by weight of water - VWR) at a concentration equal to 0.5 mg / ml was deposited by spin-coating, operating at a rotation speed equal to 3000 rpm (acceleration equal to 100 rpm / s), for 30 seconds: the whole was subjected to heat treatment (annealing), at 100°C, for 10 minutes. The layer based on a hole transport material (“Hole Transport Layer” -HTL) is a self-assembly monolayer with a thickness of < 1 nm.

[0114] On top of the layer based on a hole transport material (“Hole Transport Layer” - HTL) was deposited the caesium methylammonium lead iodide bromide layer [Cso.o5(CH3NH3)o.95Pbl2.55Bro.45) (band gap equal to 1.67 eV) operating as follows. For this purpose, caesium iodide (CsI) (ultra dry purity 99.999% - Alfa Aesar) (15.6 mg - 0.06 mmoles), lead iodide (PbI2) (ultra dry purity 99.999% -Alfa Aesar) (428.7 mg - 0.93 mmoles), lead bromide (PbBr2) (ultra dry purity 99.999% - Alfa Aesar) (99 mg - 0.27 mmoles) were dissolved in a mixture of N, N-dimethylformamide anhydrous (DMF) (purity 99.9% - Merck) (628.8 pl) and dimethyl sulphoxide anhydrous (DMSO) (purity 99.8% - Merck) (157.2 pl), operating under stirring, at 130°C, for 5 minutes. Subsequently, after allowing the temperature to drop spontaneously to room temperature (25°C), methylammonium iodide (MAI) (CH3NH3I) - (Merck) 181.5 mg - 1.14 mmol) was added to the obtained solution and the whole was left, under stirring, at roomtemperature (25°C) for 10 minutes.

[0115] The solution thus obtained was deposited on top of the layer based on a hole transport material (“Hole Transport Layer” - HTL), by means of spin coating operating at a rotation speed equal to 4000 rpm (acceleration equal to 1000 rpm / s), for 30 seconds, with the addition of 300 μl of antisolvent (i.e. ethylacetate - Merck) after 8 seconds from the start of the operation, and the whole was subjected to heat treatment (annealing), at 100°C, for 30 minutes, operating in an uncontrolled atmosphere, in the presence of air. The thickness of the layer of perovskite was found to be 330 nm.

[0116] The substrate thus obtained was ready for the deposition of the layer based on an electron transport material (“Electron Transport Layer” - ETL). For this purpose, a filtered solution of methyl ester of [6,6]-phenyl-C6i-butyric acid (PCeiBM) (Nano-C Products) (25 mg) in anhydrous chlorobenzene (purity 99.8% - Merck) (1 ml), was deposited, by spin coating operating at a rotation speed equal to 2000 rpm (acceleration equal to 500 rpm / s), for 60 seconds: the substrate obtained was allowed to rest, at room temperature (25 °C), for 5 minutes. The thickness of the layer based on an electron transport material (“Electron Transport Layer” - HTL) was found to be equal to 50 nm.

[0117] The substrate thus obtained was ready for the deposition of a layer based on a hole blocking material (“Hole Blocking Layer” - HBL). For this purpose, a solution of 2,9-dimethyl-4,7-diphenyl-1,10-phenatroline (Batocuproin - BCP) (purity 96% - Merck) (9 mg) in anhydrous iso-propyl alcohol (purity 99.5%-Merck) (18 ml) obtained by operating under stirring at 60°C, for 3 hours, was deposited, by spin coating operating at a rotation speed equal to 6000 rpm (acceleration equal to 1000 rpm / s), for 20 seconds, the substrate obtained was allowed to rest, at room temperature (25°C), for 5 minutes. The thickness of the layer based on a hole blocking material (“Hole Blocking Layer” - HBL) was found to be equal to 5 nm.

[0118] Subsequently, silver (Ag) back contact (cathode) was deposited on said layer based on a hole blocking material (“Hole Blocking Layer” - HBL) by evaporation. For this purpose, a Kurt J. Lesker evaporator was used, operating at a pressure equal to 2x10-6mmHg and a speed equal to 0.1 Angstrom / sec, suitably maskingthe area of the solar cell so as to obtain an active area equal to 4 mm2. The thickness of the silver (Ag) back contact (cathode) was found to be equal to 80 nm.

