Perovskite based photovoltaic cells and process for the preparation thereof

Abstract

Perovskite-based photovoltaic cell (or solar cell) comprising at least one layer comprising: at least one compound having general formula (I): (I) wherein: R represents a hydrogen atom; or is selected from C1-C30, preferably C1-C12, linear or branched, saturated or unsaturated, alkyl groups, optionally containing heteroatoms; optionally substituted aryl groups; optionally substituted heteroaryl groups; optionally substituted cycloalkyl groups; optionally substituted heterocyclic groups; R1 represents a hydrogen atom; or is selected from C1-C12, preferably C1-C8, linear or branched, saturated or unsaturated, alkyl groups, optionally containing heteroatoms; optionally substituted aryl groups; optionally substituted heteroaryl groups; optionally substituted cycloalkyl groups; optionally substituted heterocyclic groups; R2 is selected from divalent C1-C12, preferably C1-C8, linear or branched, saturated or unsaturated, alkylene groups; optionally substituted arylene groups; optionally substituted heteroarylene groups; optionally substituted cycloalkylene groups; optionally substituted divalent heterocyclic groups; a and b, identical or different from each other, are 0 or 1; T represents a group having general formula (II) or (III): -SO3+X" (II) -SO4+X" (III) wherein: X represents a hydrogen atom; or represents a monovalent metal such as, for example, lithium, sodium, potassium, rubidium, caesium, copper, silver, preferably sodium, potassium, caesium; or represents an ammonium ion having general formula (IV): (IV) wherein: R3, R4 and R5, identical or different from each other, represent a hydrogen atom; or are selected from C1-C12, preferably C1-C8, linear or branched, saturated or unsaturated, alkyl groups, optionally halogenated; optionally substituted aryl groups; or, at least one compound having general formula (V): (V) wherein: m is a fractional number comprised between 0 and 0.5, preferably comprised between 0 and 0.3; p is an integer comprised between 10 and 5000, preferably comprised between 15 and 2000; Y represents a group having general formula (VI): (VI) wherein R1, R2, and T, have the same meanings reported above; or Y represents a group having general formula (VII): (VII) wherein R6 represents a group having general formula (I) provided that R is different from hydrogen. Said perovskite-based photovoltaic cell (or solar cell) ("Perovskite Solar Cell" - PSC) can be part of a tandem perovskite / silicon photovoltaic cell (or solar cell). Said perovskite-based photovoltaic cell (or solar cell) ("Perovskite Solar Cell" - PSC) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be advantageously used in various applications that require the production of electric energy by exploiting light energy, in particular the energy of solar radiation, such as, for example: photovoltaic fields (or photovoltaic parks), residential use, commercial buildings. Said perovskite-based photovoltaic cell (or solar cell) ("Perovskite Solar Cell" - PSC) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be used both in stand-alone mode and in modular systems.

Description

[0001] PEROVSKITE BASED PHOTOVOLTAIC CELLS AND PROCESS FOR THE PREPARATION THEREOF

[0002] The present invention relates to perovskite-based photovoltaic cells (or solar cells).

[0003] More in particular, the present invention relates to a perovskite-based photovoltaic cell (or solar cell) comprising at least one layer comprising at least one compound having the specific general formula (I) or (V) reported below.

[0004] Said perovskite-based photovoltaic cell (or solar cell) (" Perovskite Solar Cell" - PSC) can be part of a tandem perovskite / silicon photovoltaic cell (or solar cell). Said perovskite-based photovoltaic cell (or solar cell) (" Perovskite Solar Cell" - PSC) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be advantageously used in various applications that require the production of electric energy by exploiting light energy, in particular the energy of solar radiation, such as, for example: photovoltaic fields (or photovoltaic parks), residential use, commercial buildings. Said perovskite-based photovoltaic cell (or solar cell) (" Perovskite Solar Cell" - PSC) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be used both in stand-alone mode and in modular systems.

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

[0006] A further object of the present invention is a process for the preparation of said perovskite-based photovoltaic cell (or solar cell).

[0007] A further object of the present invention is also a composition comprising at least one perovskite and at least one compound having the specific general formula (I) or (V) reported below.

[0008] Photovoltaic cells (or solar cells) are devices capable of converting the energy of a light radiation into electric energy. At present, most photovoltaic cells (or solar cells) that can be used for practical applications exploit the chemicalphysical properties of inorganic-type photoactive materials, more in particular both crystalline and amorphous silicon, most particularly high-purity crystallinesilicon.

[0009] Over the last decade, various new technologies related to photovoltaic cells (or solar cells) have attracted the attention of several research groups around the world with the aim of improving the characteristics of silicon-based photovoltaic cells (or solar cells) such as, for example, access to new fields of application, improved efficiencies and possibly lower production costs.

[0010] In particular, perovskite-based photovoltaic cells (or solar cells) (" Perovskite Solar Cells" - PSCs) have rapidly become, in recent years, a promising alternative as they combine a high power conversion efficiency [" Power Conversion Efficiency" - (PCE)], which has currently reached a certified value higher than 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, light weight, flexibility and the simplicity of the manufacturing process which, starting from appropriate mixtures of the various precursors, can make it possible to produce photovoltaic cells (or solar cells) by means of well-known and established printing processes (including continuous printing) under mild conditions and at a sustainable cost. Furthermore, in recent years it has been demonstrated that particular perovskite-based photovoltaic cells (or solar cells) (" Perovskite Solar Cells" - PSCs) can exploit solar radiation not absorbed by the photovoltaic cells (or solar cells) based on silicon and therefore, once appropriately coupled with silicon-based photovoltaic cells (or solar cells), 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.

[0011] However, perovskite-based photovoltaic cells (or solar cells) (" Perovskite Solar Cells" - " PSCs") can also have certain structural drawbacks which can also affect the macroscopic behaviour of said perovskite-based photovoltaic cells (or solar cells) (" Perovskite Solar Cells" - PSCs), such as, for example, a relatively high density of defects (for example, crystallinity defects, ion vacancies, etc.) both within the perovskite photoactive layer ("bulk") and at the edges of the crystalline grains, and on the surface of said perovskite photoactive layer. Indeed, material interfaces represent an area of discontinuity in the perovskite-based photovoltaiccell (or solar cell) (" Perovskite Solar Cell" - PSC), and are the cause of the greatest gap between the theoretical performance of perovskite-based photovoltaic cells (or solar cells) (" Perovskite Solar Cells" - PSCs) (without any loss due to corollary phenomena) and the actual performance due to the high electron-hole recombination rate at the interface. More precisely, said defects reduce the overall efficiency of perovskite-based photovoltaic cells (or solar cells) (" Perovskite Solar Cells" - PSCs) and also facilitate the beginning of degradation phenomena too.

[0012] In order to fill the aforesaid gap, research is focusing on the use of agents capable of passivating defects commonly present both on the surface (by surface treatment) and within the photoactive layer of perovskite (by "in 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, several compounds containing various functional groups capable of interacting through more or less strong bonds, with the perovskite surface were used as passivating agents. Common passivating agents include, for example, certain fullerene derivatives, transition metal salts, alkali earth metal salts and lanthanide salts, urea, propylene carbonate, hexafluoroisopropanol, nitrogen-doped reduced graphene oxide, tris(pentafluorophenyl)phosphine, trioctylphosphinoxide, tribenzylphosphinoxide, acetic acid, conjugated molecules with donour-7t bridgeacceptor structure, conjugated molecules with rhodanine groups, thiophene, pyridine, mercaptopyridine, benzylamine, lead sulphate, pentaerythritol tetrakis(3-mercaptopropionate), butanethiol, phenylethylammonium iodide, phenylethylammonium chloride, butylammonium iodide, octylammonium iodide, octyldiammonium iodide, benzyl ammonium 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,pentafluorophenyl ammonium iodide, 2-(4-fluorophenyl)ethylammonium iodide. The 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) is an amine group, the functional group (B) is a carboxyl group and the functional group (C) is 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 aldehyde group, an aromatic group, a cyano group and a sulphonate group. The aforesaid 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, butanethiol, are compounds having a high vapour pressure and a relatively low boiling point (well below 200°C). Since during the manufacturing process of perovskite-based photovoltaic cells (or solar cells) (" 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 available non-volatile compounds or compounds with a boiling or sublimation temperature significantly higher than that to which the perovskitebased photovoltaic cells (or solar cells) (" 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 set forth above, it is clear that it is important to find other compounds capable of being used as passivating agents both within the photoactive layer of perovskite (by "in bulk" treatment) and on its surface (by surface treatment), which would make it possible to obtain perovskite-basedphotovoltaic cells (or solar cells) (" Perovskite Solar Cells" - PSC) capable of having a good power conversion efficiency [" Power Conversion Efficiency" -(PCE)], as well as a process for their construction suitable to be used in the "scaling up" stage for the construction of large-area photovoltaic cells (or solar cells).

