Inverted polymer photovoltaic cells and methods of making the same

Abstract

Inverted polymer photovoltaic cell (or solar cell) comprising: - an anode; - a first anode interlayer (buffer layer) based on PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate]; - an active layer comprising at least one photoactive organic polymer as electron donor and at least one electron acceptor organic compound; - a cathode interlayer (buffer layer); - an anode; wherein a second anode interlayer (buffer layer) comprising at least one heteropolyacid and optionally at least one amino compound is interposed between said first anode interlayer (buffer layer) and said active layer. Said inverted polymer photovoltaic cell (or solar cell) shows good values of photoelectric conversion efficiency (power conversion efficiency - PCE) (η) and, in particular, good levels of adhesion between the different layers, more particularly between the active layer and said first anode interlayer (buffer layer).

Description

Technical Field

[0001] This invention relates to inverted polymer photovoltaic cells (or solar cells).

[0002] More specifically, the present invention relates to an inverted polymer photovoltaic cell (or solar cell) comprising: an anode; a first anode intermediate layer (buffer layer) based on PEDOT:PSS poly(3,4-ethylenedioxythiophene):polystyrene sulfonate; an active layer comprising at least one photoactive organic polymer as an electron donor and at least one organic electron acceptor compound; a cathode intermediate layer (buffer layer); a cathode; and a second anode intermediate layer (buffer layer) comprising at least one heteropolyacid and optionally at least one amino compound disposed between the first anode intermediate layer (buffer layer) and the active layer.

[0003] The inverted polymer photovoltaic cell (or solar cell) exhibits a good photoelectric conversion efficiency (PCE) (η) value and, in particular, a good level of adhesion between different layers, more specifically between the active layer and the first anode intermediate layer (buffer layer).

[0004] The present invention also relates to a method for preparing the aforementioned inverted polymer photovoltaic cell (or solar cell). Background Technology

[0005] Photovoltaic devices (or solar energy devices) are devices that convert the energy of light radiation into electrical energy. Currently, most photovoltaic devices (or solar energy devices) available for practical applications utilize the physicochemical properties of photoactive inorganic materials, particularly high-purity crystalline silicon. However, due to the high production cost of silicon, scientific research has been dedicated to developing alternative organic materials with polymer structures [the so-called "polymer photovoltaic cells (or solar cells)"]. In fact, unlike high-purity crystalline silicon, these organic materials are characterized by relatively easy synthesis, low production costs, associated weight reduction in photovoltaic devices (or solar energy devices), and the ability to recycle the organic materials at the end of the device's lifespan.

[0006] Therefore, although the photoelectric conversion efficiency (η) of organic photovoltaic devices (or solar energy devices) is lower than that of inorganic photovoltaic devices (or solar energy devices), the aforementioned advantages make the use of said organic materials attractive both energy-wise and economically.

[0007] Organic photovoltaic devices (or solar devices), such as polymer photovoltaic cells (or solar cells), operate based on the combined use of electron acceptor compounds and electron donor compounds.

[0008] In the prior art, the most commonly used electron donor compound in constructing polymer photovoltaic cells (or solar cells) is the regio-regular poly(3-hexylthiophene) (P3HT). This polymer possesses excellent electronic and optical properties [e.g., good HOMO and LUMO orbital values, good molar absorption coefficient (ε)], good solubility in solvents used to manufacture polymer photovoltaic cells (or solar cells), and good electron-hole mobility.

[0009] Other examples of polymers that can be advantageously used as electron donor compounds are: polymer PCDTBT{poly[N-9"-heptadecyl-2,7-carbazole-alternating-5,5-(4',7'-di-2-thiophene-2',1',3'-benzothiadiazole]}, polymer PCPDTBT{poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopentano[2,1-b;3,4-b']-dithiophene)-alternating-4,7-(2,1,3-benzothiadiazole)]}, polymer PffBT4T-2OD{poly[(5,6-difluoro-2,1... ,3-benzothiadiazole-4,7-diyl)-alternating-(3,3"'-bis(2-octyldodecyl)-2,2';5',2";5",2”'-tetrathiophene-5,5”'-diyl)]}、polymer PBDB-T{poly[[4,8-bis(5-(2-ethylhexyl)-2-thiophene]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]-2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c']dithiophene-1,3-diyl]]}.

[0010] In the prior art, the most commonly used electron acceptor compounds for producing polymer photovoltaic cells (or solar cells) are fullerene derivatives, such as [6,6]-phenyl-C 61 methyl butyrate (PCBM), [6,6]-phenyl-C 71 methyl butyrate (PC) 71 BM). When mixed with electron donor compounds selected from the following, the fullerene derivatives result in the greatest photoelectric conversion efficiency (η): conjugated polymers, such as polythiophene (η>5%), polycarbazole (η>6%), derivatives of poly(thienothiophene)benzodithiophene (PTB) (η>8%), and fluorinated polymers of benzothiadiazole (η>10%).

[0011] The fundamental process of converting light into electric current in polymer photovoltaic cells (or solar cells) occurs through the following stages:

[0012] 1. Photons are absorbed by electron donor compounds to form excitons, which are electron-electron-hole charge carrier pairs;

[0013] 2. Excitons diffuse in the region of the electron donor compound until they reach the interface with the electron acceptor compound, where they can dissociate.

[0014] 3. Excitons dissociate into two types of charge carriers: electrons (-) in the acceptor phase (i.e., in the electron acceptor compound) and electron holes (+) in the donor phase (i.e., in the electron donor compound);

[0015] 4. The charges thus formed are transferred to the cathode [electrons (-) pass through the electron acceptor compound] and the anode [electron holes (+) pass through the electron donor compound], generating current in the circuit of the polymer photovoltaic cell (or solar cell).

[0016] The photoabsorption process, which involves exciton formation and subsequent electron transfer to the electron acceptor compound, involves exciting electrons from the HOMO (highest occupied molecular orbital) to the LUMO (lowest unoccupied molecular orbital) of the electron donor compound, and then transferring them from there to the LUMO of the electron acceptor compound.

[0017] Since the efficiency of polymer photovoltaic cells (or solar cells) depends on the number of free electrons generated by exciton dissociation, one of the key structural features of the electron donor compound that affects this efficiency is the energy difference (the so-called band gap) between the HOMO and LUMO orbitals of the electron donor compound. The wavelength of the photons that the electron donor compound can collect and efficiently convert into electrical energy (the so-called photon trapping or light-trapping process) depends in particular on this energy difference.

[0018] From an electronic perspective, material-related improvements for realizing polymer photovoltaic cells (or solar cells) can be achieved by designing the molecular structures of electron donor and electron acceptor compounds to tune their optimal energy levels (HOMO-LUMO). Specifically, to achieve the dissociation of excitons formed in the process and avoid charge retransfer, the difference between the HOMO and LUMO of the electron donor and acceptor compounds must have an optimal value of 0.3 eV to 0.5 eV. Furthermore, the band gap, i.e., the energy difference between the HOMO and LUMO of the electron donor compound, cannot be too high to allow the absorption of the maximum number of photons, nor can it be too low, as this would reduce the voltage of the polymer photovoltaic cell (or solar cell) electrodes.

[0019] Another important feature of materials used to construct polymer photovoltaic cells (or solar cells) is the mobility of electrons in electron acceptor compounds and electron holes in electron donor compounds, which determines the ease with which charges reach the electrodes once photogenerated.

[0020] Electron mobility (i.e., the mobility of electrons in electron acceptor compounds and electron holes in electron donor compounds) is not only an inherent property of molecules, but is also strongly influenced by the morphology of the active layer containing them, which in turn depends on the miscibility and solubility of the compounds used in the active layer. Therefore, the phases of the active layer must be neither too dispersed nor too separated.

[0021] The morphology of the active layer is also crucial for the dissociation efficiency of photogenerated electron-hole pairs. In fact, the average lifetime of excitons allows them to diffuse into organic materials over an average distance of no more than 10-20 nm. Therefore, the phases of the electron donor and acceptor compounds must be organized into nanodomains with a size comparable to this diffusion distance. Furthermore, the contact area between the electron donor and acceptor compounds must be as large as possible, and there must be a preferred path for electrical contact. Moreover, this morphology must be reproducible and not change over time.

[0022] In its simplest form, a polymer photovoltaic cell (or solar cell) is fabricated by introducing a thin layer (approximately 100 nanometers) (bulk heterojunction) of a mixture of an electron acceptor compound and an electron donor compound between two electrodes, typically composed of indium tin oxide (ITO) (anode) and aluminum (Al) (cathode). Typically, to produce this type of layer, a solution of both components (i.e., the electron acceptor compound and the electron donor compound) is prepared, and starting from this solution, an active layer is formed on the anode [indium tin oxide (ITO)] using a suitable deposition technique, such as spin coating, spray coating, inkjet printing, slot extrusion coating, gravure printing, screen printing, etc. Finally, the electrode [i.e., the aluminum cathode (Al)] is deposited on the dried active layer using known techniques such as evaporation. Optionally, additional layers (called intermediate layers or buffer layers) capable of performing specific functions such as electrical, optical, or mechanical properties may be introduced between the anode and the active layer and / or between the cathode and the active layer.

[0023] Typically, for example, in order to facilitate the arrival of electrons and holes at the anode [indium tin oxide (ITO)] while simultaneously blocking electron transport, thereby improving charge collection at the anode and suppressing recombination, a layer is deposited starting from an aqueous suspension containing PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate] using suitable deposition techniques, such as spin coating, spray coating, inkjet printing, slot extrusion coating, gravure printing, screen printing, etc., before generating the active layer from a mixture of electron acceptor and electron donor compounds as described above.

[0024] More details about different deposition techniques can be found, for example, by Krebs FC et al., in "Solar Energy Materials & Solar Cells" (2009), Vol. 93, pp. 394-412.

[0025] On the other hand, inverted polymer photovoltaic cells (or solar cells) typically reported in the literature include the following layers: (i) a transparent material carrier; (ii) an indium tin oxide (ITO) cathode; (iii) a cathode buffer layer that acts as an electron carrier and electron-hole blocking layer, typically containing zinc oxide; (iv) an active layer that contains electron donor and electron acceptor compounds typically selected from those reported above; (v) an anode intermediate layer (buffer layer) that acts as an electron-hole carrier and electron blocking layer, including hole transport materials typically selected from: molybdenum oxide, tungsten oxide, vanadium oxide; and (vi) an anode that is typically silver (Ag), gold (Au), or aluminum (Al).

[0026] Typically, in order to protect the polymer photovoltaic cells (or solar cells) with conventional and inverted structures from mechanical stress and atmospheric factors, and for their use under practical conditions, the photovoltaic cells (or solar cells) are encapsulated in suitable materials [e.g., a mixed multilayer film based on polyethylene terephthalate and inorganic oxides].

[0027] Typically, the aforementioned anode intermediate layer (buffer layer) is obtained through a molybdenum oxide (or tungsten oxide or vanadium oxide) deposition process, which involves high temperature and high vacuum (e.g., 10...). -5 mmHg-10 -7 The molybdenum oxide is evaporated at a pressure of 100 mmHg. However, the deposition process has several drawbacks, such as: the need for a long time to bring the deposition chamber to the required pressure and for sufficient time to achieve the material thickness required for the final photovoltaic cell (or solar cell) to operate, resulting in extended process time and increased process cost; high energy consumption; and significant material waste, mainly due to the oxide vapor filling the deposition chamber and being uniformly deposited on a surface much larger than actually needed (corresponding to the final photovoltaic cell (or solar cell)).

