WO2013098746A1

WO2013098746A1 - Fullerenes functionalized with thienylene for photovoltaics

Info

Publication number: WO2013098746A1
Application number: PCT/IB2012/057628
Authority: WO
Inventors: Riccardo BARBIERI; Luisa Fiocca
Original assignee: Eni S.P.A.
Priority date: 2011-12-28
Filing date: 2012-12-21
Publication date: 2013-07-04
Also published as: ITMI20112401A1

Abstract

A compound comprising at least one fullerene functionalized with at least one divalent organic group containing at least one thienylene unit and with at least one aromatic or heteroaromatic group. Said 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.

Description

FULLERENES FUNC IONALIZED WITH THIENYLENE FOR PHOTOVOLTAICS

The present invention relates to a compound comprising at least one fullerene functionalized with aromatic and heteroaromatic groups.

More specifically, the present invention relates to a compound comprising at least one fullerene functionalized with at least one divalent organic group containing at least one thienylene unit and with at least one aromatic or heteroaromatic group.

The present invention also relates to the use of said compound comprising at least one fullerene functionalized with at least one divalent organic group containing at least one thienylene unit and with at least one aromatic or heteroaromatic group, 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 including at least one compound comprising at least one fullerene functionalized with at least one divalent organic group containing at least one thienylene unit and with at least one aromatic or heteroaromatic group.

Photovoltaic devices are devices capable of converting the energy of a light 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, however, has for some time been orienting its efforts towards the development of alternative materials of the organic type, having a polymeric structure (so-called polymer photovoltaic cells). Unlike high-purity crystalline silicon, in fact, organic polymers are characterized by a relative synthesis easiness, a low production cost, a reduced weight of the relative photovoltaic device, and also allow 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 devices is based on the combined use of an electron-acceptor compound and of 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 group of polyparaphenylenevinylenes and polythiophenes . The former can be used not only as donor compounds, but also as acceptor compounds, on the basis of the electronic properties determined by the substituent groups of the polymeric chain. The latter are normally used as donor compounds. Among acceptor compounds, fullerene derivatives are the most widely used. 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 separate charge transporters [electron (-) and electronic gap (or hole) (+) ] ;

. transporting of the charges thus formed to the cathode (electron, through the acceptor compound) and 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 subsequent yielding of the electron to the acceptor compound leads to 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 that 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 that the donor compound is capable of collecting and of effectively converting into electric energy, (so-called "photon harvesting" or "light- harvesting" process), depends on this difference.

From the point of view of electronic characteristics, improvements with respect to the materials used in the production of photovoltaic devices are possible, for example, through projecting 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 retransfer of the charge, it is preferable for the difference in energy between the HOMO of the donor compound and of the acceptor compound (ΔΕ_ΗΟΜΟ) and between the LUMO of the donor compound and of the acceptor compound (AE_LUMO) , to have an optimal value ranging from 0.3 eV to 0.5 eV or, in any case, to have a lower value with respect to the values obtained using known donor compounds and acceptor compounds.

Furthermore, the band-gap, i.e. the difference in energy between HOMO and LUMO of the donor compound, must not be excessively high to allow the absorption of the highest number of photons, but at the same time not excessively low as it could reduce the voltage at the electrodes of the device. In order to optimally exploit solar radiation and consequently to improve the efficiency of the photovoltaic cell, it is preferable for the acceptor compound to have a more extensive absorption spectrum within the visible range, i.e. 400 nm - 700 nm, and also a higher molar absorption coefficient (s) (e.g. > 50000 l*mol^_1*cirf¹ ) with respect to the known acceptor compounds.

Another important characteristic of the materials used in the production of 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 easiness with which the electric charges, once photogenerated, reach the electrodes. This electronic mobility is not only an intrinsic property of the molecules but is also strongly 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 should be neither excessively dispersed, nor too segregated.

The morphology of the photoactive layer is critical also with respect to the efficacy of the dissociation of the electronic gap (hole) -electron pairs photogenerated. The average lifetime of the electron is in fact such that it is able to be diffused in the organic material for an average distance not greater than 10 nm - 20 nm. The phases of the donor compound and of the acceptor compound must therefore be organized in nanodomains having dimensions comparable with this diffusion distance. Furthermore, the donor compound- acceptor compound contact area must be as wide as possible and there must be preferential routes towards the electric contacts. This morphology must also be reproducible and 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 (architecture known as "bulk heterojunction") , between two electrodes, normally consisting of indium-tin oxide (ITO) (anode) and of aluminium (Al) (cathode) . In order to produce a layer of this type, a solution of the two components is generally prepared and a photoactive film 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 film. 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 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 LUMO orbital values, good molar adsorption coefficient (ε) ] , a good solubility in the solvents used in the construction of polymer 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- thienyl-2' , 1' , 3' -benzothiadiazole] } , the polymer

PCPDTBT {poly [2, 6- (4, 4-bis- (2-ethylhexyl) -4H-cyclo- penta [2, l-b;3, 4-b' ] -dithiophene) -alt-4, 7- (2, 1, 3- benzothiadiazole) ] } .

Usually, the most widely-used acceptor compounds are derivates of fullerene (C₆o or C₇₀) , in particular [ 6, 6] -phenyl-C₆i-butyric acid methyl ester ( [ 60] PCB ) , or phenyl-Cvi-butyric acid methyl ester ([70] PCBM). Said fullerene derivatives are capable of reaching maximum conversion efficiencies of solar radiation of up to 8%.

Usually, 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 the electrons, thus allowing an improved collection of the charges on the part of the electrode and inhibiting recombination phenomena, before creating the photoactive film, starting from the mixture of acceptor compound and of donor compound as described above, a film is deposited, starting from an aqueous suspension of PEDOT: PSS [poly (3, 4-ethylenedioxythiophene) - polystyrene sulfonate] , resorting to suitable deposition techniques such as, for example, "spin- coating", "spray-coating", "ink-jet printing", and the like.

There are numerous studies relating to donor compounds capable of improving the efficiency of polymer photovoltaic cells.

Donor compounds capable of improving the efficiency of polymer photovoltaic cells are described, for example, by: Roncali J., in the review "Synthetic

Principles for Bandgap Control in Linear ^-Conjugated

Systems", Chemical Reviews (1997), Vol. 97, pages 173- 205; Kroon R. et al. in the review "Small Bandgap

Polymers for Organic Solar Cells (Polymer Material

Development in the Last 5 Years)", Polymer Reviews

(2008), Vol. 48, pages 531-582.

Studies relating to acceptor compounds capable of improving the efficiency of polymer photovoltaic cells are also known.

Acceptor compounds capable of improving the efficiency of polymer photovoltaic cells are described, for example, by: Roncali J. in the review "Linear π- conjugated systems derivatized with C6o~fullerene as molecular heteroj unctions for. organic photovoltaics", Chemical Society Reviews (2005), pages 483-495; Mishra A. et al in the review "Functional Oligothiophenes : Molecular Design for Multidimensional Nanoarchitectures and Their Applications", Chemical Reviews (2009) , pages 1141-1276; Kharisov B. I. et al . in the review "Recent Advances in the Synthesis, Characterization, and Applications of Fulleropyrrolidines" , Industrial and Engineering Chemical Research (2009), Vol. 48, pages 545-571; He Y. et al. in the article "Fullerene derivative acceptors for high performance polymer solar cells", Physical Chemistry Chemical Physics (2011) , Vol.13, pages 1970-1983.

The acceptor compounds described therein, however, can have various drawbacks such as, for example, a low solubility in the solvents normally used in the production of polymer photovoltaic cells, a low molecular weight, a low polydispersity, in addition to high process costs for obtaining them.

Studies relating to the development of new acceptor compounds, in particular of modified fullerenes capable of improving the efficiency of photovoltaic devices, in particular of polymer photovoltaic cells, are still of interest .

The Applicant has therefore considered the problem of finding a new modified fullerene capable of improving the efficiency of photovoltaic devices, in particular of polymer photovoltaic cells.

The Applicant has now found a new compound comprising at least one fullerene functionalized with at least one divalent organic group containing at . least one thienylene unit and with at least one aromatic or heteroaromatic group that can be used as acceptor compound in the construction of photovoltaic devices, in particular of polymer photovoltaic cells, capable of improving the efficiency of said photovoltaic devices.

Said compound comprising a functionalized fullerene has electronic properties, i.e. HOMO, LUMO and band-gap energy level values which are such as to be able to be optimally combined with the energy levels of the donor compound commonly used in photovoltaic devices, i.e. regioregular poly ( 3-hexylthiophene) (P3HT) . In particular, with respect to the fullerene derivative normally used in photovoltaic devices, i.e. [6,6]- phenyl-C₆i-butyric acid methyl ester ( [60] PCB ) , when combined with poly (3-hexylthiophene) (P3HT), it can be observed that the energy difference between the LUMO of the donor and the LUMO of the acceptor diminishes (ΔΕ LUM0_D - LUMO_ft) . In the same way, the energy difference between the HOMO of the donor and the HOMO of the acceptor also diminishes (ΔΕ HOMO_D - HOMO_A) .