[0015] The Applicant therefore set itself the problem of finding a perovskite-based photovoltaic cell (or solar cell) capable of having a good power conversion efficiency [" Power Conversion Efficiency" - (PCE)], as well as a process for its construction suitable to be used in the "scaling up" stage for the construction of large-area photovoltaic cells (or solar cells).

[0016] The Applicant has now found a perovskite-based photovoltaic cell (or solar cell) which comprises at least one layer comprising at least one compound having the specific general formula (I) or (V) reported below, capable of having a good power conversion efficiency [" Power Conversion Efficiency" - (PCE)] (i.e. PCE > 16%), as well as a process for its construction that involves the deposition of the photoactive layer of perovskite, in an uncontrolled atmosphere, in the presence of air. Said process is, therefore, suitable to be used in the "scaling up" phase for the construction of large-area photovoltaic cells (or solar cells). In addition, said perovskite-based photovoltaic cell (or solar cell) is able to maintain good photoelectric properties, i.e. good values of FF (" Fill Factor"), Voc (" Open Circuit Voltage"), Jsc ("short-circuit photocurrent density"). Said perovskite-based photovoltaic cell (or solar cell) can be part of a tandem perovskite / silicon photovoltaic cell (or solar cell). Said perovskite-based photovoltaic cell (or solar cell) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be advantageously used in various applications that require the production of electricity harnessing light energy, especially solar radiation energy such as, for example: building integrated photovoltaic (BIPV) systems; photovoltaic windows; greenhouses; photo-bioreactors; noise barriers; lighting; design; advertising; automotive industry. Said perovskite-based photovoltaic cell (or solar cell) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be used both in stand-alone mode and in modular systems.

[0017] Therefore, the object of the present invention is a perovskite-basedphotovoltaic cell (or solar cell) comprising:

[0018] at least one compound having general formula (I):

[0019]

[0020] wherein:

[0021] R represents a hydrogen atom; or is selected from C1-C30, preferably C1-C12, linear or branched, saturated or unsaturated, alkyl groups, optionally containing heteroatoms; optionally substituted aryl groups, optionally substituted heteroaryl groups; optionally substituted cycloalkyl groups; optionally substituted heterocyclic groups;

[0022] Ri represents a hydrogen atom; or is selected from C1-C12, preferably Ci-Cs, linear or branched, saturated or unsaturated, alkyl groups, optionally containing heteroatoms; optionally substituted aryl groups; optionally substituted heteroaryl groups; optionally substituted cycloalkyl groups; optionally substituted heterocyclic groups;

[0023] R2 is selected from divalent C1-C12 alkylene groups, preferably Ci-Cs, linear or branched, saturated or unsaturated; optionally substituted arylene groups; optionally substituted heteroarylene groups; optionally substituted cycloalkylene groups; optionally substituted divalent heterocyclic groups;

[0024] a and b, identical or different from each other, are 0 or 1;

[0025] T represents a group having general formula (II) or (III):

[0026] -SO3-X+(II)

[0027] -SO4-X+(III)

[0028] wherein:

[0029] X represents a hydrogen atom; or represents a monovalent metal such as, for example, lithium, sodium, potassium, rubidium, caesium, copper, silver, preferably sodium, potassium, caesium;or represents an ammonium ion having general formula (IV):

[0030] R3

[0031] H— N— R4(IV)

[0032]

[0033] R5

[0034] wherein:

[0035] R3, R4 and R5, identical or different from each other, represent a hydrogen atom; or are selected from C1-C12, preferably Ci-Cs, linear or branched, saturated or unsaturated, alkyl groups, optionally halogenated; optionally substituted aryl groups;

[0036] or, at least one compound having general formula (V):

[0037]

[0038] wherein:

[0039] m is a fractional number comprised between 0 and 0.5, preferably comprised between 0 and 0.3;

[0040] p is an integer comprised between 10 and 5000, preferably comprised between 15 and 2000;

[0041] Y represents a group having general formula (VI):

[0042] o

[0043] (VI)

[0044]

[0045] Ri

[0046] wherein Ri, R2, and T, have the same meanings reported above; or Y represents a group having general formula (VII):

[0047] o

[0048] JI A

[0049]

[0050] (VII)wherein Re represents a group having general formula (I) provided that R is different from hydrogen.

[0051] For the purpose of the present description and of the following claims, the definitions of the number ranges always include the extremes if not otherwise indicated.

[0052] 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.

[0053] In accordance with a preferred embodiment of the present invention, said at least one layer is the perovskite photoactive layer.

[0054] In accordance with a further preferred embodiment of the present invention, said at least one layer is a layer placed above and / or below the perovskite photoactive layer, preferably is a layer placed above the perovskite photoactive layer.

[0055] In accordance with a further preferred embodiment of the present invention, said perovskite-based photovoltaic cell (or solar cell) (" Perovskite Solar Cell" -PSC) comprises:

[0056] at least one layer placed 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) or (V); and a perovskite photoactive layer comprising at least one compound having general formula (I) or (V).

[0057] 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:

[0058] A represents a monovalent organic cation such as, for example, methylammonium (CH3NH3+), formamidinium [CH(NH2)2+],

[0059]

[0060] 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 monovalentorganic cation and at least one monovalent inorganic cation;

[0061] B represents a divalent metallic cation such as, for example, lead (Pb2+), tin (Sn2+), or combinations thereof;

[0062] X represents a halide anion such as, for example, iodide (I"), chloride (Cl’), bromide (Br‘), or combinations thereof.

