WO2012084941A1

WO2012084941A1 - Fullerene functionalized with oxazoline or dihydrooxazine groups

Info

Publication number: WO2012084941A1
Application number: PCT/EP2011/073400
Authority: WO
Inventors: Luisa Fiocca; Riccardo Po`
Original assignee: Eni SpA
Current assignee: Eni SpA
Priority date: 2010-12-21
Filing date: 2011-12-20
Publication date: 2012-06-28
Anticipated expiration: 2013-06-21
Also published as: WO2012084941A9; IT1406152B1; ITMI20102345A1

Abstract

Fullerene functionalized with at least one oxazoline or dihydro-oxazine group. Said fullerene can be advantageously used in the construction of photovoltaic devices such as, for example, photovoltaic cells, photovoltaic modules, solar cells, solar modules, on both rigid and flexible supports.

Description

FULLERENE FUNCTIONAL! ZED WITH OXAZOLINE OR DIHYDRO-

OXAZI E GROUPS

DESCRIPTION

The present invention relates to a fullerene functionalized with at least one oxazoline or dihydro- oxazine group.

More specifically, the present invention relates to a fullerene functionalized with at least one oxazoline or dihydro-oxazine group wherein said oxazoline or dihydro-oxazine group can be bound to fullerene through a condensed ring, or through a polyvalent organic group, or directly.

The present invention also relates to a linear, branched or crosslinked polymer obtained by polymerization and/or crosslinking of said fullerene functionalized with at least one oxazoline or dihydro- oxazine group.

The present invention also relates to an acceptor compound-donor compound structure, linear or co- crosslinked, obtained by the reaction of at least one fullerene functionalized with at least one oxazoline or dihydro-oxazine group, and at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups.

The present invention also relates to the use of said fullerene functionalized with at least one oxazoline or dihydro-oxazine group, as well as of said linear, branched or crosslinked polymer obtained by polymerization of said fullerene functionalized with at least one oxazoline or dihydro-oxazine group, as well as of said acceptor compound-donor compound structure, in the construction of photovoltaic devices such as, for example, photovoltaic cells, photovoltaic modules, solar cells, solar modules, on both rigid and flexible supports .

The present invention also relates to a photovoltaic device comprising at least one fullerene functionalized with at least one oxazoline or dihydro- oxazine group, or at least one linear, branched or crosslinked polymer obtained by polymerization and/or crosslinking of said fullerene functionalized with at least one oxazoline or dihydro-oxazine group, or at least one linear or co-crosslinked acceptor compound- donor compound structure obtained by reaction between at least one fullerene functionalized with at least one oxazoline or dihydro-oxazine group and at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups, as well as to processes for the preparation thereof.

Photovoltaic devices are capable of converting the energy of a luminous radiation into electric energy. At present, most photovoltaic devices which can be used for practical applications exploit the physico-chemical properties of photoactive materials of the inorganic type, in particular high-purity crystalline silicon. As a result of the high production costs of silicon, scientific research has long been orienting its efforts towards the development of alternative organic materials having a polymeric structure (so-called polymer photovoltaic cells} . Unlike high-purity crystalline silicon, in fact, organic polymers are characterized by a relative synthesis facility, a low production cost, a reduced weight of the relative photovoltaic device, in addition to allowing the recycling of said polymer at the end of the life-cycle of the device in which it is used.

The functioning of polymer photovoltaic cells is based on the combined use of an electron acceptor compound and an electron donor compound. In the state of the art, the most widely-used electron donor compounds in photovoltaic devices are π-conj ugated polymers belonging to the groups of polyparaphenylene- vinylenes and of polythiophenes. The former ones can be used as both acceptor compounds and as donor compounds, on the basis of the electronic properties determined by the substituent groups of the polymeric chain. The latter ones are normally used as donor compounds. Derivatives of fullerene are most widely-used as acceptor compounds.

The basic conversion process of light into electric current in a polymer photovoltaic cell takes place through the following steps:

1. absorption of a photon on the part of the donor compound with the formation of an exciton, i.e. a pair of electron-electronic gap (or hole) charge transporters ;

2. diffusion of the exciton in a region of the donor compound in which its dissociation can take place;

3. dissociation of the exciton in the two charge transporters [electron (-) and electronic gap (or hole)

{+) ] separated;

4. transporting of the charges thus formed to the cathode (electron through the acceptor compound) and to the anode [ (electronic gap (or hole) through the donor compound] , with the generation of an electric current in the circuit of the device.

The photo-absorption process with the formation of the exciton and the subsequent yielding of the electron to the acceptor compound involves the excitation of an electron from the HOMO (Highest Occupied Molecular Orbital) to the LUMO {Lowest Unoccupied Molecular Orbital) of the donor compound and, subsequently, the passage from this to the LUMO of the acceptor compound.

As the efficiency of a polymer photovoltaic cell depends on the number of free electrons which are generated by dissociation of the excitons, one of the structural characteristics of donor compounds which mostly influences said efficiency is the difference in energy existing between the HOMO and LUMO orbitals of the donor compound (so-called band-gap} . The wavelength of the photons which the donor compound is capable of collecting and of effectively converting into electric energy (so-called photon harvesting or light harvesting process) depends, in particular, on this difference.

With respect to the electronic characteristics, improvements relating to the materials used in the production of photovoltaic devices are possible through the designing of the molecular structure of the donor compound and of the acceptor compound in order to optimally regulate the energy levels (HOMO-LUMO) of both. In particular, in order to obtain the dissociation of the exciton formed in the process and to avoid the charge retransfer, it is necessary that both the difference between the HOMO of the donor compound and of the acceptor compound, and between the LUMO of the donor compound and of the acceptor compound, must have an optimal value ranging from 0.3 to 0.5 eV. Furthermore, the band-gap, i.e. the energy difference between HOMO and LUMO of the donor compound, if on one hand must not be excessively high in order to enable the greatest number of photons to be absorbed, on the other must not be excessively low, as it could decrease the voltage to the electrodes of the device.

Another important characteristic of the materials used for producing photovoltaic devices is the mobility of the electrons in the acceptor compound and of the electronic gaps (or holes) in the donor compound, which determines the facility with which the electric charges, once photo-generated, reach the electrodes.

The electronic mobility, i.e. the mobility of the electrons in the acceptor compound and of the electronic gaps (or holes} in the donor compound, is not only an intrinsic property of the molecules, but is also greatly influenced by the morphology of the photoactive layer, which, in its turn, depends on the reciprocal miscibility of the compounds used in said photoactive layer and on their solubility. For this purpose, the phases of said photoactive layer must neither be excessively dispersed nor excessively segregated .

The morphology of the photoactive layer is also critical with respect to the dissociation efficacy of the electronic gap (hole ) -electron pairs photo- generated. The average lifetime of the exciton is in fact such that this is able to be diffused in the organic material for an average distance not greater than 10 nm - 20 run. The donor compound and the acceptor compound phases must therefore be organized in nanodomains having dimensions comparable with this diffusion distance. Furthermore, the contact area of the donor compound-acceptor compound must be as large as possible and there must be preferential paths towards the electric contacts. This morphology, moreover, must be reproducible and must not change with time .

In the simplest way of operating, polymer photovoltaic cells are produced by introducing a thin layer (about 100 nanometres) of a mixture of the acceptor compound and of the donor compound (generally known as bulk heteroj unction) , between two electrodes, normally consisting of indium-tin oxide (ITO) (anode) and aluminium (Al) (cathode) . In order to produce a layer of this type, a solution of the two components is generally prepared and a photoactive layer is subsequently created on the anode [indium-tin oxide (ITO)] starting from this solution, resorting to suitable deposition techniques such as, for example, spin-coating, spray-coating, ink-jet printing, and the like. Finally, the counter-electrode [i.e. the aluminium cathode (Al) ] is deposited on the dried photoactive layer. Optionally, other additional layers (called interlayers or buffer layers), capable of exerting specific functions of an electric, optical or mechanical nature, can be introduced between the anode and the photoactive film.

The donor compound which is most commonly used in the construction of polymer photovoltaic cells is regioregular poly ( 3-hexylthiophene ) (P3HT). This polymer has optimal electronic and optical characteristics (e.g., good HOMO and LU O orbital values, good adsorption coefficient) , a good solubility in the solvents used in the construction of photovoltaic cells and a reasonable mobility of the electronic gaps (or holes).

Other examples of polymers which can be advantageously used as donor compounds are: the polymer MDMO-PPV { (poly [2-methoxy-5- (3, 7-dimethyloctyloxy) -1, 4- phenylene] -alt- ( vinylene) } , the polymer PCDTBT {poly[N- 9"-heptadecanyl-2, 7-carbazole-alt-5, 5- (4' , 7 ' -di-2-thi- enyl-2' , 1' , 3' -benzothiadiazole ] } , the polymer PCPDTBT {poly [2, 6- (4, -bis- (2-ethylhexyl) -4H-cyclopenta [2, 1- b;3, 4-b' ] dithiophene) -alt- 4, 7- (2,1,3- benzothiadiazole) ] } .

The most widely-used acceptor compounds are generally derivatives of fullerene (C50 or C₇o) , in particular methyl phenyl-Cgi-butyrate (PCBM), or methyl phenyl-C₇i-butyrate (PC70BM) . Said derivatives of fullerene are generally capable of obtaining maximum conversion efficiencies of solar radiation of up to 8%.

In order to facilitate the electronic gaps {or holes) in reaching the anode [indium-tin oxide (ITO)], and at the same time to block the transporting of electrons, thus improving the collection of the charges on the part of the electrode and inhibiting recombination phenomena, before creating the photoactive film starting from the mixture of the acceptor compound and of the donor compound as described above, a film starting from an aqueous suspension of PEDOT:PSS [poly (3, 4- ethylenedioxythiophene ) sulfonated polystyrene] is generally deposited, using suitable deposition techniques such as, for example, spin-coating, spray- coating, ink-jet printing, and the like.

It is known that the morphology of the photoactive layer can be controlled by using, for example, suitable solvents in the deposition of the photoactive layer in which the acceptor compound and the donor compound have solubilities which are such as to form domains in the required dimensions. As described in "Organic Photovoltaics . Mechanism, materials and devices" (2005), Sun S. S. and Sariciftci N. S., Taylor & Francis Ed., pages 226-228, for example, the use of chlorobenzene as deposition solvent of the poly (3-hexylthiophene) (P3HT) - methyl phenyl- C₆₀-butyrate (PCBM) pair, allows finer morphologies of the photoactive layer to be obtained with respect to the use of toluene and, consequently, allows to obtain photovoltaic cells having a higher efficiency. The use of chlorobenzene, however, can lead to the formation of excessively dispersed morphologies of the photoactive layer and, consequently, to a limited mobility of the electric charges towards the electrodes. Said drawback can be at least partially overcome by using mixtures of solvents, or by carrying out thermal treatment (annealing) on the final photovoltaic devices, in order to favour a certain de-mixing degree. The control of the experimental conditions for obtaining the desired result, however, remains extremely critical.

Further methods envisage the addition to the donor compound and acceptor compound mixture, of a third compound such as an alkanedithiol (for example, 1,4- butanedithiol , 1, 6-hexanedithiol, 1, 8-octanedithiol, 1 , 9-nonanedithiol ) , as described by Peet J. et al. in the article "Efficiency enhancement in low-bandgap polymer solar cells by processing with alkane dithiols", published in "Nature Materials" (2007), pages 497-500; or a 1 , 8-di (R) octane (e.g., 1,8- diiodine-octane, 1 , 8-dichloro-octane , 1,8-dibromo- octane, 1 , 8-dicyano-octane ) as described by Lee J. K. et al. in the article "Processing Additives for Improved Efficiency from Bulk Heterojunction Solar Cells", published in "Journal of American Chemical Society" (2008), Vol. 130, pages 3619-3623. The addition of this third compound is capable of modifying the relative solubility of the acceptor compound and of the donor compound and, consequently, the final morphology of the photoactive layer. Also in the case of the above methods, however, finding the right concentrations of the various compounds and the appropriate solvent can be a long and difficult task, as each time the donor compound and the acceptor compound change, the most suitable operating conditions must be found.