Furthermore, said compound comprising at least one functionalized fullerene has a wider absorption spectrum (i.e. it absorbs within a wider wavelength range) . Said compound comprising at least one functionalized fullerene also has a higher molar absorption coefficient (ε) with respect to [ 6, 6] -phenyl- C₆i-butyric acid methyl ester ([60]PCBM) (e.g., a value > 50, 000 l*mol^_1*cm^_1) .

An object of the present invention therefore relates to a compound containing at least one functionalized fullerene having general formula (I) or (ID :

C_x-Ai-Y_m-B_n-Y -B'_n'-Y"_m"-A'i_'-K_p (I)

Cx-[Ai-Y_m-B_n-YV-BV-Y' 'm"-A'i'] (II) wherein

C_x represents a fullerene group;

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

A and A' , the same or different from each other, represent a condensed ring with the fullerene group selected from cycloalkyl groups having from 3 to 6 carbon atoms, or heterocyclic groups having from 3 to 6 atoms containing from 1 to 3 heteroatoms selected from nitrogen, oxygen, sulfur;

i and i', the same or different from each other, represent 0 or 1;

- Y, Y' and Y' ' , the same or different from each other, represent an aromatic or heteroaromatic divalent organic group, optionally substituted with linear or branched Ci-C₂o alkyl groups, linear or branched C2-C20 alkenyl groups, linear or branched C2-C20 alkinyl groups, linear or branched C₂-C₂o alkoxyl groups, ester groups -COORi wherein Ri represents a linear or branched Ci-C₂o alkyl group; Y, Y' and Y' ' being different from a divalent organic group containing at least one thienylene unit;

m, m' and m' ' , the same or different from each other, represent 0 or 1, with the proviso that at least one of m, m' and m' ' is different from 0;

B and B' , the same or different from each other, represent a divalent organic · group containing at least one thienylene unit, · optionally substituted with linear or branched C1-C20 alkyl groups, linear or branched C2-C20 alkenyl groups, linear or branched C2-C20 alkinyl groups, linear or branched C2-C20 alkoxyl groups, ester groups -COORi wherein Ri represents a linear or branched C1-C20 alkyl group;

n and n' , the same or different from each other, represent 0 or 1, with the proviso that at least one of n and n' is different from 0;

the sum of m + n + m' + n' + m' ' , said m + n + m' + n' + m' ' being the same or different from each other, ranges from 2 to 5, and is preferably 3, with the proviso that in general formula (I) and in general formula (II) at least one group Y, Y' or Y' ' and at least one group B or B' are present, and that groups Y and/or Y' and/or Y' ' alternate with groups B and/or B' ;

K represents, when i' is 0, a C_x fullerene group, a linear or branched C1 -C20 alkyl group, a linear or branched C2 -C20 alkenyl group, a linear or branched

C2 -C20 alkinyl group, a linear or branched C2 -C20 alkoxyl group, an aldehydes group -CHO, an ester group -COORx wherein Ri represents a linear or branched C1 -C20 alkyl group; or, when i' is 1, a C_x fullerene group;

p represents an integer ranging from 0 to 5, preferably ranging from 1 to 3;

with the proviso that:

when K is a C_x fullerene group, A and A' are an N- alkyl pyrrolidine group, m and m" are 0, and B and

B' are a divalent organic group containing at least one thienylene unit, Y' is not an N-alkyl pyrrole group;

when K is a C_x fullerene group, A and A' are an N- alkyl pyrrolidine group, Y and Y' ' are a phenyl, and B and B^r are a divalent organic group containing at least one thienylene unit, Y' is not an N-alkyl pyrrole group.

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

It should be noted that the present invention relates to a compound comprising:

a fullerene functionalized with the group -Ai-Y_m-B_n- Υ' _π,_'-Β' η.-Υ' .-A' i- - K_p wherein A, Y, B, Y' , B' , Y" , A', i, m, n, m' , n' , m' ' and p, have the same meanings described above, i' is 0 and K does not represent a C_x fullerene group [compound having general formula (I)];

a fullerene functionalized with the group -Ai-Y_m-B_n- Y -B'_n<-Y" m_"-A' i ' - _p wherein A, Y, B, Y' , B' , Y" , A' , i, m, n, m' , n' , m' ' , i' and p, have the same meanings described above and K represent a C_x fullerene group [compound having general formula ( I ) ] ;

a fullerene f nctionalized with the group -Ai-Y_m-B_n- Y'_m'-BV-Y"_m..-A' - wherein A, Y, B, Y' , B' , Y" , A', i, m, n, m' , n' , m' ' and i' , have the same meanings described above, and said group -Ai-Y_m- B_n-Y'_m'-B'n_'-Y' 'm"-A'i'- is bound to the bridge on the same C_x fullerene [compound having general formula ( II] .

For the purposes of the present description and of the following claims, the term "fullerene group" refers to 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 structure ("closed shell") that can be, for example, spherically or semi- spherically shaped. Alternatively, the carbon skeleton can form a not completely closed structure 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. The term "fullerene group" also refers to both a substituted and non-substituted fullerene.

According to a preferred embodiment of the present invention, said groups A and A' can be selected from cycloalkyl or heterocyclic groups having the following formulae :

wherein R ' represents a hydrogen atom, a linear or branched C1 -C20 alkyl group, a linear or branched C1-C20 alkoxyl group, an ester group -COORi wherein R_x represents a linear or branched C1 -C20 alkyl group.

According to a preferred embodiment of the present invention, said groups Y, Y' and Y", can be selected from aromatic or heteroaromatic divalent organic groups, optionally substituted, having the following formulae:

wherein R' represents a hydrogen atom, a linear or branched Ci-C₂o alkyl group, a linear or branched Ci-C₂o alkoxyl group, an ester group -COORi wherein Ri represents a linear or branched C₁-C20 alkyl group.

According to a further preferred embodiment of the present invention, said groups Y, Y' and Y", can be selected from aromatic or heteroaromatic divalent organic groups, optionally substituted, having the following formulae:

According to a preferred embodiment of the present invention, said groups B and B' , can be selected from divalent organic groups containing at least one thienylene unit, optionally substituted, having the following formulae:

According to a further preferred embodiment of the present invention, said groups B and B' , can be selected from divalent organic groups containing at least one thienylene unit, optionally substituted, having the following formulae:

According to a preferred embodiment of the present invention, said functionalized fullerene having general formula (I) can be selected from fullerenes having the following formulae:

wherein Ri, R₂, R₃, , Rs^ Κβ/· 7 and R₈, the same or different from each other, represent:

a group -Y_m-B_n-Y' _m' -B' _n- -Y' ' _m> > -A' i> -K_p wherein Y, B, Υ', Β', Y" , A' , m, η, m' , η' , m" , ρ and Κ, have the same meanings described above, i is 1, i' is 0, and K does not represent a C_x fullerene group;

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 proviso that at least one of Ri, R₂, R₃, R₄, R5, R₆, R7 and R₈, represents a group -Y_m-B_n-Y' _m< -B' _n' -Y' ' m" -

wherein :

Ri5 represents a group -Y_m-B_n-Y' _m< -B' _n- -Y' ' _m" wherein Y, B, Y' , B' , Y' ' , m, n, m' , n' and m' ' have the same meanings described above, i, i' and are 1 and K represents a C_x fullerene group; Rlf R R6i R7 R8r 9 , RlO / ll/ Rl2 r Rl3 and Ri , the same or different from each other, represent 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 preferred embodiment of the present invention, said functionalized fullerene having general formula (II) can be selected from fullerenes having the following formulae:

wherein :

- Ri5 represents a group -Y_m-B_n-Y' _m» -B' _n< -Y' - wherein Y, B, Y' , B' , Y" , m, n, m' , n' and m" , have the same meanings described above, i and i' are 1;

- Ri, R2, R3, R4, R8 R9_f RiOi Rii i2_/ R13 and Ri4, the same or different from each other, represent 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 preferred embodiment of the present invention, in said general formula (I):

C_x represents a fullerene group wherein x is 60;

A and A' represent an N-methylpyrrolidine group condensed with the fullerene group;

i and i' are 1;

Y' is 9 , 9-dioctylfluorene ;

- m' is 1;

m and m" are 0;

- B and B' represent a 2 , 5-thienylene group having general formula (III):

wherein Ri₆ and Ri₇ represent a hydrogen atom;

n and n' are 1;

K represents a C_x fullerene group, wherein x is 60; - p is 1.