[0063] In accordance with a further preferred embodiment of the present invention, said perovskite may be selected, for example, from: methylammonium lead iodide [CHsNthPbh], 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(lS[H2)2)i-x-yPbl3], methylammonium lead bromide [CHaNHaPbB^], formamidinium lead bromide [CHlNBL^PbBn], caesium lead bromide [CsPbBn], methylammonium formamidinium lead bromide [(CH3NH3)x(CH(NH2)2)i-xPbBr3], caesium methylammonium lead bromide [Csx(CH3NH3)i-xPbBr3], caesium formamidinium lead bromide [CSX(CH(NH2)2)I-xPbBr3], caesium methylammonium formamidinium lead bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbBr3], methylammonium lead chloride [CHsNEhPbCh], formamidinium lead chloride [CH(NH2)2PbCh], caesium lead chloride [CsPbCh], methylammonium formamidinium lead chloride [(CHaNHa (CH(NH2)2)i-xPbC13], caesium methylammonium lead chloride [CSX(CH3NH3)I-xPbCh], caesium formamidinium lead chloride [Csx(CH(NH2)2)i-xPbC13], caesium methylammonium formamidinium lead chloride [(CS CH3NH )V(CH(NH2)2)I-X-yPbCh], methylammonium lead iodide bromide [CH3NH3PbI3-wBrw], formamidinium lead iodide bromide [CH(NH2)2PbI3-wBrw], caesium lead iodide bromide [CsPbI3-wBrw], methylammonium formamidinium lead iodide bromide [(CH3NH3)x(CH(NH2)2)i-xPbl3-wBrw], caesium methylammonium lead iodide bromide [Csx(CH3NH3)1-xPbI3-wBrw], caesium formamidinium lead iodide bromide [Cs (CH(NH2)2)i-xPbl3-wBrw], caesium methylammonium formamidinium lead iodide bromide [(Cs CH3NH3)y(CH(NH2)2)i-XxvPbl3-wBrw], methylammonium lead iodide chloride [CftNHaPbh-wClw], formamidinium leadiodide chloride [CH(NH2)2Pbl3-wClw], caesium lead iodide chloride [CsPbh-wClw], methylammonium formamidinium lead iodide chloride [(CH3NH3)x(CH(NH2)2)i-xPbl3-wClw], caesium methylammonium lead iodide chloride [Csx(CH3NH3)i-xPbl3-wClw], caesium formamidinium lead iodide chloride [Csx(CH(NH2)2)i-xPbl3-wClw], caesium methylammonium formamidinium lead iodide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-wClw], methylammonium lead bromide chloride [CH3NH3PbBr3-wClw], formamidinium lead bromide chloride [CH(NH2)2PbBr3-wClw], caesium lead bromide chloride [CsPbBn-wClw], methylammonium formamidinium lead bromide chloride [(CHaNHa (CH(NH2)2)i-xPbBr3-wClw], caesium methylammonium lead bromide chloride [Csx(CH3NH3)i-xPbBr3-wClw], caesium formamidinium lead bromide chloride [Csx(CH(NH2)2)i-xPbBr3-wClw], caesium methylammonium formamidinium lead bromide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbBr3-wClw], methylammonium lead iodide bromide chloride [CftNHaPbh-w-vBrwClv], formamidinium lead iodide bromide chloride [CH(NH2)2Pbl3-w-vBrwClv], caesium lead iodide bromide chloride [CsPbl3-w-vBrwClv], methylammonium formamidinium lead iodide bromide chloride [(CH3NH3)x(CH(NH2)2)i-xPbl3-w-vBrwClv], caesium methylammonium lead iodide bromide chloride [Csx(CH3NH3)i-xPbl3-w-vBrwClv], caesium formamidinium lead iodide bromide chloride [Csx(CH(NH2)2)i-xPbl3-w-vBrwClv], caesium methylammonium formamidinium lead iodide bromide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-w-vBrwClv], methylammonium tin iodide [CH NHaSnB], formamidinium lead iodide [CH(NH2)2Snl3], caesium tin iodide [CsSnh], methylammonium formamidinium tin iodide [(CH3NH3)x(CH(NH2)2)i-xSnl3], caesium methylammonium tin iodide [Csx(CH3NH3)i-xSnl3], caesium formamidinium tin iodide [Csx(CH(NH2)2)i-xSnl3], caesium methylammonium formamidinium tin iodide [(CsxCH3NH3)y(CH(NH2)2)i-x-ySnl3], methylammonium tin bromide [CHaNHaSnB^], formamidinium tin bromide [CHlNBL^SnBn], caesium tin bromide [CsSnBn], methylammonium formamidinium tin bromide [(CH3NH3)x(CH(NH2)2)i-xSnBr3], caesium methylammonium tin bromide [Csx(CH3NH3)i-xSnBr3], caesium formamidinium tin bromide [CSX(CH(NH2)2)I-xSnBr3], caesium methylammonium formamidinium tin bromide[(CsxCH3NH3)y(CH(NH2)2)1-x-ySnBr3], methylammonium tin chloride [CJbNEhSnCh], formamidinium tin chloride [CHlNJL^SnCh], caesium tin chloride [CsSnCh], methylammonium formamidinium tin chloride [(CH3NH3)x(CH(NH2)2)i-xSnC13], caesium methylammonium tin chloride [Csx(CH3NH3)i-xSnC13], 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)2SnI3-wBrw], caesium tin iodide bromide [CsSnI3-wBrw], methylammonium formamidinium tin iodide bromide [(CH3NH3)x(CH(NH2)2)1-xSnI3-wBrw], caesium methylammonium tin iodide bromide [Csx(CH3NH3)i-xSnl3-wBrw], caesium formamidinium lead 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)2SnI3-wClw], caesium tin iodide chloride [CsSnI3-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 methylammonium formamidinium tin bromide chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-ySnBr3-wClw], methylammonium tin iodide bromide chloride [CH3NH3SnI3-w-vBrwClv], formamidinium tin iodide bromide chloride [CH(NH2)2SnI3-w-vBrwClv], caesium tin iodide bromide chloride [CsSnI3-w-vBrwClv], methylammonium formamidinium tin iodide bromide chloride [(CH3NH3)x(CH(NH2)2)1-xSnI3-w-vBrwClv], caesium methylammonium tin iodide bromide chloride [Csx(CH3NH3)1-xSnI3-w-vBrwClv], caesium formamidinium tiniodide 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 e 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 being different from 0, in the case where only the index w is present, w is comprised between 0.01 and 2.99, in the 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 being different from 0. Preferably, 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)i-xPbl3], caesium methylammonium formamidinium lead iodide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3], methylammonium lead iodide bromide [CH3NH3PbI3-wBrw], formamidinium lead iodide bromide [CH(NH2)2PbI3-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)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)1-x-yPbI3-wBrw]; even more preferably between: formamidinium lead iodide [CH(NH2)2PbI3], 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].

[0064] In accordance with a further preferred embodiment of the present invention, said perovskite can be selected, for example from among the 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.

[0065] For the purpose of the present description and of the following claims, the terms " C1-C30 alkyl groups" and " C1-C12 alkyl groups" indicate alkyl groupshaving from 1 to 30 carbon atoms and alkyl groups having from 1 to 12 carbon atoms, respectively, linear or branched, saturated or unsaturated. Specific examples of C1-C30 and C1-C12 alkyl groups are: methyl, ethyl, w-propyl, iso-propyl, / / -butyl, zso-butyl, / c / V-butyl, pentyl, 2-ethyl-hexyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl.

[0066] For the purpose of the present description and of the following claims, the terms " C1-C30 alkyl groups optionally containing heteroatoms" and " C1-C12 alkyl groups optionally containing heteroatoms" indicate alkyl groups having from 1 to 30 carbon atoms and alkyl groups having from 1 to 12 carbon atoms, linear or branched, saturated or unsaturated, wherein at least one of the hydrogen atoms is substituted with a heteroatom selected from: halogens such as, for example, fluorine, chlorine, bromine, preferably fluorine; nitrogen; sulfur; oxygen. Specific examples of C1-C30 and C1-C12 alkyl groups optionally containing heteroatoms are: fluoromethyl, difluoromethyl, trifluoromethyl, trichloromethyl, 2,2,2-trifluoroethyl, 2,2,2-trichloroethyl, 2,2,3,3-tetrafluoropropyl, 2, 2, 3,3,3-pentafluoropropyl, perfluoropentyl, perfluoroctyl, perfluorodecyl, oxymethyl, oxyethyl, oxybutylthiomethyl, thioethyl, dimethylamino, propylamino, dioctylamino, methylthioether, ethylthioether, butylthioether, ethyl -2-methoxy, propyl-3 -ethoxy, butyl-2-thioethoxy, hexyl-4-amino, hexyl-3-7V,7V’-dimethylamino, methyl- / ' / , / ' / ’-dioctylamino, 2-methyl-hexyl-4-amino.

[0067] For the purpose of the present description and of the following claims, the term "optionally halogenated C1-C12 alkyl groups" indicates alkyl groups having from 1 to 12 carbon atoms, linear or branched, saturated or unsaturated, wherein at least one of the hydrogen atoms is substituted with a halogen atom such as, for example, fluorine, chlorine, bromine, preferably fluorine. Specific examples of optionally halogenated C1-C12 alkyl groups are: fluoromethyl, difluoromethyl, trifluoromethyl, trichloromethyl, 2,2,2-trifluoroethyl, 2,2,2-trichloroethyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, perfluoropentyl, perfluoroctyl.

[0068] For the purpose of the present description and of the following claims, the term "aryl groups" indicates aromatic carbocyclic groups containing from 6 to 60 carbon atoms. Said aryl groups can optionally be substituted with one or moregroups, identical or different from each other, selected from: halogen atoms such as, for example, fluorine, chlorine, bromine, preferably fluorine; hydroxyl groups; C1-C12 alkyl groups; C1-C12 alkoxyl groups C1-C12 thioalkoxyl groups; C3-C24 trialkylsilyl groups; polyethylene oxyl groups; cyano groups; amino groups; C1-C12 mono- or di-alkylamine groups; nitro groups. Specific examples of aryl groups are: phenyl, methylphenyl, trimethylphenyl, methoxyphenyl, hydroxyphenyl, phenyl oxy phenyl, fluorophenyl, pentafluorophenyl, chlorophenyl, bromophenyl, nitrophenyl, dimethylaminophenyl, naphthyl, phenylnaphthyl, phenanthrene, anthracene, phenoxy phenyl, 4-nitro-phenyl, 4-amino-phenyl, 3 -chloro-phenyl, trihy droxyphenyl.

[0069] For the purpose of the present description and of the following claims, the term "heteroaryl groups" indicates aromatic heterocyclic penta- or hexa-atomic groups, also benzo condensates or heterobicyclic, containing from 4 to 60 carbon atoms and from 1 to 4 heteroatoms selected from nitrogen, oxygen, sulfur, silicon, selenium, phosphorus. Said heteroaryl groups can optionally be substituted with one or more groups, identical or different from each other, selected from: halogen atoms such as, for example, fluorine, chlorine, bromine, preferably fluorine; hydroxyl groups; C1-C12 alkyl groups; C1-C12 alkoxyl groups; C1-C12 thioalkoxyl groups; C3-C24 tri-alkylsilyl groups; polyethyleneoxyl groups; cyano groups; amino groups; C1-C12 mono- or di-alkylamino groups; nitro groups. Specific examples of heteroaryl groups are: pyridine, methylpyridine, methoxypyridine, phenylpyridine, fluoropyridine, aminopyridine, pyrimidine, pyridazine, pyrazine, triazine, tetrazine, quinoline, quinoxaline, quinazoline, furan, thiophene, hexylthiophene, bromothiophene, dibromothiophene, pyrrole, oxazole, thiazole, isothiazole, oxadiazole, thiadiazole, pyrazole, imidazole, triazole, tetrazole, indole, benzofuran, benzothiophene, benzooxazole, benzothiazole, benzooxadiazole, benzothiadi azole, benzopyrazole, benzimidazole, benzotri azole, triazolopyridine, coumarin.

