INVERTED POLYMER PHOTOVOLTAIC CELL AND METHOD FOR PREPARATION THEREOF

Abstract

An inverted polymer photovoltaic cell (or solar cell) includes an anode; a first anodic interlayer (buffer layer) based on PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate]; an active layer having at least one photoactive organic polymer as an electron donor and at least one electron acceptor organic compound; a cathodic interlayer (buffer layer); and a cathode. A second anodic interlayer (buffer layer) includes at least one heteropolyacid and, optionally, at least one amino compound is placed between the first anodic interlayer (buffer layer) and the active layer.

The inverted polymer photovoltaic cell (or solar cell) shows good values of photoelectric conversion efficiency (power conversion efficiency—PCE) (η) and, in particular, a good level of adhesion between the different layers, more specifically between the active layer and the first anodic interlayer (buffer layer).

Claims

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

2. The inverted polymer photovoltaic cell (or solar cell) according to claim 1, wherein said anode is made of metal, said metal being selected from silver (Ag), gold (Au), aluminum (Al); or it consists of grids in conductive material, said conductive material being selected from silver (Ag), copper (Cu), graphite, graphene, and of a transparent conductive polymer, said transparent conductive polymer being PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate]; or it consists of an ink based on metal nanowires, said metal being selected from silver (Ag) and copper (Cu).