According to a preferred embodiment of the present invention, in said general formula (I) : C_x represents a fullerene group wherein x is 60;

A represents an N-methylpyrrolidine group condensed with the fullerene group;

i is 1 ;

i' is 0;

Y' is 9, 9-dioctylfluorene;

m' is 1;

m and m" are 0;

B and B' represent a 2 , 5-thienylene group having general formula (III):

wherein R₁₆ and R₁₇ represent a hydrogen atom;

n and n' are 1;

K represents an aldehyde group;

- p is 1.

According to a preferred embodiment of the present invention, in said general formula (II) :

- C_x represents a fullerene group wherein x is 60;

- i and i' are 1;

- Y' is 9, 9-dioctylfluorene;

- m and m" are 0;

- m' is 1;

- B and B' represent a 2 , 5-thienylene group having general formula (III) :

wherein Ri6 and Ri₇ represent a hydrogen atom;

n and n' are 1.

According to a preferred embodiment of the present invention, in said general formula (II):

- C_x represents a fullerene group wherein x is 60;

- i and i' are 1;

- Y' is 9, 9-dioctylfluorene;

- m and m" are 0 ;

- m' is 1;

- B and B' represent a 2 , 2 ' -dithienylene group having general formula (Ilia):

wherein Ri6, R17, Ria and Ri₉ represent a hydrogen atom; n and n' are 1.

The functionalized fullerenes having general formula (I) or (II) object of the present invention, can be obtained through various processes known in the art. Examples of said processes are provided hereunder.

Methanofullerenes having general formula:

wherein C_x represents a fullerene group, x has the same meaning described above, Ri and R₂, the same or different from each other, represent:

a group -Y_m-B_n-Y -B' _n. -Y' ' _m- . -A' i -K_p wherein Y, B, Y' , B' , Y" , A', m, n, m' , n' , m" , i' , p, and K, 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) a process (Bingel reaction) which comprises reacting at least one fullerene having 60, 70, or

84 carbon atoms, with at least one a-halogen- ketone or an a-halogen-ester having general formula ( IV) :

R!-CHX-R₂ (IV)

wherein X represents a bromine atom, or a chlorine atom, Ri and R₂, the same or different from each other, represent: a group -CO-Y_m-B_n-Y' _m- -B' _n' ^_Y' ' m" -A' _±> -K_p, or a group -CO-0-Y_m-B_n-YV-BV-Y' ' m_''-A'_±'-Kp, wherein Y, B, Y' , B' , Y" , A', i, m, n, m' , n' , m' ' , i' , p, and K, have the same meanings described above;

or a hydrogen atom;

with the proviso that at least one of Ri and R_2f represents a group -C0-Y_m-B_n-Y' _m' -B' _n< -Y' ' _m>> -A' i< -K_p, or a group -CO-0-Y_m-B_n-Y' _m> -B' _n- -Y' ' _m< . -A' i- -K_p, in the presence of at least one chlorinated or non- chlorinated aromatic solvent such as, for example, chlorobenzene, toluene or mixtures thereof, and of at 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^~ RiR₂ (V)

wherein Ri and R2, the same or different from each other, represent:

- a group -Y_m-B_n-YV-B'_n'-Y"_m>.-A' i--K_p wherein Y, B, Y' , B' , Y' ' , A', m, n, m' , n' , m' ' , i' , p, and K, have the same meanings described above;

or a hydrogen atom;

with the proviso that at least one of Ri and R2, represents a group -Y_m-B_n-Y' _m- -B' _n< -Y' ' _m" -A' i- -K_p, 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^"R₁R₂ (VI)

wherein Ri and R₂, the same or different from each other, represent:

- a group -Y_m-B_n-Y' _m, -B' _n' -Y' _' -A' ±> -K_p wherein Y, B, Y' , B' , Y" , A', m, n, m' , n' , m" , i' , p, and K, 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 proviso that at least one of Ri and R₂, represents a group -Y_m-B_n-Y' _m' -B' _n» -Y' ' _m" -A' ±> -K_p, 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 a diazoderivative) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one diazoderivative having general formula (VII) :

RiR₂C=N₂ (VII)

wherein R_x and R₂, the same or different from each other, represent:

a group -Y_m-B_n-Y' _m, -B' _n> -Y' ' _m- -A' _±- -K_p, wherein Y, B, Y' , B', Y" , A', m, n, m' , n' , m" , i' , p, e K, have the same meanings described above;

or a hydrogen atom;

with the proviso that at least one of Ri and R₂ , represents a group -Y_m-B_n-Y' _m' -B' _n> -Y' ' _m-< -A' i- -K_p, 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, Ri represents a group -Y_m-B_n- Y'm'-B'n_'-Y' 'm"-A'i_'-K_p wherein Y, B, Y' , B' , Y" , A', m, n, m' , n' , m^r ' , i' , p, and K, have the same meanings described above, can be obtained through the following processes :

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

Ri-N₃ (VIII)

wherein Ri represents a group -Y_m-B_n-Y'_m' -B' _n< -Y' ' _m<< - A'i_'-K_p wherein Y, B, Y' , B' , Y" , A', m, n, m' , n' , m' ' , i' , p, and K, have the same meanings described above, in the presence of at least one chlorinated or non-chlorinated 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 a nitrene) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one nitrene having general formula (IX):

R1-OOC-N3 (IX) wherein Ri represents a group -Y_m-B_n-Y' _m> -B' _n- -Y' ' _m^ - A'i'-K_p, wherein Y, B, Y' , B' , Y" , A', m, n, m' , n' , m' ' , i' , p, and K, have the same meanings described above, in the presence of at least one chlorinated or non-chlorinated aromatic solvent such as, for example, tetrachloroethane, chloronaphthalene, 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, R_lf R2, R3 and R₄, the same or different from each other, represent:

- a group -Y_m-B_n-Y'_m' -B' _n ^» -Y' . -A' i -K_p, wherein Y, B, Y' , B', Y" , A' , m, n, m' , n' , m" , i', p, and K, 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 alkoxyl groups; carbonyl groups of the ketone or ester type;

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) :

RiR₂C=CR₃R₄ (X)

wherein R_lf R₂, R₃ and R₄, the same or different from each other, have the same meanings described above, with the proviso that at least one of Ri, R₂, R₃ and R₄, represents a group -Y_m-B_n-Y' _m' -B' _n' -Y' ' _m> · -A' -K_p, 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:

group -Y_m-B_n-Y'_m'-B' _n.-Y' '_m..-A' i_'-Kp, wherein Y' , Β' , Υ" , Α' , ra, η, m' , η' , πι" , ι' , ρ, and Κ, have the same meanings described above;

or a hydrogen atom;

can be obtained through a process (addition of a ketene) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one ketene, generated "in situ" by the reaction between the corresponding acyl chloride and triethylamine having general formula (XI) :

RiR₂-C=C=0 (XI)

wherein Ri and R₂, the same or different from each other, have the same meanings described above, with the proviso that at least one of Ri and R₂, represents a group -Y_m-B_n-Y'._m' -B' n- -Y' '_m, <-Α' i_'-K_p, 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].

Fulleropyrrolidines having general formula:

wherein C_x represents a fullerene group, x has the same meaning described above; Ri , R₂ , R3 R₄ and R₅ , the same or different from each other, represent:

- a group -Y_m-B_n-Y' _m- -B' _n> -Y' ' _m- -A' -K_p, wherein Y, B, Y' , B' , Y" , A', m, n, m' , n' , m" , i' , p, and K, 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 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 (XII) and at least one aldehyde compound having general formula (XIII) , or with at least one amino acid (for example a substituted glycine) having general formula (XII) and at least one ketone compound having general formula (XIV) :

R₁NH-CR2R3-COOH (XII)

OHC-R4 (XIII)

0=C-R₄R₅ (XIV)

wherein, in general formula (XII), Ri, R₂, R3, the same or different from each other, in general formula (XIII) R₄, and in general formula (XIV) R₄ and R₅, the same or different from each other, represent:

- a group -Y_m-B_n-Y' _m' -B' _n» -Y' ' _m< < -A' i> -K_p, wherein Y, B, Y', B', Y", A', m, n, m' , n' , m" , i' , p, and K, have the same meanings described above;

or a hydrogen atom;

with the proviso that at least one of R_lf R₂, R3, in general formula (XII), R₄ in general formula (XIII) and at least one of R₄ and R₅ in general formula (XIV) , represent a group -Y_m-B_n-Y' _m< -B' _n' ^_Y' ' m" -A' _±-K_p, 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].