[0070] For the purpose of the present description and of the following claims, the term "cycloalkyl groups" indicates cycloalkyl groups having from 5 to 60 carbon atoms. Said cycloalkyl groups can optionally be substituted with one or more groups, identical or different from each other, selected from: halogen atoms suchas, for example, fluorine, chlorine, bromine, preferably fluorine; hydroxyl groups; C1-C12 alkyl groups; C1-C12 alkoxyl groups; C1-C12 thioalkoxyl groups; C3-C24 trialkylsilyl groups; polyethyleneoxyl groups; cyano groups; amino groups; C1-C12 mono- or di-alkylamino groups; nitro groups. Specific examples of cycloalkyl groups are: cyclopropyl, 2,2-difluorocyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, methylcyclohexyl, methoxycyclohexyl, fluorocyclohexyl, phenylcyclohexyl, decalin, norbomyl, abietyl.

[0071] For the purpose of the present description and of the following claims, the term "heterocyclic groups" indicates rings having from 3 to 12 atoms, saturated or unsaturated, containing at least one heteroatom selected from nitrogen, oxygen, sulfur, silicon, selenium, phosphorus, optionally condensed with other aromatic or non-aromatic rings. Said heterocyclic groups can optionally be substituted with one or more groups, identical or different from each other, selected from: halogen atoms such as, for example, fluorine, chlorine, bromine, preferably fluorine; hydroxyl groups; C1-C12 alkyl groups; C1-C12 alkoxyl groups; C1-C12 thioalkoxyl groups; C3-C24 tri-alkylsilyl groups; polyethyleneoxyl groups; cyano groups; amino groups; C1-C12 mono- or di-alkylamino groups; nitro groups. Specific examples of heterocyclic groups are: pyrrolidine, methoxypyrrolidine, piperidine, fluoropiperidine, methylpiperidine, dihydropyridine, piperazine, morpholine, thiazine, indoline, phenylindoline, 2-ketoazetidine, diketopiperazine, tetrahydrofuran, tetrahydrothiophene.

[0072] For the purpose of the present description and of the following claims, the term " C1-C12 alkylene groups" indicates divalent alkylene groups having from 1 to 12 carbon atoms, linear or branched, saturated or unsaturated. Said alkylene groups can optionally be substituted with one or more groups, identical or different from each other, selected from: halogen atoms such as, for example, fluorine, chlorine, bromine, preferably fluorine; hydroxyl groups; C1-C12 alkyl groups; Ci-C12 alkoxyl groups; C1-C12 thioalkoxyl groups; C3-C24 tri-alkylsilyl groups; polyethyleneoxyl groups; cyano groups; amino groups; C1-C12 mono- or di-alkylamino groups; nitro groups. Specific examples of C 1-C16 alkylene groups are: ethylene, w-propylene, / .w-propylene, n butylene, / .w-butylene, tert-butylene, pentylene, 2-ethyl-hexylene, hexylene, heptylene, octylene, nonylene, decylene,dodecylene, as well as the following groups represented as radicals:

[0073]

[0074] wherein the asterisks represent the nitrogen atom and the T group of the general formula (I) or of the general formula (VI).

[0075] For the purpose of the present description and of the following claims, the term "arylene groups" indicates aromatic carbocyclic groups containing from 6 to 16 carbon atoms. Said arylene groups can optionally be substituted with one or more groups, identical or different from each other, selected from: halogen atoms such as, for example, fluorine, chlorine, bromine, preferably fluorine; hydroxyl groups; C1-C12 alkyl groups; C1-C12 alkoxyl groups; C1-C12 thioalkoxyl groups; C3-C24 tri-alkylsilyl groups; polyethyleneoxyl groups; cyano groups; aminogroups; C1-C12 mono- or di-alkylamino groups; nitro groups. Specific examples of arylene groups are: phenylene, methylphenylene, trimethylphenylene, methoxyphenylene, hydroxyphenylene, phenyl oxy phenylene, dimethylaminophenylene, naphthylene, phenylnaphthylene, phenanthrenylene, anthracenylene, phenoxyphenylene, 4-aminophenylene, trihydroxyphenylene.

[0076] For the purpose of the present description and of the following claims, the term "cycloalkylene groups" indicates cycloalkylene groups having from 5 to 60 carbon atoms. Said cycloalkylene groups can optionally be substituted with one or more groups, identical or different from each other, selected from: halogen atoms such as, for example, fluorine, chlorine, bromine, preferably fluorine; hydroxyl groups; C1-C12 alkyl groups; C1-C12 alkoxyl groups; C1-C12 thioalkoxyl groups; C3-C24 tri-alkylsilyl groups; polyethyleneoxyl groups; cyano groups; amino groups; C1-C12 mono- or di-alkylamino groups; nitro groups. Specific examples of cycloalkylene groups are: cyclopropylene, 2,2-cyclobutylene, cyclopentylene, cyclohexylene, methylcyclohexylene.

[0077] For the purpose of the present description and of the following claims, the term "divalent heterocyclic groups" indicates rings having from 3 to 12 atoms, saturated or unsaturated, and two bonding positions, containing at least one heteroatom selected from nitrogen, oxygen, sulfur, silicon, selenium, phosphorus, optionally condensed with other aromatic or non-aromatic rings. Said heterocyclic groups can optionally be substituted with one or more groups, identical or different from each other, selected from: halogen atoms such as, for example, fluorine, chlorine, bromine, preferably fluorine; hydroxyl groups; C1-C12 alkyl groups; Ci-C12 alkoxyl groups; C1-C12 thioalkoxyl groups; C3-C24 tri-alkylsilyl groups; polyethyleneoxyl groups; cyano groups; amino groups; C1-C12 mono- or di-alkylamino groups; nitro groups. Specific examples of heterocyclic groups are: pyrrolidine, methoxypyrrolidine, piperidine, fluoropiperidine, methylpiperidine, dihydropyridine, piperazine, morpholine, thiazine, indoline, phenylindoline, 2-ketoazetidine, diketopiperazine, tetrahydrofuran, tetrahydrothiophene.

[0078] The aforesaid compounds having general formula (I) or (V) are known in the art and commercially available.Specific examples of compounds having the general formula (I) that are advantageously usable for the purpose of the present invention are reported in Table 1.

[0079]

[0080]

[0081] Specific examples of compounds having general formula (V) that are advantageously usable for the purpose of the present invention are reported in Table 2.

[0082]

[0083]

[0084]

[0085] In accordance with a preferred embodiment of the present invention, said at least one compound having general formula (I) or (V) can be present in the perovskite photoactive layer in an amount comprised between 0.005% by weight and 20% by weight, preferably comprised between 0.008% by weight and 10% by weight, more preferably comprised between 0.01% by weight and 5% by weight, with respect to the total weight of the perovskite precursors.

[0086] In accordance with a preferred embodiment of the present invention, said perovskite-based photovoltaic cell (or solar cell) comprises:

[0087] a glass substrate covered with a layer of transparent and conductive oxide (" Transparent Conductive Oxide" - TCO), commonly fluorine-doped tin oxide (SnO2: F) (" Fluorine-doped Tin Oxide" - FTO), or indium tin oxide (" Indium Tin Oxide" - ITO) which constitutes the anode;

[0088] at least one layer based on a hole transport material (" Hole Transport Layer" - HTL), said material being preferably selected from a layer of (2-(9H- carbazol-9-yl)ethyl phosphonic acid (2PACz), (2-(3,6-dimethoxy-9H- carbazol-9-yl)ethyl phosphonic acid (MeO-2PACz)], nickel oxide (NiOx), copper sulphocyanide (CuSCN), copper iodide (Cui), copper oxide (CuOx), copper sulphide (CuS), or a combination of layers of the aforesaid materials; optionally at least one layer based on a material useful for improving wettability, preferably a layer of nanoparticles of aluminium oxide (n-Al2O3);optionally, at least one layer comprising at least one compound having general formula (I) or (V);

[0089] at least one photoactive layer comprising at least one perovskite, preferably formamidinium lead iodide (NH2CHNH2PbI3) and, optionally, at least one compound having general formula (I) or (V), preferably a compound having general formula (I), even more preferably 2-acrylamido-2- methylpropanesulphonic acid;

[0090] optionally, at least one layer comprising at least one compound having general formula (I) or (V);

[0091] 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-C6i-butyric acid (PC61BM), fullerene (C60), tin oxide (SnOx), polyethyleneimine (PEI), ethoxylated polyethyleneimine (PEIE), or a combination of layers of the aforesaid materials; optionally, at least one layer based on a hole blocking material (" Hole Blocking Layer" - HBL), preferably a layer of 2,9-dimethyl-4,7-diphenyl- 1,10-phenanthroline (Bathocuproine - BCP);

[0092] a cathode consisting of:

[0093] a metal contact known as "back contact" preferably a layer of gold, silver, or metallic aluminium; or,

[0094] a layer of transparent and conductive oxide (" Transparent Conductive Oxide" - TCO) and metal grids.