3. The inverted polymer photovoltaic cell (or solar cell) according to claim 1, wherein said photoactive organic polymer is selected from: (a) polythiophenes such as, for example, regioregular poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene), poly(3,4-ethylenedioxythiophene), or mixtures thereof, (b) alternating or statistical conjugated copolymers comprising: at least one benzotriazole (B) unit having general formula (Ia) or (Ib): ##STR00004## wherein group R is selected from alkyl groups, aryl groups, acyl groups, thioacyl groups, said alkyl, aryl, acyl and thioacyl groups being optionally substituted; at least one conjugated structural unit (A), wherein each unit (B) is connected to at least one unit (A) in any one of the positions 4, 5, 6, or 7; (c) alternating conjugated copolymers comprising benzothiadiazole units such as, for example, 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;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]}; (d) alternating conjugated copolymers comprising thieno[3,4-b]pyrazidine units; (e) alternating conjugated copolymers comprising quinoxaline units; (f) alternating conjugated copolymers comprising monomer silol units such as, for example, copolymers of 9,9-dialkyl-9-silafluorene; (g) alternating conjugated copolymers comprising condensed thiophene units such as, for example, copolymers of thieno[3,4-b]thiophene and of benzo[1,2-b: 4,5-b′]dithiophene; (h) alternating conjugated copolymers comprising benzothiadiazole or naphthothiadiazole units substituted with at least one fluorine atom and thiophene units substituted with at least one fluorine atom such as, for example, PffBT4T-2OD {poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3′″-di(2-octyldodecyl)-2,2′;5′,2″;5″,2′″-quaterthiophen-5,5′″-diyl)]}, PBTff4T-2OD {poly[(2,1,3-benzothiadiazole-4,7-diyl)-alt-4′,3″-difluoro-3,3′″-di(2-octyldodecyl)-2,2′;5′,2″;5″,2′″-quaterthiophene-5,5′″-diyl)]}, PNT4T-2OD {poly(naphtho[1,2-c:5,-c′]bis[1,2,5]thiadiazole-5,10-diyl)-alt-(3,3′″-di(2-octyldodecyl)-2,2′;5′,2″; 5″,2′″-quaterthiophene-5,5′″-diyl)]}; (i) conjugated copolymers comprising thieno[3,4-c]pyrrole-4,6-dione units such as PBDTTPD {poly[[5-(2-ethylhexyl)-[(5,6-dihydro-4,6-dioxo-4H-thieno[3,4-c]pyrrole-1,3-diyl)[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl]}; (l) conjugated copolymers comprising thienothiophene units such as PTB7 {poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]]}, PBDB-T polymer {poly[[4,8-bis[5-(2-ethylhexyl)-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl]-2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-1,3-diyl]]}; (m) polymers comprising a derivative of indacen-4-one having general formula (III), (IV) or (V): ##STR00005## wherein: W and W.sub.1, identical to or different from each other, represent an oxygen atom; a sulfur atom; an N—R.sub.3 group wherein R.sub.3 represents a hydrogen atom, or is selected from C.sub.1-C.sub.20, linear or branched alkyl groups; Z and Y, identical to or different from each other, represent a nitrogen atom; or a CR.sub.4 group wherein R.sub.4 represents a hydrogen atom, or is selected from C.sub.1-C.sub.20, linear or branched alkyl groups, optionally substituted cycloalkyl groups, optionally substituted aryl groups, optionally substituted heteroaryl groups, C.sub.1-C.sub.20, linear or branched alkoxy groups, polyethyleneoxylic groups R.sub.5—O—[CH.sub.2—CH.sub.2—O].sub.n— wherein R.sub.5 is selected from C.sub.1-C.sub.20, linear or branched alkyl groups, and n is an integer between 1 and 4, —R.sub.6—OR.sub.7 groups wherein R.sub.6 is selected from C.sub.1-C.sub.20, linear or branched alkylene groups and R.sub.7 represents a hydrogen atom or is selected from C.sub.1-C.sub.20, linear or branched alkyl groups, or is selected from polyethyleneoxylic groups R.sub.5—[—OCH.sub.2—CH.sub.2—].sub.n— wherein R.sub.5 has the same meanings reported above and n is an integer between 1 and 4, —COR.sub.8 groups wherein R.sub.8 is selected from C.sub.1-C.sub.20, linear or branched alkyl groups, —COOR.sub.9 groups wherein R.sub.9 is selected from C.sub.1-C.sub.20, linear or branched alkyl groups; or represent a —CHO group, or a cyano group (—CN); R.sub.1 and R.sub.2, identical to or different from each other, are selected from C.sub.1-C.sub.20, linear or branched alkyl groups; optionally substituted cycloalkyl groups; optionally substituted aryl groups; optionally substituted heteroaryl groups; C.sub.1-C.sub.20, linear or branched alkoxy groups; polyethyleneoxylic groups R.sub.5—O—[CH.sub.2—CH.sub.2—O].sub.n— wherein R.sub.5 has the same meanings reported above and n is an integer between 1 and 4; groups —R.sub.6—OR.sub.7 wherein R.sub.6 and R.sub.7 have the same meanings reported above; —COR.sub.8 groups wherein R.sub.8 has the same meanings reported above; —COOR.sub.9 groups wherein R.sub.9 has the same meanings reported above; or represent a —CHO group, or a cyano group (—CN); D represents an electron donor group; A represents an electron acceptor group; n is an integer between 10 and 500; and (n) polymers comprising antradithiophene derivatives having general formula (X): ##STR00006## wherein: Z, identical to or different from each other, represent a sulfur atom, an oxygen atom, a selenium atom; Y, identical to or different from each other, represent a sulfur atom, an oxygen atom, a selenium atom; R.sub.1, identical or different from each other, are selected from amino groups —N—R.sub.3R.sub.4 wherein R.sub.3 represents a hydrogen atom, or is selected from C.sub.1-C.sub.20, linear or branched alkyl groups, or is selected from optionally substituted cycloalkyl groups and R.sub.4 is selected from C.sub.1-C.sub.20, linear or branched alkyl groups, or is selected from optionally substituted cycloalkyl groups; or are selected from C.sub.1-C.sub.30, linear or branched alkoxy groups; or are selected from polyethyleneoxylic groups R.sub.5—O—[CH.sub.2—CH.sub.2—O].sub.n— wherein R.sub.5 is selected from C.sub.1-C.sub.20, linear or branched alkyl groups, and n is an integer between 1 and 4; or are selected from —R.sub.6—OR.sub.7 groups wherein R.sub.6 is selected from C.sub.1-C.sub.20, linear or branched alkylene groups and R.sub.7 represents a hydrogen atom, or is selected from C.sub.1-C.sub.20, linear or branched alkyl groups, or is selected from polyethyleneoxyl groups R.sub.5—[—OCH.sub.2—CH.sub.2—].sub.n— wherein R.sub.5 has the same meanings reported above and n is an integer between 1 and 4; or are selected from thiol groups —S—R.sub.8 wherein R.sub.8 is selected from C.sub.1-C.sub.20, linear or branched alkyl groups; R.sub.2, identical to or different from each other, represent a hydrogen atom; or are selected from C.sub.1-C.sub.20, linear or branched alkyl groups; or are selected from —COR.sub.9 groups wherein R.sub.9 is selected from C.sub.1-C.sub.20, linear or branched alkyl groups; or are selected from —COOR.sub.10 groups wherein R.sub.10 is selected from C.sub.1-C.sub.20, linear or branched alkyl groups; or are selected from optionally substituted aryl groups; or are selected from optionally substituted heteroaryl groups; A represents an electron acceptor group; n is an integer between 10 and 500; selected from: PffBT4T-2OD {poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3′″-di(2-octyldodecyl)-2,2′;5′,2″;5″,2′″-quaterthiophen-5,5′″-diyl)]}, PBDTTPD {poly[[5-(2-ethylhexyl)-5,6-dihydro-4,6-dioxo-4H-thieno[3,4-c]pyrrole-1,3-diyl)[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl]}, PTB7 {poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]]}, PBDB-T {poly[[4,8-bis[5-(2-ethylhexyl)-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl]-2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-1,3-diyl]]}; polymers comprising antradithiophene derivatives having general formula (X).

