Photovoltaic cells based on perovskite and process for preparing them

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): [R1PO3] 2-X+Y+ (I) wherein: - R1 is selected from C1-C16 alkyl groups, preferably C1-C12, 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; - X+ and Y+, identical or different from each other, represent a hydrogen ion (H+), or an ammonium ion having general formula (II): wherein: - R2 is selected from C2-C12 alkyl groups, preferably C2-C8, linear or branched, saturated or unsaturated, aryl groups, cycloalkyl groups, said alkyl, aryl and cycloalkyl groups being substituted with 1 to 5, preferably 1 to 3, hydroxyl groups and, optionally, with at least one group selected from alkyl groups, ether groups, ester groups, carbonyl groups; - R3 and R4, identical or different from each other, represent a hydrogen atom or a methyl group; or they are selected from C2-C4 alkyl groups, linear or branched, saturated, wherein one or more hydrogen atoms are optionally substituted with a hydroxyl group; preferably, a hydrogen atom. 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 production of electrical 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 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.

Description

[0001] PHOTOVOLTAIC CELLS BASED ON PEROVSKITE AND PROCESS FOR PREPARING THEM

[0002]

[0003] The present invention relates to photovoltaic cells (or solar cells) based on perovskite (“Perovskite Solar Cells” - PSCs).

[0004] More particularly, the present invention 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 the specific general formula (I) below reported.

[0005] Said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) can be part of a tandem perov skite / silicon photovoltaic cell (or solar cell). Said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) and said tandem perov skite / 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 photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) and said tandem perov skite / silicon photovoltaic cell (or solar cell) can be used either in stand-alone mode or in modular systems.

[0006] The present invention also relates to a tandem perovskite / silicon photovoltaic cell (or solar cell).

[0007] A further object of the present invention is also a process for preparing said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” -PSC).

[0008] 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) below reported.

[0009] 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, in particular bothcrystalline and amorphous silicon, most particularly high-purity crystalline silicon.

[0010] 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 photovoltaic cells (or solar cells) based on silicon such as, for example, access to new fields of application, improved efficiencies and possibly lower production costs.

[0011] In particular, photovoltaic cells (or solar cells) based on perovskite (" 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 Photovoltaic s" - 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 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 therefore, once appropriately coupled with 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.

[0012] However, photovoltaic cells (or solar cells) based on perovskite (“Perovskite Solar Cells” - PSCs) may also have certain structural drawbacks which may also affect 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 perovskite photoactive layer ("bulk") and at the edges of the crystalline grains, and on the surface of said perovskite photoactive layer. Indeed, materialinterfaces represent an area of discontinuity in the photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC), 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-hole recombination rate at the interface. More precisely, said defects reduce the overall efficiency of photovoltaic cells (or solar cells) based on perovskite (“Perovskite Solar Cells” - PSCs) and also facilitate the initiation of degradation phenomena.

[0013] To bridge the aforementioned gap, research is focusing on the use of agents capable of passivating defects commonly present both on the surface (by means of surface treatment) and within the photoactive layer of perovskite (by means of “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, pg. 2906-2953, various compounds containing various functional groups capable of interacting via more or less strong bonds, 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 7t-acceptor donor-bridge 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, 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.

[0014] 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.

[0015] However, many of the compounds used as passivating agents may have critical aspects. For example, among those above reported, hexafluoroisopropanol, acetic acid, thiophene, pyridine, benzylamine, butanethiol, 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.

[0016] 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 means of “in bulk” treatment) and on itssurface (by means of surface treatment), which would make it possible to obtain photovoltaic cells (or solar cells) based on perovskite (" Perovskite Solar Cells" -PSC) capable of having a good power conversion efficiency [" Power Conversion Efficiency" - (PCE)], as well as a process for their construction adapted to be used in the "scaling up" stage for the construction of large-area photovoltaic cells (or solar cells).

[0017] The Applicant therefore set itself the problem of finding a photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) capable of having a good power conversion efficiency [" Power Conversion Efficiency" -(PCE)], as well as a process for its construction adapted to be used in the “scaling up” stage for the construction of large-area photovoltaic cells (or solar cells).

[0018] 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 > 15%), as well as a process for its preparation involving, in the event that X+represents an ammonium ion having general formula (II), the preparation in situ in the photoactive layer of perovskite, of the aforementioned compound having general formula (I). Said process, which can be carried out in an uncontrolled atmosphere, in the presence of air, is adapted to be used in the “scaling up” stage for the construction of large-area photovoltaic cells (or solar cells). In addition, said a photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) has low hysteresis index (“Hysteresis Index” - HI) values (i.e. values lower than or equal to 1.5%). In addition, said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” -PSC) is capable of maintaining good photoelectric 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 theproduction 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 photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) and said tandem perov skite / silicon photovoltaic cell (or solar cell) can be used either in stand-alone mode or in modular systems.

[0019] 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):

[0020] [R1PO3]2-X+Y+(I)

[0021] wherein:

[0022] Ri is selected from C1-C16 alkyl groups, preferably C1-C12, 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;

[0023] X+and Y+, identical or different from each other, represent a hydrogen ion (H+), or an ammonium ion having general formula (II):

[0024] t

[0025] H - N - R2(II)

[0026] R4

[0027] wherein:

[0028] R2 is selected from C2-C12 alkyl groups, preferably C2-C8, linear or branched, saturated or unsaturated, aryl groups, cycloalkyl groups, said alkyl, aryl and cycloalkyl groups being substituted with 1 to 5, preferably 1 to 3, hydroxyl groups and, optionally, with at least one group selected from alkyl groups, ether groups, ester groups, carbonyl groups;

[0029] R3 and R4, identical or different from each other, represent a hydrogen atom or a methyl group; or they are selected from C2-C4 alkyl groups, linear or branched, saturated, wherein one or more hydrogen atoms areoptionally substituted with a hydroxyl group; preferably, a hydrogen atom.

[0030] For the purpose of the present description and of the following claims, the definitions of the numeric ranges always comprise the extremes unless specified otherwise.

[0031] 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’.