[0095] It should be noted, in fact, that in case of tandem perovskite / silicon photovoltaic cells (or solar cells), in the perovskite-based photovoltaic cell (or solar cell) (" Perovskite Solar Cell" - PSC) the aforesaid metal contact known as "back contact" will be replaced by a layer of transparent and conductive oxide (" Transparent Conductive Oxide" - TCO) and metal grids constituting the cathode.

[0096] In accordance with a preferred embodiment of the present invention, the electric energy generated by said perovskite-based photovoltaic cell (or solar cell) can be transported using a wiring system which is connected with said perovskitebased photovoltaic cell (or solar cell).

[0097] As mentioned above, a further object of the present invention is a processfor the preparation of said perovskite-based photovoltaic cell (or solar cell). Accordingly, it is a further object of the present invention to provide a process for the preparation of a perovskite-based photovoltaic cell (or solar cell) comprising the following stages:

[0098] (a) preparing a glass substrate covered with a layer of transparent and conductive oxide (“Transparent Conductive Oxide” - TCO) (anode);

[0099] (b) depositing at least one layer based on a hole transport material (" Hole Transport Layer" - HTL) on the substrate obtained in said stage (a);

[0100] (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;

[0101] (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) or (V); (e) preparing a mixture comprising perovskite precursors and optionally at least one compound having general formula (I) or (V), preferably a compound having general formula (I);

[0102] (f) depositing the mixture obtained in said stage (e) 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), or on the layer comprising at least one compound having general formula (I) or (V) obtained in stage (d), obtaining a photoactive layer;

[0103] (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) or (V);

[0104] (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) or (V) obtained in said stage (g);

[0105] (i) optionally, depositing on the layer based on an electron transport material(" Electron Transport Layer" - ETL) obtained in said stage (h), at least one layer based on a hole blocking material (" Hole Blocking Layer" - HBL); (1) depositing a cathode consisting of a metal contact known as “back contact”, preferably a layer of gold, silver, or metallic aluminium; or, consisting of a layer of transparent and conductive oxide (" Transparent Conductive Oxide" - TCO) and metal grids;

[0106] wherein said stage (f) is carried out in an uncontrolled atmosphere, in the presence of air.

[0107] It should be noted, in fact, that in 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 stage (i), a transparent and conductive oxide (" Transparent Conductive Oxide" - TCO) layer and metal grids forming the cathode will be deposited.

[0108] For the purpose of the aforesaid process, said transparent and 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.

[0109] For the purpose of the aforesaid process, said mixture comprising perovskite precursors and optionally at least one compound having general formula (I) or (V), preferably a compound having general formula (I), comprises:

[0110] at least one halide selected from the halides of the monovalent organic cations or monovalent inorganic cations reported above, preferably iodides, chlorides, bromides, more preferably iodides [for example, formamidinium iodide (NH2CHNH2)I], and at least one halide selected from the halides of the bivalent metal cations reported above, preferably iodides, chlorides, bromides, more preferably iodides [for example, lead iodide (PbI2)] as perovskite precursors;optionally at least one compound having general formula (I) or (V), preferably a compound having general formula (I).

[0111] For the purpose of the aforesaid process, said stages (b), (c), (d), (e), (f), (g), (h) and (i) can be carried out according to deposition 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 differ depending on the layer considered.

[0112] For the purpose of the aforesaid 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”).

[0113] As mentioned above, said perovskite-based photovoltaic cell (or solar cell) can be part of a tandem perovskite / silicon photovoltaic cell (or solar cell).

[0114] Accordingly, a further object of the present invention is a tandem perovskite / silicon photovoltaic cell (or solar cell) comprising:

[0115] a silicon photovoltaic cell (or solar cell);

[0116] a perovskite-based photovoltaic cell (or solar cell) comprising at least one layer comprising at least one compound having general formula (I) or (V), placed above said silicon photovoltaic cell (or solar cell).

[0117] In accordance with a preferred embodiment of the present invention, the electric energy generated by said tandem perovskite / silicon photovoltaic cell (or solar cell) can be transported using a wiring system which is connected with said tandem perovskite / silicon photovoltaic cell (or solar cell).

[0118] As mentioned above, said perovskite-based photovoltaic cell (or solar cell) (" 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 electric energy harnessing light energy, especially the energy ofsolar radiation, such as, for example: photovoltaic fields (or photovoltaic parks), residential use, commercial buildings. Said perovskite-based photovoltaic cell (or solar cell) (" Perovskite Solar Cell" - PSC) and said tandem perovskite / silicon photovoltaic cell (or solar cell) can be used both in stand-alone mode and in modular systems.

[0119] Accordingly, it is a further object of the present invention, the use of said perovskite-based photovoltaic cell (or solar cell) (" Perovskite Solar Cell" - PSC) or of said tandem perovskite / silicon photovoltaic cell (or solar cell) in: photovoltaic fields (or photovoltaic parks) residential use, commercial buildings.

[0120] As mentioned above it is also a further object of the present invention a composition comprising at least one perovskite and at least one compound having general formula (I) or (V), preferably a compound having general formula (I).

[0121] Accordingly, it is a further object of the present invention a composition comprising at least one perovskite and at least one compound having general formula (I) or (V), preferably a compound having general formula (I).

[0122] Said at least one perovskite can be selected from those reported above. The present invention will now be illustrated in greater detail through an embodiment with reference to Figure 1 reported below.

[0123] In particular, Figure 1 represents a cross-sectional view of a perovskitebased photovoltaic cell (or solar cell) (1) comprising the following layers: a glass substrate (7) covered with a layer of transparent and conductive oxide (" Transparent Conductive Oxide" - TCO) (anode) [e.g., indium tin oxide (" Indium Tin Oxide" - ITO) or fluorine-doped tin oxide (SnO2: F) (" Fluorine-doped Tin Oxide" - FTO)] (2); a layer based on a hole transport material (" Hole Transport Layer" - HTL) [e.g., (2-9H-carbazol-9-yl)ethyl phosphonic acid (2PACz)] (3); optionally a layer based on a material useful for improving wettability, [e.g., aluminium oxide nanoparticles (n-Al2O3)] (not represented in Figure 1); optionally, a layer comprising at least one compound having general formula (I) or (V) (not represented in Figure 1); a photoactive layer comprising at least one perovskite [e.g., formamidinium lead iodide (NH2CHNH2PbI3)] and optionally at least one compound having general formula (I) or (V), preferably a compound having general formula (I) (e.g., 2-acrylamido-2-methylpropanesulphonic acid)(4); optionally a further layer comprising at least one compound having general formula (I) (not represented in Figure 1) deriving from the surface treatment; optionally, a layer comprising at least one compound having general formula (I) or (V) (not represented in Figure 1); a layer based on an electron transport material [" Electron Transport Layer" (ETL)][e.g., [6,6]-phenyl-C6i-butyric acid methyl ester (PC61BM)] (5a); a layer based on a hole blocking material (" Hole Blocking Layer" - HBL) [e.g., 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (Bathocuproine - BCP) or ethoxylated polyethyleneimine (PEIE)] (5b); a metal contact known as "back contact" constituting the cathode [e.g., a layer of gold, silver or metallic aluminium] (6).

[0124] In order to better understand the present invention and to put it into practice, some illustrative and non-limiting examples thereof are reported below.

[0125] 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 (invention)

[0126] Preparation of a perovskite-based solar cell

[0127] For this purpose, a perovskite-based solar cell was prepared on a glass substrate coated with ITO (" Indium Tin Oxide") (Kintec KT18086-1) and patterned (dimensions 15x15x1 mm; sheet resistance equal to 12 Q / 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 process in 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) / .w-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.

[0128] 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 phase.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-(9H-carbazol-9-yl)ethyl phosphonic acid (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 selfassembly monolayer with a thickness < 1 nm.