Other methods are known in the art for controlling the morphology of the photoactive layer.

Cravino A. et al., for example, in the article "A novel polythiophene with pendant fullerenes: toward donor/acceptor double-cable polymers", published in "Chemical Communications" (2000), pages 2487-2488, describe the synthesis of a new bithiophene having a fullerene pendant group and its electrochemical polymerization. Measurements carried out on films obtained by electro-deposition of this bithiophene have shown the transfer of electrons from the donor (polythiophene) to the acceptor (fullerene pendant group) . The above bithiophene is said to be a good candidate for photovoltaic applications as it should not cause phase separations.

Ramos A. . et al. in the article "Photoinduced electron Transfer and Photovoltaic Devices of a Conjugated Polymer with Pendant Fullerenes", published in "Journal of American Chemical Society" (2001), Vol.

123, pages 6714-6715, describe the synthesis of a π- conjugated polymer having a covalently bound methanofullerene group. The above polymer was used for forming a photoactive layer in a photovoltaic cell and showed the capacity of forming a bi-continuous network, thus avoiding possible phase separations.

Drees M. et al. in the article "Stabilization of the nanomorphology of polymer-fullerene "bulk heterojunction" blends using a novel polymerizable fullerene derivative", published in "Journal of Materials Chemistry" (2005), Vol. 15, pages 5158-5163, describe the possibility of obtaining acceptor compound-donor compound mixtures which are stable from a morphological point of view, thanks to the use of a new polymerizable fullerene derivative, i.e. C₆i-butyric acid glycidol ester (PCBG) , capable of crosslinking . The results obtained show a stabilization from a morphological point of view which prevents the diffusion of fullerene. Photovoltaic devices were produced using this new fullerene derivative.

Hsieh C. H. et al in the article "Highly Efficient and Stable Inverted Polymer Solar Cells Integrated with a Cross-Linked Fullerene Material as an Interlayer", published in "Journal of American Chemical Society" (2010), Vol. 132, pages 4887-4893, describe a new derivative of fullerene functionalized with styryl groups, i.e. [6, 6] -phenyl Cgi-butyric styryl dendron ester (PCBSD), capable of crosslinking, forming a thin film resistant to solvents. Said crosslinking allows an active layer to be deposited on top of this thin film, thus overcoming problems relating to the solubility and producing multilayer inverted polymer solar cells through the deposition process using solvent.

The Applicant consequently considered the problem of finding a new fullerene capable of stabilizing the morphology of the photoactive layer.

The Applicant has now found a new fullerene functionalized with at least one oxazoline or dihydro- oxazine group, which can be used as acceptor compound in the construction of photovoltaic devices, capable of improving the stability of the photoactive layer. Said fullerene, moreover, is capable of improving the mobility of the electrons in the acceptor compound and of the electronic gaps {or holes) in the donor compound, consequently allowing better conversion efficiencies of solar radiation. Furthermore, said fullerene is capable of both polymerizing and crosslinking, forming polymers and/or polymer networks, or of binding itself with a functionalized photoactive organic polymer forming linear acceptor compound-donor compound structures [i.e. covalently bound by means of (thio ) e ( s ) terimide bridges] or co-crosslinked .

An object of the present invention therefore relates to a fullerene functionalized with at least one oxazoline or dihydro-oxazine group, wherein said oxazoline or dihydro-oxazine group can be bound to the fullerene through a condensed ring, or through a polyvalent organic group, or directly.

According to a preferred embodiment of the present invention, said functionalized fullerene can have one of the following general formulae ( I ) , ( I I ) or (III):

C_X-{A- [-Y- (Oxa)_m }_k (I)

Cx- t-Y-fOxaJj! (II)

C_x-(Oxa}_m ( I I I )

wherein :

- C_x represents a fullerene group;

x represents an integer ranging from 50 to 250, preferably ranging from 60 to 90, extremes included, more preferably 60, 70, 84;

m represents an integer ranging from 1 to 4, extremes included, preferably 1 or 2;

1 represents an integer ranging from 1 to 3, extremes included, preferably 1 or 2;

k represents an integer ranging from 1 to 3, extremes included, preferably 1;

A represents a ring condensed with the fullerene group selected from cycloalkyl groups having from 3 to 6 carbon atoms; or from heterocyclic groups having from 3 to 6 atoms containing from 1 to 3 heteroatoms selected from nitrogen, oxygen, sulfur; Y represents a polyvalent organic group having a valence m+1, selected from linear or branched alkylene groups, cycloalkylene groups, arylene groups, or combinations thereof; said alkylene, cycloalkylene or arylene groups optionally containing in the chain one or more heteroatoms selected from oxygen, nitrogen, sulfur, silicon, phosphorous;

- Oxa represents an oxazoline or dihydro-oxazine group, preferably a 2-oxazoline group having the formula :

or a 5, 6-dihydro-2-oxazine group having the formula :

wherein R¹, R², R³, R⁴, R⁵ and R⁵, equal to or different from each other, represent a hydrogen atom; or a linear or branched alkyl group, having from 1 to 12 carbon atoms, such as, for example, methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl; a phenyl group; a benzyl group; a hydroxyalkyl group such as, for example, a hydroxymethyl group.

For the purposes of the present description and of the following claims, the definitions of the numerical ranges always comprise the extremes unless otherwise specified .

For the purposes of the present description and of the following claims, the term "fullerene group" means a compound (e.g., a molecule) including a three- dimensional carbon skeleton having a plurality of carbon atoms. The carbon skeleton of said fullerene group generally forms a closed shell and can, for example, have a spherical or semi-spherical form. Alternatively, the carbon skeleton can form a not completely closed shell such as, for example, a tubular structure. Each carbon atom of said fullerene group is generally bound to three adjacent carbon atoms forming a tetrahedral network. Furthermore, the term "fullerene group" refers to either a substituted fullerene, or a non-substituted fullerene.

According to a further preferred embodiment of the present invention, said group Y can be selected from alkylene groups containing one or more double bonds and/or one or more triple bonds.

According to a further preferred embodiment of the present invention, said group Y can be selected from cycloalkylene groups containing, in the ring, a double and/or a triple bond.

According to a further preferred embodiment of the present invention, said group Y can be selected from arylene groups mono- or poly-condensed with cycloaliphatic rings, and/or with aromatic rings, and/or with heteroaromatic rings.

According to a further preferred embodiment of the present invention, said group Y can be selected from alkylene, cycloalkylene, or arylene groups, or combinations thereof, said alkylene, cycloalkylene, or arylene groups, being optionally substituted with alkoxyl groups and/or with carbonyl groups.

According to a further preferred embodiment of the present invention, said group Y can be selected from polyvalent organic groups having the following formulae :

wherein n, p, q, r, are integers ranging from 1 to 12, preferably from 2 to 8, extremes included.

According to a further preferred embodiment of the present invention, said fullerene functionali zed with at least one oxazoline or dihydro-oxazine group having general formula (I) can be selected from fullerenes having the following formulae:

wherein S¹ _r S² , S³, S⁴, S⁵ and S⁶, equal to or different from each other, represent:

a -[-Y-(Oxa)_m] group wherein Y, m and Oxa, have the same meanings described above;

or a hydrogen atom; group selected from: alkyl groups having from

1 to 44 carbon atoms, linear or branched, saturated or unsaturated, cyclic or acyclic; aromatic groups having from 6 to 18 carbon atoms, mono- or poly- condensed with cycloaliphatic rings, with aromatic rings or with heteroaromatic rings; heteroaromatic groups; alkoxyl groups; carbonyl groups of the ketone or ester type;

with the provision that at least one of S¹, S², S³, S⁴, S⁵ and S⁶, represents a ~[-Y-(Oxa)_m] group.

According to a further preferred embodiment of the present invention, said fullerene f nctionalized with at least one oxazoline or dihydro-oxazine group having general formula (II) can be selected from fullerenes having the following formulae:

wherein :

Oxa¹, Oxa², Oxa³, and Oxa⁴, equal to or different from each other, represent a 2-oxazoline group or a 5 , 6-dihydro-2-oxazine group;

Y has the same meaning described above ;

S¹ represents a hydrogen atom; or a group selected from: alkyl groups having from 1 to 44 carbon atoms, linear or branched, saturated or unsaturated, cyclic or acyclic; aromatic groups having from 6 to 18 carbon atoms, mono- or poly- condensed with cycloaliphatic rings, with aromatic rings or with heteroaromatic rings; heteroaromatic groups; alkoxyl groups; carbonyl groups of the ketone or ester type.

According to a further preferred embodiment of the present invention, said fullerene functionalized with at least one oxazoline or dihydro-oxazine group having general formula (III) can be selected from fullerenes having the following formulae:

wherein :

- Oxa¹ and Oxa², equal to or different from each other, represent a 2-oxazoline group or a 5, 6-dihydro-2- oxazine group;

- S¹ represents a hydrogen atom; or a group selected from: alkyl groups having from 1 to 44 carbon atoms, linear or branched, saturated or unsaturated, cyclic or acyclic; aromatic groups having from 6 to 18 carbon atoms, mono- or poly-condensed with cycloaliphatic rings, with aromatic rings or with heteroaromatic rings; heteroaromatic groups; alkoxyl groups; carbonyl groups of the ketone or ester type.

The fullerenes functionalized with at least one oxazoline or dihydro-oxazine group, object of the present invention can be obtained through various processes known in the art. Examples of these processes are provided hereunder.

Methanofullerenes having general formula:

wherein C_x represents a fullerene group, x has the same meaning described above; S¹ and S² equal to or different from each other, represent:

- a group -[-Y-(Oxa}_m] wherein Y, Oxa and m have the same meanings described above;

or a hydrogen atom;

or a group selected from: alkyl groups having from 1 to 44 carbon atoms, linear or branched, saturated or unsaturated, cyclic or acyclic; aromatic groups having from 6 to 18 carbon atoms, mono- or poly- condensed with cycloaliphatic rings, with aromatic rings or with heteroaromatic rings; heteroaromatic groups; alkoxyl groups; carbonyl groups of the ketone or ester type;

can be obtained by means of the following processes: a process {Bingel reaction) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one oc-halogen- ketone or one a-halogen-ester having general formula (IV) :

S^CHX-S² (IV)

wherein X represents a bromine atom, or a chlorine atom; S¹ and S² equal to or different from each other, represent:

- a group -CO- [-Y- (Oxa) _m] , or a group -C0-0-[-Y- (Oxa)_m] wherein Y, Oxa and m have the same meanings described above;

or a hydrogen atom;

- or a group selected from: alkyl groups having from 1 to 44 carbon atoms, linear or branched, saturated or unsaturated, cyclic or acyclic- aromatic groups having from 6 to 18 carbon atoms, mono- or poly-condensed with cycloaliphatic rings, with aromatic rings or with heteroaromatic rings; heteroaromatxc groups; alkoxyl groups; carbonyl groups of the ketone or ester type;

with the provision that at least one of S¹ and S², represents a group -CO- [-Y- (Oxa)_ra] , or a group -CO- 0- [-Y- (Oxa) _m] , in the presence of at least one chlorinated or non-chlorinated aromatic solvent such as, for example, chlorobenzene, toluene or mixtures thereof, and of least one base, such as, for example, sodium hydride, 1 , 3-dibutyl-urea (DBU) , lithium diamide, diethylamine, or mixtures thereof, at a temperature ranging from -78 °C to 25°C, for a time ranging from 1 hour to 48 hours

[further details can be found in Bingel C, "Chemische Berichte" (1993), Vol. 126 (8), pages 1957-1959] /

(b) a process (reaction with phosphorous ylide) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one phosphorous ylide having general formula (V) :

Ph₃P⁺-C^~ s (V)

wherein S¹ and S², equal to or different from each other, represent:

- a group - [-Y- (Oxa ) _m] wherein Y, Oxa and m have the same meanings described above;

- or a hydrogen atom;