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

[0033] According to 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] According to a further preferred embodiment of the present invention, a 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] According to 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 (Ci6H36N+), guanidinium [NH2(NH2)2+], or combinations thereof; or A represents a monovalent inorganic cation such as, for example, cesium (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;

[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] cesium lead iodide [CsPbI₃], methylammonium formamidinium lead iodide [(CH3NH3)x(CH(NH2)2)i-xPbl3], cesium methylammonium lead iodide [Csx(CH₃NH₃)1-xPbI₃], cesium formamidinium lead iodide [Csx(CH(NH₂)₂)1-xPbI₃], cesium methylammonium formamidinium lead iodide [(CsxCH₃NH₃)y(CH(NH₂)₂)1-x-yPbI₃], methylammonium lead bromide [CH₃NH₃PbBr₃], formamidinium lead bromide [CH(NH₂)₂PbBr₃], cesium lead bromide [CsPbBr₃], methylammonium formamidinium lead bromide [(CH3NH3)x(CH(NH2)2)i-xPbBr3], cesium methylammonium lead bromide [Csx(CH3NH3)i-xPbBr3], cesium formamidinium lead bromide [Csx(CH(NH₂)₂)1-xPbBr₃], cesium methylammonium formamidinium lead bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbBr3], methylammonium lead chloride [CH₃NH₃PbCl₃], formamidinium lead chloride [CH(NH2)2PbC13], cesium lead chloride [CsPbCl₃], methylammonium formamidinium lead chloride [(CH3NH3)x(CH(NH2)2)i-xPbC13], cesium methylammonium lead chloride [Csx(CH3NH3)i-xPbC13], cesium formamidinium lead chloride [Csx(CH(NH₂)₂)1-xPbCl₃], cesium methylammonium formamidinium lead chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbC13], methylammonium lead iodide bromide [CH₃NH₃PbI₃₋wBrw], formamidinium lead iodide bromide [CH(NH2)2Pbl3-wBrw], cesium lead iodide bromide [CsPbl3-wBrw], methylammonium formamidinium lead iodide bromide [(CH3NH3)x(CH(NH2)2)i-xPbl3-wBrw],

[0041] cesium methylammonium lead iodide bromide [Csx(CH3NH3)i-xPbl3-wBrw], cesium formamidinium lead iodide bromide [Csx(CH(NH2)2)i-xPbl3-wBrw], cesium methylammonium formamidinium lead iodide bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-wBrw], methylammonium lead iodide chloride[CHsNHsPbls-wClw], formamidinium lead iodide chloride [CH(NH2)2Pbl3-wClw], cesium lead iodide chloride [CsPbl3-wClw], methylammonium formamidinium lead iodide chloride [(CH3NH3)x(CH(NH2)2)i-xPbl3-wClw], cesium methylammonium lead iodide chloride [Csx(CH3NH3)i-xPbl3-wClw], cesium formamidinium lead iodide chloride [Csx(CH(NH2)2)i-xPbl3-wClw], cesium 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], cesium lead bromide chloride [CsPbBr3-wClw], methylammonium formamidinium lead bromide chloride [(CH₃NH₃)x(CH(NH₂)₂)1-xPbBr₃₋wClw], cesium methylammonium lead bromide chloride [Csx(CH3NH3)i-xPbBr3 wClw], cesium formamidinium lead bromide chloride [Csx(CH(NH2)2)i-xPbBr3-wClw], cesium methylammonium formamidinium lead bromide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbBr3-wClw], methylammonium lead iodide bromide chloride [CH₃NH₃PbI₃₋w₋vBrwClv], formamidinium lead iodide bromide chloride [CH(NH2)2Pbl3-w-vBrwClv], cesium lead iodide bromide chloride [CsPbl3-w-vBrwClv], methylammonium formamidinium lead iodide bromide chloride [(CH3NH3)x(CH(NH2)2)i-xPbl3-w-vBrwClv], cesium methylammonium lead iodide bromide chloride [Csx(CH3NH3)i-xPbl3-w-vBrwClv], cesium formamidinium lead iodide bromide chloride [Csx(CH(NH2)2)i-xPbl3-w-vBrwClv], cesium methylammonium formamidinium lead iodide bromide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-w-vBrwClv], methylammonium tin iodide [CH₃NH₃SnI₃] formamidinium lead iodide [CH(NH2)2SnI3], cesium tin iodide [CsSnI₃], methylammonium formamidinium tin iodide [(CH₃NH₃)x(CH(NH₂)₂)1-xSnI₃], cesium methylammonium tin iodide [Csx(CH3NH3)i-xSnl3], cesium formamidinium tin iodide [Csx(CH(NH2)2)i-xSnl3], cesium methylammonium formamidinium tin iodide [(CsxCH3NH3)y(CH(NH2)2)i-x-ySnl3], methylammonium tin bromide [CH₃NH₃SnBr₃], formamidinium tin bromide [CH(NH2)2SnBr3], cesium tin bromide [CsSnBr₃], methylammonium formamidinium tin bromide [(CH3NH3)x(CH(NH2)2)i-xSnBr3], cesium methylammonium tin bromide [Csx(CH3NH3)i-xSnBr3], cesium formammidinium tin bromide [Csx(CH(NH2)2)i-xSnBr3], cesium methylammonium formamidiniumtin bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-ySnBr3], methylammonium tin chloride [CH₃NH₃SnCl₃], formamidinium tin chloride [CH(NH2)2SnC13], cesium tin chloride [CsSnCl₃], methylammonium formamidinium tin chloride [(CH₃NH₃)x(CH(NH₂)₂)1-xSnCl₃], cesium methylammonium tin chloride [Csx(CH3NH3)i-xSnC13], cesium formamidinium tin chloride [Csx(CH(NH2)2)i-xSnCh], cesium methylammonium formamidinium tin chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-ySnC13], methylammonium tin iodide bromide [CH₃NH₃SnI₃₋wBrw], formamidinium tin iodide bromide [CH(NH2)2Snl3-wBrw], cesium tin iodide bromide [CsSnl3-wBrw], methylammonium formamidinium tin iodide bromide [(CH₃NH₃)x(CH(NH₂)₂)1-xSnI₃₋wBrw], cesium methylammonium tin iodide bromide [Csx(CH3NH3)i-xSnl3-wBrw], cesium formamidinium tin iodide bromide [Csx(CH(NH₂)₂)1-xSnI₃₋wBrw], cesium methylammonium formamidinium tin iodide bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-ySnl3-wBrw], methylammonium tin iodide chloride [CH₃NH₃SnI₃₋wClw], formamidinium tin iodide chloride [CH(NH2)2Snl3-wClw], cesium tin iodide chloride [CsSnl3-wClw], methylammonium formamidinium tin iodide chloride [(CH3NH3)x(CH(NH2)2)i-xSnl3-wClw], cesium methylammonium tin iodide chloride [Csx(CH3NH3)i-xSnl3-wClw], cesium formamidinium tin iodide chloride [Csx(CH(NH2)2)i-xSnl3-wClw], cesium methylammonium formamidinium tin iodide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-ySnl3-wClw], methylammonium tin bromide chloride [CH₃NH₃SnBr₃₋wClw], formamidinium tin bromide chloride [CH(NH2)2SnBr3-wClw], cesium tin bromide chloride [CsSnBr₃₋wClw], methylammonium formamidinium tin bromide chloride [(CH₃NH₃)x(CH(NH₂)₂)1-xSnBr₃₋wClw], cesium methylammonium tin bromide chloride [Csx(CH₃NH₃)1-xSnBr₃₋wClw], cesium formamidinium tin bromide chloride [Csx(CH(NH2)2)i-xSnBr3 wClw], cesium methylammonium formamidinium 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], cesium tin iodide bromide chloride [CsSnI₃₋w₋vBrwClv], methylammonium formamidinium tin iodide bromide chloride [(CH3NH3)x(CH(NH2)2)i-xSnl3-w-vBrwClv], cesium methylammonium tin iodide bromide chloride [Csx(CH3NH3)i-xSnl3-w-vBrwClv], cesium formamidinium tiniodide bromide chloride [Csx(CH(NH2)2)i- Snl3-w-vBrwClv], cesium methylammonium formamidinium tin iodide bromide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-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 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 different from 0. Preferably, said perovskite can be selected, for example, from: methylammonium lead iodide [CH₃NH₃PbI₃], formamidinium lead iodide [CH(NH₂)₂PbI₃], cesium lead iodide [CsPbI₃], methylammonium formamidinium lead iodide [(CH3NH3)x(CH(NH2)2)i- Pbl3], cesium methylammonium lead iodide [Csx(CH₃NH₃)1-xPbI₃], cesium formamidinium lead iodide [Csx(CH(NH₂)₂)1-xPbI₃], cesium 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], cesium lead iodide bromide [CsPbl3-wBrw], methylammonium formamidinium lead iodide bromide [(CH₃NH₃)ₓ(CH(NH₂)₂)₁₋ₓPbI₃₋wBrw], cesium methylammonium lead iodide bromide [Csx(CH3NH3)i-xPbl3-wBrw], cesium formamidinium lead iodide bromide [Csx(CH(NH2)2)i- Pbl3-wBrw], cesium methylammonium formamidinium lead iodide bromide [(CsxCH3NH3)y(CH(NH2)2)i- -yPbl3-wBrw]; even more preferably between: cesium methylammonium lead iodide bromide [Csx(CH3NH3)i-xPbl3-wBrw], cesium formamidinium lead iodide bromide [Csx(CH(NH2)2)i- Pbl3-wBrw], cesium methylammonium formamidinium lead iodide bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-wBrw].