4. The inverted polymer photovoltaic cell (or solar cell) according to claim 1, wherein said organic electron acceptor compound is selected from: fullerene derivatives such as [6,6]-phenyl-C.sub.61-butyric acid methyl ester (PCBM), [6,6]-phenyl-C.sub.71-butyric acid methyl ester (PC.sub.71BM), indene-C.sub.60 bis-adduct (ICBA), bis(1-[3-(methoxycarbonyl)propyl]-1-phenyl)-[6,6]C.sub.62 (Bis-PCBM); selected from [6,6]-phenyl-C.sub.61-butyric acid methyl ester (PCBM), [6,6]-phenyl-C.sub.71-butyric acid methyl ester (PC.sub.71BM); or non-fullerene compounds, optionally polymeric, such as compounds based on perylene-diimides or naphthalene-diimides and fused aromatic rings; indacenothiophenes with electron-poor terminal groups; compounds having an aromatic core capable of symmetrical rotation, such as derivatives of corannulene or truxenone; from: 3,9-bis{2-methylene-[3-(1,1-dicyanomethylene)-indanone]}-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3‘-d’]-s-indacene[1,2-b:5,6-b′]-dithiophene, poly{[N,N-bis(2-octyldodecyl)-1,4,5,8-naphthalenediamine-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)}.

5. The inverted polymer photovoltaic cell (or solar cell) according to claim 1, wherein said cathodic interlayer (buffer layer) comprises zinc oxide, titanium oxide.

6. The inverted polymer photovoltaic cell (or solar cell) according to claim 1, wherein said cathode is of a material selected from: indium-tin oxide (ITO), fluorine-doped tin oxide (FTO), zinc oxide doped with aluminium (AZO), zinc oxide doped with gadolinium oxide (GZO); or it consists of grids in conductive material, said conductive material being selected from silver (Ag), copper (Cu), graphite, graphene, and of a transparent conductive polymer, said transparent conductive polymer being PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate]; or it consists of an ink based on metal nanowires, said metal being selected from silver (Ag), copper (Cu).

7. The inverted polymer photovoltaic cell (or solar cell) according to claim 1, wherein said cathode is associated with a support layer which is of transparent rigid material such as glass, or of flexible material such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethyleneimine (PI), polycarbonate (PC), polypropylene (PP), polyimide (PI), triacetyl cellulose (TAC), or copolymers thereof.

8. The inverted polymer photovoltaic cell (or solar cell) according to claim 1, wherein said at least one heteropolyacid is selected from heteropolyacids having general formula (I):
H.sub.x[A(MO.sub.3).sub.yO.sub.z]  (I) wherein: A represents a silicon atom, or a phosphorus atom; M represents an atom of a transition metal belonging to group 5 or 6 of the Periodic Table of the Elements, x is an integer that depends on the valence of A; y is 12 or 18; z is 4 or 6.

9. The inverted polymer photovoltaic cell (or solar cell) according to claim 1, wherein said at least one heteropolyacid is selected from heteropolyacids having general formula (II):
H.sub.x[A(MO).sub.p(V).sub.qO.sub.40]  (II) wherein: A represents a silicon atom, or a phosphorus atom; x is an integer that depends on the valence of A; p is 6 or 10; q is 2 or 6.