- or a group selected from: alkyl groups having from 1 to 44 carbon atoms, linear or branched, saturated or unsaturated, cyclic or acyclic; aromatic groups having from 6 to 18 carbon atoms, mono- or poly- condensed with cycloaliphatic rings, with aromatic rings or with heteroaromatic rings; heteroaromatic groups; alkoxyl groups; carbonyl groups of the ketone or ester type;

with the provision that at least one of S¹ and S², represents a group - [-Y- (Oxa ) _m] , in the presence of at least one aromatic solvent such as, for example, toluene, at a temperature ranging from 25° C to 50°C [further details can be found in Bestmann H. J. et al., "Tetrahedron Letters" (1994), Vol. 35 (48), pages 9017-9020] ;

(c) a process (reaction with sulfur ylide) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one sulfur ylide having general formula (VI) :

(CH₃) ₂S⁺"C^"S¹S² (VI)

wherein S¹ and S², equal to or different from each other, represent:

- a group - [-Y- (Oxa) _ra] wherein Y, Oxa and m have the same meanings described above;

- or a hydrogen atom;

with the provision that at least one of S¹ and S², represents a group - [-Y- (Oxa) _m] , in the presence of at least one aromatic solvent such as, for example, toluene, at a temperature ranging from 25° C to 50°C [further details can be found in Wang Y. et al . , "Tetrahedron Letters" (1995), Vol. 36 (38), pages 6843-6846] ;

(d) a process (addition of diazoderivative) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one diazoderivative having general formula (VII):

S¹S²C=N₂ (VII)

wherein S¹ and S², equal to or different from each other, represent:

- a group -[-Y-(Oxa)_m] wherein Y, Oxa and m have the same meanings described above;

- or a hydrogen atom;

with the provision that at least one of S¹ and S², represents a group - [-Y- (Oxa)_m] , in the presence of at least one chlorinated aromatic solvent such as, for example, 1 , 2-dichlorobenzene, at room temperature (25° C) , for a time ranging from 24 hours to 72 hours, preferably 24 hours [Hummelen J. C. et al., "Journal of Organic Chemistry" (1995), Vol. 60 (3), pages 532-538].

Azomethanofullerenes having general formula:

wherein C_x represents a fullerene group, x has the same meaning described above, S¹ represents a group -[-Y- (Oxa)_m] wherein Y, Oxa and m have the same meanings described above, can be obtained through the following processes :

(a) a process (addition of azide) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one azide having general formula (VIII} :

S¹-N₃ (VIII)

wherein S¹ represents a group - [-Y- (Oxa) _m] wherein Y, Oxa and m have the same meanings described above, in the presence of at least one chlorinated or non-chorinated aromatic solvent such as, for example, chloronaphthalene, chlorobenzene, toluene, or mixtures thereof, at a temperature ranging from 60°C to the reflux temperature of the solvent used, for a time ranging from 1 hour to 24 hours [further details can be found in Grosser T. et al., "Angewante Chemie" (1995), Vol. 34, pages 1343- 1345; Prato M. et al . , "Journal of the American Chemical Society" (1993), Vol. 115 (3), pages 1148- 1150] ;

(b) a process (addition of nitrene) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one azide having general formula (IX) :

S¹-00C-N₃ (IX)

wherein S¹ represents a group - [ -Y- (Oxa ) _m] , wherein Y, Oxa and m have the same meanings described above, in the presence of at least one chlorinated solvent or non-chorinated aromatic solvent such as, for example, tetrachloroethane, chloro-naphthalene, toluene, or mixtures thereof, at a temperature ranging from 110°C to 160°C, for a time ranging from a few minutes to 1 hour [further details can be found in Smith A.B. et al . , "Tetrahedron" (1996), Vol. 52 (14), pages 5257-5262].

Cyclobutane-fullerenes having general formula:

wherein C_x represents a fullerene group, x has the same meaning described above, S¹, S², S³ and S⁴, equal to or different from each other, represent:

- a group - [ ~Y~ {Oxa ) _m] wherein Y, Oxa and m have the same meanings described above;

- or a hydrogen atom;

with the provision that at least one of S¹, S², S³ and S , represents a group - [-Y- (Oxa) _m] , can be obtained through a process (addition of alkene) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one alkene having general formula (X) :

S¹S²C=CS³S⁴ (X)

wherein S¹, S², S³ and S⁴, equal to or different from each other, have the same meanings described above, with the provision that at least one of S¹, S², S³ and S⁴, represents a group - [-Y- (Oxa)_m] , in the presence of at least one aromatic solvent such as, for example, benzene, toluene, or mixtures thereof, at the reflux temperature of the solvent used, for a time ranging from 12 hours to 24 hours [further details can be found in Zhang X. Et al., "Journal of Organic Chemistry" (1996), Vol. 61 (16), pages 5456-5461].

Cyclobutene-fullerenes having general formula:

wherein C_x represents a fullerene group, x has the same meaning described above, S¹ and S², equal to or different from each other, represent:

- or a hydrogen atom;

with the provision that at least one of S¹ and S² _r represents a group - [ -Y- (Oxa ) _m] , can be obtained through the following processes :

(a) a process (photochemical addition of alkine} which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one alkine having general formula (XI):

S¹-C≡C-S² (XI)

wherein S¹ and S², equal to or different from each other, have the same meanings described above, with the provision that at least one of S¹ and S², represents a group - [-Y- (Oxa) _m] , in the presence of an aromatic solvent such as, for example, toluene, at room temperature (25°C), in an inert atmosphere, for irradiation at λ > 530 nm, for a time ranging from 1 minute to 30 minutes [further details can be found in Zhang X. et al., "Journal of the American Chemical Society" (1993), Vol. 115 (23), pages 11024-11025] ;

(b) a process (addition of ketene) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one ketene, generated in situ from the reaction between the corresponding acyl chloride and triethylamine, having general formula (XII) :

S¹S²-C=C=0 (XII)

wherein S¹ and S², equal to or different from each other, have the same meanings described above, with the provision that at least one of S¹ and S², represents a group - [-Y- (Oxa) _m] , in the presence of a chlorinated solvent such as, for example, chlorobenzene, at room temperature (25°C) , for a time ranging from 1 hour to 24 hours [further details can be found in Matsui S. et al., "Tetrahedron Letters" (1999), Vol. 40 (5), pages 899-902] .

Cyclopentane-fullerenes having general formula:

- a group - [-Y- (Oxa)_m] wherein Y, Oxa and m have the same meanings described above;

- or a hydrogen atom;

with the provision that at least one of Ξ¹ and S² represents a group - [-Y- (Oxa) _m] , can be obtained through a process (addition of trimethylenemethane) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one trimethylenemethane having general formula (XIII):

wherein at least one of S¹ and S² represents a group - [-Y- (Oxa)_m] , wherein Y, Oxa and m have the same meanings described above, in the presence of at least one chlorinated solvent such as, for example, 1,2- dichlorobutane (DCB) , at a temperature ranging from 50°C to 100°C, for a time ranging from 12 hours to 24 hours [further details can be found in Prato M. et al . , "Journal of the American Chemical Society" (1993), Vol. 115 (4), pages 1594-1595].

Fulleropyrrolidines having general formula:

wherein C_x represents a fullerene group, x has the same meaning described above; S¹, S², S³ and S⁴, equal to or different from each other, represent:

- a group -[-Y-(0xa)_m] wherein Y, Oxa and m have the same meanings described above;

- or a hydrogen atom;

with the provision that at least one of S¹, S², S³ and S⁴, represents a group - [ -Y- (Oxa ) _m] , can be obtained through a process (Prato reaction, addition of azomethine-ylide) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one amino acid (for example a substituted glycine) having general formula (XIV) and at least one aldehyde compound having general formula (XV) or at least one amino acid (for example, a substituted glycine) having general formula (XIV) and at least one ketone compound having general formula (XVI):

S¹NH-CS²S³~COOH (XIV)

OHC-S⁴ (XV)

0=C-S⁴S⁵ (XVI)

wherein : in general formulae (XIV), (XV), (XVI), S¹, S², S³, S⁴ and S⁵ represent a group - [-Y- (Oxa)_m] , wherein Y, Oxa and m have the same meanings described above; or a hydrogen atom; or a group selected from: alkyl groups having from 1 to 44 carbon atoms, linear or branched, saturated or unsaturated, cyclic or acyclic; aromatic groups having from 6 to 18 carbon atoms, mono- or poly-condensed with cycloaliphatic rings, with aromatic rings or with heteroaromatic rings; heteroaromatic groups; alkoxyl groups; carbonyl groups of the ketone or ester type;

in the presence of at least one aromatic solvent such as, for example, toluene, or of at least one chlorinated solvent such as, for example, chlorobenzene, o-dichlorobenzene, chloroform, methylene chloride, trichloroethylene, or mixtures thereof, at the reflux temperature of the solvent used, for a time ranging from 1 hour to 24 hours, preferably ranging from 2 hours to 12 hours [further details can be found in Maggini M. et al, "Journal of the American Chemical Society" (1993), Vol. 115 (21), pages 9798-9799] .

Fulleroiso-oxazolines having general formula:

can be obtained through a process (addition of nitrile oxides) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one compound having general formula (XVII), obtained from the corresponding oxime S¹-CH=N-OH by treatment first with N-chlorosuccinimide and anhydrous pyridine and subsequently with a base such as, for example, triethylamine :

S¹-C≡N⁺-0^~ (XVII)

wherein S¹ represents a group - [ -Y- (Oxa) _m] , wherein Y, Oxa and m have the same meanings described above, in the presence of at least one chlorinated solvent such as, for example, chlorobenzene, at a temperature ranging from 25°C to 50°C, for a time ranging from 1 hour to 24 hours [further details can be found in Martin N. et al., "Journal of Organic Chemistry" (2000), Vol. 65 (19), pages 5986-5995].

Fulleropyrazolxnes having general formula:

wherein C_x represents a fullerene group, x has the same meaning described above; S¹ and S², equal to or different from each other, represent:

- or a hydrogen atom;

with the provision that at least one of S¹ and S², represents a group - [-Y- (Oxa) _m] , can be obtained through a process (addition of nitrile imines) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one compound having general formula (XVIII), obtained from the corresponding hydrazone S¹-NH-N=CH-S² by treatment first with N- bromosuccinimide and subsequently with triethylamine :

S¹-N^"-N=C⁺-S² (XVIII)

wherein S¹ and S², equal to or different from each other, have the same meanings described above, with the provision that at least one of S¹ and S² represents a group - [-Y- (Oxa) _m] , in the presence of at least one aromatic solvent such as, for example, benzene, at room temperature (25°C) , for a time ranging from 24 hours to several days [further details can be found in Muthu S. et al., "Tetrahedron Letters" (1994), Vol. 35 (11) pages 1763-1766] .

Furanofullerenes having general formula:

wherein C_x represents a fullerene group, x has the meaning described above; Ξ¹ represents a group (Oxa)_m], wherein Y, Oxa and m have the same meanings described above, can be obtained through a process (addition of carbonyl ylide) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one compound having general formula (XIX) , obtained from the corresponding diazo- pentandione by means of a reaction catalyzed by Rh(II):

wherein S¹ represents a group - [-Y- (Oxa)_m] , wherein Y, Oxa and m have the same meanings described above, in the presence of at least one aromatic solvent such as, for example, toluene, at room temperature (25°C) , for a time ranging from 30 minutes to 60 minutes [further details can be found in Nair V. et al., "Tetrahedron Letters" (1999), Vol. 40 (27), pages 5087-5090; Nair V. et al., "Tetrahedron" (2002), Vol. 58 (15), pages 3009- 3013] .