[0129] A material for improving the wettability was deposited on the substrate thus obtained. For this purpose, a solution of aluminium oxide nanoparticles (n-ALCL) (particle size < 50 nm - Merck) in Ao-propanol (purity 99.5% - Merck) at a concentration equal to 0.2 mg / ml was deposited, by spin coating operating at a rotation speed equal to 3000 rpm (acceleration equal to 1000 rpm / s), for 30 seconds and, subsequently, the whole was subjected to heat treatment (annealing), at 100°C, for 5 minutes.

[0130] On top of the layer based on a material for improving wettability, a layer of formamidinium lead iodide [CH(NH2)2PbI3] and 2-acrylamido-2-methylpropanesulphonic acid was deposited, operating as follows. For this purpose, in a first container, lead iodide (PbI2) (ultra dry purity 99.999% - Alfa Aesar) (461.0 mg - 1.0 mmol), formamidinium iodide (FAI) (NH2CHNH2I) (GreatCell Solar) (172.0 mg - 1.0 mmol) and methylammonium chloride (MAC1) (CH3NH3CI) - (Merck) (13.5 mg - 0.2 mmol) were dissolved in a mixture of N, N-dimethylformamide anhydrous (DMF) (purity 99.9% - Merck) (582.7 μl) and N-methyl-2-pyrrolidone anhydrous (NMP) (purity 99.8% - Merck) (96.3 μl), operating under stirring, at room temperature (25°C), for 1 hour.

[0131] In a second container, 2-acrylamido-2-methylpropanesulphonic acid (purity 99% - Merck) (10 mg - 0.04 mmol) was dissolved in

[0132]

[0133] -di methyl form am ide anhydrous (DMF) (purity 99.9% - Merck) (1 ml), by operating under stirring, at room temperature (25°C), for 1 hour and, subsequently, 7.9 μl (equivalent to 0.32 μmoles of 2-acrylamido-2-methylpropanesulphonic acid) of the obtained solutionwere added to the solution of the perovskite precursors (first container): the whole was kept, under stirring, at 60°C, for 3 hours, obtaining a solution containing 49.2% by weight of perovskite precursors and 0.006% by weight of 2-acrylamido-2-methylpropanesulphonic acid, i.e. 0.0125% by weight of 2-acrylamido-2-methylpropanesulphonic acid with respect to the total weight of the other solid components [i.e. lead iodide (PbI2) + formamidinium iodide (FAI) (NH2CHNH2I) perovskite precursors]. The solution thus obtained was deposited on said layer based on a material useful for improving wettability, by spin coating operating at a rotation speed equal to 5000 rpm (acceleration equal to 1000 rpm / s), for 17 seconds, with the addition of 300 μl of antisolvent (i.e. ethyl acetate - Merck) after 8 seconds from the start of the operation, and the whole was subjected to heat treatment (annealing), at 100°C, for 1 minute and at 165 °C for 12 minutes, operating in an uncontrolled atmosphere, in the presence of air. The thickness of the perovskite and 2-acrylamido-2-methylpropanesulphonic acid layer was found to be equal to 330 nm.

[0134] 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 (PC61BM) (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 1000 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" - ETL) was found to be equal to 50 nm.

[0135] 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-phenanthroline (Bathocuproine - BCP) (purity 96% - Aldrich) (9 mg) in anhydrous / .w-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 thelayer based on a hole blocking material (" Hole Blocking Layer" - HBL) was found to be equal to 5 nm.

[0136] Subsequently, the 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 masking the 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.

[0137] The thicknesses were measured by scanning electron microscopy using 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.

[0138] The electrical characterization of the perovskite-based solar cell thus obtained was carried out at room temperature (25°C). The current-voltage density (J-V) curves were acquired with a Keithley® 2400 digital sourcemeter connected to a personal computer for data collection. The photocurrent was measured by exposing the solar cell to the light of a Newport 91160 A solar simulator (Newport Corp), placed at a distance of 10 mm from said solar cell, equipped with a 300 W Xenon light source, using an illumination spot equal to 100 mm x 100 mm: Table 3 reports the characteristic parameters as average values.

[0139] The light intensity was calibrated with a standard silicon solar cell (" VLSI Standard" - SRC-100-RTD-KG5).

[0140] In particular, Table 3 shows, in the following order: the number of the Reference Example; the composition of the photoactive layer of perovskite and 2-acrylamido-2-methylpropanesulphonic acid; FF (" Fill Factor"); Voc (" Open Circuit Voltage"); Jsc ("short-circuit photocurrent density"); PCE (" Power Conversion Efficiency").

[0141] EXAMPLE 2 (invention)

[0142] Preparation of a perovskite-based solar cell

[0143] A perovskite-based solar cell was prepared by operating as described in Example 1, with the only difference being the use of a different amount of 2-acrylamido-2-methylpropanesulphonic acid.

[0144] For this purpose, in a first container, lead iodide (Pbh) (ultra dry purity 99.999% - Alfa Aesar) (461.0 mg - 1.0 mmol), formamidinium iodide (FAI) (NH2 CHNH2I) (GreatCell Solar) (172.0 mg - 1.0 mmol) and methylammonium chloride (MAC1) (CH3NH3CI) - (Merck) (13.5 mg - 0.2 mmol) were dissolved in a mixture of A, A-dimethylformamide anhydrous (DMF) (purity 99.9% - Merck) (574.9 µl) and A-methyl-2-pyrrolidone anhydrous (NMP) (purity 99.8% - Merck) (96.3 µl), operating under stirring, at room temperature (25°C), for 1 hour.

[0145] In a second container, 2-acrylamido-2-methylpropanesulphonic acid (purity 99% - Merck) (10 mg - 0.04 m mol) was dissolved in

[0146]

[0147] dimethylformamide anhydrous (DMF) (purity 99.9% - Merck) (1 ml), operating under stirring, at room temperature (25°C), for 1 hour and, subsequently, 15.8 µl (equivalent to 0.64 µmol of 2-acrylamido-2-methylpropanesulphonic acid) of the obtained solution were added to the solution of the perovskite precursors (first container): the whole was kept, under stirring, at 60°C, for 3 hours, obtaining a solution containing 49.2% by weight of perovskite precursors and 0.012% by weight of 2-acrylamido-2-methylpropanesulphonic acid, i.e. 0.025% by weight of 2-acrylamido-2-methylpropanesulphonic acid with respect to the total weight of the other solid components [i.e. lead iodide (Pbh) + formamidinium iodide (FAI) (NH2CHNH2I) perovskite precursors].

[0148] The electrical characterization of the obtained perovskite-based solar cell was carried out as described above: Table 3 reports the characteristic parameters as average values.

[0149] EXAMPLE 3

[0150] Preparation of a perovskite-based solar cell (invention)

[0151] A perovskite-based solar cell was prepared by operating as described in Example 1, with the only difference being the use of a different amount of 2-acrylamido-2-methylpropanesulphonic acid.

[0152] For this purpose, in a first container, lead iodide (Pbh) (ultra dry purity 99.999% - Alfa Aesar) (461.0 mg - 1.0 mmol), formamidinium iodide (FAI) (NH2CHNH2I) (GreatCell Solar) (172.0 mg - 1.0 mmol) and methylammonium chloride(MAC1) (CH3NH3CI) - (Merck) (13.5 mg - 0.2 mmol) were dissolved in a mixture of A, A-dimethylformamide anhydrous (DMF) (purity 99.9% - Merck) (559.1 µl) and A-methyl-2-pyrrolidone anhydrous (NMP) (purity 99.8% - Merck) (96.3 µl), operating under stirring, at room temperature (25°C), for 1 hour.

[0153] In a second container, 2-acrylamido-2-methylpropanesulfonic acid (purity 99% - Merck) (10 mg - 0.04 m mol) was dissolved in

[0154]

[0155] dimethylformamide anhydrous (DMF) (purity 99.9% - Merck) (1 ml), operating under stirring, at room temperature (25°C), for 1 hour and, subsequently, 31.6 µl (equivalent to 1.28 µmol of 2-acrylamido-2-methylpropanesulfonic acid) of the obtained solution were added to the solution of the perovskite precursors (first container): the whole was kept, under stirring, at 60°C, for 3 hours, obtaining a solution containing 49.2% by weight of perovskite precursors and 0.024% by weight of 2-acrylamido-2-methylpropanesulphonic acid, i.e. 0.050% by weight of 2-acrylamido-2-methylpropanesulphonic acid with respect to the total weight of the other solid components [i.e. lead iodide (Pbh) + formamidinium iodide (FAI) (NH2CHNH2I) perovskite precursors].