Fulleroisooxazolines having general formula:

wherein C_x represents a fullerene group, x has the same meaning described above, and Ri represents a group -Y_m- B_n-YV-B'n_'-Y"m_"-A' i<-K_p, wherein Y, B, Y' , B' , Y" , A', m, n, m' , n' , m' ' , i' , p, and K, have the same meanings described above, can be obtained through a process (addition of nitrileoxides ) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one compound having general formula (XV) , obtained from the corresponding oxime Ri~CH=N-OH by treatment first with N-chlorosuccinimide and anhydrous pyridine and subsequently with a base such as, for example, triethylamine :

Ri-C≡N⁺-0^~ (XV)

wherein Ri represents a group -Y_m-B_n-Y' _m' -B' _n' -Y' ' m" ^_A' _±> - K_p, wherein Y, B, Y' , B' , Y" , A', m, n, m' , n' , m" , i' , p, and K 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; Rj_. and R₂, the same or different from each other, represent:

- a group -Y_m-B_n-Y' _m> -B' _n> -Y' ' _m- -A' -K_p, wherein Y, B, Y' , B' , Y" , A', m, n, m' , n' , m" , i' , p, and K, have the same meanings described above;

or a hydrogen atom;

can be obtained through a process (addition of nitriloimines ) which comprises reacting at least one fullerene having 60, 70, or 84 carbon atoms, with at least one compound having general formula (XVI), obtained from the corresponding hydrazone Ri-NH-N=CH-R₂ by treatment first with N-bromosuccinimide and subsequently with triethylamine:

Ri-N^"-N=C⁺-R₂ (XVI)

wherein Ri and R₂, the same or different from each other, have the same meanings described above, with the proviso that at least one of Ri and R₂ represents a group -Y_m-B_n-Y' m' -B^r _n>-Y' ' _m>> -A' ±> -K_p, 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].

Cyclohexanefullerenes and cyclohexenefullerenes having general formula:

wherein C_x represents a fullerene group, x has the same meaning described above; Ri, R₂, R3, R4, R5 and R₆, the same or different from each other, represent:

- a group -Y_m-B_n-Y' _m, -B' _n- -Y' ' _m- -A' _L> -K_p, wherein Y, B, Y', B' , Y", A', m, n, m' , n' , m" , i' , p, and K, have the same meanings described above;

or a hydrogen atom;

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 (XVII) :

wherein Ri, R₂, R3, R₄, R5 and R₆, the same or different from each other, have the same meanings described above, with the proviso that at least one of Ri, R₂, R3, R₄, R₅ and R₆, represents a group -Y_m-B_n-Y' _m- -B' _n< -Y' ' _m<- - A'i_'-Kp, 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 5033-5_.042; Chronakis N. et al., "Journal of Organic Chemistry" (2002), Vol. 67(10), pages 3284-3289].

Diorganofullerenes having general formula:

wherein C_x represents a fullerene group, x has the same meaning described above; Ri and R₂, the same or different from each other, represent:

- a group -Y_m-B_n-Y' _m- -B' _n- - ' ' m" -K_p, wherein Y, B, Y' , B',^' Y' ' , m, n, m' , n' , m' ' , p, and K, have the same meanings described above;

or a hydrogen atom;

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 a chlorinated solvent such as, for example, 1,2- dichlorobenzene, with a solution of at least one compound (Grignard compound) having general formula (XVIII) :

Ri-MgX (XVIII)

wherein X represents a chlorine atom or a bromine atom, and Ri has 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 (Ν,Ν-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 (XIX) :

R₂-X (XIX)

wherein X represents a chlorine atom, a bromine atom, or an iodine atom, and R₂ has 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;

with the proviso that at least one of Ri and R₂ represents a group -Y_m-B_n-Y' _m> -B' _n- -Y' ' _m" -K_p . Further details relating to the above process for the preparation of diorganofullerenes can be found in Matsuo Y. et al., "Journal of the American Chemical Society" (2008), Vol. 130(46), pages 15429-15436.

A further object of the present invention also relates to the use of a compound comprising at least one functionalized fullerene having general formula (I) or (II), 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 compound comprising at least one functionalized fullerene having general formula (I) or (II).

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

EXAMPLES

Reagents and materials

The following reagents and materials used in the following examples of the invention are listed hereunder, together with their producer:

- 9 , 9-dioctylfluorene-2 , 7-diboronic acid (96%) (Sigma-Aldrich) : used as such;

5-bromo-2-thiophene carbaldehyde (95%) (Sigma- Aldrich) : used as such;

palladium (tetrakis ) triphenylphosphine (Sigma- Aldrich) : used as such;

N, N-dimethylformamide (Carlo Erba, RPE) : used as such;

sodium carbonate ("reagent grade") (Rudipont): used as such;

- fullerene C₆o (99,5%) (Sigma-Aldrich): used as such; sarcosine (98%) (Acros Organics) : used as such;

toluene (Carlo Erba, RPE) : used as such;

chloroform (Carlo Erba, RS): used as such; methanol (Carlo Erba, RS) : used as such;

2, 2 ' -dithiophene-5-carbaldehyde (98%) (Sigma-

Aldrich.) : used as such;

N-bromosuccimide (99%) ( Sigma-Aldrich) : used as such;

dichloromethane (Carlo Erba, RS) : used as such;

sodium thiosulfate anhydrous (Carlo Erba, RE) : used as such;

n-heptane (Carlo Erba, RPE) : used as such;

ethyl acetate (Carlo Erba, RPE) : used as such;

petroleum ether (40°C-70°C) (Carlo Erba, RPE): used as such,

chlorobenzene (Carlo Erba, RPE) : used as such;

1, 2-dichlorobenzene (Carlo Erba, RPE): used as such;

silica gel 60A (Carlo Erba, RS) : used as such;

deuterochloroform (CDCI₃) (Acros Organics) : used as such;

[ 6, 6] -phenyl-C6i~butyric acid methyl ester ([60]PCBM) (Sigma-Aldrich): used as such;

regioregular poly (3-hexylthiophene) (P3HT)

("electronic grade" - 99,995%) (Sigma-Aldrich): used as such.

The following analysis and characterization methods were used.

1H-NMR Spectroscopy

The ¹H-NMR spectra of the compounds comprising at least one functionalized fullerene object of the present invention, were registered by means of a nuclear magnetic resonance spectrometer Bruker Avance 400, at a temperature of 25°C, using deuterochloroform (CDCI3) . The signal of the solvent used [i.e. deuterochloroform (CDCI3) ] at 7.26 ppm was used as reference for the chemical shifts.

Solutions of the compounds comprising at least one functionalized fullerene object of the present invention, having concentrations equal to 5 mg - 10 mg of compound comprising at least one functionalized fullerene to be analyzed in 0.75 ml of solvent, were used for the purpose.

1³C CP-MAS NMR Spectroscopy

The ¹³C CP-MAS NMR spectra of the compounds comprising at least one functionalized fullerene object of the present invention, were registered by means of a nuclear magnetic resonance spectrometer Bruker Avance 400 B, using a probe having a diameter of 4 mm and a rotation rate of the sample of 10,000 Hz/s. A contact time of 3 ms and a delay of 5 s were used for the pulse sequence. 20,000 scannings were carried out for each spectrum.

IR Spectroscopy

The infrared spectra of the compounds comprising at least one functionalized fullerene object of the present invention, were registered by means of a Thermo Nexus 670 spectrometer, within the range of 4000 cm^""1 to 400 cm^"1 with 64 scannings and a resolution of 2 cm^"1. The samples were analyzed in transmission with the potassium bromide (KBr) tablet technique.

Cyclic Voltammetry

The cyclic voltammetry (CV) measurements were carried out with an Autolab PGSTAT12 potentiostat interfaced with a computer (PC) (with GPES Ecochemie software) in a three-electrode cell. A saturated calomel electrode (SCE) was used as reference electrode, a platinum electrode (Methrom) as counterelectrode and a glassy graphite electrode (Glassy Carbon - Amel - surface 0.071 cm²), as operating electrode. For this purpose, samples of compounds comprising at least one functionalized fullerene object of the present invention, were dissolved in 1,2- dichlorobenzene at a concentration equal to 10^~3 M and were then deposited on the operating electrode, using a calibrated capillary tube, so as to form a film. The electrodes were immersed in an 0.1 M electrolytic solution of tetrabutylammonium tetrafluoroborate (TBABF₄) (Fluka, electrochemical grade) in acetonitrile (MeCN) (Carlo Erba, HPLC grade) . The samples were then subjected to a triangle wave cycle potential. The current which verifies oxidation or reduction reactions of the species present was contemporaneously monitored in relation to the potential difference applied. The data were obtained using the redox pair ferrocene/ferrocine (Fc/Fc⁺) as reference, in accordance with IUPAC recommendations. The voltammetric curves of the compounds comprising at least one functionalized fullerene object of the present invention, and of the reference compound, [6, 6] -phenyl-C₆i-butyric acid methyl ester ([60]PCBM) (acceptor compound), are indicated in Figure 1.

Determination of HOMO, LUMP and BAND-GAP

The determination of the HOMO and LUMO values of the compounds comprising at least one functionalized fullerene object of the present invention, was carried out by means of the cyclic voltammetry technique (CV) . With this technique, it is possible to measure the formation potentials of the cation radical and of the anion radical of the sample under examination. When inserted in a specific equation, these values allow the HOMO and LUMO values of the compound to be analyzed, to be obtained. The difference between HOMO and LUMO gives the value of the electrochemical band-gap.