Cyclohexane-fullerenes and cyclohexene-fullerenes having general formula:

wherein C_x represents a fullerene group, x has the same meaning described above; S¹, S², S³, S⁴ , S⁵ and S⁶, equal to or different from each other, represent:

- or a hydrogen atom;

with the provision that at least one of S¹, S², S³, S⁴, S⁵ and S⁶, represents a group - [-Y- (Oxa) _m] , can be obtained through a process (Diels-Alder reaction) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one acyclic diene having general formula (XX) or (XXI):

wherein S¹, S², S³, s\ S⁵ and S⁶, equal to or different from each other, have the same meanings described above, with the provision that at least one of S¹, S², S³, S⁴, S⁵ and S⁶, represents a group - [-Y- (Oxa) _m] , in the presence of at least one aromatic solvent such as, for example, benzene, toluene, or mixtures thereof, at a temperature ranging from 25°C to 90 °C, for a time ranging from 1 hour to 48 hours [further details can be found in Krautler B. et al., "Tetrahedron" (1996) , Vol. 52 (14), pages 5033-5042; Chronakis N. et al., "Journal of Organic Chemistry" (2002), Vol. 67 (10), pages 3284- 3289] .

Diorganofullerenes having general formula:

wherein _x represents a fullerene group, x has the same meaning described above; S¹ and S², equal to or different from each other, represent:

- a group -[-Y-{Oxa)_ra] wherein Y, Oxa and m have the same meanings described above;

- or a hydrogen atom;

- or a group selected from: alkyl groups having from 1 to 44 carbon atoms, linear or branched, saturated or unsaturated, cyclic or acyclic; aromatic groups having from 6 to 18 carbon atoms, mono- or poly- condensed with cycloaliphatic rings, with aromatic rings or with heteroaromatic rings; heteroaromatic groups; alkoxyl groups; carbonyl groups of the ketone or ester type; with the provision that at least one of S¹ and S² _r represents a group - [-Y- (Oxa}_m] , can be obtained through a process comprising:

- reacting a solution of at least one fullerene having 60, 70, or 84 carbon atoms, in the presence of at least one chlorinated solvent such as, for example, 1 , 2-dichlorobenzene , with a solution of at least one compound (Grignard compound) having general formula (XXII ) :

S^ gX (XXII)

in cui X represents a chlorine atom or a bromine atom, and S¹ represents a group - [-Y- (Oxa) _m] wherein Y, Oxa and m have the same meanings described above, with at least one aliphatic solvent such as, for example, tetrahydrofuran, in the presence of at least one additive such as, for example, dimethylsulfoxide (DMSO) , N, N-dimethylformamide (N,N-DMF), or mixtures thereof, at a temperature ranging from 25°C to 150° C, for a time ranging from a few minutes to 10 hours;

reacting the derivative thus obtained with a solution of potassium t-butoxide and, subsequently, with a solution of at least one compound having general formula (XXIII) :

S²-X (XXIII)

wherein X represents a chlorine atom or a bromine atom, and S² represents a group - [-Y- (Oxa)_m] , wherein Y, Oxa and m have the same meanings described above, with at least one aromatic solvent (benzonitrile) , at a temperature ranging from 25°C to 150° C, for a time ranging from a few minutes to 8 hours .

Further details relating to the above process for the preparation of diorganofullerenes can be found in atsuo Y. et al . , "Journal of the American Chemical Society" (2008), Vol. 130 (46), pages 15429-15436.

A further object of the present invention relates to a polymer, linear, branched or crosslinked, obtained by the polymerization and/or crosslinking of said fullerene functionalized with at least one oxazoline or dihydro-oxazine group.

Said polymer, linear, branched or crosslinked, can be obtained by means of polymerization and/or crosslinking processes "in situ" known in the art, starting from the fullerene functionalized with at least one oxazoline or dihydro-oxazine group object of the present invention. Examples of said processes can be found in Frump J. A., "Chemical Reviews" (1971), Vol. 71 (5), pages 483-505; Kobayashi S. et al., "Encyclopedia of Polymers Science and Engineering" (1987), Vol. 4, 2nd Ed., Wiley, New York, pages 525™ 537.

Said polymer, linear, branched or crosslinked, can be obtained, for example, by means of a polymerization and/or crosslinking process "in situ" which comprises: preparing a solution including at least one fullerene functionalized with at least one oxazoline or dihydro-oxazine group having general formula ( I ) , ( I I ) or (III), at least one initiator, and at least one organic solvent, and maintaining it at a temperature ranging from 15 °C to 35 °C, preferably ranging from 20 °C to 30 °C, for a time ranging from 15 minutes to 48 hours, preferably ranging from 20 minutes to 24 hours, optionally in an inert atmosphere (argon, nitrogen) ;

evaporating the organic solvent at a temperature ranging from 15°C to 35°C, preferably ranging from 20°C to 30°C, at a pressure ranging from 0.05 mm/Hg to 760 mm/Hg, for a time ranging from 1 hour to 12 hours, preferably ranging from 2 hours to 8 hours, obtaining a film;

subjecting said film to heating to a temperature ranging from 50°C to 200°C, preferably ranging from 100°C to 160°C, for a time ranging from 5 minutes to 2 hours, preferably ranging from 20 minutes to 1.5 hours, optionally in an inert atmosphere (argon, nitrogen) , obtaining a polymer.

A further object of the present invention relates to an acceptor compound-donor compound structure, linear or co-crosslinked, obtained by the reaction of at least one fullerene functionalized with at least one oxazoline or dihydro-oxazine group {acceptor compound) with at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups (donor compound) .

Said acceptor compound-donor compound structure, linear or co-crosslinked, can be obtained by means of polymerization and/or crosslinking processes "in situ" known in the art, by reaction of the fullerene functionalized with at least one oxazoline or dihydro- oxazine group object of the present invention, with a photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups. Examples of said processes can be found in Kagiya T. et al. "Polymer Letters" (1996), Vol. 4, pages 257-260; Nishikubo T. et al., "Macromolecular Chemie" (1984), Vol.185, pg . 1307- 1316.

Said acceptor compound-donor compound structure, linear or co-crosslinked, can be obtained, for example, by means of a polymerization and/or crosslinking process "in situ" which comprises:

preparing a solution including at least one fullerene functionalized with an oxazoline or dihydro-oxazine group having general formula (I), (II) or (III) (acceptor compound), at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups (donor compound) , and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35°C, preferably ranging from 20°C to 30°C, for a time ranging from 15 minutes to 48 hours, preferably ranging from 20 minutes to 24 hours, in an inert atmosphere (argon, nitrogen) ; evaporating the organic solvent at a temperature ranging from 15°C to 35°C, preferably ranging from 20°C to 30°C, at a pressure ranging from 0.05 mm/Hg to 760 mm/Hg, for a time ranging from 1 hour to 12 hours, preferably ranging from 2 hours to 8 hours, obtaining a film;

- subjecting said film to heating to a temperature ranging from 50°C to 200°C, preferably ranging from 100°C to 150°C, for a time ranging from 8 hours to 72 hours, preferably ranging from 9 hours to 60 hours, optionally in an inert atmosphere (argon, nitrogen) , obtaining an acceptor compound-donor compound structure.

Said fullerene functionalized with at least one oxazoline or dihydro-oxazine group, as well as said polymer, linear, branched or crosslinked, obtained by the polymerization and/or crosslinking of said fullerene functionalized with at least one oxazoline or dihydro-oxazine group, as well as said acceptor compound-donor compound structure, linear or co- crosslinked, obtained by the reaction of at least one fullerene functionalized with at least one oxazoline or dihydro-oxazine group (acceptor compound) with at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups (donor compound) , can be advantageously used in the construction of photovoltaic devices such as, for example, photovoltaic cells, photovoltaic modules, solar cells, solar modules, on both rigid and flexible supports.

A further object of the present invention therefore relates to the use of said fullerene functionalized with at least one oxazoline or dihydro-oxazine group, or of said polymer, linear, branched or crosslinked, obtained by the polymerization and/or crosslinking of said fullerene functionalized with at least one oxazoline or dihydro-oxazine group, or of said acceptor compound-donor compound structure, linear or co- crosslinked; obtained by the reaction of at least one fullerene functionalized with at least one oxazoline or dihydro-oxazine group (acceptor compound) with at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups (donor compound) , in the construction of photovoltaic devices such as, for example, photovoltaic cells, photovoltaic modules, solar cells, solar modules.

A further object of the present invention also relates to a photovoltaic device comprising at least one fullerene functionalized with at least one oxazoline or dihydro-oxazine group, or at least one polymer, linear, branched or crosslinked, obtained by the polymerization and/or crosslinking of said fullerene functionalized with at least one oxazoline or dihydro-oxazine group, or at least one acceptor compound-donor compound structure, linear or co- crosslinked, obtained by the reaction of at least one fullerene functionalized with at least one oxazoline or dihydro-oxazine group (acceptor compound) with at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups (donor compound) .

Said photovoltaic device can be prepared by means of various processes.

Said photovoltaic device can be prepared, for example, by means of processes in which the polymerization of the fullerene functionalized with one oxazoline or dihydro-oxazine group having general formula (I) wherein k x 1 x m = 1, or having general formula (II) wherein 1 x m = 1, or having general formula (III) wherein m = 1 (acceptor compound), is carried out "in situ" obtaining a linear polymer.

A further object of the present invention therefore relates to a process for the preparation of a photovoltaic device in which the polymerization of the fullerene functionalized with an oxazoline or dihydro- oxazine group is carried out "in situ", which comprises:

preparing a solution including at least one fullerene functionalized with an oxazoline or dihydro-oxazine group having general formula (I) wherein k x 1 x m = 1, or having general formula (II) wherein 1 x m = 1, or having general formula

(III) wherein m = 1 (acceptor compound), at least one photoactive organic polymer (donor compound) , at least one initiator, and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35 °C, preferably ranging from 20°C to 30°C, for a time ranging from 15 minutes to 48 hours, preferably ranging from 30 minutes to 24 hours ;

depositing said solution on the anode [e.g., an anode consisting of indium-tin oxide (ITO)], after having optionally previously deposited, on said anode, at least one layer of poly ( 3 , 4 -ethylene- dioxythiophene) polystyrene sulfonate (PED0T:PSS), obtaining the evaporation of the organic solvent and the formation of an anode-photoactive film structure ;

optionally, subjecting said structure to heating to a temperature ranging from 50°C to 200 °C, preferably ranging from 80°C to 160°C, for a time ranging from 5 minutes to 2 hours, preferably ranging from 20 minutes to 1 hour;

depositing a cathode [e.g., a cathode consisting of aluminium] on said structure.

A further object of the present invention relates to a process for the preparation of a photovoltaic device in which the polymerization of the fullerene functionalized with an oxazoline or dihydro-oxazine group is carried out "in situ", which comprises:

preparing a solution including at least one fullerene functionalized with an oxazoline or dihydro-oxazine group having general formula (I) wherein k x 1 x m = 1, or having general formula

(II) wherein 1 x m = 1, or having general formula

(III) wherein m = 1 (acceptor compound), at least one photoactive organic polymer (donor compound) , at least one initiator, and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35°C, preferably ranging from 20°C to 30°C, for a time ranging from 15 minutes to 48 hours, preferably ranging from 30 minutes to 24 hours ;

depositing said solution on the anode [e.g., an anode consisting of indium-tin oxide (ITO)], after having optionally previously deposited, on said anode, at least one layer of poly ( 3 , 4-ethylene- dioxythiophene) polystyrene sulfonate (PEDOT:PSS), obtaining the evaporation of the organic solvent and the formation of an anode-photoactive film structure ;

depositing a cathode [e.g., a cathode consisting of aluminium] on said structure;

optionally, subjecting said structure to heating to a temperature ranging from 50°C to 200°C, preferably ranging from 80°C to 160°C, for a time ranging from 5 minutes to 2 hours, preferably ranging from 20 minutes to 1 hour.

Alternatively, said photovoltaic device can be prepared by means of processes in which the crosslinking of the fullerene functionalized with at least two oxazoline or dihydro-oxazine groups having general formula (I) wherein k x 1 x m > 1, or having general formula ( I I ) wherein 1 x m > 1, or having general formula (III) wherein m > 1 (acceptor compound) , is carried out "in situ" obtaining a branched and/or crosslinked polymer.