[0156] The electrical characterization of the obtained perovskite-based solar cell was carried out as described above: Table 3 reports the characteristic parameters as average values.

[0157] EXAMPLE 4 (comparative)

[0158] Preparation of a perovskite-based solar cell

[0159] A perovskite-based solar cell was prepared by operating as described in Example 1, with the only difference being the absence of 2-acrylamido-2-methylpropanesulphonic acid.

[0160] For this purpose, in a first container, lead iodide (Pbh) (ultra dry purity 99.999% - Alfa Aesar) (461.0 mg - 1.0 mmol), formamidinium iodide (FAI) (NH2CHNH2I) (GreatCell Solar) (172.0 mg - 1.0 mmol) and methylammonium chloride (MAC1) (CH3NH3CI) - (Merck) (13.5 mg - 0.2 mmol) were dissolved in a mixture of A, A-dimethylformamide anhydrous (DMF) (purity 99.9% - Merck) (590.7 µl) and A-methyl-2-pyrroli done anhydrous (NMP) (purity 99.8% - Merck) (96.3 µl), operating under stirring, at 60°C, for 3 hours, obtaining a solutioncontaining 49.2% by weight of perovskite precursor.

[0161] The electrical characterization of the obtained perovskite-based solar cell was carried out as described above: Table 3 reports the characteristic parameters as average values.

[0162] Table 3

[0163] Example Photoactive layer FF< D Voc(2)Jsc(3)PCE(4)

[0164] (%) (V) (mA / cm2) (%) 1 NH2CHNH2PbI3(49.2)<5)+ 75.7 1.07 21.7 17.6 (invention) 2-acrylamido-2- methylpropanesulphonic acid

[0165] (0.0125)<6>

[0166] 2 NH2CHNH2PbI3(49.2)<5)+ 79.8 1.07 23.4 20.0 (invention) 2-acrylamido-2- methylpropanesulphonic acid

[0167] (0.025)<6>

[0168] 3 NH2CHNH2PbI3(49.2)<5)+ 76.5 1.07 24.1 19.8 (invention) 2-acrylamido-2- methylpropanesulphonic acid

[0169] (0.050)<6>

[0170] 4 NH2CHNH2PbI3(49.2)<5)70.8 0.99 22.9 16.1 (comparative)

[0171]

[0172] (1): " Fill Factor";

[0173] (2): " Open Circuit Voltage";

[0174] (3): "short-circuit photocurrent density";

[0175] (4): " Power Conversion Efficiency";

[0176] (5): formamidinium lead iodide (NH2CHNH2PbI3) [(in brackets % by weight of perovskite precursors (i.e. lead iodide (Pbh) + formamidinium iodide (FAI) (NH2CHNH2I) + methylammonium chloride (MAC1) (CH3NH3CI)];

[0177] (6): 2-acrylamido-2-methylpropanesulphonic acid (in brackets % by weight of 2-acrylamido-2-methylpropanesulphonic acid with respect to the total weight of the other solid components [i.e. lead iodide (Pbh) + formamidinium iodide (FAI) (NH2 CHNH2I) + methylammonium chloride (MAC1) (CH3NH3CI)].From the data reported in Table 3 it can be seen that the perovskite-based solar cell subject-matter of the present invention shows that it has a good energy conversion efficiency [" Power Conversion Efficiency" - (PCE)] (i.e. PCE > 16%), both good electrical properties, i.e. good values of FF (" Fill Factor"), Voc (" Open Circuit Voltage"); Jsc ("short-circuit photocurrent density").

Claims

CLAIMS1. Perovskite-based photovoltaic cell (or solar cell) comprising at least one layer comprising:at least one compound having general formula (I):wherein:R represents a hydrogen atom; or is selected from C1-C30, preferably C1-C12, linear or branched, saturated or unsaturated, alkyl groups, optionally containing heteroatoms; optionally substituted aryl groups; optionally substituted heteroaryl groups; optionally substituted cycloalkyl groups; optionally substituted heterocyclic groups;Ri represents a hydrogen atom; or is selected from C1-C12, preferably Ci-Cs, linear or branched, saturated or unsaturated, alkyl groups, optionally containing heteroatoms; optionally substituted aryl groups; optionally substituted heteroaryl groups; optionally substituted cycloalkyl groups; optionally substituted heterocyclic groups;R2 is selected from divalent C1-C12, preferably Ci-Cs, linear or branched, saturated or unsaturated, alkylene groups; optionally substituted arylene groups; optionally substituted heteroarylene groups; optionally substituted cycloalkylene groups; optionally substituted divalent heterocyclic groups;a and b, identical or different from each other, are 0 or 1;T represents a group having general formula (II) or (III):-SO3-X+(II)-SO4-X+(III)wherein:X represents a hydrogen atom; or represents a monovalent metalsuch as, for example, lithium, sodium, potassium, rubidium, caesium, copper, silver, preferably sodium, potassium, caesium; or represents an ammonium ion having general formula (IV):H— N— R4(IV)wherein:R3, R4 and R5, identical or different from each other, represent a hydrogen atom; or are selected from C1-C12, preferably Ci-Cs, linear or branched, saturated or unsaturated, alkyl groups, optionally halogenated; optionally substituted aryl groups;or, at least one compound having general formula (V):wherein:m is a fractional number comprised between 0 and 0.5, preferably comprised between 0 and 0.3;p is an integer comprised between 10 and 5000, preferably comprised between 15 and 2000;Y represents a group having general formula (VI):T (VI)wherein Ri, R2, and T, have the same meanings reported above; or Y represents a group having general formula (VII):oII / K(VII)wherein Re represents a group having general formula (I) provided that R is different from hydrogen.

2. Perovskite-based photovoltaic cell (or solar cell) according to claim 1, wherein said at least one layer is the perovskite photoactive layer.

3. Perovskite-based photovoltaic cell (or solar cell) according to claim 1, wherein said at least one layer is a layer placed above and / or below the perovskite photoactive layer, preferably it is a layer placed above the perovskite photoactive layer.

4. Perovskite-based photovoltaic cell (or solar cell) according to claim 1, comprising:at least one layer placed above and / or below the perovskite photoactive layer, preferably a layer placed above the perovskite photoactive layer comprising at least one compound having general formula (I) or (V); and a perovskite photoactive layer comprising at least one compound having general formula (I) or (V).

5. Perovskite-based photovoltaic cell (or solar cell) 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 methylammonium (CH3NH3+), formamidinium [CH(NH2)2+], / / -butylammonium (C4H9NH3+), tetra-butylammonium (C16H36N+), guanidinium [NH2(NH2)2+], or combinations thereof; or A represents a monovalent inorganic cation such as 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 lead (Pb2+), tin (Sn2+), or combinations thereof;X represents a halide anion such as iodide (P), chloride (CP), bromide (Br‘),or combinations thereof.