[0042] 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.

[0043] For the purpose of the present description and of the following claims, the term “C1-C16 alkyl groups” indicates alkyl groups having from 1 to 16 carbonatoms, linear or branched, saturated or unsaturated. Said alkyl groups may be optionally 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-C16 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, hexadecyl.

[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 may be optionally 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.

[0045] For the purpose of the present description and of the following claims, the term “cycloalkyl groups” indicates cycloalkyl groups having from 3 to 12 carbon atoms. These cycloalkyl groups may be optionally 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, as well as the following groups represented as radicals:

[0046]

[0047] the camphor-derived radical;

[0048]

[0049] the menthol-derived radical;

[0050]

[0051] the pinene-derived radical;

[0052]

[0053] the carvone-derived radical;

[0054] wherein the asterisk represents the phosphorus atom of general formula (I).

[0055] For the purpose of the present description and of the following claims, the term “C2-C12 alkyl groups substituted with 1 to 5 hydroxyl groups” indicates alkyl groups having from 1 to 12 carbon atoms, linear or branched, saturated or unsaturated in which one or more hydrogen atoms are substituted with a hydroxyl group. Said C2-C12 alkyl groups substituted with 1 to 5 hydroxyl groups may be optionally substituted with one or more groups, identical or different from each other, selected from: alkyl groups; ether groups; ester groups; carbonyl groups. Specific examples of C2-C12 alkyl groups substituted with 1 to 5 hydroxyl groups are the following groups represented as radicals:

[0056] HO * OH

[0057] OH OH

[0058]

[0059] OH

[0060]

[0061] wherein the asterisk represents the nitrogen atom of general formula (II).

[0062] For the purpose of the present description and following claims, the term "aryl groups substituted with 1 to 5 hydroxyl groups" indicates aryl groups having from 6 to 14 carbon atoms in which one or more hydrogen atoms are substituted with a hydroxyl group. Said aryl groups substituted with 1 to 5 hydroxyl groups may optionally be substituted with one or more groups, identical or different from each other, selected from: alkyl groups; ether groups; ester groups; carbonyl groups. Specific examples of aryl groups substituted with 1 to 5 hydroxyl groups are the following groups represented as radicals:

[0063]

[0064] wherein the asterisk represents the nitrogen atom of general formula (II).

[0065] For the purpose of the present description and of the following claims, the term "cycloalkyl groups substituted with 1 to 5 hydroxyl groups" indicates cycloalkyl groups having from 3 to 10 carbon atoms in which one or more hydrogen atoms are substituted with a hydroxyl group. Said cycloalkyl groups substituted with 1 to 5 hydroxyl groups may optionally be substituted with one or more groups, identical or different from each other, selected from: alkyl groups; ether groups; ester groups; carbonyl groups. Specific examples of cycloalkyl groups substituted with 1 to 5 hydroxyl groups are the following groups represented as radicals:

[0066] OH

[0067]

[0068] OH

[0069]

[0070] *

[0071] wherein the asterisk represents the nitrogen atom of general formula (II).

[0072] Specific examples of “C2-C4 alkyl groups, linear or branched, saturated, wherein one or more hydrogen atoms are optionally substituted with a hydroxyl group” are: 2-hydroxyethyl, 2-hydroxypropyl, 3 -hydroxypropyl, 4-hydroxybutyl.

[0073] The above compound having general formula (I), where X+represents an ammonium ion having general formula (II), can be prepared according to processes known in the art. For example, the compound having general formula (I) can be prepared by a process involving reacting at least one phosphonic acid having general formula (III):

[0074] R₁-PO₃H₂ (III)

[0075] wherein Ri has the same meanings above reported, with at least one amino alcohol having general formula (IV):

[0076] N— R2(IV)

[0077]

[0078] R4

[0079] wherein R2, R3 and R4 have the same meanings above reported, in the presence of water or of at least one organic solvent, having a boiling point lower than 300°C, preferably comprised between 30°C and 210°C, operating at a temperature comprised between 20°C and 80°C, preferably comprised between 25 °C and 50°C, for a time comprised between 10 minutes and 2 hours, preferably comprised between 15 minutes and 1 hour, obtaining a solution containing the compound having general formula (I).