A further object of the present invention therefore relates to a process for the preparation of a photovoltaic device in which the crosslinking of the fullerene functionalized with at least two oxazoline or dihydro-oxazine groups is carried out "in situ", which comprises :

preparing a solution including at least one fullerene functionalized with at least two oxazoline or dihydro-oxazine groups having general formula (I) wherein k x 1 x m > 1, or having general formula (II) wherein 1 x m > 1, or having general formula ( I I I ) wherein m > 1 (acceptor compound) , at least one photoactive organic polymer (donor compound) , at least one initiator, and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35°C, preferably ranging from 20°C to 30°C, for a time ranging from 15 minutes to 48 hours, preferably ranging from 30 minutes to 24 hours;

depositing said solution on the anode [e.g. an anode consisting of indium-tin oxide (ITO)], after having optionally previously deposited, on said anode, at least one layer of poly ( 3 , 4-ethylene- dioxythiophene) polystyrene sulfonate (PEDOT .* PSS) , obtaining the evaporation of the organic solvent and the formation of an anode-photoactive film structure;

optionally, subjecting said structure to heating to a temperature ranging from 50°C to 200°C, preferably ranging from 80°C to 160°C, for a time ranging from 5 minutes to 2 hours, preferably ranging from 20 minutes to 1 hour;

A further object of the present invention relates to a process for the preparation of a photovoltaic device in which the crosslinking of the fullerene functionalized with at least two oxazoline or dihydro- oxazine groups is carried out "in situ", which comprises :

- preparing a solution including at least one fullerene functionalized with at least two oxazoline or dihydro-oxazine groups having general formula ( I ) wherein k x 1 x m > 1, or having general formula ( I I ) wherein 1 x m > 1, or having general formula (III) wherein m > 1 (acceptor compound) , at least one photoactive organic polymer (donor compound) , at least one initiator, and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35°C, preferably ranging from 20°C to 30°C, for a time ranging from 15 minutes to 48 hours, preferably ranging from 30 minutes to 24 hours;

depositing said solution on the anode [e.g., an anode consisting of indium-tin oxide (ITO)], after having optionally previously deposited, on said anode, at least one layer of poly ( 3 , 4-ethylene- dioxythiophene ) polystyrene sulfonate (PEDOTiPSS), obtaining the evaporation of the organic solvent and the formation of an anode-photoactive film structure ;

It should be pointed out that, if a photovoltaic device comprising at least one fullerene functionalized with at least one oxazoline or dihydro-oxazine group having general formula (I), ( I I ) or (III), is to be obtained, it is sufficient to apply the above processes without the initiator.

Alternatively, said photovoltaic device can be prepared by means of processes in which there is the formation of a linear acceptor compound-donor compound structure in which the acceptor compound is a fullerene functionalized with an oxazoline or dihydro-oxazine group having general formula (I) wherein k x 1 x m = 1, or having general formula (II) wherein 1 x m = 1, or having general formula (III) wherein m = 1 (acceptor compound) , and the donor compound is a photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups. In said linear acceptor compound- donor compound structure, said acceptor compound and said donor compound are bound by means of ( thio ) e ( s ) tereimide bridges.

A further object of the present invention therefore relates to a process for the preparation of a photovoltaic device in which there is the formation of a linear acceptor compound-donor compound structure, which comprises:

(II) wherein 1 x m = 1, or having general formula

(III) wherein m = 1 {acceptor compound), at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups (donor compound) , and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35°C, preferably ranging from 20°C to 30°C, for a time ranging from 15 minutes to 48 hours, preferably ranging from 30 minutes to 24 hours;

depositing said solution on the anode [e.g., an anode consisting of indium-tin oxide (ITO)], after having optionally previously deposited, on said anode, at least one layer of poly ( 3, 4-ethylene- dioxythiophene) polystyrene sulfonate (PEDOTrPSS), obtaining the evaporation of the organic solvent and the formation of an anode-photoactive film structure ;

optionally, subjecting said structure to heating to a temperature ranging from 90°C to 160°C, preferably ranging from 130°C to 150°C, for a time ranging from 1 hour to 48 hours, preferably ranging from 2 hours to 24 hours;

A further object of the present invention relates to a process for the preparation of a photovoltaic device in which there is the formation of a linear acceptor compound-donor compound structure, which comprises :

(II) wherein 1 x m = 1, or having general formula

(III) wherein m = 1 (acceptor compound), at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups (donor compound) , and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35°C, preferably ranging from 20°C to 30°C, for a time ranging from 15 minutes to 48 hours, preferably ranging from 30 minutes to 24 hours; depositing said solution on the anode [e.g., an anode consisting of indium-tin oxide (ITO) ] , after having optionally previously deposited, on said anode, at least one layer of poly (3, 4-ethylene- dioxythiophene) polystyrene sulfonate ( PEDOT : PSS ) , obtaining the evaporation of the organic solvent and the formation of an anode-photoactive film structure ;

optionally, subjecting said structure to heating to a temperature ranging from 90°C to 160°C, preferably ranging from 130°C to 150°C, for a time ranging from 1 hour to 48 hours, preferably ranging from 2 hours to 24 hours.

Alternatively, said photovoltaic device can be prepared by means of processes in which there is the formation of a co-crosslinked acceptor compound-donor compound structure in which the acceptor compound is a fullerene functionalized with at least two oxazoline or dihydro-oxazine groups having general formula (I) wherein k x 1 x m > 1, or having general formula (II) wherein 1 x m > 1, or having general formula (III) wherein m > 1 (acceptor compound) , and the donor compound is a^' photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups.

A further object of the present invention therefore relates to a process for the preparation of a photovoltaic device in which there is the formation of a co-crosslinked acceptor compound-donor compound structure, which comprises:

- preparing a solution including at least one fullerene functionalized with at least two oxazoline or dihydro-oxazine groups having general formula (I) wherein k x 1 x m > 1, or having general formula (II) wherein 1 x m > 1, or having general formula (III) wherein m > 1 (acceptor compound) , at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups (donor compound) , and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35°C, preferably ranging from 20°C to 30°C, for a time ranging from 15 minutes to 48 hours, preferably ranging from 30 minutes to 24 hours; - depositing said solution on the anode [e.g., an anode consisting of indium-tin oxide (ITO)], after having optionally previously deposited, on said anode, at least one layer of poly (3, 4-ethylene- dioxythiophene ) polystyrene sulfonate (PEDOT:PSS), obtaining the evaporation of the organic solvent and the formation of an anode-photoactive film structure ;

A further object of the present invention relates to a process for the preparation of a photovoltaic device in which there is the formation of a co- crosslinked acceptor compound-donor compound structure, which comprises:

preparing a solution including at least one fullerene functionalized with at least two oxazoline or dihydro-oxazine groups having general formula (I) wherein k x 1 x m > 1 , or having general formula (II) wherein 1 x m > 1, or having general formula (III) wherein m > 1 (acceptor compound) , at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups (donor compound) , and at least one organic solvent, and maintaining it at a temperature ranging from 15 °C to 35 °C, preferably ranging from 20°C to 30°C, for a time ranging from 15 minutes to 48 hours, preferably ranging from 30 minutes to 24 hours ;

depositing said solution on the anode [e.g., an anode consisting of indium-tin oxide (ITO)], after having optionally previously deposited, on said anode, at least one layer of poly ( 3 , 4 -ethylene- dioxythiophene ) polystyrene sulfonate (PEDOT:PSS)_r obtaining the evaporation of the organic solvent and the formation of an anode-photoactive film structure ;

- depositing a cathode [e.g., a cathode consisting of aluminium] on said structure;

According to a further embodiment of the present invention, said processes can comprise, before depositing the cathode, depositing on said anode- photoactive film structure, at least one layer (cathodic buffer layer) comprising at least one carbonate of an alkaline metal such as, for example, caesium carbonate, or at least one oxide of a transition metal such as, for example, titanium dioxide .

According to a further embodiment of the present invention, said processes can comprise, before depositing said solution on the anode, depositing on said anode, in substitution of said layer of poly (3,4- ethylenedioxythiophene ) polystyrene sulfonate ( PE DOT : PSS) , at least one layer (anodic buffer layer) comprising at least one oxide of a transition metal such as, for example, vanadium oxide ( V2O5 ) , molybdenum oxide ( 0O₃) , or at least one phthalocyanine of a transition metal such as, for example, copper phthalocyanine .

According to a preferred embodiment of the present invention, said photoactive organic polymer can be selected from:

(a) polythiophenes such as, for example, poly (3- hexylthiophene ) (P3HT), poly { 3-octylthiophene ) , poly (3, 4-ethylenedioxythiophene) , or mixtures thereof;

(b) alternating conjugated copolymers comprising benzothiadiazole units such as, for example, PCDTBT {poly [N-9"-heptadecanyl-2 , 7-carbazole-alt-5 , 5-

(4' , ' -di-2-thienyl-2' , 1' , 3' -benzothiadiazole] } , PCPDT BT (poly [2, 6- (4, 4-bis- (2-ethylhexyl) -4H- cyclopenta- [2, 1-b; 3, 4-b' ] -dithiophene ) -alt-4, 7- {2,1, 3-benzothiadiazole) ] } ;

(c) alternating conjugated copolymers comprising thieno [3, 4-b] pyrazidine units;

(d) alternating conjugated copolymers comprising quinoxaline units;

(e) alternating conjugated copolymers comprising silole such as, for example, copolymers of 9, 9-dialkyl-9- silafluorene ;

(f) alternating conjugated copolymers comprising condensed thiophene units such as, for example, copolymers of thieno [ 3, -b] thiophene and of benzo [1, 2-b : 4 , 5-b' ] dithiophene .

More details relating to alternating conjugated copolymers comprising benzothiadiazole units (b) , alternating conjugated copolymers comprising thieno [3, 4-b] pyrazidine units (c) , alternating conjugated copolymers comprising quinoxaline units (d) , alternating conjugated copolymers comprising silole monomeric units (e) , alternating conjugated copolymers comprising condensed thiophene units (f) , can be found, for example, in "Accounts of chemical research" (2009) , Vol. 42, No. 11, pag. 1709-1718, "Development of Novel Conjugated Donor Polymers for High-Efficiency Bulk- Heterojunction Photovoltaic Devices" (Chen et al.) .

According to a further preferred embodiment of the present invention, said photoactive organic polymer can be selected from poly ( 3-hexylthiophene } (P3HT) , or from polymers having the following general formulae:

61

wherein R is a C1-C2₀, preferably C₆-Ci₅, linear or branched alkyl group; and n is an integer ranging from 2 to 500, preferably from 5 to 100.

Poly (3-hexylthiophene) (P3HT) is preferred.

According to a preferred embodiment of the present invention, said photoactive organic polymer functional! zed with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups can be selected from polythiophenes functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups such as poly (3- hexylthiophene) (P3HT) functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups, poly ( 3-octylthiophene) functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups, poly (3, 4-ethylenedioxythiophene) functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups; or mixtures thereof. Poly ( 3-hexylthiophene ) (P3HT) functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups, is preferred.

According to a preferred embodiment of the present invention, said initiator can be selected from Lewis acids such as, for example, boron trifluoride, iron trichloride, strong protic acids or their esters such as, for example, methyl tosylate (MeOTs) , methyl triflate (MeOTf) ; alkyl or aryl halides such as, for example, methyl iodide, benzyl bromide; or mixtures thereof. Methyl tosylate (MeOTs) , methyl triflate (MeOTf) , or mixtures thereof, are preferred.

According to a preferred embodiment of the present invention, said polymerization initiator can be used in an amount ranging from 0.1% in moles to 5% in moles, preferably from 0.5% in moles to 3% in moles, with respect to the number of moles of fullerene functionalized with at least one oxazoline or dihydro- oxazine group having general formula (I), (II), or (III) ·

According to a preferred embodiment of the present invention, said organic solvent can be selected from aprotic polar solvents such as, for example, N-methyl- 2-pyrrolidone (NMP) , N, -dimethylacetate ( , -DMAc) , N, -dimethylformamide (Ν,Ν-DMF), dimethylsulfoxide (DMSO) , acetonitrile ; aromatic solvents such as, for example, toluene, xylene; chlorinated solvents such as, for example, chlorobenzene , 1, 2-dichlorobenzene, chloroform, methylene chloride, trichloroethylene; or mixtures thereof. Chloroform, chlorobenzene, 1,2- dichlorobenzene, or mixtures thereof, are preferred.