The oxidation process corresponds to the removal of an electron from the HOMO, whereas the reduction cycle corresponds to the introduction of an electron into the LUMO. The formation potentials of the cation radical and of the anion radical were obtained from the peak onset value ( E_onset ) which is determined from molecules and/or chain segments with HOMO-LUMO levels closer to the borders of the bands. The electrochemical potentials can be correlated with those relating to the electronic levels if both refer to vacuum. For this purpose, the potential of ferrocene under vacuum, known in literature and equal to -4.8 eV, was taken as reference. The intersolvential redox pair ferrocene/ferrocine (Fc/Fc⁺) was selected as it has a redox potential independent of the operating solvent.

The general formula for calculating the energies of the HOMO-LUMO levels is therefore given by the following equation:

E (eV) = -4,8 + [Ei 2 SCE (FC / FC⁺) - E_onset SCE (fullerene) ] wherein :

- E = HOMO or LUMO depending on the E_onSet value inserted;

^~ Ei/2 SCE = half-wave potential of the peak corresponding to the redox pair ferrocene/ferrocine (Fc/Fc⁺) measured under the same analysis conditions as the sample and with the same tern of electrodes used for the sample;

~ E_onSetscE = onset potential measured for the compound comprising at least one functionalized fullerene object of the present invention in the anode zone when the HOMO is to be calculated and in the cathode zone when the LUMO is to be calculated :.

- fullerene = compound comprising at least one functionalized fullerene object of the present invention .

The graph of the energy levels and HOMO, LUMO and band-gap values express in eV of the compounds comprising at least one functionalized fullerene object of the present invention and of the reference compounds i.e. [ 6, 6] -phenyl-C6i-butyric acid methyl ester ([60]PCBM) - in Figure 2 indicated as PCBM) (acceptor compound) and regioregular poly ( 3-hexylthiophene ) (P3HT) (donor compound), are indicated in Figure 2 and in Table 1.

Table 2, on the other hand, indicates the energy differences between the LUMO of the donor compound and the LUMO of the acceptor compound (ΔΕ LUMO_D - LUMO_a) , the energy differences between the HOMO of the donor compound and the HOMO of the acceptor compound (ΔΕ HOMO_D - HOMO_A) and the energy differences between the LUMO of the acceptor compound and the HOMO of the donor compound (ΔΕ LUMO_A - HOMO_D) , relating to the use of the compounds comprising at least one functionalized fullerene object of the present invention as acceptor compound and of the regioregular poly ( 3-hexylthiophene)

(P3HT) as donor compound. For comparative purposes,

Table 2 also indicates the above energy differences for the reference compounds, i.e. [ 6, 6] -phenyl-C₆i-butyric acid methyl ester ([60] PCBM) (acceptor compound) and regioregular poly (3-hexylthiophene) (P3HT) (donor compound) .

UV-Vis Spectroscopy

The UV-Vis spectra of the compounds comprising at least one functionalized fullerene object of the present invention, were registered at room temperature by means of a Lambda 950 spectrophotometer (Perkin- Elmer) . For this purpose, samples were prepared by dissolving the compounds comprising at least one functionalized fullerene object of the present invention in chlorobenzene, at three different concentrations (1CT⁷ M, 1CT⁶ M, 10^"5 M) , and registering the transmission spectra with a cell having an optical path of 10 mm.

Determination of the molar absorption coefficient ( ε )

The molar absorption coefficient ( ε ) ( l*mol^_1*cm^_1) of the compounds comprising at least one functionalized fullerene object of the present invention, was determined by means of the Lambert-Beer equation:

A=sbC

wherein :

A = absorbance;

b = optical path (in cm) ;

C = concentration (in moles/litre) of the compound to be analyzed.

Assuming that b = 1, the molar absorption coefficient ( ε ) is obtained by putting in graph the absorbance (A) in relation to the concentration (C) . In this case, the molar absorption coefficient ( ε ) was calculated from the slope of the line passing through the origin of the axes (y = mx+q, with q = 0), obtained by bringing the maximum absorbance values (A) within the wavelength range (λ) from 300 nm to 450 nm, in relation to the concentration (C) of the solution for each compound to be analyzed. The curves relating to the variation in the molar absorption coefficient (ε) in relation to the wavelength (λ) for the compounds comprising at least one functionalized fullerene object of the present invention and for the reference compound, i.e. [6,6]- phenyl-C₆i-butyric acid methyl ester ([60]PCBM) (acceptor compound), are indicated in Figure 3.

Table 3 indicates the molar absorption coefficient

(ε) values at the maximum wavelength

of both the compounds comprising at least one functionalized fullerene object of the present invention and the reference compound, i.e. [6, 6] -phenyl-C₆i-butyric acid methyl ester ([60]PCBM) (acceptor compound).

EXAMPLE 1

Synthesis of Compound (1)

The synthesis of Compound (1) was carried out in accordance with Scheme 1 indicated hereunder:

Compound (1)

heme 1

For this purpose, a mixture of 9, 9-dioctylfluorene-

2 , 7-diboronic acid (730 mg, 1.52 mmoles) , 5-bromo-2- thiophene carbaldehyde (530 mg, 2.76 mmoles), and palladium (tetrakis) triphenylphosphine [Pd(Ph₃P)₄] (36 mg, 0.03 mmoles), in N, N-dimethylformamide (N,N-DMF) (15 ml) and sodium carbonate (Na₂C0₃) (2 ml of an aqueous solution 2 M) , was heated to reflux temperature for 4 hours, under a stream of argon. The reaction mixture was left to cool to room temperature (25°C), 100 ml of distilled water were added and the whole mixture was then filtered, obtaining a solid which was recovered .

The solid thus obtained was partially dissolved in ethyl acetate (100 ml), subsequently filtered and the liquid phase obtained was concentrated under vacuum obtaining a reaction raw product. The reaction raw product thus obtained was purified by means of column chromatography [silica gel, gradients from n-heptane 100% to n- heptane/ethyl acetate = 8:2 (v/v) as eluent] obtaining 537 mg (57.9% in moles) of Compound (1).

Said Compound (1) was characterized by means of ^""Ή-

NMR (400 MHz, CDC1₃) obtaining the following spectrum: δ = 9.93 ppm (s, 2H, -CHO) ; 7.80-7.75 ppm (m, 4H, H^-CH-Th + Ph-CH-CH-CHO) ; 7.72 - 7.70 ppm (q, 2H, H_m-CH-T.h) ; 7.67 - 7.63 ppm (d, 2H, Ho~Th) ; 7.52-7.49 ppm (d, 2H, Ph-CH- CH-CHO) ; 2.10-2.03 ppm (m, 4H, C- (C¾) ₂- (CH₂) 12-CH3) ; 1.22-1.04 ppm (m, 24H, C- (CH₂) ₂- (CH2) 12-CH3) ; 0.84-0.76 ppm (t, 6H, C- (CH₂)₂- (CH₂) 12-CH3) .

Said Compound (1) was also characterized by means of IR (KBr) spectrum showing the following bands: v = 1660 cm^"1 (aldehyde C-0 stretching) ; 1527 cm^"1 (thienyl stretching) .

EXAMPLE 2

Synthesis of Compound (2) (compound according to the present invention)

The synthesis of Compound (2) (compound according to the present invention) was carried out in accordance with Scheme 2 indicated hereunder:

For this purpose, a mixture of Compound (1) (170 mg, 0.278 mmoles) obtained as described in Example 1, fullerene C₆₀ (200 mg, 0.278 mmoles), and sarcosine (N- methylglycine) (250 mg, 2.78 mmoles), in toluene (100 ml) , was heated to reflux temperature for 3 hours, under a stream of argon. After being cooled to room temperature (25°C), the reaction mixture was filtered and the solution thus obtained was concentrated under vacuum obtaining a reaction raw product.

The reaction raw product thus obtained was purified by means of column chromatography [silica gel, gradients toluene/petroleum ether 8:2 (v/v), toluene 100% and toluene/ethyl acetate = 8:2 (v/v) as eluent] obtaining 47 mg (12.4% in moles) of Compound (2) .

Said Compound (2) was characterized by means of ¹H-

NMR (400 MHz, CDC1₃) obtaining the following spectrum: δ = 9.97 ppm (s, 1H, -CHO) ; 7.84-7.81 ppm (d, 1H, Ph-CH-

CH-CHO) ; 7.80-7.71 ppm (m, 4H, Th-C-CH-CH-C) ; 7.70-7.60 ppm (m, 2H, Th-C-CH-C) ; 7.58-7.52 ppm (d, 1H, Ph-CH-CH- CHO); 7.51-7.46 ppm (d, 1H, Ph-CH-CH-Pyrrolidine) ; 7.45-7.40 ppm (d, 1H, Ph-CH-CH-Pyrrolidine); 5.40 ppm <s, 1H, Th-CH-C (NCH₃) -CH-H) ; 5.20-5.00 ppm (d, 1H, Th- CH-C (NCH₃) -CH-H) ; 4.40-4.30 ppm (d, 1H, Th-CH-C (NCH₃) - CH-H), 3.10 ppm (s, 3H, Th-CH-C (NCH3) -CH-H) ; 2.20-1.95 ppm (m, 4H, C- (C¾) ₂- (CH₂) 12-CH3) ; 1.30-0.97 ppm (m, 24H, C- (CH₂) 2- (¾) 12-CH3) ; 0.96-0.80 ppm , (m, 6H, C-(CH₂)₂- (CH₂)i2-CH3) .