10. The inverted polymer photovoltaic cell (or solar cell) according to claim 8, wherein said at least one heteropolyacid is selected from: hydrated phosphomolybdic acid {H.sub.3[P(MoO.sub.3).sub.12O.sub.4].Math.nH.sub.2O}, phosphomolybdic acid {H.sub.3[P(MoO.sub.3).sub.12O.sub.4]} in alcoholic solution, hydrated phosphotungstic acid {H.sub.3[P(WO.sub.3).sub.12O.sub.4].Math.nH.sub.2O}, phosphotungstic acid in alcoholic solution {H.sub.3[P(WO.sub.3).sub.12O.sub.4]}, hydrated silicomolybdic acid {H.sub.4[Si(MoO.sub.3).sub.12O.sub.4].Math.nH.sub.2O}, silicomolybdic acid {H.sub.4[Si(MoO.sub.3).sub.12O.sub.4]} in alcoholic solution, hydrated silicotungstic acid {H.sub.4[Si(WO.sub.3).sub.12O.sub.4].Math.nH.sub.2O}, silicotungstic acid {H.sub.4[Si(WO.sub.3).sub.12O.sub.4]} in alcoholic solution, hydrated phosphomolybdovanadic acid {H.sub.3[P(Mo).sub.6(V).sub.6O.sub.40].Math.nH.sub.2O}, phosphomolybdovanadic acid {H.sub.3[P(Mo).sub.6(V).sub.6O.sub.40]} in alcoholic solution, hydrated phosphomolybdovanadic acid {H.sub.3[P(Mo).sub.10(V).sub.2O.sub.40].Math.nH.sub.2O}, phosphomolybdovanadic acid {H.sub.3[P(Mo).sub.10(V).sub.2O.sub.40]} in alcoholic solution or mixtures thereof.

11. The inverted polymer photovoltaic cell (or solar cell) according to claim 1, wherein said amino compound is selected from: low molecular weight aliphatic amines, containing from 8 to 24 carbon atoms, linear or branched, primary, secondary or tertiary, such as n-octylamine, n-dodecylamine, n-hexadecylamine, di-n-octylamine, or mixtures thereof; conjugated polymers containing chain or side amino groups such as poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), poly(N,N-bis-4-butylphenyl-N,N-bisphenyl)benzidine (polyTPD), poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyl-fluorene)] (PFN), or mixtures thereof; or mixtures thereof.

12. A process for preparing the inverted polymer photovoltaic cell (or solar cell) according to claim 1, the process including the following steps: forming the cathode by sputtering; or by electron beam assisted deposition; or by depositing a transparent conductive polymer via spin coating, or gravure printing, or flexographic printing, or slot die coating, preceded by deposition of grids in conductive material via evaporation, or screen-printing, or spray-coating, or flexographic printing; or by depositing an ink based on metal nanowires via spin coating, or gravure printing, or flexographic printing, or slot die coating; forming the cathodic interlayer (buffer layer) by spin coating, or gravure printing, or flexographic printing, or slot die coating above said cathode; forming the active layer by spin coating, or gravure printing, or slot-die coating, above said cathodic interlayer (buffer layer); forming the second anodic interlayer (buffer layer) by spin coating, or gravure printing, or screen-printing, or flexographic printing, or slot-die coating above said active layers; forming the first anodic interlayer (buffer layer) by spin coating, or gravure printing, or screen-printing, or flexographic printing, or slot-die coating, above said second anodic interlayer (buffer layer); and forming the anode by vacuum evaporation, or screen-printing, or spray-coating, or flexographic printing, above said first anodic interlayer (buffer layer); or by deposition of a transparent conductive polymer via spin coating, or gravure printing, or flexographic printing, or slot die coating, followed by deposition of grids in conductive material via evaporation, or screen-printing, or spray-coating, or flexographic printing, above said first anodic interlayer (buffer layer); or by deposition of an ink based on metal nanowires via spin coating, or gravure printing, or flexographic printing, or slot die coating, above said first anodic interlayer (buffer layer).