[0080] Preferably, in the aforementioned process, said phosphonic acid having general formula (III) and said amino alcohol having general formula (IV) can be used in molar ratios comprised between 0.5:1 and 1:0.5, preferably in a 1:1 molar ratio.Specific examples of phosphonic acids having general formula (III) advantageously usable for the purpose of the present invention are: methylphosphonic acid, laurylphosphonic acid, phenylphosphonic acid, p-toluenphosphonic acid, (lS)-(+)-10-camphor-phosphonic acid, (lR)-(-)-10-camphor-phosphonic acid, racemic mixture of (lS)-(+)-10-camphor-phosphonic acid and (lR)-(-)-10-camphor-phosphonic acid, 1-naphthylphosphonic acid, 2-naphthylphosphonic acid, or mixtures thereof. Methylphosphonic acid, phenylphosphonic acid, are preferred.

[0081] Specific examples of amino alcohols having general formula (IV) advantageously usable for the purpose of the present invention are: ethanolamine, 3-aminopropane-l,2-diol, 2-aminopropane- 1,3 -diol (serinol), 2-amino-2-hydroxymethylpropane- 1,3-diol (tromethamine), 4-(2-aminoethyl)benzene- 1,2-diol (dopamine), 4-aminoresorcinol, or mixtures thereof. Ethanolamine, 3-aminopropane-l,2-diol, 2-aminopropane- 1,3 -diol (serinol), 2-amino-2-hydroxymethylpropane-l,3-diol (tromethamine), are preferred.

[0082] Specific examples of solvents 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; nitriles such as, for example, acetonitrile, propionitrile, butyronitrile, benzonitrile, or mixtures thereof; alcohols such as, for example, methanol, ethanol, n-propanol, iso-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.

[0083] At the end of the aforementioned process:

[0084] in case where 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 above reported, 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 obtained solution is deposited above and / or below the perovskite photoactive layer, preferably above; or

[0085] in case where the solvent used in the aforementioned 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 above reported, the aforementioned solution containing the compound having general formula (I) may be used directly in a mixture with the perovskite precursors with subsequent formation of the perovskite photoactive layer ("in bulk" treatment); or

[0086] the compound having general formula (I) can be isolated and purified from the aforementioned solution by evaporation of the solvent and subsequently dissolved in a suitable solvent selected from those above reported, depending on whether it is used in surface treatment or “in bulk” treatment; in particular:

[0087] the purified compound having general formula (I) can be dissolved in a solvent selected from the solvents defined as perovskite antisolvents above reported, obtaining a solution containing the compound having general formula (I) that can be directly used for surface treatment of the perovskite photoactive layer (surface treatment) in which a layer of the obtained solution is deposited above and / or below the perovskite photoactive layer, preferably above; or

[0088] the purified compound having general formula (I) can be dissolved ina solvent selected from those capable of dissolving the perovskite above reported in a mixture with the perovskite precursors with subsequent formation of the perovskite photoactive layer (“in bulk” treatment).

[0089] Said compound having general formula (I) can also be prepared in situ (“in bulk” treatment) by adding to the mixture of perovskite precursors at least one phosphonic acid having general formula (III) and at least one amino alcohol having general formula (IV), in the presence of at least one solvent selected from among the solvents capable of dissolving the perovskite above reported, said phosphonic acid having general formula (III) and said amino alcohol having general formula (IV) being preferably used in molar ratios comprised between 0.5:1 and 1:0.5, preferably in molar ratios of 1:1.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] In accordance with a preferred embodiment of the present invention, said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” -PSC) comprises:

[0094] 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) (" Fluorine-doped 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;

[0095] at least one layer based on a hole transport layer (“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);

[0096] optionally, at least one layer comprising at least one compound having general formula (I);

[0097] a photoactive layer comprising at least one perovskite preferably selected from cesium methylammonium lead iodide bromide [Cs₀.₀₅(CH₃NH₃)₀.₉₅PbI₂.₅₅Br₀.₄₅], cesium formamidinium lead iodide bromide [Cs₀.₀₅FA₀.₉₅PbI₂.₅₅Br₀.₄₅], more preferably cesium methylammonium lead iodide bromide [Cs₀.₀₅(CH₃NH₃)₀.₉₅PbI₂.₅₅Br₀.₄₅], and, optionally, at least one compound having general formula (I), preferably a compound obtained by the reaction between 3-aminopropane-1,2-diol, 2-aminopropane-l,3-diol (serinol), 2-amino-2-hydroxymethylpropane-l,3-diol (tromethamine), with methylphosphonic acid or with phenylphosphonic acid;

[0098] optionally, at least one layer comprising at least one compound having general formula (I);

[0099] 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);

[0100] a cathode consisting of:

[0101] a metal contact known as "back contact" preferably a layer of gold, silver, or metallic aluminium; or,

[0102] a layer of transparent and conductive oxide (" Transparent Conductive Oxide" - TCO) and metal grids.

[0103] 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 replaced by a layer of transparent and conductive oxide (“Transparent Conductive Oxide”-TCO) and metal grids forming the cathode.

[0104] 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) may be transported using a wiring system which is connected with said photovoltaic cell (or solar cell) based on perovskite.

[0105] Said photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) can be prepared in accordance with processes known in the art. However, as mentioned above, the present invention also relates to a process which provides for the preparation in situ in the photoactive layer of perovskite, of the aforementioned compound having general formula (I).

[0106] Accordingly, it is a further object of the present invention a process for preparing a photovoltaic cell (or solar cell) based on perovskite (“Perovskite Solar Cell” - PSC) comprising the following stages:

[0107] (a) preparing a glass substrate covered with a layer of transparent and conductive oxide (TCO) (anode);

[0108] (b) depositing at least a layer based on a hole transport material (" Hole Transport Layer" - HTL) on the substrate obtained in said stage (a);

[0109] (c) optionally, depositing on the layer based on a hole transport material (" HoleTransport Layer" - HTL) obtained in said stage (b) a layer based on a material for improving wettability;

[0110] (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);

[0111] (e) preparing a mixture comprising perovskite precursors, at least one phosphonic acid having general formula (III) and at least one amino alcohol having general formula (IV);

[0112] (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 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) obtained in said stage (d), obtaining a photoactive layer;

[0113] (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);

[0114] (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);

[0115] (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);

[0116] (1) depositing a cathode consisting of a metal contact known as a "back contact" preferably a gold, silver or aluminium metal 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).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.

[0117] 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 set forth above.

[0118] For the purpose of the aforementioned process, said mixture comprising perovskite precursors and, optionally at least one compound having general formula (I), comprises:

[0119] at least one halide selected from among the halides of the monovalent organic cations or monovalent inorganic cations above reported, preferably iodides, chlorides, bromides, more preferably iodides and bromides, and at least one halide selected from among the halides of the bivalent metal cations listed above, preferably iodides, chlorides, bromides, more preferably iodides and bromides [for example, cesium iodide (CsE), lead iodide (PbE), lead bromide (PbBri)] as perovskite precursors; optionally at least one compound having general formula (I).