[0119] Thicknesses were measured by scanning electron microscopy using a Sigma-Zeiss Scanning Electron Microscope (SEM), equipped with a field emission electron gun, operating at an accelerating voltage equal to 5 kV, and exploiting the signal from secondary electrons.

[0120] The electrical characterization of the obtained perovskite-based solar cell was carried out at room temperature (25°C) operating as follows.

[0121] The current-voltage density (J-V) curves were acquired with a Keithley® 2400 digital multimeter connected to a personal computer for data collection. The photocurrent was measured by exposing the solar cell to the light of a Sinus-270 solar simulator (Class AAA - Wavelabs) placed at a distance of 10 mm from said solar cell, providing a solar spectrum classified as AM 1.5G and having an irradiance equivalent to 1 sun (100 mW / cm2), using an illumination spot of 100 mm x 100 mm. The AM 1.5G spectrum was calibrated using a certified silicon cell (Open RR-1002, KG5 window). Current-voltage characteristic curves were acquired in both the reverse scan direction i.e. from Voc(" Open Circuit Voltage") to Jsc ("short-circuit photocurrent density") and the forward scan direction i.e. from Jsc ("short-circuit photocurrent density") to Voc(" Open Circuit Voltage"), keeping the other acquisition parameters fixed. Table 1 shows the average and maximum power conversion efficiency [" Power Conversion Efficiency" - (PCE)] and the “Hysteresis Index” (HI) calculated as the difference between the power conversion efficiency [" Power Conversion Efficiency" - (PCE)] in the reverse scan direction and the power conversion efficiency [" Power Conversion Efficiency" - (PCE)] in the forward scan direction, divided by the power conversion efficiency [" Power Conversion Efficiency" - (PCE)] in the reverse scan direction, all multiplied by 100, according to the following formula:

[0122] HY (%) = |(PCE reverse scan - PCE forward scan) / PCE reverse scan × 100|

[0123]

[0124] I PCEreversescan I The result obtained is shown in Table 1 as an absolute value. Table 1 also shows the values of FF (“Fill Factor”), Voc (“Open Circuit Voltage”) and Jsc (“short-circuit photocurrent density”).EXAMPLE 2 (invention)

[0125] Preparation of a perovskite-based solar cell (bulk treatment)

[0126] A perovskite-based solar cell was prepared by operating as described in Example 1, with the only difference being the bulk treatment of the perovskite photoactive layer.

[0127] For this purpose, 24.3 mg of TAPS (Merck) (0.1 mmol) [0.083 millimoles of compound having general formula (I) relative to millimoles of lead] was added to the solution of perovskite precursors obtained as above reported in Example 1, and the obtained solution was heated to 45°C, for 30 minutes, under stirring. Subsequently, 20 (11 of the solution thus obtained was deposited on top of the layer based on a hole transport material (“Hole Transport Layer” - HTL), by means of spin coating operating at a rotation speed equal to 4000 rpm (acceleration equal to 1000 rpm / s), for 30 seconds, with the addition of 300 (11 of antisolvent (i.e. ethylacetate - Merck) after 8 seconds from the start of the operation, and the whole was subjected to heat treatment (annealing), at 100°C, for 30 minutes, operating in an uncontrolled atmosphere, in the presence of air. The thickness of the layer of perovskite was found to be 330 nm.

[0128] The electrical characterisation of the perovskite-based solar cell obtained was carried out as described above: Table 1 shows the results obtained.

[0129] EXAMPLE 3 (invention)

[0130] Preparation of a perovskite-based solar cell (bulk treatment)

[0131] A perovskite-based solar cell was prepared by operating as described in Example 1, with the only difference being the bulk treatment of the perovskite photoactive layer.

[0132] For this purpose, 60.8 mg of TAPS (Merck) (0.245 mmol) [0.204 millimoles of compound having general formula (I) relative to millimoles of lead] was added to the solution of perovskite precursors obtained as above reported in Example 1, and the obtained solution was heated to 45°C, for 30 minutes, under stirring. Subsequently, 20 (ll of the solution thus obtained was deposited on top of the layer based on a hole transport material (“Hole Transport Layer” - HTL), by means of spin coating operating at a rotation speed equal to 4000 rpm (acceleration equal to 1000 rpm / s), for 30 seconds, with the addition of 300 (ll of antisolvent (i.e.ethylacetate - Merck) after 8 seconds from the start of the operation, and the whole was subjected to heat treatment (annealing), at 100°C, for 30 minutes, operating in an uncontrolled atmosphere, in the presence of air. The thickness of the layer of perovskite was found to be 330 nm.