13. The inverted polymer photovoltaic cell (or solar cell) according to claim 1, wherein: the anode has a thickness ranging between 50 nm and 150 nm; the first anodic interlayer (buffer layer) has a thickness ranging between 10 nm and 2000 nm; the second anodic interlayer (buffer layer) has a thickness ranging between 1 nm and 100 nm; the active layer has a thickness ranging between 50 nm and 500 nm; the cathodic interlayer (buffer layer) has a thickness ranging between 10 nm and 100 nm; and the cathode has a thickness ranging between 50 nm and 150 nm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0144] The present disclosure will now be illustrated in greater detail through an embodiment with reference to FIG. 1 below reported which represents a cross-sectional view of an inverted polymer photovoltaic cell (or solar cell) object of the present disclosure.

DETAILED DESCRIPTION OF THE DRAWING AND DISCLOSURE

[0145] With reference to FIG. 1, the inverted polymer photovoltaic cell (or solar cell) (1) comprises: [0146] a transparent support (7), for example, a glass or plastic support; [0147] a cathode (2), for example an indium tin oxide (ITO) cathode; or a cathode obtained by depositing a transparent conductive polymer via spin coating, or gravure printing, or flexographic printing, or slot die coating, preceded by deposition of grids in conductive material via evaporation, or screen-printing, or spray-coating, or flexographic printing; or a cathode obtained by depositing an ink based on metal nanowires via spin coating, or gravure printing, or flexographic printing, or slot die coating; [0148] a cathodic interlayer (buffer layer) (3), comprising, for example, zinc oxide; [0149] a layer of photoactive material (4) comprising at least one photoactive organic polymer, for example, a polymer comprising antradithiophene derivatives having general formula (X) (for example copolymer having formula (Xb) below reported), and at least one derivative of fullerene, for example, [6,6]-phenyl-C.sub.71-butyric acid methyl ester (PC.sub.71BM), or at least one non-fullerene compound, optionally polymeric; [0150] a second anodic interlayer (buffer layer) (5b), comprising an alcohol solution of at least one heteropolyacid having general formula (I) or (II) above reported, for example, phosphomolybdic acid trihydrate; or an alcoholic solution of at least one heteropolyacid having general formula (I) or (II) above reported, for example, phosphomolybdic acid trihydrate and at least one low molecular weight aliphatic amine, for example n-dodecylamine; or a solution in tetrahydrofuran of at least one heteropolyacid having general formula (I) or (II) above reported, for example, phosphomolybdic acid trihydrate and at least one conjugated polymer containing chain or side amino groups, for example, poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN); [0151] a first anodic interlayer (buffer layer) (5a), comprising, for example, PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate]; [0152] an anode (6), for example, a silver (Ag) anode; or an anode obtained by depositing a transparent conductive polymer via spin coating, or gravure printing, or flexographic printing, or slot die coating, followed by deposition of grids in conductive material via evaporation, or screen-printing, or spray-coating, or flexographic printing; or an anode obtained by depositing an ink based on metal nanowires via spin coating, gravure printing, flexographic printing, or slot die coating.

[0153] In order to better understand the present disclosure and to put it into practice, it is reported below some illustrative and non-limiting examples of the same.

Example 1 (Disclosure)

[0154] SOLAR cell with copolymer (Xb):PC.sub.71BM, phosphomolybdic acid and PEDOT:PSS

[0155] A polymer-based device was prepared on a substrate of polyethylene terephthalate (PET) coated with ITO (indium tin oxide) (Fom Technologies—Denmark) (100 nm), previously subjected to a cleaning procedure with a stream of compressed nitrogen and then, by means of an air plasma device (Diener Electronic GmbH & Co.—Germany), immediately before proceeding to the next step.

[0156] The substrate thus treated was ready for the deposition of the cathodic interlayer (buffer layer). For this purpose, the zinc oxide interlayer (buffer layer) was obtained starting from a 2.6% by weight solution of zinc oxide nanoparticles (Aldrich) in iso-propanol (Aldrich). The solution was deposited, in the air, on the substrate using a slot-die tool (Roller Coater—FOM Technologies—Denmark) operating under the following conditions: [0157] flow: 30 μl/min; [0158] speed of substrate: 0.5 m/min; [0159] gap: 50 m.

[0160] Immediately after deposition of the cathodic interlayer (buffer layer), the formation of zinc oxide was obtained by treating everything thermally at 140° C., for 3 minutes, in a ventilated air oven. The cathodic interlayer (buffer layer) thus obtained had a thickness of 70 nm.