6. Photovoltaic cell (or solar cell) based on perovskite 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)i-xPbl3], caesium methylammonium lead iodide [Csx(CH3NH3)i-xPbl3], caesium formamidinium lead iodide [Csx(CH(NH2)2)i-xPbl3], caesium methylammonium formamidinium lead iodide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3], methylammonium lead bromide [CH3NH3PbBr3], formamidinium lead bromide [CHlNBL^PbBn], caesium lead bromide [CsPbBn], methylammonium formamidinium lead bromide [(CH3NH3)x(CH(NH2)2)i-xPbBr3], caesium methylammonium lead bromide [Csx(CH3NH3)i-xPbBr3], caesium formamidinium lead bromide [CSX(CH(NH2)2)I-xPbBr3], caesium methylammonium formamidinium lead bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbBr3], methylammonium lead chloride [CHsNEhPbCh], formamidinium lead chloride [CH(NH2)2PbCh], caesium lead chloride [CsPbCh], methylammonium formamidinium lead chloride [(CH3NH3 (CH(NH2)2)i-xPbC13], caesium methylammonium lead chloride [CSX(CH3NH3)I-xPbCh], caesium formamidinium lead chloride [Csx(CH(NH2)2)i-xPbC13], caesium methylammonium formamidinium lead chloride [(CS CH3NH3)V(CH(NH2)2)I-\-yPbCh], methylammonium lead iodide bromide [CH3NH3PbI3-wBrw], formamidinium lead iodide bromide [CH(NH2)2PbI3-wBrw], caesium lead iodide bromide [CsPbI3-wBrw], methylammonium formamidinium lead iodide bromide [(CH3NH3)x(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], methylammonium lead iodide chloride [CftNHaPbh-wClw], formamidinium lead iodide chloride [CH(NH2)2Pbl3-wClw], caesium lead iodide chloride [CsPbh-wClw], methylammonium formamidinium lead iodide chloride [(CH3NH3)x(CH(NH2)2)i-xPbl3-wClw], caesium methylammonium lead iodide chloride [Csx(CH3NH3)i-xPbl3-wClw], caesium formamidinium lead iodidechloride [Csx(CH(NH2)2)i-xPbl3-wClw], caesium methylammonium formamidinium lead iodide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-wClw], methylammonium lead bromide chloride [CH3NH3PbBr3-wClw], formamidinium lead bromide chloride [CH(NH2)2PbBr3-wClw], caesium lead bromide chloride [CsPbBn-wClw], methylammonium formamidinium lead bromide chloride [(CHaNHa (CH(NH2)2)i-xPbBr3-wClw], caesium methylammonium lead bromide chloride [Csx(CH3NH3)i-xPbBr3-wClw], caesium formamidinium lead bromide chloride [Csx(CH(NH2)2)i-xPbBr3-wClw], caesium methylammonium formamidinium lead bromide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbBr3-wClw], methylammonium lead iodide bromide chloride [CftNHaPbh-w-vBrwClv], formamidinium lead iodide bromide chloride [CH(NH2)2Pbl3-w-vBrwClv], caesium lead iodide bromide chloride [CsPbl3-w-vBrwClv], methylammonium formamidinium lead iodide bromide chloride [(CH3NH3)x(CH(NH2)2)i-xPbl3-w-vBrwClv], caesium methylammonium lead iodide bromide chloride [Csx(CH3NH3)i-xPbl3-w-vBrwClv], caesium formamidinium lead iodide bromide chloride [Csx(CH(NH2)2)i-xPbl3-w-vBrwClv], caesium methylammonium formamidinium lead iodide bromide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-w-vBrwClv], methylammonium tin iodide [CH NHaSnB], formamidinium lead iodide [CH(NH2)2Snl3], caesium tin iodide [CsSnh], methylammonium formamidinium tin iodide [(CH3NH3)x(CH(NH2)2)i-xSnl3], caesium methylammonium tin iodide [Csx(CH3NH3)i-xSnl3], caesium formamidinium tin iodide [Csx(CH(NH2)2)i-xSnl3], caesium methylammonium formamidinium tin iodide [(CsxCH3NH3)y(CH(NH2)2)i-x-ySnl3], methylammonium tin bromide [CHaNHaSnB^], formamidinium tin bromide [CHlNBL^SnBn], caesium tin bromide [CsSnBn], methylammonium formamidinium tin bromide [(CH3NH3)x(CH(NH2)2)i-xSnBr3], caesium methylammonium tin bromide [Csx(CH3NH3)i-xSnBr3], caesium formamidinium tin bromide [CSX(CH(NH2)2)I-xSnBr3], caesium methylammonium formamidinium tin bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-ySnBr3], methylammonium tin chloride [CJbNEhSnCh], formamidinium tin chloride [CHlNJL^SnCh], caesium tin chloride [CsSnCh], methylammonium formamidinium tin chloride [(CH3NH3)x(CH(NH2)2)i-xSnC13], 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)2SnI3-wBrw], caesium tin iodide bromide [CsSnI3-wBrw], methylammonium formamidinium tin iodide bromide [(CH3NH3)x(CH(NH2)2)1-xSnI3-wBrw], caesium methylammonium tin iodide bromide [Csx(CH3NH3)i-xSnl3-wBrw], caesium formamidinium lead 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)2SnI3-wClw], caesium tin iodide chloride [CsSnI3-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 methylammonium formamidinium tin bromide chloride [(CsxCH3NH3)y(CH(NH2)2)1-x-ySnBr3-wClw], methylammonium tin iodide bromide chloride [CH3NH3SnI3-w-vBrwClv], formamidinium tin iodide bromide chloride [CH(NH2)2SnI3-w-vBrwClv], caesium tin iodide bromide chloride [CsSnI3-w-vBrwClv], methylammonium formamidinium tin iodide bromide chloride [(CH3NH3)x(CH(NH2)2)1-xSnI3-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 e 0.99, in the case where theindices x and y are present, the sum of x+y is comprised between 0.01 and 0.99 with x and y being different from 0, in the case where only the index w is present, w is comprised between 0.01 and 2.99, in the 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 being different from 0; preferably, it 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(b>[H2)2)i-x-yPbl3], methylammonium lead iodide bromide [CH3NH3PbI3-wBrw], formamidinium lead iodide bromide [CH(NH2)2PbI3-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 from: formamidinium lead iodide [CH(NH2)2PbI3], 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. Perovskite-based photovoltaic cell (or solar cell) 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. Perovskite-based photovoltaic cell (or solar cell) according to any one of the preceding claims, wherein said at least one compound having general formula (I) or (V) is present in the perovskite photoactive layer in an amount comprised between 0.005% by weight and 20% by weight, preferably comprised between 0.008% by weight and 10% by weight, more preferably comprised between 0.01% by weight and 5% by weight, with respect to the total weight of the perovskiteprecursors.

9. Perovskite-based photovoltaic cell (or solar cell) according to any one of the preceding claims, wherein said perovskite-based photovoltaic cell (or solar cell) comprises:a glass substrate covered with a layer of transparent and conductive oxide (" Transparent Conductive Oxide" - TCO), commonly fluorine-doped tin oxide (SnO2: F) (" Fluorine-doped Tin Oxide" - FTO), or indium tin oxide (" Indium Tin Oxide" - ITO) which constitutes the anode;at least one layer based on a hole transport material (" Hole Transport Layer" - HTL), said material being preferably selected from a layer of (2-(9H- carbazol-9-yl)ethyl phosphonic acid (2PACz), (2-(3,6-dimethoxy-9H- carbazol-9-yl)ethyl phosphonic acid (MeO-2PACz)], nickel oxide (NiOx), copper sulphocyanide (CuSCN), copper iodide (Cui), copper oxide (CuOx), copper sulphide (CuS), or a combination of layers of the aforesaid materials; optionally at least one layer based on a material useful for improving wettability, preferably a layer of nanoparticles of aluminium oxide (n-Al2O3);optionally, at least one layer comprising at least one compound having general formula (I) or (V);at least one photoactive layer comprising at least one perovskite, preferably formamidinium lead iodide (NH2CHNH2PbI3) and, optionally, at least one compound having general formula (I) or (V), preferably a compound having general formula (I), even more preferably 2-acrylamido-2- methylpropanesulphonic acid;optionally, at least one layer comprising at least one compound having general formula (I) or (V);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-C6i-butyric acid (PC61BM), fullerene (C60), tin oxide (SnOx), polyethyleneimine (PEI), ethoxylated polyethyleneimine (PEIE), or a combination of layers of the aforesaid materials; optionally at least one layer based on a hole blocking material (" HoleBlocking Layer" - HBL), preferably a layer of 2,9-dimethyl-4,7-diphenyl- 1,10-phenanthroline (Bathocuproine - 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.

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

11. Process for the preparation of a perovskite-based photovoltaic cell (or solar cell) comprising the following stages:(a) preparing a glass substrate covered with a layer of transparent and conductive oxide (“Transparent Conductive Oxide” - TCO) (anode);(b) depositing at least one layer based on a hole transport material (" Hole Transport Layer" - HTL) on the substrate obtained in said stage (a);(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;(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) or (V); (e) preparing a mixture comprising perovskite precursors and optionally at least one compound having general formula (I) or (V), preferably a compound having general formula (I);(f) depositing the mixture obtained in said stage (e) 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), or on the layer comprising at least one compound havinggeneral formula (I) or (V) obtained in said stage (d), obtaining a photoactive layer;(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) or (V);(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) or (V) obtained in said stage (g);(i) optionally, depositing on the layer based on an electron transport material (" Electron Transport Layer" - ETL) obtained in said stage (h), at least one layer based on a hole blocking material (" Hole Blocking Layer" - HBL); (1) depositing a cathode consisting of a metal contact known as “back contact”, preferably a layer of gold, silver, or metallic aluminium; or, consisting of a layer of transparent and conductive oxide (" Transparent Conductive Oxide" - TCO) and metal grids;wherein said stage (f) is carried out in an uncontrolled atmosphere, in the presence of air.

12. Tandem perovskite / silicon photovoltaic cell (or solar cell) comprising: a silicon photovoltaic cell (or solar cell);a perovskite-based photovoltaic cell (or solar cell) comprising at least one layer comprising at least one compound having general formula (I) or (V) according to claim 1, arranged 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 perovskite-based photovoltaic cell (or solar cell) 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 and at least one compound having general formula (I) or (V) according to claim 1, preferably a compound having general formula (I).

16. Composition according to claim 15, wherein said perovskite is selected from those reported in any one of claims 5 to 7.

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