[0133] The electrical characterisation of the perovskite-based solar cell obtained was carried out as described above: Table 1 shows the results obtained.

[0134] EXAMPLE 4 (invention)

[0135] Preparation of a perovskite-based solar cell (bulk treatment)

[0136] A perovskite-based solar cell was prepared by operating as described in Example 1, with the only difference being the bulk treatment of the perovskite photoactive layer.

[0137] For this purpose, 25.9 mg of TAPSO (Merck) (0.1 mmol) [0.083 millimoles of compound having general formula (I) relative to millimoles of lead] was added to the solution of perovskite precursors obtained as above reported in Example 1, and the obtained solution was heated to 45°C, for 30 minutes, under stirring. Subsequently, 20 pl of the solution thus obtained was deposited on top of the layer based on a hole transport material (“Hole Transport Layer” - HTL), by means of spin coating operating at a rotation speed equal to 4000 rpm (acceleration equal to 1000 rpm / s), for 30 seconds, with the addition of 300 pl of antisolvent (i.e. ethylacetate - Merck) after 8 seconds from the start of the operation, and the whole was subjected to heat treatment (annealing), at 100°C, for 30 minutes, operating in an uncontrolled atmosphere, in the presence of air. The thickness of the layer of perovskite was found to be 330 nm.

[0138] EXAMPLE 5 (invention)

[0139] Preparation of a perovskite-based solar cell (bulk treatment)

[0140] A perovskite-based solar cell was prepared by operating as described in Example 1, with the only difference being the bulk treatment of the perovskite photoactive layer.

[0141] For this purpose, 64.8 mg of TAPSO (Merck) (0.25 mmol) [0.208 millimoles of compound having general formula (I) relative to millimoles of lead] was added to the solution of perovskite precursors obtained as above reported in Example 1, and the obtained solution was heated to 45°C, for 30 minutes, understirring. Subsequently, 20 pl of the solution thus obtained was deposited on top of the layer based on a hole transport material (“Hole Transport Layer” - HTL), by means of spin coating operating at a rotation speed equal to 4000 rpm (acceleration equal to 1000 rpm / s), for 30 seconds, with the addition of 300 μl of antisolvent (i.e. ethylacetate - Merck) after 8 seconds from the start of the operation, and the whole was subjected to heat treatment (annealing), at 100°C, for 30 minutes, operating in an uncontrolled atmosphere, in the presence of air. The thickness of the layer of perovskite was found to be 330 nm.

[0142] The electrical characterisation of the perovskite-based solar cell obtained was carried out as described above: Table 1 shows the results obtained.

[0143] EXAMPLE 6 (invention)

[0144] Preparation of a perovskite-based solar cell (bulk treatment)

[0145] A perovskite-based solar cell was prepared by operating as described in Example 1, with the only difference being the bulk treatment of the perovskite photoactive layer.

[0146] For this purpose, 21.3 mg of BES (Merck) (0.1 mmol) [0.083 millimoles of compound having general formula (I) relative to millimoles of lead] was added to the solution of perovskite precursors obtained as above reported in Example 1, and the obtained solution was heated to 45°C, for 30 minutes, under stirring. Subsequently, 20 pl of the solution thus obtained was deposited on top of the layer based on a hole transport material (“Hole Transport Layer” - HTL), by means of "spin coating" operating at a rotation speed equal to 4000 rpm (acceleration equal to 1000 rpm / s), for 30 seconds, with the addition of 300 pl of antisolvent (i.e. ethylacetate - Merck) after 8 seconds from the start of the operation, and the whole was subjected to heat treatment (annealing), at 100°C, for 30 minutes, operating in an uncontrolled atmosphere, in the presence of air. The thickness of the layer of perovskite was found to be 330 nm.

[0147] The electrical characterisation of the perovskite-based solar cell obtained was carried out as described above: Table 1 shows the results obtained.

[0148] EXAMPLE 7 (invention)

[0149] Preparation of a perovskite-based solar cell (bulk treatment)

[0150] A perovskite-based solar cell was prepared by operating as described inExample 1, with the only difference being the bulk treatment of the perovskite photoactive layer.