[0161] A solution of 14 mg/ml of the copolymer having formula (Xb) obtained as described in Example 6 of the international patent application WO 2019/175367 above reported and 24.5 mg/ml of [6,6]-phenyl-C.sub.71-butyric acid methyl ester (PC.sub.71BM) (Nano-C), in o-xylene (Aldrich), was prepared. The active layer was deposited, in the air, starting from the solution thus obtained, using a slot-die tool (Roller Coater of FOM Technologies—Denmark) operating under the following conditions: [0162] flow: 120 μl/min; [0163] speed of substrate: 0.75 m/min; [0164] gap: 50 μm.

[0165] Immediately after the deposition of the active layer, everything was thermally treated at 120° C., for 2 minutes, in a ventilated air oven. The active layer thus obtained had a thickness of 300 nm.

[0166] Above the active layer thus obtained, the second anodic interlayer (buffer layer) was deposited in the air, starting from a solution of phosphomolybdic acid trihydrate (Aldrich) in iso-propanol (Aldrich) (6 mg/ml) through a slot-die tool (Roller Coater of FOM Technologies—Denmark) operating under the following conditions: [0167] flow: 100 μl/min; [0168] speed of substrate: 0.75 m/min; [0169] gap: 50 μm.

[0170] The second anodic interlayer (buffer layer) thus obtained had a thickness of 5 nm.

[0171] Above said second anodic interlayer (buffer layer), the first anodic interlayer (buffer layer) was deposited in the air, starting from a suspension comprising PEDOT:PSS [poly(3,4-ethylenedioxythiophene):polystyrene sulfonate] (Clevios™ HTL Solar 388—Heraeus Co.) with a concentration of PEDOT:PSS equal to 1.2 mg/ml, using a slot-die tool (Roller Coater of FOM Technologies—Denmark) operating under the following conditions: [0172] flow: 360 μl/min; [0173] speed of substrate: 1 m/min; [0174] gap: 100 μm.

[0175] Immediately after the deposition of the first anodic interlayer (buffer layer), everything was thermally treated at 120° C., for 2 minutes, in a ventilated air oven. The first anodic interlayer (buffer layer) thus obtained had a thickness of 150 nm.

[0176] Above said first anodic interlayer (buffer layer) the silver (Ag) anode was deposited, having a thickness of 100 nm, by vacuum evaporation, suitably masking the area of the device in order to obtain an active area equal to 0.25 mm.sup.2.

[0177] The deposition of the anode was carried out in a standard vacuum evaporation chamber containing the substrate and an evaporation vessel equipped with a heating element containing 10 silver (Ag) shots (diameter 1 mm-3 mm) (Aldrich). The evaporation process was carried out under vacuum, at a pressure of about 1×10.sup.−6 bar. The silver (Ag), after evaporation, was condensed in the non-masked parts of the device.

[0178] The thicknesses were measured with a Dektak 150 profilometer (Veeco Instruments Inc.).

[0179] Measurement of photoelectric conversion efficiency (power conversion efficiency—PCE) (η) of the obtained device was carried out in a controlled atmosphere (nitrogen) in a glove box at room temperature (25° C.). The current-voltage curves (I-V) were acquired with a Keithley® 2600A multimeter connected to a personal computer for data collection. The photocurrent was measured by exposing the device to the light of an ABET SUN® 2000-4 solar simulator, capable of providing 1.5G AM radiation with an intensity of 100 mW/cm.sup.2 (1 sun), measured with a powermeter Ophir Nova® II connected to a 3A-P thermal sensor. The measurement was carried out on 35 devices and the average value of photoelectric conversion efficiency (power conversion efficiency—PCE) (η) was equal to 7.32%.

[0180] In order to establish the level of adhesion, on the semi-finished device after the deposition of the double interlayer, i.e. after the deposition of the second anodic interlayer (buffer layer) and the first anodic interlayer (buffer layer), a rectangle of adhesive tape was applied. The tape was pressed with a finger and then torn off. The tear did not allow the removal of any layers.