[0120] For the purpose of the aforementioned process, said steps (b), (c), (d), (e), (f), (g), (h) and (i) may be carried out according to depositing techniques known in the art such as, for example, “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 willvary depending on the layer considered.

[0121] For the purpose of the aforementioned process, said step (1) may be carried out according to techniques known in the art such as, for example, evaporation, cathodic sputtering, electron beam assisted depositing, “Physical Vapor Deposition” (PVD), “Radio Frequency Sputtering” (“RF- sputtering”), “Direct Current sputtering” (“DC-sputtering”).

[0122] 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).

[0123] Accordingly, it is a further object of the present invention a tandem perovskite / silicon photovoltaic cell (or solar cell) comprising:

[0124] a silicon photovoltaic cell (or solar cell);

[0125] 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), deposited above said silicon photovoltaic cell (or solar cell).

[0126] In accordance with a preferred embodiment of the present invention, the electric energy generated by said tandem perovskite / silicon photovoltaic cell (or solar cell) may be transported using a wiring system which is connected with said tandem perovskite / silicon photovoltaic cell (or solar cell).

[0127] 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 exploiting 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.

[0128] 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 of said tandem perovskite / silicon photovoltaic cell (or solar cell) in:photovoltaic fields (or photovoltaic parks), residential use, commercial buildings. 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).

[0129] 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).

[0130] Said at least one perovskite can be selected from among those above reported.

[0131] The present invention will now be illustrated in greater detail through an embodiment with reference to Figure 1 reported below.

[0132] In particular, Figure 1 depicts a cross-sectional view of a perovskite-based photovoltaic cell (or solar cell) (“Perovskite Solar Cell” - PSC) (1) comprising the following layers: a glass substrate (7) covered with at least one 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., cesium methylammonium lead iodide bromide [Cs₀.₀₅(CH₃NH₃)₀.₉₅PbI₂.₅₅Br₀.₄₅]] and optionally at least one compound having general formula (I), preferably a compound obtained by the reaction of ethanolamine, or 3 -aminopropane- 1,2 -diol, or 2-aminopropane-l,3-diol (serinol), or 2-amino-2-hydroxymethylpropane-l,3-diol (tromethamine), with methylphosphonic acid or with phenylphosphonic acid (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-C6i-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 (Batocuproine - BCP)] (5b); a metal contact known as a back contact that formsthe cathode [e.g., a silver layer] (6).

[0133] In order to better understand the present invention and to put it into practice, some illustrative and non-limiting examples thereof are reported below.

[0134] 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)

[0135] Preparation of a perovskite-based solar cell (“Perovskite Solar Cell” - PSC)

[0136] 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 / cm2) and 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 processes 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) zso-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.

[0137] 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.

[0138] 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.

[0139] On top of the layer based on a hole transport material (“Hole Transport Layer” - HTL) the cesium methylammonium lead iodide bromide layer [Cso.o5(CH3NH3)o.95Pbl2.55Bro.45) was deposited (“band gap” of 1.67 eV) operating as follows. For this purpose, cesium iodide (CsI) (ultra dry purity 99.999% - Alfa Aesar) (15.6 mg - 0.06 mmoles), lead iodide (Pbh) (ultra dry purity 99.999% -Alfa Aesar) (428.7 mg - 0.93 mmoles), lead bromide (PbBn) (ultra dry purity 99.999% - Alfa Aesar) (99 mg - 0,27 mmoles) were dissolved in a mixture of anhydrous A. V-di methyl formamide (DMF) (purity 99.9% - Merck) (628.8 pl) and anhydrous dimethyl sulphoxide (DMS) (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 room temperature (25 °C), for 10 minutes.

[0140] 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 equal to 330 nm.

[0141] 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.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-l,10-phenatroline (Batocuproine - BCP) (purity 96% - Merck) (9 mg) in anhydrous Lo-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.

[0142] 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 2xl0-6mmHg and at 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.

[0143] 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 coming from secondary electrons.

[0144] The electrical characterization of the obtained perovskite-based solar cell was carried out at room temperature (25°C) operating as follows.

[0145] 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 equal to 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” (PCE) and the “Hysteresis Index” (HI) calculated as the difference between the “Power Conversion Efficiency” (PCE) in the “reverse scan” direction and the “Power Conversion Efficiency” (PCE) in the “forward scan” direction, divided by the “Power Conversion Efficiency” (PCE) in the “reverse scan direction”, all multiplied by 100, according to the following formula:

[0146] / / y (0 / ) I ^^^Teverse scan~PCE forward scan^ 10Q|

[0147]

[0148] 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”).

[0149] EXAMPLE 2 (invention)

[0150] Preparation of a perovskite-based solar cell (“bulk” treatment)

[0151] 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.

[0152] To this end, 9.6 mg of methylphosphonic acid (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 shown in Example 1 above, and the resulting 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 ptl 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 equal to 330 nm.

[0153] The electrical characterisation of the perovskite-based solar cell obtained was carried out as described above: Table 1 shows the results obtained.EXAMPLE 3 (invention)

[0154] Preparation of a perovskite-based solar cell (“bulk” treatment)

[0155] 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.

[0156] To this end, 24 mg of methylphosphonic acid (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 shown in Example 1 above, and the resulting 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 (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 equal to 330 nm.

[0157] The electrical characterisation of the perovskite-based solar cell obtained was carried out as described above: Table 1 shows the results obtained.

[0158] EXAMPLE 4 (invention)

[0159] Preparation of a perovskite-based solar cell (“bulk” treatment)

[0160] 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.

[0161] For this purpose, 9.6 mg of methylphosphonic acid (Merck) (0.1 mmol) and 9.2 mg of serinol (Merck) (0.1 mmol) [0.083 millimoles of compound having general formula (I) to millimoles of lead] were added to the solution of the perovskite precursors obtained as shown in Example 1 above, and the solution thus obtained 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 to1000 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 equal to 330 nm.

[0162] The electrical characterisation of the perovskite-based solar cell obtained was carried out as described above: Table 1 shows the results obtained.

[0163] EXAMPLE 5 (invention)

[0164] Preparation of a perovskite-based solar cell (“bulk” treatment)

[0165] 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.

[0166] For this purpose, 24 mg of methylphosphonic acid (Merck) (0.25 mmol) and 23 mg of serinol (Merck) (0.25 mmol) [0.208 millimoles of compound having general formula (I) to millimoles of lead] were added to the solution of the perovskite precursors obtained as shown in Example 1 above, and the solution thus obtained was heated to 45°C, for 30 minutes, under stirring. Subsequently, 20 µl 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 equal to 330 nm.