[0151] For this purpose, 53.3 mg of BES (Merck) (0.25 mmol) [0.208 millimoles of compound having general formula (I) relative to millimoles of lead] was added to the solution of perovskite precursors obtained as above reported in Example 1, and the obtaioned solution was heated to 45°C, for 30 minutes, under stirring. Subsequently, 20 J_tl of the solution thus obtained was deposited on top of the layer based on a hole transport material (“Hole Transport Layer” - HTL), by means of spin coating operating at a rotation speed equal to 4000 rpm (acceleration equal to 1000 rpm / s), for 30 seconds, with the addition of 300 J_tl of antisolvent (i.e. ethylacetate - Merck) after 8 seconds from the start of the operation, and the whole was subjected to heat treatment (annealing), at 100°C, for 30 minutes, operating in an uncontrolled atmosphere, in the presence of air. The thickness of the layer of perovskite was found to be 330 nm.

[0152] The electrical characterisation of the perovskite-based solar cell obtained was carried out as described above: Table 1 shows the results obtained.

[0153] Table 1

[0154] Example PCE(1)PCE(1)HI'2’ FF(3) Voc(4)Jsc(5)Average maximum (%)

[0155] (%) (V) (mA / cm2) 1 13.87 14.97 2.00 69.50 1.104 18.1 (comparative)

[0156] 2 16.80 18.00 0.77 82.0 1.146 17.8 (invention)

[0157] 3 18.50 19.00 0.52 81.4 1.155 19.6 (invention)

[0158] 4 17.60 18.30 1.03 81.6 1.135 19.0 (invention)

[0159] 5 17.00 17.90 1.10 81.1 1.132 18.5 (invention

[0160] 6 17.50 18.10 0.32 81.6 1.155 18.5 (invention)

[0161] 7 18.00 18.60 0.64 82.5 1.150 19.0

[0162]

[0163] (invention)

[0164] (1): Power Conversion Efficiency;

[0165] (2): Hysteresis Index;

[0166] (3): Fill Factor;

[0167] (4): Open Circuit Voltage;

[0168] (5): short-circuit photocurrent density.From the data shown in Table 1, it can be seen that the perovskite-based solar cells object of the present invention (Examples 2-7) have both good power conversion efficiency [“Power Conversion Efficiency” (PCE)] (i.e. PCE > 16%) [higher than that of the comparison solar cell (Example 1)], and low hysteresis values (i.e. values lower than 1.5%) [lower than those of the comparison solar cell (Example 1)], and good electrical properties, i.e. good values of FF (‘Fill Factor’), Voc (‘Open Circuit Voltage’); Jsc (‘short-circuit photocurrent density’).

Claims

CLAIMS1. Photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) comprising at least one layer comprising at least one compound having general formula (I):wherein:n is 0 or 1;X represents a hydrogen atom, or a hydroxyl group;R4 is selected from C1-C6, preferably C1-C4, linear or branched, saturated, alkylene groups, preferably it is methylene;when n is 0 or 1 and X represents a hydrogen atom:Ri, R2 and R3, identical or different from each other, represent a hydrogen atom; or they are selected from C1-C12 alkyl groups, preferably C1-C8, linear or branched, saturated or unsaturated, aryl groups, cycloalkyl groups, said alkyl, aryl and cycloalkyl groups being optionally substituted with at least one group selected from alkyl groups, hydroxyl groups, ether groups, ester groups, carbonyl groups; provided that at least one of Ri, R2 and R3 is different from hydrogen and that at least one of Ri, R2 and R3 contains at least one hydroxyl group;or, any two of Ri, R2 and R3, can optionally be linked together so as to form, together with the other atoms to which they are linked, a heterocyclic group containing from 2 to 16 atoms, containing from 1 to 3 heteroatoms, preferably 2 heteroatoms, selected, for example, from oxygen, sulphur, nitrogen, silicon, phosphorus, selenium, preferably oxygen, nitrogen, said heterocyclic group being substituted with at least one hydroxyl group and optionally with at least one sulfonic group;when n is 1 and X represents a hydroxyl group:Ri, R2 and R3, identical or different from each other, represent a hydrogen atom; or they are selected from C1-C12 alkyl groups, preferably C1-C8, linear or branched, saturated or unsaturated, aryl groups, cycloalkyl groups, said alkyl, aryl and cycloalkyl groups being optionally substituted with at least one group selected from alkyl groups, hydroxyl groups, ether groups, ester groups, carbonyl groups; or, any two of Ri, R2 and R3, can optionally be linked together so as to form, together with the other atoms to which they are linked, a heterocyclic group containing from 2 to 16 carbon atoms, containing from 1 to 3 heteroatoms, preferably 2 heteroatoms, selected, for example, from oxygen, sulphur, nitrogen, silicon, phosphorus, selenium, preferably oxygen, nitrogen, said heterocyclic group being optionally substituted with at least one hydroxyl group and / or with at least one sulfonic group.

2. Photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) according to claim 1, wherein said at least one layer is the perovskite photoactive layer.

3. Photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) according to claim 1, wherein said at least one layer is a layer positioned above and / or below the perovskite photoactive layer, preferably it is a layer positioned above the perovskite photoactive layer.

4. Photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) according to claim 1, comprising:at least one layer positioned above and / or below the perovskite photoactive layer, preferably a layer positioned above the perovskite photoactive layer, comprising at least one compound having general formula (I); and a perovskite photoactive layer comprising at least one compound having general formula (I).

5. Photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) according to any one of the preceding claims, wherein said perovskite is selected from organometallic trihalides having general formula ABX3 wherein:A represents a monovalent organic cation such as, for example,methylammonium (CH3NH3+), formamidinium [CH(NH2)2+], n- butylammonium (C4H9NH3+), tetra-butylammonium (C16H36N+), guanidinium [NH2(NH2)2+], or combinations thereof; or A represents a monovalent inorganic cation such as, for example, caesium (Cs+), rubidium (Rb+), potassium (K+), lithium (Li+), sodium (Na+), copper (Cu+), silver (Ag+), or combinations thereof; or combinations of at least one monovalent organic cation and at least one monovalent inorganic cation;B represents a divalent metallic cation such as for example lead (Pb2+), tin (Sn2+), or combinations thereof;X represents a halide anion such as, for example, iodide (I ), chloride (Cl ), bromide (Br ), or combinations thereof.

6. Photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) according to any one of the preceding claims, wherein said perovskite is selected from: methylammonium lead iodide [CH3NH3PbI3], formamidinium lead iodide [CH(NH2)2PbI3], caesium lead iodide [CsPbI3], methylammonium formamidinium lead iodide [(CH3NH3)x(CH(NH2)2)1-xPbI3], caesium methylammonium lead iodide [Csx(CH3NH3)1-xPbI3], caesium formamidinium lead iodide [Csx(CH(NH2)2)1-xPbI3], caesium methylammonium formamidinium lead iodide [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbI3], methylammonium lead bromide [CH3NH3PbBr3], formamidinium lead bromide [CH(NH2)2PbBr3], caesium lead bromide [CsPbBr3], methylammonium formamidinium lead bromide [(CH3NH3)x(CH(NH2)2)1-xPbBr3], caesium methylammonium lead bromide [Csx(CH3NH3)1-xPbBr3], caesium formamidinium lead bromide [Csx(CH(NH2)2)1-xPbBr3], caesium methylammonium formamidinium lead bromide [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbBr3], methylammonium lead chloride [CH3NH3PbCl3], formamidinium lead chloride [CH(NH2)2PbCl3], caesium lead chloride [CsPbCl3], methylammonium formamidinium lead chloride [(CH3NH3)x(CH(NH2)2)1-xPbCl3], caesium methylammonium lead chloride [Csx(CH3NH3)1-xPbCl3], caesium formamidinium lead chloride [Csx(CH(NH2)2)1-xPbCl3], caesium methylammonium formamidinium lead chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbCl3], methylammonium lead iodide bromide [CH3NH3PbI3-wBrw], formamidinium lead iodide bromide [CH(NH2)2Pbl3-wBrw], cesium lead iodidebromide [CsPbI3-wBrw], methylammonium formamidinium lead chloride bromide [(CH3NH3)x(CH(NH2)2)1-xPbI3-wBrw],caesium methylammonium lead iodide bromide [Csx(CH3NH3)1-xPbI3-wBrw], caesium formamidinium lead iodide bromide [Csx(CH(NH2)2)1-xPbI3-wBrw], caesium methylammonium formamidinium lead iodide bromide [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbI3-wBrw], methylammonium lead iodide chloride [CH3NH3PbI3-wClw], formamidinium lead iodide chloride [CH(NH2)2Pbl3-wClw], caesium lead iodide chloride [CsPbl3-wClw], methylammonium formamidinium lead iodide chloride [(CH3NH3)x(CH(NH2)2)1-xPbI3-wClw], caesium methylammonium lead iodide chloride [Csx(CH3NH3)i-xPbl3-wClw], caesium formamidinium lead iodide chloride [Csx(CH(NH2)2)1-xPbI3-wClw], caesium methylammonium formamidinium lead iodide chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbI3-wClw], methylammonium lead bromide chloride [CH3NH3PbBr3-wClw], formamidinium lead bromide chloride [CH(NH2)2PbBr3-wClw], caesium lead bromide chloride [CsPbBr3-wClw], methylammonium formamidinium lead bromide chloride [(CH3NH3)x(CH(NH2)2)1-xPbBr3-wClw], caesium methylammonium lead bromide chloride [Csx(CH3NH3)1-xPbBr3-wClw], caesium formamidinium lead bromide chloride [Csx(CH(NH2)2)1-xPbBr3-wClw], caesium methylammonium formamidinium lead bromide chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbBr3-wClw], methylammonium lead iodide bromide chloride [CH3NH3PbI3-w-vBrwClv], formamidinium lead iodide bromide chloride [CH(NH2)2Pbl3-w-vBrwClv], caesium lead iodide bromide chloride [CsPbI3-w-vBrwClv], methylammonium formamidinium lead iodide bromide chloride [(CH3NH3)x(CH(NH2)2)1-xPbI3-w-vBrwClv], caesium methylammonium lead iodide bromide chloride [Csx(CH3NH3)1-xPbI3-w-vBrwClv], cesium formamidinium lead iodide bromide chloride [Csx(CH(NH2)2)1-xPbI3-w-vBrwClv], caesium methylammonium formamidinium lead iodide bromide chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbI3-w-vBrwClv], methylammonium tin iodide [CH3NH3SnI3] formamidinium tin iodide [CH(NH2)2SnI3], caesium tin iodide [CsSnI3], methylammonium formamidinium tin iodide [(CH3NH3)x(CH(NH2)2)1-xSnI3], caesium methylammonium tin iodide [Csx(CH3NH3)1-xSnI3], caesium formamidinium tin iodide [Csx(CH(NH2)2)1-xSnI3], caesium methylammoniumformamidinium tin iodide [(CsxCH3NH3)y(CH(NH2)2)i- -ySnl3], methylammonium tin bromide [CH3NH3SnBr3], formamidinium tin bromide [CH(NH2)2SnBr3], caesium tin bromide [CsSnBr3], methylammonium formamidinium tin bromide [(CH3NH3)x(CH(NH2)2)1-xSnBr3], caesium methylammonium tin bromide [Csx(CH3NH3)1-xSnBr3], caesium formamidinium tin bromide [Csx(CH(NH2)2)1-xSnBr3], caesium