Said Compound (2) was also characterized by means of IR (KBr) spectrum showing the following bands: v = 1665 cm^"1 (aldehyde C-0 stretching), 526 cm^"1 (radial deformation of the fullerene) .

Said Compound (2) was also characterized by means of cyclic voltammetry, operating as described above: the graph obtained is indicated in Figure 1. For comparative purposes, Figure 1 also indicates the characterization of [ 6, 6] -phenyl-C6i~butyric acid methyl ester ([60] PCBM) (acceptor compound).

Said Compound (2) was also characterized by means of HOMO, LUMO and band-gap determination operating as described above: the values obtained are indicated in Figure 2 and in Table 1. For comparative purposes, Figure 2 and Table 1 also indicate the values obtained for [ 6, 6] -phenyl-C₆i-butyric acid methyl ester ( [ 60] PCBM - in Figure 2 indicated as PCBM) (acceptor compound) .

Table 2 on the other hand indicates the energy differences between the LUMO of the donor compound and the LUMO of the acceptor compound (ΔΕ LUM0_D - LUMO A ) , the energy differences between the HOMO of the donor compound and the HOMO of the acceptor compound (ΔΕ HOMO_D - HOMO_A) and the energy differences between the LUMO of the acceptor compound and the HOMO of the donor compound (ΔΕ LUMO_A - HOMO_D) , obtained using said Compound (2) as acceptor compound and regioregular poly (3-hexylthiophene) (P3HT) as donor compound. For comparative purposes, Table 2 also indicates the above energy differences obtained using [ 6, 6] -phenyl-C6i- butyric acid methyl ester ([60JPCBM) as acceptor compound and regioregular poly ( 3-hexylthiophene) (P3HT) as donor compound.

Said Compound (2) was also subjected to UV-Vis spectroscopy measurements as described above: the spectrum obtained is indicated in Figure 3.

Finally, said Compound (2) was subjected to determination of the molar absorption coefficient ( ε ) , operating as described above, the value obtained is indicated in Table 3.

EXAMPLE 3

Synthesis of Compound (3) (compound according to the present invention)

The synthesis of Compound (3) (compound according to the present invention was carried out in accordance with Scheme 3 indicated hereunder:

For this purpose, a mixture of Compound (1) (170 mg, 0.278 mmoles) obtained as described in Example 1, fullerene Οεο (200 mg, 0.278 mmoles), and sarcosine (N- methylglycine) (250 mg, 2.78 mmoles), in toluene (100 ml) , was heated to reflux temperature for' 16 hours, under a stream of argon. After being cooled to room temperature (25°C) , the reaction mixture was filtered and the solution thus obtained was concentrated under vacuum obtaining a reaction raw product.

The reaction raw product thus obtained was purified by means of column chromatography [silica gel, gradients toluene/petroleum ether 8:2 (v/v) , toluene 100% and toluene/ethyl acetate = 8:2 (v/v) as eluent] obtaining 80 mg (13.6% in moles) of Compound (3) .

Said Compound (3) was characterized by means of ^XH- NMR (400 MHz, CDCl₃) obtaining the following spectrum: δ = 7.80-7.70 ppm (m, 2H, Th-C-CH-CH-C); 7,70-7.60 ppm (m, 2H, Th-C-CH-CH-C); 7.50-7.40 ppm (d, 2H, Ph-CH-CH- Pyrrolidine); 7.40-7.30 ppm (d, 2H, Ph-CH-CH-

Pyrrolidine) ; 5.40 ppm (s, 2H, Th-CH-C (NCH₃) -CH-H) ;

5.20-5.10 ppm (d, 2H, Th-CH-C (NCH₃) -CH-H) ; 4.40-4.30 ppm

(d, 2H, Th-CH-C (NCH₃) -CH-H) ; 3.10 ppm (s, 6H, Th-CH-

C (NCH3) -CH-H) ; 2.20-1.95 ppm (m, 4H, C- (CH2) ₂~ (CH₂) 12- CH₃), 1.90-1.20 ppm (m, 24H, C- (CH₂) ₂- (C¾) 12-CH3) ; 0.96- 0.60 ppm (m, 6H, C- (CH₂) ₂~ (CH₂) 12-CH3) .

Said Compound (3) was also characterized by means of IR (KBr) spectrum showing the following bands: v = 2780 cm^"1 (N-CH₃ stretching), 526 cm^-1 (radial deformation of the fullerene) .

Said Compound (3) was also characterized by means of cyclic voltammetry, operating as described above: the graph obtained is indicated in Figure 1. For comparative purposes, Figure 1 also indicates the characterization of [ 6, 6] -phenyl-C₆i-butyric acid methyl ester ([60JPCBM) (acceptor compound).

Said Compound (3) was also characterized by means of HOMO, LUMO and band-gap determination operating as described above: the values obtained are indicated in Figure 2 and in Table 1. For comparative purposes, Figure 2 and Table 1 also indicate the values obtained for [6, 6] -phenyl-C₆i-butyric acid methyl ester ([60]PCBM - in Figure 2 indicated as PCBM) (acceptor compound) .

Table 2 on the other hand indicates the energy differences between the LUMO of the donor compound and the LUMO of the acceptor compound (ΔΕ LUM0_D - LUMO_A) , the energy differences between the HOMO of the donor compound and the HOMO of the acceptor compound (ΔΕ HOMO_D - HOMO_A) and the energy differences between the LUMO of the acceptor compound and the HOMO of the donor compound (ΔΕ LUMO_a - HOMO_D) , obtained using said Compound (3) as acceptor compound and regioregular poly ( 3-hexylthiophene) (P3HT) as donor compound. For comparative purposes, Table 2 also indicates the above energy differences obtained using [ 6, 6 ] -phenyl-C_5:L- butyric acid methyl ester ([60]PCBM) as acceptor compound and regioregular poly ( 3-hexylthiophene ) (P3HT) as donor compound.

Said Compound (3) was also subjected to UV-Vis spectroscopy measurements as described above: the spectrum obtained is indicated in Figure 3.

Finally, said Compound (3) was subjected to determination of the molar absorption coefficient (ε) , operating as described above, the value obtained is indicated in Table 3.

EXAMPLE 4

Synthesis of Compound (4) (compound according to the present invention) ^v

The synthesis of Compound (4) (compound according to the present invention) was carried out in accordance with Scheme 4 indicated hereunder:

Compound (4)

Scheme 4

For this purpose, a mixture of Compound (1) (300 mg, 0.52 mmoles) obtained as described in Example 1, fullerene C₆o (190 mg, 0.26 mmoles) , and sarcosine (N- methylglycine ) (150 mg, 1.68 mmoles), in chlorobenzene (60 ml), was heated to reflux temperature for 16 hours, under a stream of argon. After being cooled to room temperature (25°C), the reaction mixture was filtered and the solution thus obtained was concentrated under vacuum obtaining a reaction raw product.

The reaction raw product thus obtained was purified by means of washings in chloroform (300 ml) , toluene (300 ml) and methanol (300 ml) , respectively, obtaining 495 mg (83.4% in moles) of Compound (4).

Said Compound (4) was characterized by means of ¹³C

CP-MAS NMR (400 MHz) obtaining the following spectrum: δ = 156-135 ppm; 134-127 ppm; 126-110 ppm; 80-70 ppm; 68 ppm; 52 ppm; 47-34 ppm; 33-10 ppm.

Said Compound (4) was also characterized by means of IR (KBr) spectrum showing the following bands: v = 2773 cm^'1 (N-CH₃ stretching), 523 cm^-1 (radial deformation of the fullerene) .

Said Compound (4) was also characterized by means of cyclic voltammetry, operating as described above: the graph obtained is indicated in Figure 1. For comparative purposes, Figure 1 also indicates the characterization of [ 6, 6] -phenyl-C6i-butyric acid methyl ester ([60]PCBM) (acceptor compound).

Said Compound (4) was also characterized by means of HOMO, LUMO and band-gap determination operating as described above: the values obtained are indicated in Figure 2 and in Table 1. For comparative purposes, Figure 2 and Table 1 also indicate the values obtained for [ 6, 6] -phenyl-C₆i-butyric acid methyl ester ([60]PCBM - in Figure 2 indicated as PCBM) (acceptor compound) .