[0028] In order to enable the aforementioned inverted polymer photovoltaic cells (or solar cells) to find large-scale industrial applications, it is necessary to develop suitable production methods that can overcome the above-mentioned shortcomings. Therefore, efforts have been made in this direction.

[0029] For example, M et al., in "Nanoscale" (2015), Vol. 7, pp. 9570-9580, describe a process for manufacturing organic photovoltaic (OPV) modules with inverted structures using roll-to-roll (R2R) molding with the following deposition techniques: gravure printing and rotary screen printing. In the inverted structure OPV module, the anode intermediate layer (buffer layer) comprises PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate] and is obtained by rotary screen printing.

[0030] However, as reported by Dkhil SB et al. in "Advanced Energy Materials" (2016), Vol. 6, 1600290, the use of an anode interlayer (buffer layer) containing materials other than molybdenum oxide generally leads to a reduction in the efficiency of the resulting organic solar cell: in fact, organic solar cells in which the anode interlayer (buffer layer) is obtained by a molybdenum oxide deposition process (by vacuum evaporation of said molybdenum oxide) can achieve efficiencies higher than 9%.

[0031] Furthermore, the use of PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate] as the anode interlayer (buffer layer) material, typically in aqueous suspensions or mixed water / alcohol solvents, has several disadvantages known to those skilled in the art from a practical point of view. The first disadvantage is the strong acidity of the solution used, typically with a pH of 2 or 3, which determines the long-term instability of the polymer photovoltaic cell (or solar cell) due to the anode or cathode in contact with the anode interlayer (buffer layer) in high-temperature environments. + The corrosion is caused by the slow diffusion of ions through the active layer. A second drawback is the very poor wettability of the aqueous suspension on the active layer: this leads to uneven coverage of the layer itself, thus reducing the effectiveness of the anodic intermediate layer (buffer layer) in functioning through the electron-hole carrier layer. This drawback can be overcome by adding a suitable surfactant to modify the suspension, but this increases material costs and reduces the conductivity of the anodic intermediate layer (buffer layer) because the surfactant acts as an electrical insulator.

[0032] Therefore, using PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate] in the manufacture of polymer photovoltaic cells (or solar cells) is not the optimal solution, and thus it is of great interest to identify alternative routes.

[0033] Among the soluble alternatives to PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate] proposed by the scientific community, we can cite, for example, soluble derivatives of molybdenum or vanadium. For instance, Xu M.-F. et al., in "Organic Electronics" (2013), Vol. 14, pp. 657-664, describe the use of an aqueous solution of molybdenum oxide (MoO3) to produce an anode interlayer (bulk heterojunction) organic solar cell [containing poly(3-hexylthiophene) (P3HT) and fullerene]. However, this solution cannot be used for inverted organic solar cells because the aqueous solution does not adequately wet the active layer.

[0034] Jouane Y. et al., in the *Journal of Materials Chemistry C* (2014), Vol. 2, pp. 158-163, described the use of an ammonia solution of molybdenum oxide (MoO3) to produce an anode intermediate layer (buffer layer), which was spin-coated onto the anode [indium tin oxide (ITO)] followed by heat treatment (annealing) at 150 °C for 20 minutes. Furthermore, this solution is used for conventional dispersed heterojunction (bulk heterojunction) organic solar cells [including poly(3-hexylthiophene) (P3HT) and fullerenes], and cannot be used for inverted organic solar cells due to the same drawbacks mentioned above. Additionally, the aforementioned heat treatment (annealing) is performed at a temperature incompatible with the use of flexible plastic carriers and requires too long a time for high-speed deposition processes (10-50 m / min).

[0035] Murase S. et al., in "Advanced Materials" (2012), Vol. 24, pp. 2459-2462, described the use of a MoO3 solution obtained by thermal decomposition of ammonium heptamolybdate as a precursor in deionized water to produce an anode intermediate layer (buffer layer), which was then spin-coated onto the anode [indium tin oxide (ITO)]. Similarly, in this case, the solution is used in conventional organic solar cells (i.e., without an inverted structure) due to wettability issues with the active layer.

[0036] Hammond SR et al., in the Journal of Materials Chemistry (2012), Vol. 22, pp. 3249-3254, described the use of molybdenum oxide (MoO) obtained by thermal decomposition in acetonitrile via molybdenum tricarbonyltripropionitrile as a precursor. xA solution of molybdenum tricarbonyltripropionitrile (Mo) is prepared to produce an anolyte intermediate (buffer layer), which is then deposited on the anode [indium tin oxide (ITO)] by spin coating. Due to the instability of the precursor, the acetonitrile solution of Mo is prepared in an inert atmosphere. The instability, the very high cost of the precursor, and the known toxicity of carbonyl metal derivatives make the method described herein unsuitable for large-scale industrial processes.

[0037] Zilberg K. et al., in "Applied Materials & Interfaces" (2012), Vol. 4, pp. 1164-1168, describe the use of MoO2 obtained by thermal decomposition of bis(2,4-glutaric acid) molybdenum dioxide (IV) as a precursor in isopropanol (containing about 0.1% water). x The solution is used to create an anodic intermediate layer (buffer layer), which is then spin-coated onto the anode (Ag) and subsequently heat-treated (annealed) at 110°C for 1 hour. These times are completely incompatible with high-speed deposition processes (10-50 m / min).

[0038] Zhu Y. et al., in the *Journal of Materials Chemistry* (2014), Vol. 2, pp. 1436-1442, described the use of a solution of phosphomolybdic acid (PMA) in isopropanol to produce an anode interlayer (buffer layer), which was deposited on the anode (Ag) by spin-coating followed by heat treatment (annealing) at 150°C for 90 minutes. It is claimed that inverted organic solar cells incorporating this interlayer have efficiencies comparable to or slightly higher than those of inverted solar cells incorporating the anode interlayer (buffer layer), which is obtained via a molybdenum oxide deposition process (by evaporating the molybdenum oxide). However, the prolonged heat treatment is incompatible with roll-to-roll (R2R) forming processes.

[0039] Chinese patent application CN103400941 relates to an organic solar cell based on a modified anode layer. The cell includes: a cathode, a modified cathode intermediate layer (buffer layer), an active layer having a dispersed heterojunction (bulk heterojunction), a modified anode intermediate layer (buffer layer), and an anode; wherein the modified anode intermediate layer (buffer layer) is based on a layer having formula H... x (MM' 12 OR 40 (where M is phosphorus (P) or silicon (Si), M' is molybdenum (Mo) or tungsten (W), and X is 3 or 4) heteropolyacids; the cathode is indium tin oxide (ITO); the modified anode intermediate layer (buffer layer) is zinc oxide; the active layer with a bulk heterojunction is a mixture of compounds such as poly(3-hexylthiophene) (P3HT) and fullerenes; the anode is silver or aluminum.

[0040] Vasilopoulou M. et al., in the Journal of Materials Chemistry (2015), Vol. 137, pp. 6844-6856, described the use of Keggin and Dawson type polyoxometalates (POMs) as cathode interlayers (buffer layers) in high-efficiency optoelectronic devices. These cathode buffer layers function as both electron transport materials and hole blockers.

[0041] Kim J.-H. et al., in *Electronic Materials Letters* (2016), Vol. 12, No. 3, pp. 383-387, describe an inverted organic solar cell based on P3HT:PCBM, which exhibits improved charge transport due to the use of molybdenum oxide nanoparticles (MoO3 NPs) as a hole transport interlayer between the active layer P3HT:PCBM and the anode interlayer PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate]. The photoelectric conversion efficiency (PCE) (η) of this organic solar cell is 4.11%, which is higher than the PCE of organic solar cells without the aforementioned molybdenum oxide nanoparticle (MoO3 NP) hole transport interlayer (actually 3.70%).

[0042] The applicant has noted that, in addition to the aforementioned drawbacks, the adhesion between different layers of an inverted polymer photovoltaic cell (or solar cell), particularly between the active layer and the anode intermediate layer (buffer layer), is generally poor.

[0043] Therefore, the problem facing the applicant is to find an inverted polymer photovoltaic cell (or solar cell) that has good performance and good adhesion between different layers, especially between the active layer and the anode intermediate layer (buffer layer), while maintaining a good photoelectric conversion efficiency (power conversion efficiency - PCE) (η) value. Summary of the Invention

[0044] The applicant has now discovered that using a first anode interlayer (buffer layer) and a second anode interlayer (buffer layer) based on PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate], wherein the second anode interlayer (buffer layer) comprises at least one heteropolyacid and optionally at least one amino compound, allows for the acquisition of inverted polymer photovoltaic cells (or solar cells) with good performance. In particular, the applicant has now discovered that using the first anode interlayer (buffer layer) and the second anode interlayer (buffer layer) allows for the acquisition of inverted polymer photovoltaic cells (or solar cells) that not only have good photoelectric conversion efficiency (PCE) values ​​(η), but also exhibit a good level of adhesion between the different layers, and more particularly between the active layer and the first anode interlayer (buffer layer).

[0045] Therefore, the object of the present invention is an inverted polymer photovoltaic cell (or solar cell) comprising:

[0046] -anode;

[0047] - First anode intermediate layer (buffer layer), which is based on PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate];

[0048] - An active layer comprising at least one photoactive organic polymer as an electron donor and at least one organic compound as an electron acceptor;

[0049] - Cathode intermediate layer (buffer layer);

[0050] -cathode;

[0051] A second anode intermediate layer (buffer layer) comprising at least one heteropoly acid and optionally at least one amino compound is disposed between the first anode intermediate layer (buffer layer) and the active layer.

[0052] For the purposes of this specification and the following claims, unless otherwise stated, the definition of a numerical range always includes the endpoint values.

[0053] For the purposes of this specification and the following claims, the terms first anode intermediate layer (buffer layer) and second anode intermediate layer (buffer layer) should be understood as a simple descriptive order rather than as the deposition order in the method described below for preparing the inverted polymer photovoltaic cell (or solar cell).

[0054] According to a preferred embodiment of the present invention, the anode may be made of metal, preferably selected from, for example, silver (Ag), gold (Au), and aluminum (Al); or it may be composed of a grid of conductive material and a transparent conductive polymer, preferably selected from, for example, silver (Ag), copper (Cu), graphite, and graphene, and the transparent conductive polymer is preferably PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate]; or it may be composed of metal nanowire-based ink, preferably selected from, for example, silver (Ag) and copper (Cu).

[0055] The anode can be obtained by depositing the metal on the first anode intermediate layer (buffer layer) using deposition techniques known in the art, such as vacuum evaporation, flexographic printing, edge coating, spraying, or screen printing. Alternatively, the anode can be obtained by depositing the transparent conductive polymer on the first anode intermediate layer (buffer layer) using spin coating, gravure printing, flexographic printing, or slot extrusion coating, followed by depositing a grid of the conductive material using evaporation, screen printing, spraying, or flexographic printing. Alternatively, the anode can be obtained by depositing the ink based on metal nanowires on the first anode intermediate layer (buffer layer) using spin coating, gravure printing, flexographic printing, or slot extrusion coating.