methylammonium formamidinium tin bromide [(CsxCH3NH3)y(CH(NH2)2)1-x-ySnBr3], methylammonium tin chloride [CH3NH3SnCl3], formamidinium tin chloride [CH(NH2)2SnCl3], caesium tin chloride [CsSnCl3], methylammonium formamidinium tin chloride [(CH3NH3)x(CH(NH2)2)1-xSnCl3], caesium methylammonium tin chloride [Csx(CH3NH3)1-xSnCl3], caesium formamidinium tin chloride [Csx(CH(NH2)2)1-xSnCl3], caesium methylammonium formamidinium tin chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-ySnCl3], methylammonium tin iodide bromide [CH3NH3SnI3-wBrw], formamidinium tin iodide bromide [CH(NH2)2Snl3-wBrw], caesium tin iodide bromide [CsSnl3-wBrw], methylammonium formamidinium tin iodide bromide [(CH3NH3)x(CH(NH2)2)1-xSnI3-wBrw], caesium methylammonium tin iodide bromide [Csx(CH3NH3)1-xSnI3-wBrw], caesium formamidinium tin iodide bromide [Csx(CH(NH2)2)1-xSnI3-wBrw], caesium methylammonium formamidinium tin iodide bromide [(CsxCH3NH3)y(CH(NH2)2)1-x-ySnI3-wBrw], methylammonium tin iodide chloride [CH3NH3SnI3-wClw], formamidinium tin iodide chloride [CH(NH2)2Snl3-wClw], caesium tin iodide chloride [CsSnl3-wClw], methylammonium formamidinium tin iodide chloride [(CH3NH3)x(CH(NH2)2)1-xSnI3-wClw], caesium methylammonium tin iodide chloride [Csx(CH3NH3)1-xSnI3-wClw], caesium formamidinium tin iodide chloride [Csx(CH(NH2)2)1-xSnI3-wClw], caesium methylammonium formamidinium tin iodide chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-ySnI3-wClw], methylammonium tin bromide chloride [CH3NH3SnBr3-wClw], formamidinium tin bromide chloride [CH(NH2)2SnBr3-wClw], caesium tin bromide chloride [CsSnBr3-wClw], methylammonium formamidinium tin bromide chloride [(CH3NH3)x(CH(NH2)2)1-xSnBr3-wClw], caesium methylammonium tin bromide chloride [Csx(CH3NH3)1-xSnBr3-wClw], caesium formamidinium tin bromide chloride [Csx(CH(NH2)2)1-xSnBr3-wClw], caesium methylammoniumformamidinium tin bromide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-ySnBr3-wClw], methylammonium tin iodide bromide chloride [CH3NH3SnI3-w-vBrwClv], formamidinium tin iodide bromide chloride [CH(NH2)2Snl3-w-vBrwClv], caesium tin iodide bromide chloride [CsSnl3-w-vBrwClv], methylammonium formamidinium tin iodide bromide chloride [(CH3NH3)x(CH(NH2)2)i- Snl3-w-vBrwClv], caesium methylammonium tin iodide bromide chloride [Csx(CH3NH3)1-xSnI3-w-vBrwClv], caesium formamidinium tin iodide bromide chloride [Csx(CH(NH2)2)1-xSnI3-w-vBrwClv], caesium methylammonium formamidinium tin iodide bromide chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-ySnI3-w-vBrwClv], wherein in the case where only the index x is present, x is comprised between 0.01 and 0.99, in the case where the indices x and y are present, the sum of x+y is comprised between 0.01 and 0.99 with x and y different from 0, in case where only index w is present, w is comprised between 0.01 and 2.99, in case where the indices w and v are present, the sum of w+v is comprised between 0.01 and 2.99 with w and v different from 0; preferably, between: methylammonium lead iodide [CH3NH3PbI3], formamidinium lead iodide [CH(NH2)2PbI3], caesium lead iodide [CsPbI3], methylammonium formamidinium lead iodide [(CH3NH3)x(CH(NH2)2)1-xPbI3], caesium methylammonium lead iodide [Csx(CH3NH3)1-xPbI3], caesium formamidinium lead iodide [Csx(CH(NH2)2)1-xPbI3], caesium methylammonium formamidinium lead iodide [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbI3], methylammonium lead iodide bromide [CH3NH3PbI3-wBrw], formamidinium lead iodide bromide [CH(NH2)2Pbl3-wBrw], caesium lead iodide bromide [CsPbI3-wBrw], methylammonium formamidinium lead iodide bromide [(CH3NH3)x(CH(NH2)2)1-xPbI3-wBrw], caesium methylammonium lead iodide bromide [Csx(CH3NH3)1-xPbI3-wBrw], caesium formamidinium lead iodide bromide [Csx(CH(NH2)2)1-xPbI3-wBrw], caesium methylammonium formamidinium lead iodide bromide [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbI3-wBrw]; even more preferably between: caesium methylammonium lead iodide bromide [Csx(CH3NH3)1-xPbI3-wBrw], caesium formamidinium lead iodide bromide [Csx(CH(NH2)2)1-xPbI3-wBrw], caesium methylammonium formamidinium lead iodide bromide [(CsxCH3NH3)y(CH(NH2)2)1-x-yPbI3-wBrw].

7. Photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) according to any one of the preceding claims, wherein said perovskite is selected from perovskites having a band gap value comprised between 1.60 eV and 1.78 eV, preferably comprised between 1.65 eV and 1.72 eV.

8. Photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) according to any one of the preceding claims, wherein said at least one compound having general formula (I) is present in the perovskite photoactive layer in an amount comprised between 0.01 millimoles and 5 millimoles, preferably comprised between 0.02 millimoles and 2 millimoles, with respect to the millimoles of lead.

9. Photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) according to any one of the preceding claims, wherein said at least one compound having general formula (I) is present in the solution used in the surface treatment in order to obtain the layer positioned above and / or below the perovskite photoactive layer, in concentration comprised between 0.01 millimoles / litre and 100 millimoles / litre, preferably comprised between 0.1 millimoles / litre and 20 millimoles / litre.

10. Photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) according to any one of the preceding claims, comprising:a glass substrate covered with at least one layer of transparent and conductive oxide (" Transparent Conductive Oxide" - TCO), said oxide being preferably selected from fluorine doped tin oxide (SnO2: F) (" Fluorinedoped Tin Oxide" - FTO), indium tin oxide (" Indium Tin Oxide" - ITO), aluminium zinc oxide (AZO), indium zinc oxide (" Indium Zinc Oxide" IZO), hydrogenated indium oxide (" Hydrogenated Indium Oxide - IO: H), which constitutes the anode;at least one layer based on a hole transport material (" Hole Transport Layer" - HTL), said material being preferably selected from (2-(3,6-dimethoxy-9H- carbazol-9-yl)ethyl phosphonic acid (MeO-2PACz)], 2-(9H-carbazol-9- yl)ethyl phosphonic acid (2PACz), nickel oxide (NiOx), copper sulfocyanide (CuSCN), copper iodide (Cui), copper oxide (CuOx), copper sulphide (CuS), or a combination of layers of the aforementioned materials;optionally at least one layer based on a material useful for improving wettability, preferably a layer of nanoparticles of aluminium oxide (n- AI2O3);optionally, at least one layer comprising at least one compound having general formula (I);a photoactive layer comprising at least one perovskite preferably selected from caesium methylammonium lead iodide bromide [Cs0,05(CH3NH3)0,95PbI2,55Br0,45], caesium formamidinium lead iodide bromide [Cs0.17FA0.83PbI2.79Br0.3], more preferably caesium methylammonium lead iodide bromide [Cs0,05(CH3NH3)0,95PbI2,55Br0,45], and, optionally, at least one compound having general formula (I); optionally, at least one layer comprising at least one compound having general formula (I);at least one layer based on an electron transport material (" Electron Transport Layer" - ETL), said material being preferably selected from methyl ester of the [6,6]-phenyl-C61-butyric acid (PC61BM), fullerene (C60), tin oxide (SnOx), polyethyleneimine (PEI), ethoxylated polyethyleneimine (PEIE), or a combination of layers of the aforementioned materials; optionally, at least one layer based on a hole blocking material (" Hole Blocking Layer" - HBL), preferably 2, 9-dimethyl-4, 7 -diphenyl- 1,10- phenanthroline (Batocuproine - BCP);a cathode consisting of:a metal contact known as back contact preferably a layer of gold, silver, or metallic aluminium; or,a layer of transparent and conductive oxide (" Transparent Conductive Oxide" - TCO) and metal grids.

11. Photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) according to any one of the preceding claims, wherein the electric energy generated by said at least one perovskite-based photovoltaic cell (" Perovskite Solar Cell" - PSC) is transported using a wiring system which is connected with said perovskite-based photovoltaic cell (or solar cell).

12. Tandem perovskite / silicon photovoltaic cell (or solar cell) comprising:a silicon photovoltaic cell (or solar cell);a photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) comprising at least one layer comprising at least one compound having general formula (I) according to any one of the preceding claims, disposed above said silicon photovoltaic cell (or solar cell).

13. Tandem perovskite / silicon photovoltaic cell (or solar cell) according to claim 12, wherein the electric energy generated by said tandem perovskite / silicon photovoltaic cell (or solar cell) is transported using a wiring system which is connected with said tandem perovskite / silicon photovoltaic cell (or solar cell).

14. Use of a photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) according to any one of claims 1 to 11, or of a tandem perovskite / silicon photovoltaic cell (or solar cell) according to claim 12 or 13 in: photovoltaic fields (or photovoltaic parks), residential use, commercial buildings.

15. Composition comprising at least one perovskite according to any one of claims 5 to 7, and at least one compound having general formula (I) according to claim 1.

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