Said solution can be deposited on the anode by means of techniques known in the art such as, for example, spin-coating, spray-coating, ink-jet printing, and the like.

Some illustrative and non-limiting examples are provided for a better understanding of the present invention and for its practical embodiment.

EXAMPLE 1

Synthesis of Compound (1)

The synthesis of compound (1) was carried out according to Scheme 1 provided hereunder

( 1 )

Scheme 1.

For this purpose, a mixture of p- hydroxybenzaldehyde (11 g, 90.2 mmoles) , potassium carbonate (K₂C0₃) (62.5 g, 452 mmoles), and l-iodo-2-[2- (2-iodoethoxy) ethoxy] ethane (50 g, 135.1 mmoles) in acetone (500 ml) was heated, at reflux, for 12 hours. The reaction mixture was left to cool to room temperature (25°C), and was subsequently filtered and dry concentrated under vacuum.

The oily residue obtained was purified by column chromatography [silica gel, toluene/ethyl acetate = 9:1 (v/v) as eluent] obtaining 8.9 g (27% in moles) of Compound (1) which was characterized by ¹H-NMR (400 MHz, CDC1₃) obtaining the following spectrum: 5 9.88 ppm (s, 1H, -CHO) , 7.83-7.01 (m, 4H, -CH_ar) , 4.22 (t, 2H, -OCH₂) , 3.90 (t, 2H, -OCH₂), 3.77-3.68 (m, 6H, -OCH₂, -CH₂-, -CH₂-), 3.25 (t, 2H, -CH₂I) .

Said Compound (1) was also characterized by IR spectrum (KBr) showing the following bands: v = 2734 cm^-1 (aldehyde C-H stretching) ; 1684 crrf¹ (aldehyde C-0 stretching) ; 1601 cm^-1, 1578 cm^-1, 1510 crrf¹ (aromatic rings stretching) ; 1258 cm^-1 (aryl ether C-0 stretching) ; 519 cm^"1 (C-I stretching) .

Said Compound (1) was also characterized by "Desorption Chemical Ionization - Spectrum Mass (DCI- MS) obtaining the following values: m/z 365.2 [M+H]⁺. EXAMPLE 2

Synthesis of Compound (2)

The synthesis of compound (2) was carried out according to Scheme 2 provided hereunder:

Compound (2)

Scheme 2

For this purpose, a mixture of methyl 4- hydroxybenzoate (30.4 g, 0.20 moles) and 2-aminoethanol

(100.3 g, 1.64 moles), was heated to 130°C, for 4 hours . The excess of 2-aminoethanol was concentrated under heat and the solid residue obtained by precipitation was re-crystallized from ethanol and subsequently dried in an oven, under vacuum, at 60 °C , obtaining 18.9 g (52% in moles) of Compound (2) which was characterized by ¹H-NMR (400 MHz, DMSO-d₆) obtaining the following spectrum: δ 9.7 ppm (s, 1H, C₆H₄-OH) , 8.2 (t, 1H, -NHCO) , 6.8-7.7 (m, 4H, -CH_ar) , 4.8 (s, 1H, CH₂-0H) , 3.5 (m, 2H, -CH₂OH) , 3.3 (m, 2H, -CH₂NH) .

Said Compound (2) was also characterized by

"Desorption Chemical Ionization - Spectrum Mass" {DCI- MS) obtaining the following values: m/z 182.2 [MH]⁺.

EXAMPLE 3

Synthesis of Compound (3)

The synthesis of Compound (3) was carried out in accordance with Scheme 3 provided hereunder:

Compound (2) Compound (3)

Scheme 3.

For this purpose, 21 ml (281 mmoles) of thionyl chloride (S0C1₂) were slowly added dropwise to a solution of Compound (2) (18.9 g, 104 mmoles) in 230 ml of methylene chloride (CH₂C1₂) , maintained at a temperature of 0°C. The reaction mixture was maintained under magnetic stirring, at 0°, for 1 hour and was subsequently left to cool to room temperature (25°C) for 22 hours. The solid reaction product obtained was filtered, washed with methylene chloride (CH₂C1₂) and then introduced, in small pieces, by means of a small spatula, into 1 1 of a 0.3 M aqueous solution of sodium bicarbonate (NaHC0₃) . The suspension obtained was kept under stirring, for 1 hour, and then filtered.

The reaction product obtained, a white solid, was dried in an oven, under vacuum, at 60°C, obtaining 15.8 g (93% in moles) of Compound (3) which was characterized by ¹H-NMR (400 MHz, acetone-d₆) obtaining the following spectrum: δ 10.0 ppm (s, 1H, C_sH₄-OH) , 6.8-7.7 (m, 4H, -CH_ar) , 3.85-4.25 (m, 4H, -CH₂-CH₂-) .

Said Compound (3) was also characterized by means of "Desorption Chemical Ionization - Spectrum Mass" (DCI-MS) obtaining the following values: m/z 164.3 [M+H] ⁺.

EXAMPLE 4

Synthesis of Compound (4)

The synthesis of Compound (4) was carried out in accordance with Scheme 4 provided hereunder:

Compound (T

Scheme 4.

For this purpose, a mixture of Compound (1) (3.04 g, 8.3 mmoles) , potassium carbonate (K2CO3) (4.79 g, 34.8 mmoles) and Compound (3) (1.08 g, 6.65 mmoles) in acetone (300 ml), was heated, at reflux, for 7 hours. The reaction mixture was then left to reach the room temperature (25°C), and then filtered and dry concentrated under vacuum.

The oily residue obtained was purified by column chromatography [silica gel, pentane/2-propanol = 75:25 (v/v) as eluent] obtaining 1.10 g (41% in moles) of Compound (4) which was characterized by ¹H-NMR (400 MHz, acetone-dg) obtaining the following spectrum: δ 9.88 ppm (s, 1H, -CHO), 7.86 (m, 2H, 0-C₅H₄-CHO) , 7.84 (m, 2H, 0-C₆H₄-_OX) , 7.12 (m, 2H, 0-C₆H₄-CHO) , 6.99 (m, 2H, 0-C₆H₄ -ox ) , 4.36 (t, 2H, -CH₂-_ox) , 4.26-4.23 (m, 2H, O-CH2-), 4.20-4,17 (m, 2H, CH₂-0) , 3.93 (t, 2H, -CH₂ ~₀x ) , 3.87-3.83 (m, 4H, 0-CH₂-CH₂) , 3.69 (s, 4H, 0-CH₂-CH₂) .

Said Compound (4) was also characterized by IR spectrum (KBr) showing the following bands: v = 2720 cm^-1 (aldehyde C-H stretching); 1688 cm^"1 (aldehyde C-0 stretching}; 1646 cm^"1 (oxazoline C-N stretching); 1613, 1603, 1576, 1510 cm^"1 (aromatic rings stretching}; 1253 cm^"1 (C-0 aryl ether stretching) .

Said Compound (4) was also characterized by means of "Desorption Chemical Ionization - Spectrum Mass" (DCI-MS) obtaining the following values: m/z 400.3 [M+H] ⁺.

EXAMPLE 5

Synthesis of Compound (5) (fullerene functionalized according to the present invention)

The synthesis of Compound (5) (fullerene functionalized according to the present invention) was carried out in accordance with Scheme 5 provided hereunder :

C

Scheme 5

For this purpose, a mixture of Compound (4) (102 mg, 0.25 mmoles), sarcosine (N-methylglycine) (35 mg, 0.375 mmoles) and fullerene C₆o (362 mg, 0.5 mmoles) in 125 ml of chlorobenzene, was placed at reflux, for 10 hours. After cooling to room temperature (25°C) , the reaction mixture was filtered and then concentrated under vacuum until a volume of about 30 ml was reached.

The reaction product obtained was purified by column chromatography [silica gel, toluene/ethyl acetate = 9:1 (v/v) as eluent] obtaining 41 mg (14% in moles) of Compound (5) which was characterized by ¹H-NMR

(400 MHz, CDC1₃) obtaining the following spectrum: δ = 7.86-7.84 ppm (d, 2H, CH_o-_ox) , 7.68-7.67 (d, 2H, CH_m-OCH₂CH₂) , 6.96-6.93 (d, 2H, CH₀-OCH₂CH₂) , 6.90-6.88

(d, 2H, CH_jg-_o , 4.97-4.95 (d, 1H, -CH_2pirr) , 4.86 (s, 1H, - Hpirr) , 4,39 (t, 2H, -CH_2ox), 4.24-4.21 (d, 1H, -CH_2pirr) , 4.13 (m, 4H, CH₂-CH₂-0, 1,1'), 4.02 (t, 2H, -CH₂₀x) , 3.85-3.83 ( m, 4H, CH₂-CH₂-0, 2,2'), 3.72 (s, 4H, CH2-CH2-O, 3,3'), 2.75 {s, 3H, CH₃-N) .

Said Compound (5) was also characterized by ¹³C-NMR

(400 MHz, CDCI₃) obtaining the following spectrum: δ = 159 ppm ( 4 C_ar) , 131-130 (2 C_ar) , 115-114 (2 C_ar) , 83 (CH), 71-67 (7 O-CH2) , 55 (N-CH₂) , 40 (N-CH₃), 30 (CH₂-N) .

Said Compound (5) was also characterized by IR spectrum (KBr) showing the following bands: v = 1646 cm^"1 (oxazoline C-N stretching) ; 1609, 1581, 1511 cm^-1 aromatic rings stretching) ) ; 1250 cm^-1 (C-0 aryl ether stretching) ; 527 cm^-1 (radial deformation of the fullerene structure) .

Said Compound (5) was also characterized by means of "Desorption Chemical Ionization - Spectrum Mass" (DCI-MS) obtaining the following values: m/z 1145.5 [ΜΓ.

EXAMPLE 6

Synthesis of Compound (6)

The synthesis of Compound (6) was carried out in accordance with Scheme 6 provided hereunder:

For this purpose, a mixture of dimethyl-5- hydroxyisophthalate (8.4 g, 40 mmoles) and 2- aminoethanol (40.1 g, 655 mmoles), was heated to 130°C, for 4 hours. The 2-aminoethanol in excess was concentrated under heat and the solid residue obtained by precipitation was recrystallized from ethanol and subsequently dried in an oven, under vacuum, at 60 °C, obtaining 6.7 g (62% in moles} of Compound (6) which was characterized by ¹H-NMR (400 MHz, DMSO-d₆) obtaining the following spectrum: δ 9.64 ppm (s, 1H, C₆H₃OH) , 8.37 (t, 2H, NHCO), 7.74 (m, 1H, CH^) , 7.35 (m, 2H, C₆H₂ar ) , 4.72 (t, 2H, CH₂0H) , 3.50 (m, 4H, CH₂OH) , 3.32 (m, 4H, CH₂NH) .

Said Compound (6) was also characterized by "Electrospray Ionization Mass Spectrometry" (ESI-MS) obtaining the following values: m/z 267.1 [M]^~.

EXAMPLE 7

Synthesis of Compound (7)

The synthesis of Compound (7) was carried out in accordance with Scheme 7 provided hereunder:

Compound (6)

Compound (7)

Scheme 7.

For this purpose, 9.4 ml (129 mmoles) of thionyl chloride (S0C1₂) were slowly added dropwise to a solution of Compound (6) {6.7 g, 25 mmoles) in 130 ml of methylene chloride (CH₂C1₂) , maintained at a temperature of 0°C. The reaction mixture was kept under magnetic stirring, at 0°C, for 30 minutes and then left to reach the room temperature (25°C), for 22 hours.

The solid reaction product obtained was filtered, washed with methylene chloride (CH₂C1₂) and subsequently introduced, in small pieces, using a small spatula, into 1 litre of an 0.6 M aqueous solution of sodium bicarbonate (NaHC0₃) . The suspension thus obtained was maintained under stirring, for 1 hour, and then filtered.