Table 2 on the other hand indicates the energy differences between the LUMO of the donor compound and the LUMO of the acceptor compound (ΔΕ LUM0_D - LUMO_a) , the energy differences between the HOMO of the donor compound and the HOMO of the acceptor compound (ΔΕ HOMO_D - HOMO_A) and the energy differences between the LUMO of the acceptor compound and the HOMO of the donor compound (ΔΕ LUMO_A - HOMO_D) , obtained using said Compound (4) as acceptor compound and regioregular poly ( 3-hexylthiophene ) (P3HT) as donor compound. For comparative purposes, Table 2 also indicates the above energy differences obtained using [ 6, 6] -phenyl-C6i~ butyric acid methyl ester ([60] PCBM) as acceptor compound and regioregular poly ( 3-hexylthiophene ) (P3HT) as donor compound.

Said Compound (4) was also subjected to UV-Vis spectroscopy measurements as described above: the spectrum obtained is indicated in Figure 3.

Finally, said Compound (4) was subjected to determination of the molar absorption coefficient (ε) , operating as described above, the value obtained is indicated in Table 3.

EXAMPLE 5

Synthesis of Compound (5) The synthesis of Compound (5) was carried out in accordance with Scheme 5 indicated hereunder:

reflux

Compound (5)

Scheme 5

For this purpose, a mixture of 2 , 2 ' -dithiophene-5- carbaldehyde (3960 mg, 20.4 mmoles) and N- bromosuccinimide (NBS) (3630 mg, 20.4 mmoles), in dichloromethane (CH₂C1₂) (80 ml) , was put under stirring, for 1 night, under a stream of argon, at room temperature (25°C) . Sodium thiosulfate (100 ml of an aqueous solution 1 M) was then added, the organic phase was separated from the aqueous phase by extracting twice with dichloromethane (100 ml x 2). The organic phase thus obtained was then anhydrified on sodium sulfate (Na₂S0₄) and concentrated under vacuum obtaining a reaction raw product.

The reaction raw product thus obtained was purified by means of column chromatography [silica gel, gradients from n-heptane 100% to n- heptane/ethyl acetate = 8:2 (v/v) as eluent] obtaining 3430 mg (61.8% in moles) of Compound (5) .

Said Compound (5) was characterized by means of ^XH-

NMR (400 MHz, CDC1₃) obtaining the following spectrum: δ = 9.87 ppm (s, 1H, -CHO) ; 7.70-7.65 ppm (d, 1H, Br-Th- CH-CH-CHO) ; 7.20-7.18 ppm (d, 1H, Br-Th-CH-CH-CHO) , 7.13-7.10 ppm (d, 1H, CHO-Th-CH-CH-Br) ; 7.07-7.04 ppm (d, 1H, CHO-Th-CH-CH-Br) .

Said Compound (5) was also characterized by means of IR (KBr) spectrum showing the following bands: v = 1652 cm^-1 (aldehyde C . = 0 stretching) , 460 cm^"1 (deformation C - Br of the thiophene) .

EXAMPLE 6

Synthesis of Compound (6)

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

For this purpose, a mixture of 9, 9-dioctylfluorene- 2, 7-diboronic acid (1450 mg, 3.04 mmoles) , Compound (5) (1500 mg, 5.52 mmoles) and palladium (tetrakis ) - triphenylphosphine [Pd(Ph₃P)₄] (176 mg, 0.152 mmoles), in N, -dimethylformamide (N, -DMF) (140 ml) and sodium carbonate (Na₂C0₃) (10 ml of an aqueous solution 2 M) , was heated to reflux temperature for 4 hours, under a stream of argon. The reaction mixture was left to cool to room temperature (25°C) , 100 ml of distilled water were added and the whole mixture was then filtered, obtaining a solid which was recovered.

The solid thus obtained was partially dissolved in ethyl acetate (100 ml), subsequently filtered and the liquid phase obtained was concentrated under vacuum obtaining a reaction raw product.

The reaction raw product thus obtained was purified by means of column chromatography [silica gel, gradients from n-heptane 100% to n-heptane/ethyl acetate = 8:2 (v/v) as eluent] obtaining 1060 mg (67.4% in moles) of Compound (6).

Said Compound (6) was characterized by means of ¹H- NMR (400 MHz, CDC1₃) obtaining the following spectrum: δ = 9.90 ppm (s, 1H, -CHO) ; 7.75-7.72 ppm (d, 2H, Hm-CH-

Th) ; 7.72-7.70 ppm (d, 2H, Th-CH-CH-CHO) ; 7.66-7.62 ppm

(q, 2H, H_m-CH-Th) ; 7.59-7.57 ppm (d, 2H, Ho-Th) ; 7.41-

7.39 ppm (d, 2H, CH-CH-Th-CHO) ; 7.38-7.36 ppm (d, 2H, CH-CH-Th-CHO); 2.10-2.03 ppm (m, 4H, C- (CH2) ₂- (CH₂) 12-

CH₃), 1.22-1.04 ppm (m, 24H, C- (CH₂) ₂- (C¾) 12-CH3) ; 0.84-

0.76 ppm (t, 6H, C- (CH₂) ₂- (CH₂) ₁₂-CH₃_) .

Said Compound (6) was also characterized by means of IR ( Br) spectrum showing the following bands: v = 1662 cm^-1 (aldehyde C-0 stretching) ; 1515 cm^"1 (ring mode of the thiophenes), 795 cm^-1 (deformation conjugated dithienyls) .

EXAMPLE 7

Synthesis of Compound (7) (compound according to the present invention)

The synthesis of Compound (7) (compound according to the present invention) was carried out in accordance with Scheme 7 indicated hereunder:

Compound (7)

Scheme 7

For this purpose, a mixture of Compound (6) (1060 mg, 1.34 mmoles) obtained as described in Example 6, fullerene C^Q (482 mg, 0.67 mmoles), and sarcosine (N- methylglycine) (418 mg, 4.69 mmoles), in 1,2- dichlorobenzene (150 ml), was heated to reflux temperature for 16 hours, under a stream of argon. After being cooled to room temperature (25°C), the reaction mixture was filtered and the solution thus obtained was concentrated under vacuum obtaining a reaction raw product.

The reaction raw product thus obtained was purified by means of washings in dichloromethane (500 ml) , toluene (500 ml) and methanol (500 ml), respectively, obtaining 847.8 mg (81.6% in moles) of Compound (7).

Said Compound (7) was . characterized by means of ¹³C

CP-MAS NMR (400 MHz) obtaining the following spectrum: δ = 168-151 ppm; 150-132 ppm; 131-110 ppm; 90-74 ppm; 73-

61 ppm; 60-51 ppm; 50-37 ppm; 36-27 ppm, 26-19 ppm, 28- 10 ppm .

Said Compound (7) was also characterized by means of IR (KBr) spectrum showing the following bands: v = 2776 cm^-1 (N-CH₃ stretching) , 793 cm^-1 (deformation conjugated dithienyls) , 524 cm^-1 (radial deformation of fullerene) .

Said Compound (7) was also characterized by means of cyclic voltammetry, operating as described above: the graph obtained is indicated in Figure 1. For comparative purposes, Figure 1 also indicates the characterization of [ 6, 6] -phenyl-C₆i-butyric acid methyl ester ([60]PCBM) (acceptor compound).

Said Compound (7) was also characterized by means of HOMO, LUMO and band-gap determination operating as described above: the values obtained are indicated in Figure 2 and in Table 1. For comparative purposes, Figure 2 and Table 1 also indicate the values obtained for [6, 6] -phenyl-C₆i-butyric acid methyl ester ([60]PCBM

- in Figure 2 indicated as PCBM) (acceptor compound) .

Table 2 on the other hand indicates the energy differences between the LUMO of the donor compound and the LUMO of the acceptor compound (ΔΕ LUMO_D - LUMO_A) , the energy differences between the HOMO of the donor compound and the HOMO of the acceptor compound (ΔΕ HOMO_D

- HOMO_a) and the energy differences between the LUMO of the acceptor compound and the HOMO of the donor compound (ΔΕ LUMO_A - HOMO_D) , obtained using said Compound (7) as acceptor compound and regioregular poly ( 3-hexylthiophene ) (P3HT) as donor compound. For comparative purposes, Table 2 also indicates the above energy differences obtained using [6, 6] -phenyl-C6i^_ butyric acid methyl ester ([60JPCBM) as acceptor compound and regioregular poly ( 3-hexylthiophene) (P3HT) as donor compound.

Said Compound (7) was also subjected to UV-Vis spectroscopy measurements as described above: the spectrum obtained is indicated in Figure 3.

Finally, said Compound (7) was subjected to determination of the molar absorption coefficient (ε) , operating as described above, the value obtained is indicated in Table 3.