[0056] The dispersion or solution of PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate] that is advantageously used for the purposes of this invention and is currently commercially available is the Heraeus product Clevios. TM Agfa's product Orgacon TM .

[0057] To improve the deposition and properties of the first anode intermediate layer (buffer layer), one or more additives may be added to the dispersion or solution, such as: polar solvents, such as alcohols (e.g., methanol, ethanol, propanol), dimethyl sulfoxide, or mixtures thereof; anionic surfactants, such as esters of carboxylates, α-methyl olefin sulfonates, alkylbenzene sulfonates, alkyl sulfonates, alkyl ether sulfonates, triethanolamine alkyl sulfonates, or mixtures thereof; cationic surfactants, such as alkyl trimethylammonium salts, dialkyl dimethyl ammonium chloride, alkyl pyridinium chloride, or mixtures thereof; amphoteric surfactants, such as alkyl carboxybetaine, or mixtures thereof; nonionic surfactants, such as carboxylic acid diethanolamide, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, or mixtures thereof; polar compounds (e.g., imidazole), or mixtures thereof; or mixtures thereof. For more details on the addition of the aforementioned additives, see, for example: Synooka O et al., “ACS Applied Materials & Interfaces” (2014), Vol. 6 (14), pp. 11068-11081; Fang G et al., “Macromolecular Chemistry and Physics” (2011), Vol. 12, No. 17, pp. 1846-1851.

[0058] The first anode intermediate layer (buffer layer) can be obtained by depositing PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate] in dispersion or solution form onto the anode using deposition techniques known in the art, such as vacuum evaporation, spin coating, droplet casting, doctor blade casting, slot extrusion coating, gravure printing, flexographic printing, edge scraping, spraying, and screen printing.

[0059] According to a preferred embodiment of the present invention, the photoactive organic polymer may be selected from, for example:

[0060] (a) Polythiophenes, such as regio-regular poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene), poly(3,4-ethylenedioxythiophene), or mixtures thereof;

[0061] (b) Alternating or statistically conjugated copolymers, including:

[0062] - At least one benzotriazole unit (B) having the general formula (Ia) or (Ib):

[0063]

[0064] Wherein the group R is selected from alkyl, aryl, acyl, and thioacyl, and the alkyl, aryl, acyl, and thioacyl groups may optionally be substituted;

[0065] - At least one conjugate structural unit (A), wherein each unit (B) is connected to at least one unit (A) at any one of positions 4, 5, 6 or 7, preferably at position 4 or 7;

[0066] (c) Alternating conjugated copolymers containing benzothiadiazole units, such as PCDTBT{poly[N-9"-heptadecyl-2,7-carbazole-alternating-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole]}, PCPDTBT{poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopentano[2,1-b;3,4-b']-dithiophene)-alternating-4,7-(2,1,3-benzothiadiazole)]};

[0067] (d) Alternating conjugated copolymers containing thiopheno[3,4-b]pyrazidine units;

[0068] (e) Alternating conjugated copolymers containing quinoxaline units;

[0069] (f) Alternating conjugated copolymers containing monomeric silyl units, such as copolymers of 9,9-dialkyl-9-silylfluorene;

[0070] (g) Alternating conjugated copolymers containing fused thiophene units, such as copolymers of thiopheno[3,4-b]thiophene and benzo[1,2-b:4,5-b' dithiophene;

[0071] (h) Alternating conjugated copolymers comprising benzothiadiazole units or naphthiadiazole units substituted with at least one fluorine atom and thiophene units substituted with at least one fluorine atom, such as PffBT4T-2OD{poly[(5,6-difluoro-2,1,3-benzothiadiazole-4,7-diyl)-alternating-(3,3"'-bis(2-octyldodecyl)-2,2',5',2";5",2"'-tetrathiophene-5,5"'-diyl)]}, PBTff4T-2OD{poly[(2,1,3- Benzothiadiazole-4,7-diyl)-alternating-4',3”-difluoro-3,3”'-bis(2-octyldodecyl)-2,2'; 5',2”; 5”,2”-tetrathiophene-5,5”-diyl)]}、PNT4T-2OD{poly(naphtho[1,2-c:5,-c]bis[1,2,5]thiadiazole-5,10-diyl)-alternating-(3,3”'-bis(2-octyldodecyl)-2,2'; 5',2”; 5”,2”'-tetrathiophene-5,5”'-diyl)]};

[0072] (i) Conjugated copolymers containing thieno[3,4-c]pyrrole-4,6-dione units, for example, PBDTTPD{poly[[5-(2-ethylhexyl)-5,6-dihydro-4,6-dioxo-4H-thieno[3,4-c]pyrrole-1,3-diyl][4,8-bis[(2-ethylhexyl)oxy]benzo-[1,2-b:4,5-b']dithieno-2,6-diyl]};

[0073] (l) Conjugated copolymers containing thiophene-thiophene units, such as PTB7{poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thiophene-3,4-b]thiophene-diyl]]}, PBDB-T polymer{poly[[4,8-bis(5-(2-ethylhexyl)-2-thiophene]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]-2,5-thiophene-diyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c']dithiophene-1,3-diyl]-2,5-thiophene-diyl]};

[0074] (m) Polymers comprising indara-4-one derivatives having the general formula (III), (IV), or (V):

[0075]

[0076] in:

[0077] -W and W1, which may be the same or different from each other, preferably the same, represent: an oxygen atom; a sulfur atom; an N-R3 group, where R3 represents a hydrogen atom, or a C1-C group selected from straight-chain or branched groups. 20 C2-C is preferred. 10 alkyl;

[0078] -Z and Y, which may be the same or different from each other, preferably the same, represent nitrogen atoms; or C-R4 groups, where R4 represents hydrogen atoms or is selected from straight-chain or branched C1-C groups. 20 C2-C is preferred. 10 Alkyl, optionally substituted cycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, straight-chain or branched C1-C 20 C2-C is preferred. 10 Alkyl group, polyvinyloxy group R5-O-[CH2-CH2-O] n - where R5 is selected from C1-C of straight or branched chains. 20 C2-C is preferred. 10 Alkyl group, n is an integer from 1 to 4, -R6-OR7 group, wherein R6 is selected from straight-chain or branched C1-C6 groups.20 C2-C is preferred. 10 Alkylene, R7 represents a hydrogen atom or a C1-C atom selected from straight-chain or branched chains. 20 C2-C is preferred. 10 Alkyl groups, or those selected from polyvinyloxy groups R5-O-[CH2-CH2-O]. n - where R5 has the same meaning as above, n is an integer from 1 to 4, -COR8 group, where R8 is selected from straight-chain or branched C1-C 20 C2-C is preferred. 10 Alkyl group; -COOR9 group, wherein R9 is selected from straight-chain or branched C1-C. 20 C2-C is preferred. 10 Alkyl group; or representing -CHO group or cyano group (-CN);

[0079] -R1 and R2, which may be the same or different from each other, preferably the same, are selected from: straight-chain or branched C1-C 20 C2-C is preferred. 10 Alkyl; optionally substituted cycloalkyl; optionally substituted aryl; optionally substituted heteroaryl; straight-chain or branched C1-C 20 C2-C is preferred. 10 Alkyl group; Polyvinyl group R5-O-[CH2-CH2-O] n - where R5 has the same meaning as above, and n is an integer from 1 to 4; -R6-OR7 group, where R6 and R7 have the same meaning as above; -COR8 group, where R8 has the same meaning as above; or -COOR9 group, where R9 has the same meaning as above; or represents -CHO group or cyano (-CN);

[0080] -D represents an electron-donating group;

[0081] -A represents an electron acceptor group;

[0082] -n is an integer from 10 to 500, preferably from 20 to 300;

[0083] (n) Polymers containing an anthraquinone derivative having the general formula (X):

[0084]

[0085] in:

[0086] -Z, which may be the same or different from each other, preferably the same, representing sulfur atoms, oxygen atoms, and selenium atoms;

[0087] -Y, which may be the same or different from each other, preferably the same, representing sulfur atoms, oxygen atoms, and selenium atoms;

[0088] -R1, which may be the same as or different from each other, preferably the same as each other, are selected from: amino-N-R3R4, where R3 represents a hydrogen atom, or are selected from straight-chain or branched C1-C 20 C2-C is preferred. 10 Alkyl, or selected from optionally substituted cycloalkyl, and R4 is selected from straight-chain or branched C1-C... 20 C2-C is preferred. 10 Alkyl groups, or those selected from optionally substituted cycloalkyl groups; or those selected from straight-chain or branched C1-C... 30 C2-C is preferred. 20 Alkyl group; or selected from polyvinyloxy groups R5-O-[CH2-CH2-O]. n - where R5 is selected from C1-C of straight or branched chains. 20 C2-C is preferred. 10 Alkyl group, where n is an integer from 1 to 4; or selected from -R6-OR7 groups, wherein R6 is selected from straight-chain or branched C1-C6 groups. 20 C2-C is preferred. 10 Alkylene, where R7 represents a hydrogen atom, or is selected from straight-chain or branched C1-C atoms. 20 C2-C is preferred. 10 Alkyl groups, or those selected from polyvinyloxy groups R5-O-[CH2-CH2-O]. n - where R5 has the same meaning as above, and n is an integer from 1 to 4; or selected from -S-R8 thiol groups, where R8 is selected from straight-chain or branched C1-C 20 C2-C is preferred. 10 alkyl;

[0089] -R2, which may be the same or different from each other, preferably the same, represent hydrogen atoms; or are selected from straight-chain or branched C1-C atoms. 20 C2-C is preferred. 10 Alkyl groups; or selected from -COR9 groups, wherein R9 is selected from straight-chain or branched C1-C6 groups. 20 C2-C is preferred. 10 Alkyl; or selected from -COOR 10 Group, wherein R 10 C1-C selected from straight or branched chains 20 C2-C is preferred. 10 Alkyl; or selected from optionally substituted aryl; or selected from optionally substituted heteroaryl;

[0090] -A represents an electron acceptor group;

[0091] -n is an integer from 10 to 500, preferably from 20 to 300;

[0092] Further details relating to alternating or statistical conjugated copolymers (b) comprising at least one benzotriazole unit (B) and at least one conjugated structural unit (A) and their preparation methods can be found, for example, in international patent application WO 2010 / 046114 filed in the name of the applicant.

[0093] Further details relating to alternating conjugated copolymers containing benzothiadiazole units (c), alternating conjugated copolymers containing thieno[3,4-b]pyrazidine units (d), alternating conjugated copolymers containing quinoxaline units (e), alternating conjugated copolymers containing monomer silylation units (f), and alternating conjugated copolymers containing thiophene fusion units (g) can be found, for example, in Chen J et al., "Accounts of Chemical Research" (2009), Vol. 42, No. 11, pp. 1709-1718; and in Po'R. et al., "Macromolecules" (2015), Vol. 48(3), pp. 453-461.

[0094] Further details relating to alternating conjugated copolymers (h) comprising benzothiadiazole or naphthiadiazole units substituted with at least one fluorine atom and thiophene units substituted with at least one fluorine atom can be found, for example, in “Nature Communications” (2014), Vol. 5, No. 5293 (DOI: 10.1038 / ncomms6293) by Liu Y et al.

[0095] Further details relating to the conjugated copolymers (i) containing thieno[3,4-c]pyrrole-4,6-dione units can be found, for example, in “Chinese Chemical Letters” (2016), Vol. 27, No. 8, pp. 1277-1282, by Pan H et al.