Example 2 (Comparative)

[0181] Solar Cell with Copolymer (Xb): PC.sub.71BM and PEDOT:PSS

[0182] A polymer-based device was prepared on a substrate of polyethylene terephthalate (PET) coated with ITO (indium tin oxide) (Fom Technologies—Denmark) (100 nm), previously subjected to a cleaning procedure as described in the Example 1.

[0183] The deposition of the cathodic interlayer (buffer layer), the deposition of the active layer and the deposition of the first anodic interlayer (buffer layer), were carried out as described in Example 1; the composition of said cathodic interlayer (buffer layer), the composition of said active layer and the composition of said first anodic interlayer (buffer layer), are the same as reported in Example 1; the thickness of said cathodic interlayer (buffer layer), the thickness of said active layer and the thickness of said first anodic interlayer (buffer layer), are the same as reported in Example 1.

[0184] Above the obtained active layer, unlike Example 1, the second anodic interlayer (buffer layer) starting from a solution of phosphomolybdic acid trihydrate in iso-propanol was not deposited.

[0185] The deposition of the silver anode (Ag) was carried out as described in Example 1: the thickness of said silver anode is the same as reported in Example 1.

[0186] The thicknesses were measured with a Dektak 150 profilometer (Veeco Instruments Inc.).

[0187] The electrical characterization of the device, the current-voltage curves (I-V) and the photocurrent, were measured as described in Example 1. The measurement was carried out on 35 devices and the average value of photoelectric conversion efficiency (power conversion efficiency—PCE) (l) was equal to 6.06%.

[0188] In order to establish the level of adhesion, on the semi-finished device after the deposition of the first anodic interlayer (buffer layer), a rectangle of adhesive tape was applied. The tape was pressed with a finger and then tom off. The tear allowed the removal of the first anodic interlayer (buffer layer).

Example 3 (Comparative)

[0189] Solar Cell with Copolymer (Xb):PC.sub.71BM and Evaporated Molybdenum Oxide MoO)

[0190] A polymer-based device was prepared on a substrate of polyethylene terephthalate (PET) coated with ITO (indium tin oxide) (Fom Technologies—Denmark) (100 nm), previously subjected to a cleaning procedure as described in the Example 1.

[0191] The deposition of the cathodic interlayer (buffer layer) and the deposition of the active layer, were carried out as described in Example 1; the composition of said cathodic interlayer (buffer layer) and the composition of said active layer are the same as reported in Example 1; the thickness of said cathodic interlayer (buffer layer) and the thickness of said active layer are the same as reported in Example 1.

[0192] Above the obtained active layer, unlike Example 1, neither the first anodic interlayer (buffer layer) starting from a suspension comprising PEDOT:PSS [poly(3,4-ethylenedioxythiophene) polystyrene sulfonate] (Clevios™ HTL Solar 388—Heraeus Co.), nor the second anodic interlayer (buffer layer) starting from a solution of phosphomolybdic acid trihydrate in iso-propanol, were deposited.

[0193] Above the active layer instead, the anodic interlayer (buffer layer) was deposited, which was obtained by depositing molybdenum oxide (MoO.sub.3) (Aldrich) through a thermal process: the thickness of the anodic interlayer (buffer layer) was equal at 10 nm. The silver (Ag) anode, having a thickness of 100 nm, was deposited on the anodic interlayer (buffer layer) by vacuum evaporation, suitably masking the area of the device in order to obtain an active area equal to 0.25 mm.sup.2.

[0194] The anodic interlayer (buffer layer) and the anode depositions were carried out in a standard vacuum evaporation chamber containing the substrate and two evaporation vessels equipped with a heating resistance containing 10 mg of molybdenum oxide (MoO.sub.3) powder (Aldrich) and 10 shots of silver (Ag) (diameter 1 mm-3 mm) (Aldrich), respectively. The evaporation process was carried out under vacuum, at a pressure of about 1×10.sup.−6 bar. Molybdenum oxide (MoO.sub.3) and silver (Ag), after evaporation, are condensed in the non-masked parts of the device.

[0195] The thicknesses were measured with a Dektak 150 profilometer (Veeco Instruments Inc.).

[0196] The electrical characterization of the device, the current-voltage curves (I-V) and the photocurrent, were measured as described in Example 1. The measurement was carried out on 35 devices and the average value of photoelectric conversion efficiency (power conversion efficiency—PCE) (η) was 6.74%.