The reaction product obtained, a white solid, was dried in an oven, under vacuum, at 60°C, obtaining 5.6 g (98% in moles) of Compound (7) which was characterized by ¹H-NMR (DMS0-d₆) obtaining the following spectrum: δ 10.08 ppm (s, 1H, C₆H₃OH) , 7.80 (s, 1H, C₆Har) , 7.42-7.40 (s, 2H, C₆H_2ar) , 4.42-4.37 (m, 4H, CH₂-CH₂), 3.98-3.93 (m, 4H, CH₂-CH₂) .

Said Compound (7} was also characterized by means of "Desorption Chemical Ionization - Spectrum Mass" (DCI-MS) obtaining the following values: m/z 233.1 [M+H]⁺.

EXAMPLE 8

Synthesis of Compound (8)

The synthesis of Compound (8) was carried out in accordance with Scheme 8 provided hereunder:

Scheme

For this purpose, a mixture of Compound (1) (3.99 g, 11 mmoles) , potassium carbonate (K₂C0₃) (6.40 g, 46.3 mmoles) , and Compound (7) (2.15 g, 9.26 mmoles), in N, -dimethylformamide (250 ml), was heated, at reflux temperature, for 6 hours. After cooling to room temperature (25°C), said reaction mixture was filtered and subsequently dry concentrated.

The oily residue obtained was purified by means of column chromatography [silica gel, aceto- nitrile/methanol = 5:1 (v/v) as eluent] obtaining 1.32 g (30% in moles} of Compound (8) which was characterized by ¹H-NMR (400 MHz, acetone-d₆) : δ 9.88 ppm (s, 1H, -CHO) , 8.01 (m, 1H, 0-CH_{a r}_ox ) , 7.84-7.81 (m,

2H, O-CHar-CHO} , 7.62 (m, 2H, 0-CH_{a r}-ox ) , 7.07-7.05 (m, 2H, 0-CH_ar~CHO) , 4.52 (t, 4H, -CH₂-ox ) , 4.21 (m, 4 H ,

-CH2 -CH2-O) , 4.04 (t, 4 H , -CH₂-_OK) , 3.89-3.88 (m, 4H,

0-CH₂-CH₂) , 3.75 (s, 4 H , O- CH2 -CH2 ) .

Said Compound (8) was also characterized by IR spectrum (KBr) showing the following bands: v = 2742 cm^"1 (C-H aldehyde stretching) ; 1684 cm^"1 (C=0 aldehyde stretching} ; 1651 crrf¹ {C=N oxazoline stretching) ; 1602 cm^-1, 1579 cm^-1, 1510 cm^-1 (aromatic rings stretching)

1254 cm^-1 (C-0 aryl ether stretching) .

Said Compound (8} was also characterized by means of "Desorption Chemical Ionization - Spectrum Mass"

( DC I-MS ) obtaining the following values: m/z 469.1

[M+H] ⁺.

EXAMPLE 9

Synthesis of Compound (9) (fullerene functionalized according to the present invention)

The synthesis of Compound (9) (fullerene functional! zed according to the present invention) was carried out in accordance with Scheme 9 provided hereunder :

Scheme .

For this purpose, a mixture of Compound (8) (1.32 g, 2.82 mmoles} , sarcosine (N-methylglycine ) (377 mg, 4.23 mmoles) and fullerene Cgo (3.05 g, 4.23 mmoles) in 250 ml of chlorobenzene, was placed at reflux, for 10 hours. After cooling to room temperature (25°C), the reaction mixture was filtered and concentrated under vacuum until a volume of about 30 ml was obtained.

The reaction product obtained was purified by column chromatography [silica gel, toluene/isopropanol = 9:1 (v/v) as eluent] obtaining 211 mg (6% in moles) of Compound (9) which was characterized by means of ¹H- NMR (400 MHz, CDC1₃) obtaining the following spectrum: δ 8.08 ppm (t, 1H, CH^-ox) , 7.70 (m_br, 2H, CH_ar -OCH₂CH₂) , 7.62 (d, 2H, CHar-ox) , 6.97 (d, 2H, CH_ar-OCH₂CH₂ ) , 4.97 (d, 1H, -CH_2pirr), 4.87 (s, 1H, -CH_pirr) , 4.42 {t, 4H, ~CH_2ox), 4.24 (d, 1H, -CH_2pirr) , 4.18-4.13 {m, 4H, CH₂-CH₂~0, 1,1'), 4.05 (t, 4H, -CH_2ox) , 3.85 (m, 4H, CH₂-CH₂-0, 2,2'), 3.73 (s, 4H, CH₂-CH₂-0, 3,3'), 2.78 (s, 3H, N-CH₃) .

Said Compound (9) was also characterized by IR spectrum (KBr) showing the following bands: v = 1650 cm^-1 (C=N oxazoline stretching) ; 1609 cm^"1, 1589 cm^-1, 1510 cm^-1 (aromatic rings stretching) ; 1246 cm^-1 (C-0 aryl ether stretching) ; 527 cm^-1 (radial deformation of the fullerene structure) .

Said Compound (9) was also characterized by means of "Desorption Chemical Ionization - Spectrum Mass" (DCI-MS) obtaining the following values: m/z 1214.1 [M]^~. EXAMPLE 10

Synthesis of Compound (10) obtained by the polymerization of Compound {_5J (fullerene functionalized according to the present invention)

Compound (10) was obtained by the polymerization of

Compound (5) (fullerene functionalized according to the present invention) obtained as described in Example 5. Said polymerization was carried out in accordance with

Scheme 10 provided hereunder:

Scheme 10.

For this purpose, 0.082 ml (0.22 mg, 0.12x10^"^ mraoles) of a solution 0.0146 M of methyl tosylate

(MeOTs) in anhydrous chloroform (CHC1₃) were added to a solution of Compound (5) (31 mg, 2.7xl0^~2 mmoles) in 10 ml of anhydrous chloroform {CHCI₃) , introduced into a flask in an inert atmosphere (argon) . The solution was kept, under magnetic stirring, in an inert atmosphere, at room temperature (25°C) , for 30 minutes. The solution was then maintained at room temperature

(25°C), at a pressure of 0.1 mm/Hg, for 4 hours, in order to evaporate all the solvent and to obtain a film. The film thus obtained on the bottom of the flask, was placed in a silicon oil bath, at a temperature of 120.0 C°-120.3°C, and was left at said temperature for 30 minutes, obtaining a polymer.

The polymer thus obtained was re-dissolved in 10 ml of chloroform (CHCI₃) , at room temperature (25°C) , and subsequently poured into a flask and dried, at room temperature (25°C), by means of a mechanical pump.

19 mg (61% in moles) of Compound (10} were obtained, which was characterized by IR spectrum (KBr) , showing the following bands: v = 1646 cm^"1 (C=N oxazoline stretching} ; 1630 cm^-1 (C=0 amide stretching) ; 1609 cm^-1, 1581 cm^-1, 1511 crrf¹ (aromatic rings stretching) ; 1250 cm^"1 (C-0 aryl ether stretching) ; 527 (radial deformation of the fullerene structure) .

EXAMPLE 11

Synthesis of Compound (10) obtained by the polymerization of Compound (5) (fullerene functionalized according to the present invention) in the presence of poly (3-hexylthiophene) (P3HT)

Compound (10) was obtained by the polymerization of Compound (5} (fullerene functionalized according to the present invention) obtained as described in Example 5. Said polymerization was carried out in accordance with Scheme 11 provided hereunder:

Compound {10}

Scheme 11.

For this purpose, a solution of 5 μΐ of methyl tosylate in 2 ml of methylene chloride was initially prepared. 5 μΐ of the solution of methyl tosylate (1% in moles with respect to Compound 5) previously prepared was subsequently added to a mixture of 9.70 mg of poly { 3-hexylthiophene ) (P3HT) and 9.63 mg of Compound (5) (Fulloxal), in a vial. The mixture thus obtained was dissolved in 1 ml of chlorobenzene obtaining a solution that was kept under magnetic stirring, for a night, at room temperature (25°C) , in an inert atmosphere (nitrogen) .

300 μΐ of the solution obtained were then placed on a tablet of calcium fluoride (diameter 25 mm, thickness 2 mm) positioned in a spin coater of Chemat Technology, and subjected to a velocity increase profile of 400 revs/min for 30 seconds and 1,500 revs/min for 60 seconds.

The IR absorption spectrum and the emission spectrum were then carried out respectively on the material thus deposited on the tablet, in order to evaluate the quenching of the fluorescence. The tablet was subsequently placed on a heating plate at a temperature of 120°C, for 30 minutes. After cooling to room temperature, the spectra indicated in Figure 1 were carried out again on the material [the wavenumber in cm^"1 is reported in the abscissa, the absorbance in a.u. (arbitrary units) is reported in the ordinate] and in Figure 2 [the wavelength in nm is reported in the abscissa, the light intensity in a.u. (arbitrary units) is reported in the ordinate] .

The band shown at 1646 cm^-1 in the spectrum of Figure 1 is due to the stretching of the C=N group present in the oxazoline ring. The decrease in its intensity to the progress of the heating (i.e. a further 30 minutes at 150°C), shows that the fullerene derivative (Fulloxal, Compound 5} polymerizes: as shown in Scheme 11, in fact, the polymerization of Compound 5 involves the opening of the oxazoline ring with the consequent loss of the C=N bond.

The decrease in the intensity of the emission band of P3HT (spectrum in Figure 2) which takes place in the sample P3HT : Fulloxal , both before and after polymerization, shows the complete quenching of the fluorescence of the P3HT on the part of the fullerene derivative .

Claims

Fullerene functionalized with at least one oxazoline or dihydro-oxazine group, wherein said oxazoline or dihydro-oxazine group is bound to the fullerene through a condensed ring, or through a polyvalent organic group, or directly.

Functionali zed fullerene according to claim 1, wherein said functionalized fullerene has one of the following general formulae (I), (II) or (III):

C_x-{R-[-Y-(Oxa)_m]₁}_k (I)

C_x-[-Y-(Oxa)_m]_! (II)

C_x-{Oxa)_m (III)

wherein :

- C_x represents a fullerene group;

- x represents an integer ranging from 50 to 250, extremes included;

- m represents an integer ranging from 1 to 4, extremes included;

- 1 represents an integer ranging from 1 to 3, extremes included;

- k represents an integer ranging from 1 to 3, extremes included;

- A represents a ring condensed with the fullerene group selected from cycloalkyl groups having from 3 to 6 carbon atoms; or from heterocyclic groups having from 3 to 6 atoms containing from 1 to 3 heteroatoms selected from nitrogen, oxygen, sulfur;

- Y represents a polyvalent organic group having a valence m+1, selected from linear or branched alkylene groups, cycloalkylene groups, arylene groups, or combinations thereof; said alkylene, cycloalkylene or arylene groups optionally containing in the chain one or more heteroatoms selected from oxygen, nitrogen, sulfur, silicon, phosphorous ;

- Oxa represents an oxazoline or dihydro-oxazine group .

3. Functionalized fullerene according to claim 2, wherein Oxa represents a 2-oxazoline group having the formula :

or a 5 , 6-dihydro-2-oxazine group having the formula :

wherein R¹, R², R³, R⁴ , R⁵ and R^s, equal to or different from each other, represent a hydrogen atom; or a linear or branched alkyl group, having from 1 to 12 carbon atoms, such as methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl; a phenyl group; a benzyl group; a hydroxyalkyl group such as a hydroxymethyl group.

Functionalized fullerene according to claim 2 or 3, wherein x represents an integer ranging from 60 to 90, extremes included.

Functionalized fullerene according to any of the previous claims, wherein said group Y is selected from polyvalent organic groups having the following formulae:

wherein n, p, q, r, are integers ranging from 1 to 12, extremes included.