[0096] Further details relating to conjugated copolymers containing thiophene and thiophene units (1) can be found, for example, Liang Y et al., Journal of the American Chemical Society (2009), Vol. 131 (22), pp. 7792-7799; and Liang Y et al., Accounts of Chemical Research (2010), Vol. 43 (9), pp. 1227-1236.

[0097] Further details relating to polymers (m) containing indah-4-one derivatives can be found, for example, in international patent application WO 2016 / 180988 filed in the name of the applicant.

[0098] Further details relating to polymers (n) containing anthracene dithiophene derivatives having the general formula (X) can be found, for example, in international patent application WO 2019 / 175367 filed in the name of the applicant.

[0099] According to a particularly preferred embodiment of the present invention, the photoactive organic polymer may be selected from, for example: PffBT4T-2OD{poly[(5,6-difluoro-2,1,3-benzothiadiazole-4,7-diyl)-alternating-(3,3"'-(2-octyldodecyl)-2,2',5',2";5",2"'-tetrathiophene-5,5"'-diyl)]}, PBDTTPD{poly[[5-(2-ethylhexyl)-5,6-dihydro-4,6-dioxo-4H-thieno[3,4-c]pyrrole-1,3-diyl][4,8-bis[(2-ethylhexyl)oxy]benzo-[1,2-b:4,5-b']dithiophene-2,6-diyl]}, PTB7{poly[[4,8 -bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thienodiyl]]}, PBDB-T{poly[[4,8-bis(5-(2-ethylhexyl)-2-thienoyl]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]-2,5-thienodiyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c']dithiophene-1,3-diyl]]}, polymers containing anthracene dithiophene derivatives having the general formula (X). Polymers containing anthracene dithiophene derivatives having the general formula (X) are preferred.

[0100] According to a preferred embodiment of the present invention, the organic electron acceptor compound may be selected from, for example, fullerene derivatives, such as [6,6]-phenyl-C 61 methyl butyrate (PCBM), [6,6]-phenyl-C 71 methyl butyrate (PC) 71 BM), Indene-C 60 Biadduct (ICBA), bis(1-[3-(methoxycarbonyl)propyl]-1-phenyl)-[6,6]C 62 (Bis-PCBM). Preferably [6,6]-phenyl-C 61 methyl butyrate (PCBM), [6,6]-phenyl-C 71 methyl butyrate (PC) 71 BM).

[0101] According to another preferred embodiment of the invention, the organic electron acceptor compound may be selected from, for example: non-fullerene compounds (optionally polymerized), such as compounds based on perylene-diimide or naphthalene-diimide and fused aromatic rings; indahienylthiophene with electron-depleted terminal groups; compounds having an aromatic core capable of symmetrical rotation, such as derivatives of cyclohexene or triindone. 3,9-bis{2-methylene-[3-(1,1-dicyanomethylene)-indargen]}-5,5,11,11-tetra(4-hexylphenyl)-dithiopheno[2,3-d:2',3'-d']-s-indargeno[1,2-b:5,6-b']-dithiophene, poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenedimide-2,6-diyl]-alternate-5,5'-(2,2'-dithiophene)} is preferred.

[0102] Further details relating to the non-fullerene compounds can be found, for example, Nielsen CB et al., "Accounts of Chemical Research" (2015), Vol. 48, pp. 2803-2812; and Zhan C et al., "RSC Advances" (2015), Vol. 5, pp. 93002-93026.

[0103] The active layer can be obtained by depositing a solution containing at least one photoactive organic polymer and at least one organic electron acceptor compound selected from the above on the cathode intermediate layer (buffer layer) using a suitable deposition technique, such as spin coating, spray coating, inkjet printing, slot extrusion coating, gravure printing, or screen printing.

[0104] According to a preferred embodiment of the present invention, the cathode intermediate layer (buffer layer) may include zinc oxide and titanium oxide, preferably zinc oxide.

[0105] The cathode intermediate layer (buffer layer) can be obtained by depositing a zinc oxide precursor solution onto the cathode using known deposition techniques, such as vacuum evaporation, spin coating, droplet casting, doctor blade casting, slot extrusion coating, gravure printing, flexographic printing, edge scraping, spraying, and screen printing.

[0106] More details about the formation of the cathode intermediate layer (buffer layer) from the zinc oxide precursor solution can be found, for example, in PòR. et al., "Energy & Environmental Science" (2014), Vol. 7, pp. 925-943.

[0107] According to a preferred embodiment of the present invention, the cathode may be made of a material selected from, for example, indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), and gadolinium-doped zinc oxide (GZO); or it may be composed of a grid of conductive material and a transparent conductive polymer, wherein the conductive material is preferably selected from, for example, silver (Ag), copper (Cu), graphite, and graphene, and the transparent conductive polymer is preferably selected from, for example, PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate]; or it may be composed of an ink based on metal nanowires, wherein the metal is preferably selected from, for example, silver (Ag) and copper (Cu).

[0108] The cathode can be obtained using techniques known in the art, such as sputtering or electron beam-assisted deposition. Alternatively, the cathode can be obtained by depositing the transparent conductive polymer via spin coating, gravure printing, flexographic printing, or slot extrusion coating, followed by depositing the conductive material grid via evaporation, screen printing, spraying, or flexographic printing. Alternatively, the cathode can be obtained by depositing the ink based on metal nanowires via spin coating, gravure printing, flexographic printing, or slot extrusion coating. Deposition can occur on a carrier layer selected from those reported below.

[0109] According to a preferred embodiment of the present invention, the cathode may be combined with a carrier layer, which may be a transparent rigid material, such as glass, or a flexible material, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethyleneimine (PI), polycarbonate (PC), polypropylene (PP), polyimide (PI), cellulose triacetate (TAC), or copolymers thereof.

[0110] According to a preferred embodiment of the present invention, the at least one heteropolyacid may be selected, for example, from heteropolyacids having the general formula (I):

[0111] H x [A(MO3) y O z (I)

[0112] in:

[0113] -A represents a silicon atom or a phosphorus atom;

[0114] -M represents a transition metal atom belonging to Group 5 or 6 of the periodic table, preferably selected from molybdenum or tungsten;

[0115] -x is an integer that depends on the valence of A, preferably 3 or 4;

[0116] -y is 12 or 18;

[0117] -z is 4 or 6.

[0118] According to another preferred embodiment of the invention, the at least one heteropolyacid may be selected, for example, from heteropolyacids having the general formula (II):

[0119] H x [A(Mo) p (V) q O 40 (II)

[0120] in:

[0121] -A represents a silicon atom or a phosphorus atom;

[0122] -x is an integer that depends on the valence of A, preferably 3 or 4;

[0123] -p is 6 or 10;

[0124] -q means 2 or 6.

[0125] For the purposes of this invention, the heteropolyacid having general formula (I) and the heteropolyacid having general formula (II) may be used in hydrated form or in an alcohol solution (e.g., in ethanol, isopropanol or a mixture thereof).

[0126] According to a preferred embodiment of the present invention, the heteropolyacid having general formula (I) and the heteropolyacid having general formula (II) can be selected, for example, phosphomolybdic acid hydrate {H3[P(MoO3]} 12 O4]·nH2O}、Phosphomolybdic acid{H3[P(MoO3]} 12 O4]} alcohol solution, phosphotungstic acid hydrate {H3[P(WO3)} 12 O4]·nH2O}、Phosphotungstic acid {H3[P(WO3]} 12 O4]} alcohol solution, molybdate hydrate {H4[Si(MoO3]} 12 O4]·nH2O]}、Silicomolybdic acid{H4[Si(MoO3]} 12 O4]} alcohol solution, silicotungstic acid hydrate {H4[Si(WO3)} 12 O4]·nH2O}, silicotungstic acid {H4[Si(WO3]} 12 O4]} alcohol solution, phosphomolybdic vanadate hydrate {H3[P(Mo)6(V)6O 40 ]·nH2O]}、phosphomolybdic acid{H3[P(Mo)6(V)6O] 40 Alcoholic solution, phosphomolybdic vanadate hydrate {H3[P(Mo] )} 10 (V)2O 40 ]·nH2O]}、Phosphomolybdic acid{H3[P(Mo] 10 (V)2O 40An alcoholic solution, or a mixture thereof. Preferably, phosphomolybdic acid hydrate {H3[P(MoO3]} 12 O4]·nH2O}、Phosphomolybdic acid{H3[P(MoO3]} 12 O4]} alcohol solution, molybdate hydrate {H4[Si(MoO3]} 12 O4]·nH2O}.

[0127] Heteropolyacids having general formula (I) or (II) are commercially available, or they can be prepared according to methods known in the art, for example in U.S. Patents US 4,146,574 and US 5,792,721, or by methods described by Odyakov VF et al. in “Applied Catalysis A General” (2008), Vol. 342 (1), pp. 126-130.

[0128] According to a preferred embodiment of the present invention, the amino compound may be selected from, for example:

[0129] - Low molecular weight aliphatic amines containing 8 to 24 carbon atoms, straight-chain or branched, primary, secondary or tertiary, such as n-octylamine, n-dodecylamine, n-hexadecylamine, di-n-octylamine or mixtures thereof;

[0130] - Conjugated polymers containing chain or side amino groups, such as: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), poly(N,N'-bis-4-butylphenyl-N,N'-diphenyl)benzidine (polyTPD), poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorenyl)-alternating-2,7-(9,9-dioctyl-fluoren)] (PFN) or mixtures thereof;

[0131] Or a mixture thereof.

[0132] The second anode intermediate layer (buffer layer) can be obtained by depositing an alcoholic solution of the at least one heteropoly acid on top of the active layer using deposition techniques known in the art (e.g., vacuum evaporation, spin coating, droplet casting, doctor blade casting, slot extrusion coating, gravure printing, flexographic printing, edge scraping, spraying, screen printing), and adjusting the rheological parameters (e.g., viscosity) of the at least one heteropoly acid in solution form from time to time according to the requirements of the deposition technique used.

[0133] In the case where the second anode intermediate layer (buffer layer) also contains at least one amino compound, the second intermediate layer (buffer layer) can also be obtained by depositing the at least one heteropolyacid and the at least one amino compound in an ether solvent (such as tetrahydrofuran, dioxane) or in a hydrocarbon solvent (such as xylene, toluene), as described above in the case of an alcoholic solution of the at least one heteropolyacid.

[0134] As described above, the anode, cathode, first anode intermediate layer (buffer layer), second anode intermediate layer (buffer layer), and cathode intermediate layer (buffer layer) present in the aforementioned inverted polymer photovoltaic cell (or solar cell) can be deposited using techniques known in the art. Further details about these technologies can be found, for example, in the following: Pò R. et al., “Interfacial Layers”, in “Organic Solar Cells-Fundamentals, Devices, and Upscaling” (2014), Chapter 4, Richter H. and Rand B. Eds., Pan Stanford Publishing Pte Ltd.; Yoo S. et al., “Electrodes in Organic Photovoltaic Cells”, in “Organic Solar Cells-Fundamentals, Devices, and Upscaling” (2014), Chapter 5, Richter H. and Rand B. Eds., Pan Stanford Publishing Pte Ltd.; Angmo D. et al., “Journal of Applied Polymer Science” (2013), Vol. 129, No. 1, pp. 1-14.