[0167] The electrical characterisation of the perovskite-based solar cell obtained was carried out as described above: Table 1 shows the results obtained.

[0168] EXAMPLE 6 (invention)

[0169] Preparation of a perovskite-based solar cell (“bulk” treatment)

[0170] 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.To this end, 15.8 mg of phenylphosphonic acid (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 shown in Example 1 above, and the resulting solution was heated to 45°C, for 30 minutes, under stirring. Subsequently, 20 ptl 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 ptl 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 equal to 330 nm.

[0171] The electrical characterisation of the perovskite-based solar cell obtained was carried out as described above: Table 1 shows the results obtained.

[0172] EXAMPLE 7 (invention)

[0173] Preparation of a perovskite-based solar cell (“bulk” treatment)

[0174] 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.

[0175] To this end, 39.5 mg of phenylphosphonic acid (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 shown in Example 1 above, and the resulting 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 equal to 330 nm.

[0176] The electrical characterisation of the perovskite-based solar cell obtainedwas carried out as described above: Table 1 shows the results obtained.

[0177] EXAMPLE 8 (invention)

[0178] Preparation of a perovskite-based solar cell (“bulk” treatment)

[0179] 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.

[0180] For this purpose, 15.8 mg phenylphosphonic acid (Merck) (0.1 mmol) and 9.2 mg serinol (Merck) (0.1 mmol) [0.083 millimoles of compound having general formula (I) to millimoles of lead] were added to the solution of the perovskite precursors obtained as shown in Example 1 above, and the solution thus obtained 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 equal to 330 nm.

[0181] The electrical characterisation of the perovskite-based solar cell obtained was carried out as described above: Table 1 shows the results obtained.

[0182] EXAMPLE 9 (invention)

[0183] Preparation of a perovskite-based solar cell (“bulk” treatment)

[0184] 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.

[0185] For this purpose, 39.5 mg phenylphosphonic acid (Merck) (0.25 mmol) and 23 mg serinol (Merck) (0.25 mmol) [0.208 millimoles of compound having general formula (I) to millimoles of lead] were added to the solution of the perovskite precursors obtained as shown in Example 1 above, and the solution thus obtained was heated to 45°C, for 30 minutes, under stirring. Subsequently, 20 µl of the solution thus obtained was deposited on top of the layer based on ahole 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 equal to 330 nm.

[0186] The electrical characterisation of the perovskite-based solar cell obtained was carried out as described above: Table 1 shows the results obtained.

[0187] EXAMPLE 10 (invention)

[0188] Preparation of a solar cell based on perovskite (surface treatment)

[0189] A solar cell based on perovskite was prepared by operating as described in Example 1, with the only difference being the surface treatment of the perovskite photoactive layer.

[0190] For this purpose, 4.8 mg methylphosphonic acid (Merck) (0.05 mmol) was dissolved in 100 ml of Ao-propanol (Merck) and the solution thus obtained was heated at 45°C, for 30 minutes, under stirring. Subsequently, 40 pl of the solution thus obtained was deposited on said perovskite photoactive layer by spin coating operating at a rotational speed of 5000 rpm. (acceleration equal to 2000 rpm / s), for 30 seconds, 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 active layer was found to be equal to 330 nm.

[0191] The electrical characterisation of the solar cell based on perovskite thus obtained was carried out as described above: Table 1 shows the results obtained.

[0192] EXAMPLE 11 (invention)

[0193] Preparation of a solar cell based on perovskite (surface treatment)

[0194] A solar cell based on perovskite was prepared by operating as described in Example 1, with the only difference being the surface treatment of the perovskite photoactive layer.

[0195] For this purpose, 9.6 mg methylphosphonic acid (Merck) (0.1 mmol) was dissolved in 100 ml of iso-propanol (Merck) and the solution thus obtained was heated at 45°C, for 30 minutes, under stirring. Subsequently, 40 µl of the solutionthus obtained was deposited on said perovskite photoactive layer by spin coating operating at a rotational speed of 5000 rpm. (acceleration equal to 2000 rpm / s), for 30 seconds, 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 active layer was found to be equal to 330 nm.

[0196] The electrical characterisation of the solar cell based on perovskite thus obtained was carried out as described above: Table 1 shows the results obtained.

[0197] EXAMPLE 12 (invention)

[0198] Preparation of a solar cell based on perovskite (surface treatment)

[0199] A solar cell based on perovskite was prepared by operating as described in Example 1, with the only difference being the surface treatment of the perovskite photoactive layer.

[0200] For this purpose, 7.9 mg phenylphosphonic acid (Merck) (0.05 mmol) was dissolved in 100 ml of Ao-propanol (Merck) and the solution thus obtained was heated at 45°C, for 30 minutes, under stirring. Subsequently, 40 ptl of the solution thus obtained was deposited on said perovskite photoactive layer by spin coating operating at a rotational speed of 5000 rpm. (acceleration equal to 2000 rpm / s), for 30 seconds, 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 active layer was found to be equal to 330 nm.

[0201] The electrical characterisation of the solar cell based on perovskite thus obtained was carried out as described above: Table 1 shows the results obtained.

[0202] EXAMPLE 13 (invention)

[0203] Preparation of a solar cell based on perovskite (surface treatment)

[0204] A solar cell based on perovskite was prepared by operating as described in Example 1, with the only difference being the surface treatment of the perovskite photoactive layer.

[0205] For this purpose, 15.8 mg phenylphosphonic acid (Merck) (0.1 mmol) was dissolved in 100 ml of iso-propanol (Merck) and the solution thus obtained was heated at 45°C, for 30 minutes, under stirring. Subsequently, 40 µl of the solution thus obtained was deposited on said perovskite photoactive layer by spin coating operating at a rotational speed of 5000 rpm. (acceleration equal to 2000 rpm / s),for 30 seconds, 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 active layer was found to be equal to 330 nm.

[0206] The electrical characterisation of the solar cell based on perovskite thus obtained was carried out as described above: Table 1 shows the results obtained.

[0207] Table 1

[0208] Example PCE(1)PCE(1)HI'2’ FF(3) Voc(4)Jsc(5)Average maximum (%)

[0209] (%) (V) (mA / cm2) 1 13.87 14.97 2.00 69.5 1.104 18.1 (comparative)

[0210] 2 15.80 19.00 0.89 76.3 1.123 18.6 (invention)

[0211] 3 18.00 19.10 1.01 82.5 1.142 19.3 (invention)

[0212] 4 18.40 19.00 0.31 81.1 1.156 19.6 (invention)

[0213] 5 18.50 19.10 0.99 82.6 1.161 19.3 (invention)

[0214] 6 16.00 17.00 0.28 75.9 1.127 18.6 (invention)

[0215] 7 16.60 18.50 1.25 78.6 1.141 18.7 (invention)

[0216] 8 17.50 18.00 0.46 78.9 1.145 19.4 (invention)

[0217] 9 18.20 18.90 0.80 81.6 1.156 19.3 (invention)

[0218] 10 18.80 19.80 0.43 79.9 1.159 19.9 (invention)

[0219] 11 19.40 20.10 1.24 81.5 1.168 20.2 (invention)

[0220] 12 18.70 19.50 0.81 80.7 1.161 20.0 (invention)

[0221] 13 19.40 20.80 0.87 81.6 1.171 20.1

[0222]

[0223] (invention)

[0224] Power Conversion Efficiency;

[0225] (2) Hysteresis Index;

[0226] ® Fill Factor;

[0227] (4) Open Circuit Voltage;

[0228] (5) short-circuit photocurrent density.