Functionalxzed fullerene according to any of the previous claims, wherein said functionalized fullerene with at least one oxazoline or dihydro- oxazine group having general formula {1} is selected from fullerenes having the following formulae :

wherein S¹, S², S³, s S⁵ and S⁶, equal to or different from each other, represent:

- a -[-Y-{Oxa)_m] group wherein Y, m and Oxa, have the same meanings described above;

- or a hydrogen atom; - or a group selected from: alkyl groups having from 1 to 44 carbon atoms, linear or branched, saturated or unsaturated, cyclic or acyclic; aromatic groups having from 6 to 18 carbon atoms, mono- or poly-condensed with cycloaliphatic rings, with aromatic rings or with heteroaromatic rings; heteroaromatic groups; alkoxyl groups; carbonyl groups of the ketone or ester type;

with the provision that at least one of S¹, S², S³, S⁴, S⁵ and S⁶, represents a -[-Y-(0xa)_m] group.

Functionalized fullerene according to any of the claims from 1 to 5, wherein said functionalized fullerene with at least one oxazoline or dihydro- oxazine group having general formula (II) is selected from fullerenes having the following formulae :

wherein :

- Oxa¹, Oxa², Oxa³, and Oxa⁴, equal to or different from each other, represent a 2-oxazoline group or a 5, 6-dihydro-2-oxazine group;

- Y has the same meaning described above;

- S¹ represents a hydrogen atom; or a group selected from: alkyl groups having from 1 to 44 carbon atoms, linear or branched, saturated or unsaturated, cyclic or acyclic; aromatic groups having from 6 to 18 carbon atoms, mono- or poly- condensed with cycloaliphatic rings, with aromatic rings or with heteroaromatic rings; heteroaromatic groups; aikoxyl groups; carbonyl groups of the ketone or ester type.

8. Functionalized fullerene according to any of the claims from 1 to 5, wherein said functionalized fullerene with at least one oxazoline or dihydro- oxazine group having general formula (III) is selected from fullerenes having the following formulae:

wherein :

~ Oxa¹ and Oxa², equal to or different from each other, represent a 2-oxazoline group or a 5,6- dihydro-2-oxazine group;

- S¹ represents a hydrogen atom; or a group selected from: alkyl groups having from 1 to 44 carbon atoms, linear or branched, saturated or unsaturated, cyclic or acyclic; aromatic groups having from 6 to 18 carbon atoms, mono- or poly- condensed with cycloaliphatic rings, with aromatic rings or with heteroaromatic rings; heteroaromatic groups; alkoxyl groups; carbonyl groups of the ketone or ester type.

9. A linear, branched or crosslinked polymer, obtained by the polymerization and/or crosslinking of the fullerene functionalized with at least one oxazoline or dihydro-oxazine group according to any of the previous claims.

An acceptor compound-donor compound structure, linear or co-crosslinked, obtained by the reaction of at least one fullerene functionalized with at least one oxazoline or dihydro-oxazine group according to any of the previous claims with at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups .

Use of fullerene functionalized with at least one oxazoline or dihydro-oxazine group according to any of the claims from 1 to 8, in the construction of photovoltaic devices such as photovoltaic cells, photovoltaic modules, solar cells, solar modules .

Use of the linear, branched or crosslinked polymer according to claim 9, in the construction of photovoltaic devices such as photovoltaic cells, photovoltaic modules, solar cells, solar modules.

Use of the acceptor compound-donor compound structure, linear or co-crosslinked, according to claim 10, in the construction of photovoltaic devices such as photovoltaic cells, photovoltaic modules, solar cells, solar modules.

14. A photovoltaic device comprising at least one fullerene functionalized with at least one oxazoline or dihydro-oxazine group according to any of the claims from 1 to 8.

15. A photovoltaic device comprising at least one linear, branched or crosslinked polymer according to claim 9.

16. A photovoltaic device comprising at least one acceptor compound-donor compound structure, linear or co-crosslinked, according to claim 10.

17. A process for the preparation of a photovoltaic device according to claim 14, comprising:

- preparing a solution including at least one fullerene functionalized with an oxazoline or dihydro-oxazine group having general formula (I) wherein k x 1 x m = 1, or having general formula (II) wherein 1 x m = 1, or having general formula (III) wherein m = 1 (acceptor compound), at least one photoactive organic polymer (donor compound) , at least one initiator, and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35°C, for a time ranging from 15 minutes to 48 hours; - depositing said solution on the anode, after having optionally previously deposited, on said anode, at least one layer of poly ( 3 , 4-ethylene- dioxythiophene) polystyrene sulfonate (PEDOT:PSS), obtaining the evaporation of the organic solvent and the formation of an anode- photoactive film structure;

optionally, subjecting said structure to heating to a temperature ranging from 50°C to 200°C, for a time ranging from 5 minutes to 2 hours;

depositing a cathode on said structure.

A process for the preparation of a photovoltaic device according to claim 14, comprising:

- preparing a solution including at least one fullerene functionalized with an oxazoline or dihydro-oxazine group having general formula (I) wherein k x 1 x m = 1, or having general formula (II) wherein 1 x m = 1, or having general formula ( I I I ) wherein m = 1 (acceptor compound), at least one photoactive organic polymer (donor compound) , at least one initiator, and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35°C, for a time ranging from 15 minutes to 48 hours;

depositing said solution on the anode, after having optionally previously deposited, on said anode, at least one layer of poly (3, 4- ethylenedioxy-thiophene) polystyrene sulfonate (PEDOT:PSS), obtaining the evaporation of the organic solvent and the formation of an anode- photoactive film structure;

depositing a cathode on said structure;

optionally, subjecting said structure to heating to a temperature ranging from 50°C to 200°C, for a time ranging from 5 minutes to 2 hours.

preparing a solution including at least one fullerene functionalized with at least two oxazoline or dihydro-oxazine groups having general formula (I) wherein k x 1 x m > 1, or having general formula (II) wherein 1 x m > 1, or having general formula (III) wherein m > 1 (acceptor compound) , at least one photoactive organic polymer (donor compound) , at least one initiator, and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35°C, for a time ranging from 15 minutes to 48 hours;

depositing said solution on the anode, after having optionally previously deposited, on said anode, at least one layer of poly (3, 4- ethylenedioxy-thiophene ) polystyrene sulfonate (PEDOT:PSS), obtaining the evaporation of the organic solvent and the formation of an anode- photoactive film structure;

optionally, subjecting said structure to heating to a temperature ranging from 50°C to 2Q0°C, for a time ranging from 5 minutes to 2 hours;

depositing a cathode on said structure.

depositing said solution on the anode, after having optionally already deposited, on said anode, at least one layer of poly (3,4- ethylenedioxythio-phene) polystyrene sulfonate (PEDOTrPSS), obtaining the evaporation of the organic solvent and the formation of an anode- photoactive film structure;

depositing a cathode on said structure;

preparing a solution including at least one fullerene functionalized with an oxazoline or dihydro-oxazine group having general formula ( I ) wherein k x 1 x m = 1 , or having general formula ( I I ) wherein 1 x m = 1, or having general formula (III) wherein m = 1 (acceptor compound), at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups (donor compound) , and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35°C, for a time ranging from 15 minutes to 48 hours;

depositing said solution on the anode, after having optionally previously deposited, on said anode, at least one layer of poly (3,4- ethylenedioxythio-phene ) polystyrene sulfonate (PED0T:PSS), obtaining the evaporation of the organic solvent and the formation of an anode- photoactive film structure;

optionally, subjecting said structure to heating to a temperature ranging from 90 °C to 160 °C, for a time ranging from 1 hour to 48 hours ;

depositing a cathode on said structure.

preparing a solution including at least one fullerene functionalized with an oxazoline or dihydro-oxazine group having general formula (I) wherein k x 1 x m = 1, or having general formula (II) wherein 1 x m = 1, or having general formula (III) wherein m = 1 (acceptor compound), at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups (donor compound) , and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35°C, for a time ranging from 15 minutes to 48 hours; depositing said solution on the anode, after having optionally previously deposited, on said anode, at least one layer of poly (3,4- ethylenedioxythio-phene) polystyrene sulfonate (PEDOTrPSS), obtaining the evaporation of the organic solvent and the formation of an anode- photoactive film structure;

depositing a cathode on said structure

optionally, subjecting said structure to heating to a temperature ranging from 90°C to 160°C, for a time ranging from 1 hour to 48 hours.

preparing a solution including at least one fullerene functionali zed with at least two oxazoline or dihydro-oxazine groups having general formula (I) wherein k x 1 x m > 1, or having general formula (II) wherein 1 x m > 1, or having general formula (III) wherein m > 1 (acceptor compound) , at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups (donor compound) , and at least one organic solvent, and maintaining it at a temperature ranging from 15°C to 35°C, for a time ranging from 15 minutes to 48 hours;

depositing said solution on the anode, after having optionally previously deposited, on said anode, at least one layer of poly (3,4- ethylenedioxythio-phene ) polystyrene sulfonate (PEDOT:PSS), obtaining the evaporation of the organic solvent and the formation of an anode- photoactive film structure;

optionally, subjecting said structure to heating to a temperature ranging from 90°C to 160°C, for a time ranging from 1 hour to 48 hours;

depositing a cathode on said structure.

preparing a solution including at least one fullerene functionali zed with at least two oxazoline or dihydro-oxazine groups having general formula (1} wherein k x 1 x m > 1, or having general formula (II) wherein 1 x m > 1, or having general formula (III) wherein m > 1 (acceptor compound) , at least one photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups (donor compound) , and at least one organic solvent, and maintaining it at a temperature ranging from 15 °C to 35°C, for a time ranging from 15 minutes to 48 hours;

depositing said solution on the anode, after having optionally previously deposited, on said anode, at least one layer of poly (3, 4- ethylenedioxythio-phene) olystyrene sulfonate (PEDOT:PSS), obtaining the evaporation of the organic solvent and the formation of an anode- photoactive film structure;

depositing a cathode on said structure

optionally, subjecting said structure to heating to a temperature ranging from 90 °C to 160 °C, for a time ranging from 1 hour to 48 hours.

A process for the preparation of a photovoltaic device according to any of the claims from 17 to 20, wherein said photoactive organic polymer is selected from:

(a) polythiophenes such as poly (3- hexylthiophene) (P3HT) , poly (3 octylthiophene) , poly (3, 4 - ethylenedioxythiophene) , or mixtures thereof;

(b) alternating conj ugated copolymers comprising benzothiadiazole units such as PCDTBT {poly [N-9"-heptadecanyl-2, 7- carbazole-alt-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, -b' ] -dithiophene ) -alt- 4, 7- (2, 1, 3-benzothiadiazole) ] } ;

(c) alternating conjugated copolymers comprising thieno [3, -b] pyrazidine units;

(d) alternating conjugated copolymers comprising quinoxaline units;

(e) alternating conjugated copolymers comprising silole such as, for example, copolymers of 9, 9-dialkyl-9-silafluorene;

(f) alternating conjugated copolymers comprising condensed thiophene units such as, for example, copolymers of thieno[3,4- b] thiophene and of benzo [ 1 , 2-b : , 5- b' ] dithiophene .

A process for the preparation of a photovoltaic device according to any of the claims from 21 to 24, wherein said photoactive organic polymer functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups are selected from polythiophenes functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups such as poly ( 3-hexylthiophene ) (P3HT) functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups, poly ( 3-octylthiophene) functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups, poly (3, 4-ethylenedioxythiophene} functionalized with at least one group selected from phenol, thiophenol, carboxyl, thiocarboxyl groups; or mixtures therof.

A process for the preparation of a photovoltaic device according to any of the claims from 17 to 20, wherein said initiator is selected from Lewis acids such as boron trifluoride, iron trichloride, strong protic acids or their esters such as methyl tosylate (MeOTs) , methyl triflate (MeOTf ) ; alkyl or aryl halides such as methyl iodide, benzyl bromide; or mixtures thereof.

A process for the preparation of a photovoltaic device according to any of the claims from 17 to 24, wherein said organic solvent is selected from aprotic polar solvents such as N-methyl-2- pyrrolidone (NMP) , N, -dimethylacetate ( N , -DMAc) , N, -dimethylformamide ( , N-DMF) , dimethylsulfoxide (DMSO) , acetonitrile ; aromatic solvents such as toluene, xylene; chlorinated solvents such as chlorobenzene, 1 , 2-dichlorobenzene, chloroform, methylene chloride, trichloroethylene; or mixtures thereof .