[0135] As described above, the present invention also relates to a method for preparing the aforementioned inverted polymer photovoltaic cell (or solar cell).

[0136] According to a preferred embodiment of the present invention, a method for preparing an inverted polymer photovoltaic cell (or solar cell) includes:

[0137] - A cathode is formed by sputtering; or by electron beam-assisted deposition; or by spin coating, gravure printing, flexographic printing, or slot extrusion coating to deposit a transparent conductive polymer, followed by deposition of a grid of conductive material by evaporation, screen printing, spraying, or flexographic printing; or by deposition of metal nanowire-based ink by spin coating, gravure printing, flexographic printing, or slot coating.

[0138] - A cathode intermediate layer (buffer layer) is formed on the cathode by spin coating, gravure printing, flexographic printing, or slot extrusion coating;

[0139] - An active layer is formed on the cathode intermediate layer (buffer layer) by spin coating, gravure printing, or slot extrusion coating;

[0140] - A second anode intermediate layer (buffer layer) is formed on the active material by spin coating, gravure printing, screen printing, flexographic printing, or slot extrusion coating;

[0141] - The first anode intermediate layer (buffer layer) is formed on the second anode intermediate layer by spin coating, gravure printing, screen printing, flexographic printing, or slot extrusion coating;

[0142] - An anode is formed by vacuum evaporation, screen printing, spraying, or flexographic printing on the first anode intermediate layer (buffer layer); or by spin coating, gravure printing, flexographic printing, or slot extrusion coating on the first anode intermediate layer (buffer layer), followed by deposition of a grid of conductive material by evaporation, screen printing, spraying, or flexographic printing; or by spin coating, gravure printing, flexographic printing, or slot extrusion coating on the first anode intermediate layer (buffer layer) to deposit an ink based on metal nanowires.

[0143] According to a preferred embodiment of the present invention, in the inverted polymer photovoltaic cell (or solar cell) for the purposes of this invention:

[0144] - The anode can have a thickness in the range of 50 nm to 150 nm, preferably in the range of 80 nm to 120 nm;

[0145] - The first anode intermediate layer (buffer layer) may have a thickness in the range of 10 nm to 2000 nm, preferably in the range of 15 nm to 1000 nm;

[0146] - The second anode intermediate layer (buffer layer) can have a thickness in the range of 1 nm to 100 nm, preferably in the range of 2 nm to 40 nm;

[0147] - The active layer can have a thickness ranging from 50 nm to 500 nm, preferably from 70 nm to 360 nm;

[0148] - The cathode intermediate layer (buffer layer) can have a thickness in the range of 10 nm to 100 nm, preferably in the range of 20 nm to 80 nm;

[0149] - The cathode can have a thickness in the range of 50 nm to 150 nm, preferably in the range of 80 nm to 120 nm. Attached Figure Description

[0150] Now, we will refer to the report below. Figure 1 The present invention will be described in more detail with reference to the implementation scheme. Figure 1 A cross-sectional view of an inverted polymer photovoltaic cell (or solar cell) illustrating the purpose of this invention.

[0151] refer to Figure 1 The inverted polymer photovoltaic cell (or solar cell) (1) comprises:

[0152] - A transparent carrier (7), such as a glass or plastic carrier;

[0153] - Cathode (2), such as indium tin oxide (ITO) cathode; or cathode obtained by depositing a transparent conductive polymer by spin coating, gravure printing, flexographic printing or slot extrusion coating, and then depositing a grid of conductive material by evaporation, screen printing, spraying or flexographic printing; or cathode obtained by depositing an ink based on metal nanowires by spin coating, gravure printing, flexographic printing or slot coating.

[0154] - Cathode intermediate layer (buffer layer) (3), including, for example, zinc oxide;

[0155] - Photoactive material layer (4), comprising at least one photoactive organic polymer, such as a polymer containing anthracene dithiophene derivative having the general formula (X) (e.g., a copolymer having the formula (Xb) reported below) and at least one fullerene derivative, such as [6,6]-phenyl-C 71 methyl butyrate (PC) 71 BM) or at least one non-fullerene compound, optionally a polymer;

[0156] - A second anode intermediate layer (buffer layer) (5b) comprising an alcoholic solution of at least one heteropolyacid (e.g., triphosmolybdate hydrate) having the general formula (I) or (II) reported above; or an alcoholic solution of at least one heteropolyacid (e.g., triphosmolybdate hydrate) having the general formula (I) or (II) reported above and at least one low molecular weight fatty amine (e.g., n-dodecylamine); or a tetrahydrofuran solution of at least one heteropolyacid (e.g., triphosmolybdate hydrate) having the general formula (I) or (II) reported above and at least one conjugated polymer containing a chain or side amino group (e.g., poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorenyl)-alternating-2,7-(9,9-dioctyl-fluoren)](PFN));

[0157] - First anode intermediate layer (buffer layer) (5a), which includes, for example, PEDOT:PSS poly(3,4-ethylenedioxythiophene):polystyrene sulfonate;

[0158] - Anode (6), such as a silver (Ag) anode; or an anode obtained by depositing a transparent conductive polymer by spin coating, gravure printing, flexographic printing, or slot extrusion coating, followed by depositing a grid of conductive material by evaporation, screen printing, spraying, or flexographic printing; or an anode obtained by depositing an ink based on metal nanowires by spin coating, gravure printing, flexographic printing, or slot coating. Detailed Implementation

[0159] To better understand and put the invention into practice, some illustrative and non-limiting embodiments of the invention are reported below.

[0160] Example 1 (Invention)

[0161] The copolymer (Xb):PC 71 Solar cells using BM, phosphomolybdic acid, and PEDOT:PSS

[0162] Polymer-based devices were fabricated on a polyethylene terephthalate (PET) substrate coated with ITO (indium tin oxide) (purchased from Technologies-Denmark) (100 nm). The substrate was pre-cleaned with a compressed nitrogen stream and then through an air plasma device (Diener Electronic GmbH & Co.-Germany) before proceeding to the next step.

[0163] The substrate prepared in this way is ready for deposition of a cathode intermediate layer (buffer layer). For this purpose, a zinc oxide intermediate layer (buffer layer) is obtained starting from a solution of 2.6 wt% zinc oxide nanoparticles (Aldrich) in isopropanol (Aldrich). The solution is deposited onto the substrate in air using a slit extrusion tool (Roller Coater - FOM Technologies - Denmark) under the following conditions:

[0164] -Flow rate: 30 μl / min;

[0165] - Substrate speed: 0.5 m / min;

[0166] - Gap: 50μm.

[0167] Immediately after depositing the cathode intermediate layer (buffer layer), zinc oxide is formed by heat-treating all materials at 140°C for 3 minutes in a ventilated oven. The cathode intermediate layer (buffer layer) thus obtained has a thickness of 70 nm.

[0168] The copolymer having formula (Xb) was prepared at 14 mg / ml as described in Example 6 of the international patent application WO 2019 / 175367 reported above, and 24.5 mg / ml [6,6]-phenyl-C 71 methyl butyrate (PC)71 A solution of o-xylene (Aldrich) at the nanoscale (BM) was prepared. Starting with this solution, an active layer was deposited using a slit extrusion tool (RollerCoater of FOM Technologies - Denmark) under the following conditions in air:

[0169] -Flow rate: 120 μl / min;

[0170] - Substrate speed: 0.75 m / min;

[0171] - Gap: 50μm.

[0172] Immediately after depositing the active layer, all materials were heat-treated in a ventilated oven at 120°C for 2 minutes. The resulting active layer had a thickness of 300 nm.

[0173] On the active layer thus obtained, a second anode intermediate layer (buffer layer) is deposited in air, starting with an isopropanol solution (6 mg / ml) of phosphomolybdic acid trihydrate (Aldrich), using a slit extrusion tool (Roller Coater of FOM Technologies - Denmark) under the following conditions:

[0174] -Flow rate: 100 μl / min;

[0175] - Substrate speed: 0.75 m / min;

[0176] - Gap: 50μm.

[0177] The thickness of the second anode intermediate layer (buffer layer) thus obtained is 5 nm.

[0178] On the second anode intermediate layer (buffer layer), in air, from [containing PEDOT:PSS poly(3,4-ethylenedioxythiophene):polystyrene sulfonate](Clevios TM Starting with a suspension of HTL Solar 388-Heraeus Co. (PEDOT:PSS concentration equal to 1.2 mg / ml), the first anode intermediate layer (buffer layer) was deposited using a slit extrusion tool (Roller Coater of FOM Technologies-Denmark) under the following conditions:

[0179] -Flow rate: 360 μl / min;

[0180] - Substrate speed: 1m / min;

[0181] - Gap: 100μm.

[0182] After depositing the first anode intermediate layer (buffer layer), all materials were immediately heat-treated in a ventilated oven at 120°C for 2 minutes. The thickness of the first anode intermediate layer (buffer layer) thus obtained was 150 nm.

[0183] On the first anode intermediate layer (buffer layer), a silver (Ag) anode with a thickness of 100 nm is deposited by vacuum evaporation, appropriately masking the area of ​​the device to obtain an area equal to 0.25 mm. 2 The effective area.

[0184] Anode deposition is performed in a standard vacuum evaporation chamber comprising a substrate and an evaporation vessel equipped with a heating element and containing 10 silver (Ag) pellets (1 mm–3 mm in diameter) (Aldrich). The evaporation process is carried out under vacuum at a pressure of approximately 1 × 10⁻⁶. -6 The process is carried out under a shield. After evaporation, silver (Ag) condenses in the unmasked portion of the device.

[0185] Thickness was measured using a Dektak 150 profilometer (Veeco Instruments).

[0186] The photoelectric conversion efficiency (power conversion efficiency - PCE) (η) of the obtained device was measured in a controlled atmosphere (nitrogen) in a glove box at room temperature (25°C). The current-voltage curve (IV) was obtained using Keithley. Data was acquired using a multimeter connected to a personal computer. The photocurrent was measured by exposing the device to light from the ABET SUN 2000-4 solar simulator, which provides an intensity of 100 mW / cm². 2 The intensity of 1.5 GHz AM radiation (equivalent to 1 sun) was measured using a power meter Ophir connected to a 3A-P thermal sensor. II. Measurements were performed on 35 devices, and the average photoelectric conversion efficiency (power conversion efficiency - PCE) (η) was 7.32%.

[0187] To establish adhesion, after depositing the double interlayers—specifically, after depositing the second anode interlayer (buffer layer) and the first anode interlayer (buffer layer)—a rectangular strip of adhesive tape is applied to the semi-finished device. The tape is pressed with a finger and then peeled off. Peeling off the tape does not remove any layers.

[0188] Example 2 (Comparison)

[0189] The copolymer (Xb):PC b1 BM and PEDOT:PSS solar cells

[0190] Polymer-based devices were fabricated on a polyethylene terephthalate (PET) substrate coated with ITO (Indium Tin Oxide) (Fom Technologies-Denmark) (100 nm), which was pre-cleaned as described in Example 1.

[0191] The deposition of the cathode intermediate layer (buffer layer), the deposition of the active layer, and the deposition of the first anode intermediate layer (buffer layer) were performed as described in Example 1; the composition of the cathode intermediate layer (buffer layer), the composition of the active layer, and the composition of the first anode intermediate layer (buffer layer) were the same as those reported in Example 1; the thickness of the cathode intermediate layer (buffer layer), the thickness of the active layer, and the thickness of the first anode intermediate layer (buffer layer) were the same as those reported in Example 1.