TABLE 1

TABLE 2

TABLE 3

Claims

A compound containing at least one functionalized fullerene having general formula (I) or (II) :

C_x-Ai-Y_m-B_n-Y' _m' -B' n' -Y' ' _m" -A' i> -K_p ( I )

C_x- [Aj_.-Y_m-B_n-Y' _m' -B' n' -Y' ' m' ' ^_A' ±> ] ( II )

wherein

- C_x represents a fullerene group;

- x represents an integer ranging from 50 to 250;

- A and A' , the same or different from each other, represent a condensed ring with the fullerene group selected from cycloalkyl groups having from 3 to 6 carbon atoms, or heterocyclic groups having from 3 to 6 atoms containing from 1 to 3 heteroatoms selected from nitrogen, oxygen, sulfur;

- i and i' , the same or different from each other, represent 0 or 1;

Y, Y' and Y' ' , the same or different from each other, represent an aromatic or heteroaromatic divalent organic group, optionally substituted with linear or branched C1-C20 alkyl groups, linear or branched C2-C20 alkenyl groups, linear or branched C2-C20 alkinyl groups, linear or branched C2-C20 alkoxyl groups, ester groups - COORi wherein Ri represents a linear or branched C1-C20 alkyl group; Y, Y' and Y' ' being different from a divalent organic group containing at least one thienylene unit; m, m' and m' ' , the same or different from each other, represent 0 or 1, with the proviso that at least one of m, m' and m' ' is different from 0;

B and B' , the same or different from each other, represent a divalent organic group containing at least one thienylene unit, optionally substituted with linear or branched Ci-C₂o alkyl groups, linear or branched C2-C20 alkenyl groups, linear or branched C₂-C₂o alkinyl groups, linear or branched C2-C20 alkoxyl groups, ester groups -COORi wherein Ri represents a linear or branched C1-C20 alkyl group;

the sum of m + n + m' + n' + m' ' , said m + n + m' + n' + m' ' being the same or different from each other, ranges from 2 to 5, and is preferably 3, with the proviso that in general formula (I) and in general formula (II) at least one group Y, Y' or Y' ' and at least one group B or B' are present, and that groups Y and/or Y' and/or Y' ' alternate with groups B and/or B' ; K represents, when i' is 0, a C_x fullerene group, a linear or branched C1-C20 alkyl group, a linear or branched C2-C20 alkenyl group, a linear or branched C₂-C₂o alkinyl group, a linear or branched C2 -C20 alkoxyl group, an aldehydes group -CHO , an ester group -COORi wherein Ri represents a linear or branched C1-C20 alkyl group; or, when i' is 1, a C_x fullerene group;

- p represents an integer ranging from 0 to 5;

with the proviso that:

- when K is a C_x fullerene group, A and A' are an N-alkyl pyrrolidine group, m.and m" are 0, and B and B' are a divalent organic group containing at least one thienylene unit, Y' is not an N- alkyl pyrrole group;

- when K is a Cx fullerene group, A and A' are an N-alkyl pyrrolidine group, Y and Y' ' are a phenyl, and B and B' are a divalent organic group containing at least one thienylene unit, Y' is not an N-alkyl pyrrole group.

The compound comprising at least one functionalized fullerene according to claim 1, wherein x represents an integer ranging from 60 to 90.

The compound comprising at least one functionalized fullerene according to claim 1 or 2, wherein said groups A and A' are selected from cycloalkyl or heterocyclic groups having the following formulae:

wherein R ' represents a hydrogen atom, a linear or branched Ci -C₂o alkyl group, a linear or branched C1 -C20 alkoxyl group, an ester group -COORi wherein Ri represents a linear or branched C1 -C20 alkyl group .

The compound comprising at least one functionalized fullerene according to any of the previous claims, wherein said groups Y, Y' and Y", are selected from aromatic or heteroaromatic divalent organic groups, optionally substituted, having the following formulae:

wherein R' represents a hydrogen atom, a linear or branched C1 -C20 alkyl group, a linear or branched C1-C20 alkoxyl group, an ester group -COORi wherein Ri represents a linear or branched C 1-C20 alkyl grou .

The compound comprising at least one functionalized fullerene according to claim 4, wherein said groups Y, Y' and Y", are selected from aromatic or heteroaromatic divalent organic groups, optionally substituted, having the following formulae:

The compound comprising at least one functionalized fullerene according to any of the previous claims, wherein said groups B and B' , are selected from divalent organic groups containing at least one thienylene unit, optionally substituted, having the following formulae:

The compound comprising at least one functionalized fullerene according to claim 6, wherein said groups B and B' , are selected from divalent organic groups containing at least one thienylene unit, optionally substituted, having the following formulae:

The compound comprising at least one functionalized fullerene according to any of the previous claims, wherein said functionalized fullerene having general formula (I) is selected from fullerenes having the following formulae:

or different from each other, represent:

- a group -Y_m-B_n-Y' _m- -B' _n- -Y' ' _m.. -A' ^ -K_p wherein Y, B, Y' , B', Y" , A', m, n, m' , n' , m" , p and K, have the same meanings described above, i is 1, i' is 0, and K does not represent a C_x fullerene group;

- 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 proviso that at least one of Ri , ϊ½, R.3 , R₄ , R₅ , R₆ , R₇ and R_s , represents a group -Y_m-B_n-Y'_m»-

B' _n< -Y' ' m' _' -A' i' -Kp .

The compound comprising at least one functionalized fullerene according to any of the claims from 1 to 7, wherein said functionalized fullerene having general formula (I) is selected from fullerenes having the following formulae:

wherein :

- Ri5 represents a group -Y_m-B_n-Y' _m< -B' _n- -Y' ' _m" - wherein Y, B, Y' , B' , Y' ' , m, n, m' , n' and m' ' , have the same meanings described above, i, i' and p are 1, and K represents a C_x fullerene group;

- Ri , R2 , R3 , ¾ f R5 i

R7 , R8i 9i RlO / ll i l2 i l3 and Ri4, the same or different from each other, represent 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.

10. The compound comprising at least one functionalized fullerene according to any of the claims from 1 to 7, wherein said functionalized fullerene having general formula (II) is selected from fullerenes having the following formulae:

wherein :

Ri5 represents a group -Y_m-B_n-Y' _m- -B' _n> -Y' ' _m" - wherein Y, B, Y' , B' , Y' ' , m, n, m' , n' and m" , have the same meanings described above, i and i' are 1;

- Ri, R₂, R3, R4 R5/ ^6r 7 e* R9 RlOf Rll Rl2 Rl3 and Ri4, the same or different from each other, represent 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 compound comprising at least one functionalized fullerene according to any of the previous claims, wherein in said general formula (I) :

- C_x represents a fullerene group wherein x is 60;

- A and A' represent an N-methylpyrrolidine group condensed with the fullerene group;

- i and i' are 1;

- Y' is 9, 9-dioctylfluorene;

- m' is 1;

- m and m" are 0;

- B and B' represent a 2 , 5-thienylene group having general formula (III):

wherein Ri6 and R_i7 represent a hydrogen atom;

n and n' are 1;

K represents a C_x fullerene group, wherein 60,

- p is 1.

The compound comprising at least one functionalized fullerene according to any of the claims from 1 to 10, wherein in said general formula (I):

- C_x represents a fullerene wherein x is 60;

A represents an N-methylpyrrolidine group condensed with the fullerene group;

- i is 1;

- i' is 0;

- Y' is 9 , 9-dioctylfluorene ;

- m' is 1;

- m and m" are 0;

- B and B' represent a 2 , 5-thienylene group having general formula (III):

wherein and Ri₇ represent a hydrogen atom;

- n and n' are 1;

- K represents an aldehyde group;

- p is 1.

The compound comprising at least one functionalized fullerene according to any of the claims from 1 to 10, wherein in said general formula (II) :

- C_x represents a fullerene wherein x is 60; A and A' represent an N-methylpyrrolidine group condensed with the fullerene group;

i and i' are 1;

Y' is 9, 9-dioctylfluorene;

m and m" are 0;

m' is 1;

B and B' represent a 2 , 5-thienylene group having general formula (III):

wherein R_X 6 and R_i7 represent a hydrogen atom;

- n and n' are 1.

14. The compound comprising at least one functionalized fullerene according to any of the claims from 1 to 10, wherein in said general formula (II):

- C_x represents a fullerene wherein x is 60;

- i and i' are 1;

- Y' is 9 , 9-dioctylfluorene ;

- m and m" are 0;

- m' is 1;

B and B' represent a 2 , 2 ' -dithieylene group having general formula (Ilia):

wherein R₁₆ , 17, Ris and R_{i 9} represent a hydrogen atom;

- n and n' are 1.

515. Use of the compound comprising at least one functionalized fullerene having general formula (I) or (II) according to any of the previous claims, in the construction of photovoltaic devices such as photovoltaic cells, photovoltaic modules, solar0 cells, solar modules.

16. A photovoltaic device comprising at least one compound comprising at least one functionalized fullerene having general formula (I) or (II) according to any of the claims from 1 to 14.5