[0197] In order toto establish the level of adhesion, on the semi-finished device after the deposition of the anodic interlayer (buffer layer), a rectangle of adhesive tape was applied. The tape was pressed with a finger and then torn off. The tear allowed the removal of the anodic interlayer (buffer layer).

Example 4 (Disclosure)

[0198] Solar Cell with Copolymer (Xb):PC.sub.71BM, Phosphomolybdic Acid/n-Dodecylamine and PEDOT:PSS

[0199] A polymer-based device was prepared on a substrate of polyethylene terephthalate (PET) coated with ITO (indium tin oxide) (Fom Technologies—Denmark) (100 nm), previously subjected to a cleaning procedure as described in the Example 1.

[0200] The deposition of the cathodic interlayer (buffer layer), the deposition of the active layer and the deposition of the first anodic interlayer (buffer layer), were carried out as described in Example 1; the composition of said cathodic interlayer (buffer layer) and the composition of said active layer are the same as reported in Example 1; the thickness of said cathodic interlayer (buffer layer) and the thickness of said active layer are the same as reported in Example 1.

[0201] Above the obtained active layer, unlike Example 1, the second anodic interlayer (buffer layer) was deposited starting from a solution of 5.4 mg/ml of phosphomolybdic acid trihydrate and 0.6 mg/ml of n-dodecylamine (Aldrich) in n-propanol: the deposit was carried out as described in Example 1.

[0202] The deposition of the silver (Ag) anode was carried out as described in Example 1: the thickness of said silver anode is the same as reported in Example 1.

[0203] The thicknesses were measured with a Dektak 150 profilometer (Veeco Instruments Inc.).

[0204] The electrical characterization of the device, the current-voltage curves (I-V) and the photocurrent, were measured as described in Example 1. The measurement was carried out on 35 devices and the average value of photoelectric conversion efficiency (power conversion efficiency—PCE)(q) was equal to 5.91%.

[0205] In order to establish the level of adhesion, on the semi-finished device after the deposition of the double interlayer, i.e. after the deposition of the second anodic interlayer (buffer layer) and the first anodic interlayer (buffer layer), a rectangle of adhesive tape was applied. The tape was pressed with a finger and then torn off. The tear did not allow the removal of any layers.

Example 5 (Disclosure)

[0206] Solar Cell with Copolymer (Xb):PC.sub.71BM, Phosphomolybdic Acid/PFN and PEDOT:PSS

[0207] A polymer-based device was prepared on a substrate of polyethylene terephthalate (PET) coated with ITO (indium tin oxide) (Fom Technologies—Denmark) (100 nm), previously subjected to a cleaning procedure as described in the Example 1.

[0208] The deposition of the cathodic interlayer (buffer layer), the deposition of the active layer and the deposition of the first anodic interlayer (buffer layer), were carried out as described in Example 1; the composition of said cathodic interlayer (buffer layer) and the composition of said active layer are the same as reported in Example 1; the thickness of said cathodic interlayer (buffer layer) and the thickness of said active layer are the same as reported in Example 1.

[0209] On top of the obtained active layer, unlike Example 1, the second anodic interlayer (buffer layer) was deposited starting from a solution of 5.5 mg/ml of phosphomolybdic acid trihydrate and 0.5 mg/ml of poly[(9,9-bis (3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyl-fluorene)] (PFN) (Aldrich) in tetrahydrofuran (Aldrich): the deposit was carried out as described in Example 1.

[0210] The deposition of the silver anode (Ag) was carried out as described in Example 1: the thickness of said silver anode is the same as reported in Example 1.

[0211] The thicknesses were measured with a Dektak 150 profilometer (Veeco Instruments Inc.).

[0212] The electrical characterization of the device, the current-voltage curves (I-V) and the photocurrent, were measured as described in Example 1. The measurement was carried out on 35 devices and the average value of photoelectric conversion efficiency (power conversion efficiency—PCE) (l) was equal to 5.77%.

[0213] In order to establish the level of adhesion, on the semi-finished device after the deposition of the double interlayer, i.e. after the deposition of the second anodic interlayer (buffer layer) and the first anodic interlayer (buffer layer), a rectangle of adhesive tape was applied. The tape was pressed with a finger and then torn off. The tear did not allow the removal of any layers.