[0192] Unlike Example 1, no second anodic intermediate layer (buffer layer) starting from the isopropanol solution of phosphomolybdic acid trihydrate was deposited on the obtained active layer.

[0193] The deposition of the silver anode (Ag) was performed as described in Example 1: the thickness of the silver anode was the same as that reported in Example 1.

[0194] Thickness was measured using a Dektak 150 profilometer (Veeco Instruments).

[0195] The electrical characteristics, current-voltage curves (IV), and photocurrent of the devices were measured as described in Example 1. Measurements were performed on 35 devices, and the average photoelectric conversion efficiency (power conversion efficiency - PCE) (η) was 6.06%.

[0196] To establish adhesion, a rectangular strip of adhesive tape is applied to the semi-finished device after the first anode intermediate layer (buffer layer) has been deposited. The tape is pressed down with a finger and then peeled off. Peeling off the tape removes the first anode intermediate layer (buffer layer).

[0197] Example 3 (Comparative)

[0198] The copolymer (Xb):PC 71 Solar cells using BM and evaporated molybdenum oxide (MoO3)

[0199] Polymer-based devices were fabricated on a polyethylene terephthalate (PET) substrate coated with ITO (Indium Tin Oxide) (Fom Technologies-Denmark) (100 nm), which was pre-cleaned as described in Example 1.

[0200] The deposition of the cathode intermediate layer (buffer layer) and the active layer were performed as described in Example 1; the composition of the cathode intermediate layer (buffer layer) and the composition of the active layer were the same as those reported in Example 1; the thickness of the cathode intermediate layer (buffer layer) and the thickness of the active layer were the same as those reported in Example 1.

[0201] Unlike Example 1, no material from [Clevios:PSS poly(3,4-ethylenedioxythiophene):polystyrene sulfonate](Clevios) was deposited on the obtained active layer. TM The first anode intermediate layer (buffer layer) of HTL Solar 388-Heraeus Co. begins with a suspension, and the second anode intermediate layer (buffer layer) does not deposit from an isopropanol solution of phosphomolybdic acid trihydrate.

[0202] Conversely, an anode intermediate layer (buffer layer) is deposited on the active layer, obtained by thermally depositing molybdenum oxide (MoO3) (Aldrich): the thickness of the anode intermediate layer (buffer layer) is equal to 10 nm. A silver (Ag) anode with a thickness of 100 nm is deposited on the anode intermediate layer (buffer layer) by vacuum evaporation, with appropriate masking of the device area to obtain an area equal to 0.25 mm. 2 The effective area.

[0203] The deposition of the anode intermediate layer (buffer layer) and the anode was carried out in a standard vacuum evaporation chamber comprising a substrate and two evaporation vessels, each equipped with a heating resistor and containing 10 mg of molybdenum oxide (MoO3) powder (Aldrich) and 10 silver (Ag) pellets (1 mm–3 mm in diameter) (Aldrich). The evaporation process was carried out under vacuum at a pressure of approximately 1 × 10⁻⁶. -6 The process is carried out under the cover. After evaporation, molybdenum oxide (MoO3) and silver (Ag) condense in the unmasked portion of the device.

[0204] Thickness was measured using a Dektak 150 profilometer (Veeco Instruments).

[0205] The electrical characteristics, current-voltage curves (IV), and photocurrent of the devices were measured as described in Example 1. Measurements were performed on 35 devices, and the average photoelectric conversion efficiency (power conversion efficiency - PCE) (η) was 6.74%.

[0206] To establish adhesion, a rectangular strip of adhesive tape is applied to the semi-finished device after the first anode intermediate layer (buffer layer) has been deposited. The tape is pressed down with a finger and then peeled off. Peeling off the tape removes the anode intermediate layer (buffer layer).

[0207] Example 4 (Invention)

[0208] The copolymer (Xb):PC 71 Solar cells using BM, phosphomolybdic acid / dodecylamine, and PEDOT:PSS

[0209] Polymer-based devices were fabricated on a polyethylene terephthalate (PET) substrate coated with ITO (Indium Tin Oxide) (Fom Technologies-Denmark) (100 nm), which was pre-cleaned as described in Example 1.

[0210] The deposition of the cathode intermediate layer (buffer layer), the deposition of the active layer, and the deposition of the first anode intermediate layer (buffer layer) are performed as described in Example 1; the composition of the cathode intermediate layer (buffer layer) and the composition of the active layer are the same as those reported in Example 1; the thickness of the cathode intermediate layer (buffer layer) and the thickness of the active layer are the same as those reported in Example 1.

[0211] Unlike Example 1, a second anode intermediate layer (buffer layer) was deposited on the obtained active layer, starting with a solution of 5.4 mg / ml phosphomolybdic acid trihydrate and 0.6 mg / ml n-dodecylamine (Aldrich) in n-propanol: deposition was performed as described in Example 1.

[0212] The deposition of a silver (Ag) anode was performed as described in Example 1: the thickness of the silver anode was the same as reported in Example 1.

[0213] Thickness was measured using a Dektak 150 profilometer (Veeco Instruments).

[0214] The electrical characteristics, current-voltage curves (IV), and photocurrent of the devices were measured as described in Example 1. Measurements were performed on 35 devices, and the average photoelectric conversion efficiency (power conversion efficiency - PCE) (η) was 5.91%.

[0215] To establish adhesion, after depositing the double interlayers—specifically, after depositing the second anode interlayer (buffer layer) and the first anode interlayer (buffer layer)—a rectangular strip of adhesive tape is applied to the semi-finished device. The tape is pressed with a finger and then peeled off. Peeling off the tape does not remove any layers.

[0216] Example 5 (Invention)

[0217] The copolymer (Xb):PC 71 Solar cells using BM, phosphomolybdic acid / PFN, and PEDOT:PSS

[0218] Polymer-based devices were fabricated on a polyethylene terephthalate (PET) substrate coated with ITO (Indium Tin Oxide) (Fom Technologies-Denmark) (100 nm), which was pre-cleaned as described in Example 1.

[0219] The deposition of the cathode intermediate layer (buffer layer), the deposition of the active layer, and the deposition of the first anode intermediate layer (buffer layer) are performed as described in Example 1; the composition of the cathode intermediate layer (buffer layer) and the composition of the active layer are the same as those reported in Example 1; the thickness of the cathode intermediate layer (buffer layer) and the thickness of the active layer are the same as those reported in Example 1.

[0220] Unlike Example 1, a second anode intermediate layer (buffer layer) was deposited on top of the obtained active layer, starting with a tetrahydrofuran solution (Aldrich) of 5.5 mg / ml phosphomolybdic acid trihydrate and 0.5 mg / ml poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorenyl)-alternating-2,7-(9,9-dioctyl-fluoren)](PFN) (Aldrich): deposition was performed as described in Example 1.

[0221] The deposition of the silver anode (Ag) was performed as described in Example 1: the thickness of the silver anode was the same as that reported in Example 1.

[0222] Thickness was measured using a Dektak 150 profilometer (Veeco Instruments).

[0223] The electrical characteristics, current-voltage curves (IV), and photocurrent of the devices were measured as described in Example 1. Measurements were performed on 35 devices, and the average photoelectric conversion efficiency (power conversion efficiency - PCE) (η) was 5.77%.

[0224] To establish adhesion, after depositing the double interlayers—specifically, after depositing the second anode interlayer (buffer layer) and the first anode interlayer (buffer layer)—a rectangular strip of adhesive tape is applied to the semi-finished device. The tape is pressed with a finger and then peeled off. Peeling off the tape does not remove any layers.

Claims

1. Inverted polymer photovoltaic cell (or solar cell) comprising: - an anode; - a first anode interlayer (buffer layer) based on PEDOT:PSS [poly(3,4- ethylenedioxythiophene):polystyrene sulfonate]; - an active layer comprising at least one photoactive organic polymer as electron donor and at least one electron acceptor organic compound; - a cathode interlayer (buffer layer); - a cathode; a second anode interlayer (buffer layer) comprising at least one heteropolyacid and optionally at least one amino compound is interposed between said first anode interlayer (buffer layer) and said active layer.

2. Inverted polymer photovoltaic cell (or solar cell) according to claim 1, wherein said anode is made of metal; or said anode is constituted by a grid of conductive material and by a transparent conductive polymer; or said anode is constituted by an ink based on metal nanowires.

3. Inverted polymer photovoltaic cell (or solar cell) according to claim 2, wherein said metal is selected from silver (Ag), gold (Au), aluminum (Al), said conductive material is selected from silver (Ag), copper (Cu), graphite, graphene, said transparent conductive polymer is PEDOT:PSS [poly(3,4- ethylenedioxythiophene):polystyrene sulfonate], the metal of said metal nanowires is selected from silver (Ag) and copper (Cu).

4. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein said photoactive organic polymer is selected from: (a) polythiophenes selected from regioregular poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene), poly(3,4-ethylenedioxythiophene), or mixtures thereof; (b) alternating or statistical conjugated copolymers comprising: - at least one benzotriazole unit (B) having general formula (la) or (lb): wherein the group R is selected from alkyl, aryl, acyl, thioacyl, said alkyl, aryl, acyl and thioacyl being optionally substituted; - at least one conjugated structural unit (A), wherein each unit (B) is connected to at least one unit (A) in any one of positions 4, 5, 6 or 7; (c) alternating conjugated copolymers comprising benzothiadiazole units selected from PCDTBT {poly[N-9"-heptadeca-yl-2,7-carbazole-alternate-5,5-(4',7'-di-2-thienyl-2',1',3'- benzothiadiazole]}, PCPDTBT {poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']- dithiophene)-alternate-4,7-(2,1,3-benzothiadiazole)]}; (d) alternating conjugated copolymers comprising thieno[3,4-b]pyrazidine units; (e) alternating conjugated copolymers comprising quinoxaline units; (f) alternating conjugated copolymers comprising monomeric silyl units selected from copolymers of 9,9-dialkyl-9-silfluorene; (g) alternating conjugated copolymers comprising fused thiophene units selected from copolymers of thieno[3,4-b]thiophene and benzo[1,2-b:4,5-b']dithiophene; (h) alternating conjugated copolymers comprising benzothiadiazole units or naphthothiadiazole units substituted by at least one fluorine atom and thiophene units substituted by at least one fluorine atom selected from: PffBT4T-2OD {poly[(5,6-difluoro-2,1,3-benzothiadiazole-4,7-diyl)-alt-(3,3"'-(2-octyldodecyl)-2,2',5',2";5",2"' -tetra-thiophene-5,5"' -diyl)]}, PBTff4T-2OD {poly[(2,1,3-benzothiadiazole-4,7-diyl)-alt-(4',3"-difluoro-3,3"'-(2-octyldodecyl)-2,2';5',2";5",2"' -tetra-thiophene-5,5"' -diyl)]}, PNT4T-2OD {poly(naphtho[1,2-c:5,-c']bis[1,2,5]thiadiazole-5,10-diyl)-alt-(3,3"' -bis(2-octyldodecyl)-2,2';5',2";5",2"' -tetra-thiophene-5,5"' -diyl)]}; (i) conjugated copolymers comprising thieno[3,4-c]pyrrole-4,6-dione units selected from: PBDTTPD {poly[[5-(2-ethylhexyl)-[(5,6-dihydro-4,6-dioxo-4H-thieno[3,4-c]pyrrole-1,3-diyl)[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]}; (l) conjugated copolymers comprising thienothiophene units selected from: PTB7 {poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophene-diyl]]}, PBDB-T polymer {poly[[4,8-bis(5-(2-ethylhexyl)-2-thiophenyl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]-2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c']dithiophene-1,3-diyl]]}; (m) polymers comprising an indacen-4-one derivative having general formula (III), (IV) or (V): wherein: -W and W1, which may be the same or different from each other, represent: an oxygen atom; a sulfur atom; an N-R3 group, where R3 represents a hydrogen atom, or a C1-C group selected from straight-chain or branched groups. 20 alkyl; - Z and Y, equal to or different from each other, represent: a nitrogen atom; or a CR4group, wherein R4represents a hydrogen atom or a group selected from linear or branched C1-C 20 alkyl, optionally substituted cycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, linear or branched C1-C 20 alkoxy, polyethyleneoxy group R5-O-[CH2-CH2-O] n -, wherein R5is selected from linear or branched C1-C 20 alkyl, n is an integer from 1 to 4, -R6-OR7group, wherein R6is selected from linear or branched C1-C 20 alkylene, R7represents a hydrogen atom or a group selected from linear or branched C1-C 20 alkyl, or from a polyethyleneoxy group R5-O-[CH2-CH2-O] n -, wherein R5has the same meaning as above, n is an integer from 1 to 4, -COR8group, wherein R8is selected from linear or branched C1-C 20 alkyl; -COOR9group, wherein R9is selected from linear or branched C1-C 20 alkyl; or represents a -CHO group or a cyano group (-CN); -R1 and R2, which may be the same or different from each other, are selected from: straight or branched C1-C. 20 Alkyl; optionally substituted cycloalkyl; optionally substituted aryl; optionally substituted heteroaryl; straight-chain or branched C1-C 20 Alkyl group; Polyvinyl group R5-O-[CH2-CH2-O] n - where R5 has the same meaning as above, and n is an integer from 1 to 4; group -R6-OR7, where R6 and R7 have the same meaning as above; group -COR8, where R8 has the same meaning as above; or group -COOR9, where R9 has the same meaning as above; or represents a -CHO group or a cyano group (-CN); - D represents an electron donor group; - A represents an electron acceptor group; - n is an integer from 10 to 500; (n) polymers comprising an anthracene dithiophene derivative having general formula (X): wherein: - Z, equal to or different from each other, represent a sulfur atom, an oxygen atom, a selenium atom; - Y, equal to or different from each other, represent a sulfur atom, an oxygen atom, a selenium atom; - R1, equal to or different from each other, are selected from: amino groups -N-R3R4, wherein R3represents a hydrogen atom, or from linear or branched C1-C 20 alkyl groups, or from optionally substituted cycloalkyl groups, and R4is selected from linear or branched C1-C 20 alkyl groups, or from optionally substituted cycloalkyl groups; or from linear or branched C1-C 30 alkoxy groups; or from polyethyleneoxy groups R5-O-[CH2-CH2-O] n - wherein R5is selected from linear or branched C1-C 20 alkyl groups, n being an integer from 1 to 4; or from -R6-OR7groups, wherein R6is selected from linear or branched C1-C 20 alkylene groups, and R7represents a hydrogen atom, or from linear or branched C1-C 20 alkyl groups, or from polyethyleneoxy groups R5-O-[CH2-CH2-O] n - wherein R5has the same meaning as above, n being an integer from 1 to 4; or from -S-R8thiol groups, wherein R8is selected from linear or branched C1-C 20 alkyl groups; - R2, which may be the same or different from each other, represents a hydrogen atom; or is selected from straight-chain or branched C1-C atoms. 20 Alkyl groups; or selected from -COR9 groups, wherein R9 is selected from straight-chain or branched C1-C6 groups. 20 Alkyl; or selected from -COOR 10 Group, wherein R 10 C1-C selected from straight or branched chains 20 Alkyl; or selected from optionally substituted aryl; or selected from optionally substituted heteroaryl; - A represents an electron acceptor group; - n is an integer from 10 to 500.

5. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein the photoactive organic polymer is selected from: (a) polythiophenes selected from regioregular poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene), poly(3,4-ethylenedioxythiophene), or mixtures thereof; (b) alternating or statistical conjugated copolymers comprising: - at least one benzotriazole unit (B) having general formula (la) or (lb): wherein the group R is selected from alkyl, aryl, acyl, thioacyl, said alkyl, aryl, acyl and thioacyl being optionally substituted; - at least one conjugated structural unit (A), wherein each unit (B) is connected to at least one unit (A) in position 4 or 7; (c) alternating conjugated copolymers comprising benzothiadiazole units selected from PCDTBT {poly[N-9"-heptadeca-yl-2,7-carbazole-alternate-5,5-(4',7'-di-2-thienyl-2',1',3'- benzothiadiazole]}, PCPDTBT {poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']- dithiophene)-alternate-4,7-(2,1,3-benzothiadiazole)]}; (d) alternating conjugated copolymers comprising thieno[3,4-b]pyrazidine units; (e) alternating conjugated copolymers comprising quinoxaline units; (f) alternating conjugated copolymers comprising monomeric silyl units selected from copolymers of 9,9-dialkyl-9-silfluorene; (g) alternating conjugated copolymers comprising fused thiophene units selected from copolymers of thieno[3,4-b]thiophene and benzo[1,2-b:4,5-b']dithiophene; (h) alternating conjugated copolymers comprising benzothiadiazole units or naphthothiadiazole units substituted with at least one fluorine atom and thiophene units substituted with at least one fluorine atom selected from: PffBT4T-2OD {poly[(5,6-difluoro-2,1,3-benzothiadiazole-4,7-diyl)-alternate-(3,3"'-(2-octyldodecyl)- 2,2',5',2";5",2"' '-tetra-thiophene-5,5"' -diyl)]}, PBTff4T-2OD {poly[(2,1,3-benzothiadiazole-4,7-diyl)- alternate-(4',3''-difluoro-3,3'''-(2-octyldodecyl)-2,2';5',2'';5'',2'''-tetra-thiophene-5,5'''- diyl)]}, PNT4T-2OD {poly(naphtho[1,2-c:5,-c']di[1,2,5]thiadiazole-5,10-diyl)-alternate-(3,3'''- bis(2-octyldodecyl)-2,2';5',2'';5'',2'''-tetra-thiophene-5,5'''-diyl)]}; (i) conjugated copolymers comprising thieno[3,4-c]pyrrole-4,6-dione units selected from the group consisting of: PBDTTPD {poly[[5-(2-ethylhexyl)-[(5,6-dihydro-4,6-dioxo-4H-thieno[3,4-c]pyrrole-1,3-diyl)[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]}; (l) conjugated copolymers comprising thienothiophene units selected from the group consisting of: PTB7 {poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]]}, PBDB-T polymer {poly[[4,8-bis(5-(2-ethylhexyl)-2-thienyl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]-2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c']dithiophene-1,3-diyl]]}; (m) polymers comprising an indacene-4-one derivative having general formula (III), (IV) or (V): in which: -W and W1, which may be the same or different from each other, represent: an oxygen atom; a sulfur atom; an N-R3 group, where R3 represents a hydrogen atom, or a C2-C atom selected from straight-chain or branched groups. 10 alkyl; - Z and Y, equal to or different from each other, represent: a nitrogen atom; or a CR4group, wherein R4represents a hydrogen atom or is selected from a linear or branched C2-C 10 alkyl group, an optionally substituted cycloalkyl group, an optionally substituted aryl group, an optionally substituted heteroaryl group, a linear or branched C2-C 10 alkoxy group, a polyethyleneoxy group R5-O-[CH2-CH2-O] n -, wherein R5is selected from a linear or branched C2-C 10 alkyl group, n is an integer from 1 to 4, a -R6-OR7group, wherein R6is selected from a linear or branched C2-C 10 alkylene group, R7represents a hydrogen atom or is selected from a linear or branched C2-C 10 alkyl group, or is selected from a polyethyleneoxy group R5-O-[CH2-CH2-O] n -, wherein R5has the same meaning as above, n is an integer from 1 to 4, a -COR8group, wherein R8is selected from a linear or branched C2-C 10 alkyl group; a -COOR9group, wherein R9is selected from a linear or branched C2-C 10 alkyl group; or represents a -CHO group or a cyano group (-CN); - R1and R2, equal to or different from each other, are selected from: linear or branched C2-C 10 alkyl; optionally substituted cycloalkyl; optionally substituted aryl; optionally substituted heteroaryl; linear or branched C2-C 20 alkoxy; polyethyleneoxy R5-O-[CH2-CH2-O] n - wherein R5has the same meaning as above, n is an integer from 1 to 4; a group -R6-OR7wherein R6and R7have the same meaning as above; a -COR8group wherein R8has the same meaning as above; or a -COOR9group wherein R9has the same meaning as above; or represent a -CHO group or a cyano group (-CN); - D represents an electron donor group; - A represents an electron acceptor group; - n is an integer from 20 to 300; (n) polymers comprising an anthracene dithiophene derivative having general formula (X): in which: - Z, equal to or different from each other, represent a sulfur atom, an oxygen atom, a selenium atom; - Y, equal to or different from each other, represent a sulfur atom, an oxygen atom, a selenium atom; - R1, equal to or different from each other, are selected from: amino groups -N-R3R4, wherein R3represents a hydrogen atom, or from linear or branched C2-C 10 alkyl groups, or from optionally substituted cycloalkyl groups, and R4is selected from linear or branched C2-C 10 alkyl groups, or from optionally substituted cycloalkyl groups; or from linear or branched C2-C 20 alkoxy groups; or from polyethyleneoxy groups R5-O-[CH2-CH2-O] n -, wherein R5is selected from linear or branched C2-C 10 alkyl groups, n being an integer from 1 to 4; or from -R6-OR7groups, wherein R6is selected from linear or branched C2-C 10 alkylene groups, and R7represents a hydrogen atom, or from linear or branched C2-C 10 alkyl groups, or from polyethyleneoxy groups R5-O-[CH2-CH2-O] n -, wherein R5has the same meaning as above, n being an integer from 1 to 4; or from -S-R8thiol groups, wherein R8is selected from linear or branched C2-C 10 alkyl groups; - R2, which may be the same or different from each other, represents a hydrogen atom; or is selected from straight-chain or branched C2-C atoms. 10 Alkyl group; or selected from -COR9 groups, wherein R9 is selected from straight-chain or branched C2-C groups. 10 Alkyl; or selected from -COOR 10 Group, wherein R 10 C2-C selected from straight or branched chains 10 Alkyl; or selected from optionally substituted aryl; or selected from optionally substituted heteroaryl; - A represents an electron acceptor group; - n is an integer from 20 to 300.

6. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein said photoactive organic polymer is selected from: (i) conjugated copolymers comprising thieno[3,4-c]pyrrole-4,6-dione units selected from the group consisting of: PBDTTPD {poly[[5-(2-ethylhexyl)-[(5,6-dihydro-4,6-dioxo-4H-thieno[3,4-c]pyrrole-1,3-diyl)[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]}; (l) conjugated copolymers comprising thienothiophene units selected from the group consisting of: PTB7 {poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]]}, PBDB-T polymer {poly[[4,8-bis(5-(2-ethylhexyl)-2-thienyl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]-2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c']dithiophene-1,3-diyl]]}; (m) polymers comprising an indacene-4-one derivative having general formula (III), (IV) or (V): in which: - D represents an electron donor group; - A represents an electron acceptor group; - n is an integer from 20 to 300; (n) polymers comprising an anthracene dithiophene derivative having general formula (X): in which: - Z, equal to or different from each other, represent a sulfur atom, an oxygen atom, a selenium atom; - Y, equal to or different from each other, represent a sulfur atom, an oxygen atom, a selenium atom; - A represents an electron acceptor group; - n is an integer from 20 to 300.

6. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein said photoactive organic polymer is selected from: PffBT4T-2OD {poly[(5,6-difluoro-2,l,3-benzothiadiazole-4,7-diyl)-alt-(3,3"'- di(2-octyldodecyl)-2,2',5',2";5",2"' '-tetrathienyl-5,5"' -diyl)]}, PBDTTPD {poly[[5-(2- ethylhexyl)-5,6-dihydro-4,6-dioxo-4H-thieno[3,4-c]pyrrole-l,3-diyl][4,8-bis[(2- ethylhexyl)oxy]benzo-[l,2-b:4,5-b']dithiophene-2,6-diyl]}}, PTB7 {poly[[4,8-bis[(2- ethylhexyl)oxy]benzo[l,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2- ethylhexyl)carbonyl]thieno[3,4-b]thiophene-diyl]]}, PBDB-T {poly[[4,8-bis(5-(2- ethylhexyl)-2-thienyl)benzo[l,2-b:4,5-b']dithiophene-2,6-diyl]-2,5-thiophenediyl[5,7- bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[l,2-c:4,5-c']dithiophene-l,3-diyl]]}; polymers comprising anthracene dithiophene derivatives having general formula (X).

7. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein the photoactive organic polymer is selected from polymers comprising anthracene dithiophene derivatives having general formula (X).

8. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein the electron acceptor organic compound is selected from: - fullerene derivatives selected from: [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM), [6,6]-phenyl-C71 -butyric acid methyl ester (PCBM), indene-C 61 - butyric acid methyl ester (PCBM), [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM), indene-C 71 - butyric acid methyl ester (PCBM), [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM), indene-C 71 - butyric acid methyl ester (PCBM), [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM), indene-C 60 - butyric acid methyl ester (PCBM), [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM), indene-C 62 - butyric acid methyl ester (PCBM), [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM - non-fullerene compounds, optionally polymerized, selected from: compounds based on perylene-diimide or naphthalene-diimide and fused aromatic rings; indaceno-thiophenes bearing electron poor end groups; compounds having an aromatic core capable of symmetric rotation selected from: derivatives of corannulene or triindole ketone.

9. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein the electron acceptor organic compound is selected from: - a fullerene derivative selected from: [6,6]-phenyl-C 61 - methyl butanoate (PCBM), [6,6]-phenyl-C 71 - methyl butanoate (PC 71 BM); or - non-fullerene compounds, optionally polymerized, selected from: 3,9-bis{2-methylene-[3-(l,l-dicyanomethylene)-indacene]}-5,5,11,11-tetra(4-hexylphenyl)- dithieno[2,3-d:2',3'-d']-s-indaceno[l,2-b:5,6-b']-dithiophene, poly{[N,N'-bis(2- octyldodecyl)-l,4,5,8-naphthalene diimide-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)}.

10. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein the cathode interlayer (buffer layer) comprises zinc oxide, titanium oxide.

11. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein the cathode interlayer (buffer layer) comprises zinc oxide.

12. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein the cathode is a material selected from: indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), gadolinium oxide-doped zinc oxide (GZO); or the cathode is composed of a grid of conductive material and a transparent conductive polymer; or the cathode is composed of an ink based on metal nanowires.

13. Inverted polymer photovoltaic cell (or solar cell) according to claim 12, wherein the conductive material is selected from silver (Ag), copper (Cu), graphite, graphene, the transparent conductive polymer is PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate], the metal of the metal nanowires is selected from silver (Ag), copper (Cu).

14. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein the cathode is associated with a support layer, which is a transparent rigid material selected from glass, or a flexible material selected from polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polycarbonate (PC), polypropylene (PP), polyimide (PI), cellulose triacetate (TAC) or copolymers thereof.

15. Inverted polymer photovoltaic cell (or solar cell) according to claim 1, wherein the at least one heteropolyacid is selected from a heteropolyacid having general formula (I): H x [A(MO3) y O z ] (I) wherein: - A represents a silicon atom or a phosphorus atom; - M represents a transition metal atom belonging to group 5 or 6 of the periodic table of the elements; - x is an integer depending on the valence of A; - y is 12 or 18; - z is 4 or 6.

16. Inverted polymer photovoltaic cell (or solar cell) according to claim 15, wherein M is selected from molybdenum, tungsten and x is 3 or 4.

17. Inverted polymer photovoltaic cell (or solar cell) according to claim 1, wherein the at least one heteropolyacid is selected from a heteropolyacid having general formula (II): H x [A(Mo) p (V) q O 40 ] (II) wherein: - A represents a silicon atom or a phosphorus atom; - x is an integer depending on the valence of A; - p is 6 or 10; - q is 2 or 6.

18. Inverted polymer photovoltaic cell (or solar cell) according to claim 17, wherein x is 3 or 4.

19. The inverted polymer photovoltaic cell (or solar cell) according to any one of claims 15-18, wherein the at least one heteropoly acid is selected from: phosphomolybdic acid hydrate {H3[P(Mo03)4]·nH20}, phosphomolybdic acid {H3[P(Mo03)4]} alcohol solution, phosphotungstic acid hydrate {H3[P(W03)4]·nH20}, phosphotungstic acid {H3[P(W03)4]} alcohol solution, silicomolybdic acid hydrate {H4[Si(Mo03)4]·nH20}, silicomolybdic acid {H4[Si(Mo03)4]} alcohol solution, silicotungstic acid hydrate {H4[Si(W03)4]·nH20}, silicotungstic acid {H4[Si(W03)4]} alcohol solution, phosphomolybdovanadic acid hydrate {H3[P(Mo)6(V)60]·nH20}, phosphomolybdovanadic acid {H3[P(Mo)6(V)60]} alcohol solution, phosphomolybdovanadic acid hydrate {H3[P(Mo)2(V)20]·nH20}, phosphomolybdovanadic acid {H3[P(Mo)2(V)20]} alcohol solution, or mixtures thereof. 12 12 12 12 12 12 12 12 40 40 10 40 10 40 ​​​​​​​​​​​​​​ 20. The inverted polymer photovoltaic cell (or solar cell) according to any one of claims 15-18, wherein the at least one heteropolyacid is selected from: phosphomolybdic acid hydrate {H3[P(MoO3]} 12 O4]·nH2O}、Phosphomolybdic acid{H3[P(MoO3]} 12 O4]} alcohol solution, silicotungstic acid hydrate {H4[Si(WO3)} 12 O4]·nH2O}.

21. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein the amino compound is selected from: - a primary, secondary or tertiary low molecular weight aliphatic amine, linear or branched, containing from 8 to 24 carbon atoms, selected from: n-octylamine, n-dodecylamine, n-hexadecylamine, di-n-octylamine or mixtures thereof; - conjugated polymers containing chain or pendant amino groups chosen from: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), poly(N,N'-bis-4-butylphenyl-N,N'-diphenyl)benzidine (polyTPD), poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorenyl)-alt-2,7-(9,9-dioctyl-fluorene)] (PFN) or mixtures thereof; or mixtures thereof.

22. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein: - the anode has a thickness in the range of 50 nm to 150 nm; - the first anode intermediate layer (buffer layer) has a thickness in the range of 10 nm to 2000 nm; - the second anode intermediate layer (buffer layer) has a thickness in the range of 1 nm to 100 nm; - the active layer has a thickness in the range of 50 nm to 500 nm; - the cathode intermediate layer (buffer layer) has a thickness in the range of 10 nm to 100 nm; - the cathode has a thickness in the range of 50 nm to 150 nm.

23. Inverted polymer photovoltaic cell (or solar cell) according to claim 1 or 2, wherein: - the anode has a thickness in the range of 80 nm to 120 nm; - the first anode intermediate layer (buffer layer) has a thickness in the range of 15 nm to 1000 nm; - the second anode intermediate layer (buffer layer) has a thickness in the range of 2 nm to 40 nm; - the active layer has a thickness in the range of 70 nm to 360 nm; - the cathode intermediate layer (buffer layer) has a thickness in the range of 20 nm to 80 nm; - the cathode has a thickness in the range of 80 nm to 120 nm.

24. A method for the preparation of an inverted polymer photovoltaic cell (or solar cell) according to any one of the preceding claims, comprising: - forming the cathode by sputtering; or by electron beam assisted deposition; or by spin coating, gravure printing, flexographic printing, or slot-die coating deposition of a transparent conductive polymer followed by evaporation, screen printing, spray coating, or flexographic printing deposition of a grid of conductive material; or by spin coating, gravure printing, flexographic printing or slot-die coating deposition of a metal nanowire based ink; - forming the cathode intermediate layer (buffer layer) on the cathode by spin coating, gravure printing, flexographic printing, or slot-die coating; - forming the active layer on the cathode intermediate layer (buffer layer) by spin coating, gravure printing, or slot-die coating; - forming the second anode intermediate layer (buffer layer) on the active layer by spin coating, gravure printing, screen printing, flexographic printing, or slot-die coating; - forming the first anode intermediate layer (buffer layer) on the second anode intermediate layer by spin coating, gravure printing, screen printing, flexographic printing, or slot-die coating; ​ - the anode is formed by vacuum evaporation, screen printing, spraying, or flexographic printing on the first anode interlayer (buffer layer), or by spin coating, gravure printing, flexographic printing, or slot-die coating of a transparent conductive polymer on the first anode interlayer (buffer layer), followed by deposition of a grid of conductive material by evaporation, screen printing, spraying, or flexographic printing, or by spin coating, gravure printing, flexographic printing, or slot-die coating of a metal nanowire-based ink on the first anode interlayer (buffer layer). - the anode is formed by vacuum evaporation, screen printing, spraying, or flexographic printing on the first anode interlayer (buffer layer), or by spin coating, gravure printing, flexographic printing, or slot-die coating of a transparent conductive polymer on the first anode interlayer (buffer layer), followed by deposition of a grid of conductive material by evaporation, screen printing, spraying, or flexographic printing, or by spin coating, gravure printing, flexographic printing, or slot-die coating of a metal nanowire-based ink on the first anode interlayer (buffer layer). - the anode is formed by vacuum evaporation, screen printing, spraying, or flexographic printing on the first anode interlayer (buffer layer), or by spin coating, gravure printing, flexographic printing, or slot-die coating of a transparent conductive polymer on the first anode interlayer (buffer layer), followed by deposition of a grid of conductive material by evaporation, screen printing, spraying, or flexographic printing, or by spin coating, gravure printing, flexographic printing, or slot-die coating of a metal nanowire-based ink on the first anode interlayer (

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