[0229] From the data shown in Table 1, it can be seen that the semi-transparent perovskite-based solar cells of the present invention (Examples 2-13) have both good power conversion efficiency (PCE) (i.e. PCE > 17%) [higher than that of the comparison solar cell (Example 1)], and low hysteresis values (i.e. values lowerthan 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):[R1PO3]2-X+Y+(I)wherein:Ri is selected from C1-C16 alkyl groups, preferably C1-C12, 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;X+and Y+, identical or different from each other, represent a hydrogen ion (H+), or an ammonium ion having general formula (II):H - N - R2(II)R4wherein:R2 is selected from C2-C12 alkyl groups, preferably C2-C8, linear or branched, saturated or unsaturated, aryl groups, cycloalkyl groups, said alkyl, aryl and cycloalkyl groups being substituted with 1 to 5, preferably 1 to 3, hydroxyl groups and, optionally, with at least one group selected from alkyl groups, ether groups, ester groups, carbonyl groups;R3 and R4, identical or different from each other, represent a hydrogen atom or a methyl group; or they are selected from C2-C4 alkyl groups, linear or branched, saturated, wherein one or more hydrogen atoms are optionally substituted with a hydroxyl group; preferably, a hydrogen atom.

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 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 cesium (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 (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], cesium lead iodide [CsPbI3], methylammonium formamidinium lead iodide [(CH3NH3)x(CH(NH2)2)i-xPbI3], cesium methylammonium lead iodide [Csx(CH3NH3)i-xPbI3], cesium formamidinium leadiodide [Csx(CH(NH2)2)i-xPbl3], cesium methylammonium formamidinium lead iodide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3], methylammonium lead bromide [CH₃NH₃PbBr₃], formamidinium lead bromide [CH(NH₂)₂PbBr₃], cesium lead bromide [CsPbBr₃], methylammonium formamidinium lead bromide [(CH3NH3)x(CH(NH2)2)i-xPbBr3], cesium methylammonium lead bromide [Csx(CH3NH3)i-xPbBr3], cesium formamidinium lead bromide [Csx(CH(NH₂)₂)1-xPbBr₃], cesium methylammonium formamidinium lead bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbBr3], methylammonium lead chloride [CthNPUPbCh], formamidinium lead chloride [CH Ntk PbCh], cesium lead chloride [CsPbCl₃], methylammonium formamidinium lead chloride [(CH3NH3 (CH(NH2)2)i-xPbC13], cesium methylammonium lead chloride [CSX(CH3NH3)I- xPbCh], cesium formamidinium lead chloride [Csx(CH(NH2)2)i-xPbC13], cesium methylammonium formamidinium lead chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbCh], methylammonium lead iodide bromide [CH3NH3PbI3-wBrw], formamidinium lead iodide bromide [CH(NH2)2Pbl3-wBrw], cesium lead iodide bromide [CsPbl3-wBrw], methylammonium formamidinium lead chloride bromide [(CH3NH3)x(CH(NH2)2)i-xPbl3-wBrw],cesium methylammonium lead iodide bromide [Csx(CH3NH3)i-xPbl3-wBrw], cesium formamidinium lead iodide bromide [Csx(CH(NH2)2)i-xPbl3-wBrw], cesium methylammonium formamidinium lead iodide bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-wBrw], methylammonium lead iodide chloride [CHsNHsPbh-wClw], formamidinium lead iodide chloride [CH(NH2)2Pbl3-wClw], cesium lead iodide chloride [CsPbl3-wClw], methylammonium formamidinium lead iodide chloride [(CH3NH3)x(CH(NH2)2)i-xPbl3-wClw], cesium methylammonium lead iodide chloride [Csx(CH3NH3)i-xPbl3-wClw], cesium formamidinium lead iodide chloride [Csx(CH(NH2)2)i-xPbl3-wClw], cesium methylammonium formamidinium lead iodide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-wClw], methylammonium lead bromide chloride [CHsNHsPbBn-wClw], formamidinium lead bromide chloride [CH(NH2)2PbBr3-wClw], cesium lead bromide chloride [CsPbBr3-wClw], methylammonium formamidinium lead bromide chloride [(CH₃NH₃)x(CH(NH₂)₂)1-xPbBr₃₋wClw], cesium methylammonium lead bromide chloride[Csx(CH3NH3)i-xPbBr3-wClw], cesium formamidinium lead bromide chloride [Csx(CH(NH2)2)i-xPbBr3-wClw], cesium methylammonium formamidinium lead bromide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbBr3-wClw], methylammonium lead iodide bromide chloride [CthNtUPbh-w-vBrwClv], formamidinium lead iodide bromide chloride [CH(NH2)2Pbl3-w-vBrwClv], cesium lead iodide bromide chloride [CsPbl3-w-vBrwClv], methylammonium formamidinium lead iodide bromide chloride [(CH3NH3)x(CH(NH2)2)i-xPbl3-w-vBrwClv], cesium methylammonium lead iodide bromide chloride [Csx(CH3NH3)i-xPbl3-w-vBrwClv], cesium formamidinium lead iodide bromide chloride [Csx(CH(NH2)2)i-xPbl3-w-vBrwClv], cesium methylammonium formamidinium lead iodide bromide chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-w-vBrwClv], methylammonium tin iodide [CH3NH3SnI3], formamidinium lead iodide [CH(NH2)2Snl3], cesium tin iodide [CsSnI₃], methylammonium formamidinium tin iodide [(CH₃NH₃)x(CH(NH₂)₂)1-xSnI₃], cesium methylammonium tin iodide [Csx(CH3NH3)1-xSnI3], cesium formamidinium tin iodide [Csx(CH(NH2)2)i-xSnl3], cesium methylammonium formamidinium tin iodide [(CsxCH3NH3)y(CH(NH2)2)i-x-ySnl3], methylammonium tin bromide [CH3NH3SnBr3], formamidinium tin bromide [CH(NH2)2SnBr3], cesium tin bromide [CsSnBr₃], methylammonium formamidinium tin bromide [CH3NH3)x(CH(NH2)2)i-xSnBr3], cesium methylammonium tin bromide [Csx(CH3NH3)1-xSnBr3], cesium formammidinium tin bromide [Csx(CH(NH2)2)i-xSnBr3], cesium methylammonium formamidinium tin bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-ySnBr3], methylammonium tin chloride [CH3NH3SnCl3], formamidinium tin chloride [CH(NH2)2SnC13], cesium tin chloride [CsSnCl₃], methylammonium formamidinium tin chloride [CH(CH3)x(CH(NH2)2)i-xSnC13], cesium methylammonium tin chloride [Csx(CH3NH3)i xSnC13], cesium formamidinium tin chloride [Csx(CH(NH(NH2)2)i-xSnC13], cesium methylammonium formamidinium tin chloride [(CsxCH3NH3)y(CH(NH2)2)i-x-ySnC13], methylammonium tin iodide bromide [CH₃NH₃SnI₃₋wBrw], formamidinium tin iodide bromide [CH(NH2)2Snl3-wBrw], cesium tin iodide bromide [CsSnl3-wBrw], methylammonium formamidinium tin iodide bromide [(CH(NH3-W)x (CH(NH(NH2)2)i-xSnl3-wBrw], cesium methylammonium tin iodide bromide [Csx(CH3NH3)i-xSnl3-wBrw], cesiumformamidinium lead iodide bromide [Csx(CH(NH2)2)i- Snl3-wBrw], cesium methylammonium formamidinium tin iodide bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-ySnl3-wBrw], methylammonium tin iodide chloride [CH₃NH₃SnI₃₋wClw], formamidinium tin iodide chloride [CH(NH2)2Snl3-wClw], cesium tin iodide chloride [CsSnl3-wClw], methylammonium formamidinium tin iodide chloride [(CH3NH3)x(CH(NH2)2)i- Snl3-wClw], cesium methylammonium tin iodide chloride [Csx(CH3NH3)i-xSnl3-wClw], cesium formamidinium tin iodide chloride [Csx(CH(NH2)2)i- Snl3-wClw], cesium methylammonium formamidinium tin iodide chloride [(CsxCH3NH3)y(CH(NH2)2)i- -ySnl3-wClw], methylammonium tin bromide chloride [CH₃NH₃SnBr₃₋wClw], formamidinium tin bromide chloride [CH(NH2)2SnBr3-wClw], cesium tin bromide chloride [CsSnBr₃₋wClw], methylammonium formamidinium tin bromide chloride [(CH₃NH₃)x(CH(NH₂)₂)1-xSnBr₃₋wClw], cesium methylammonium tin bromide chloride [Csx(CH₃NH₃)1-xSnBr₃₋wClw], cesium formamidinium tin bromide chloride [Csx(CH(NH2)2)i-xSnBr3 wClw], cesium methylammonium formamidinium tin bromide chloride [(CsxCH3NH3)y(CH(NH2)2)i- -ySnBr3-wClw], methylammonium tin iodide bromide chloride [CH₃NH₃SnI₃₋w₋vBrwClv], formamidinium tin iodide bromide chloride [CH(NH2)2Snl3-w-vBrwClv], cesium tin iodide bromide chloride [CsSnI₃₋w₋vBrwClv], methylammonium formamidinium tin iodide bromide chloride [(CH3NH3)x(CH(NH2)2)i- Snl3-w-vBrwClv], cesium methylammonium tin iodide bromide chloride [Csx(CH3NH3)i-xSnl3-w-vBrwClv], cesium formamidinium tin iodide bromide chloride [Csx(CH(NH2)2)i- Snl3-w-vBrwClv], cesium 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 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 different from 0; preferably, between: methylammonium lead iodide [CtUNtUPbh], formamidinium lead iodide [CH(NH₂)₂PbI₃], cesium lead iodide [CsPbI₃], methylammonium formamidinium lead iodide [(CH3NH3)x(CH(NH2)2)i- Pbl3],cesium methylammonium lead iodide [Csx(CH3NH3)i-xPbl3], cesium formamidinium lead iodide [Csx(CH(NH2)2)i-xPbl3], cesium methylammonium formamidinium lead iodide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3], methylammonium lead iodide bromide [CH3NH3PbI3-wBrw], formamidinium lead iodide bromide [CH(NH2)2Pbl3-wBrw], cesium lead iodide bromide [CsPbl3-wBrw], methylammonium formamidinium lead iodide bromide [(CH3NH3 (CH(NH2)2)i-xPbl3-wBrw], cesium methylammonium lead iodide bromide [Csx(CH3NH3)i-xPbl3-wBrw], cesium formamidinium lead iodide bromide [Csx(CH(NH2)2)i-xPbl3-wBrw], cesium methylammonium formamidinium lead iodide bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-wBrw]; even more preferably between: cesium methylammonium lead iodide bromide [Csx(CH3NH3)i-xPbl3-wBrw], cesium formamidinium lead iodide bromide [Csx(CH(NH2)2)i-xPbl3-wBrw], cesium methylammonium formamidinium lead iodide bromide [(CsxCH3NH3)y(CH(NH2)2)i-x-yPbl3-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) (FTO), indium tin oxide (ITO), aluminium zinc oxide (AZO), indium zinc oxide (IZO), 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 cesium methylammonium lead iodide bromide [Cs₀.₀₅(CH₃NH₃)₀.₉₅PbI₂.₅₅Br₀.₄₅], cesium formamidinium lead iodide bromide [Cs₀.₀₅FA₀.₉₅PbI₂.₅₅Br₀.₄₅], more preferably cesium methylammonium lead iodide bromide [Cs₀.₀₅(CH₃NH₃)₀.₉₅PbI₂.₅₅Br₀.₄₅], and optionally at least one compound having general formula (I), preferably a compound obtained by the reaction between 3-aminopropane-l,2-diol, 2- aminopropane- 1,3-diol (serinol), 2-amino-2-hydroxymethylpropane- 1,3- diol (tromethamine), with methylphosphonic acid or with phenylphosphonic acid;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 electrical 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. Process for the preparation of a photovoltaic cell (or solar cell) based on perovskite (" Perovskite Solar Cell" - PSC) 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 a 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) a 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);(e) preparing a mixture comprising perovskite precursors, at least one phosphonic acid having general formula (III) and at least one amino alcohol having general formula (IV);(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 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) 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);(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);(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 a "back contact" preferably a gold, silver or aluminium metal 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).

13. 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, positioned above said silicon photovoltaic cell (or solar cell).

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

15. 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 13 or 14 in: photovoltaic fields (or photovoltaic parks), residential use, commercial buildings.

16. 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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