WO2010057087A1 - Organic photovoltaic devices comprising substituted endohedral metallofullerenes - Google Patents

Abstract

Improved organic electronic devices, including, photovoltaic devices, including use of a composition comprising a mixture comprising: (i) at least one p-type material, (ii) at least one n-type material, wherein the n-type material comprises an endohedral metallofullerene derivative represented by: E*-(R)n; and solvates, salts, and mixtures thereof, wherein n is at least one, E* comprises an endohedral metallofullerene having a surface which comprises six-membered and fϊve-membered rings; and R comprises at least one optionally substituted, unsaturated or saturated, carbocyclic or heterocyclic first ring, wherein the first ring directly bonds to the surface of the endohedral metallofullerene. Indenyl derivatization is a preferred embodiment.

Description

ORGANIC PHOTOVOLTAIC DEVICES COMPRISING SUBSTITUTED ENDOHEDRAL METALLOFULLERENES

RELATED APPLICATIONS

This application claims priority to US provisional application serial no. 61/115,385 filed November 17, 2008 to Williams et al., which is hereby incorporated by reference in its entirety.

BACKGROUND

A need exists to provide better materials and processes for organic photovoltaic (OPV) devices. This is driven in part by ongoing high fuel prices and unstable fuel supply. OPV devices can provide improvements over older silicon devices. See for example Perlin, John "The Silicon Solar Cell Turns 50" NREL 2004; see also, Dennler et al., "Flexible Conjugated Polymer-Based Plastic Solar Cells: From Basics to Applications," Proceedings of the IEEE, vol. 93, no. 8, August 2005, 1429-1439. Global climate change is also a motivating factor. While it is known that conducting polymers, or conjugated polymers, including for example polythiophenes can be combined with C60 fullerene to provide useful active materials in OPV devices, a need yet remains to improve device efficiency and other important PV parameters. In particular, regioregular polythiophenes are of particular importance because of their nanoscale morphology which can be applied to novel morphologies for solar cell applications.

SUMMARY

Provided herein are, among other things, compositions, devices, methods of making, and methods of using.

For example, one embodiment provides a composition comprising a mixture comprising: (i) at least one p-type material, (ii) at least one n-type material, wherein the n- type material comprises an endohedral metallofullerene derivative represented by:

E*-(R)_n

and solvates, salts, and mixtures thereof, wherein n is at least one, E* comprises an endohedral metallofullerene having a surface which comprises six-membered and five- membered rings; and R comprises at least one optionally substituted, unsaturated or saturated, carbocyclic or heterocyclic first ring, wherein the first ring directly bonds to the surface of the endohedral metallofullerene.

In one embodiment, the first ring is substituted, and in another embodiment, the first ring is not substituted. In one embodiment, the first ring is an unsaturated ring, and in another embodiment,, the first ring is a saturated ring. In one embodiment, the first ring is a carbocyclic ring. In one embodiment, the first ring is a heterocyclic ring. In one embodiment, the first ring is an optionally substituted four-membered, five-membered, or six- membered ring. In one embodiment, the ring is an optionally substituted five-membered ring. In one embodiment, R further comprises a second ring which is bonded to or fused with the first ring. In one embodiment, R further comprises an optionally substituted second ring which is fused to the first ring. In one embodiment, R further comprises an optionally substituted second ring which is an aryl group and is fused to the first ring. In one embodiment, R is optionally substituted indene, optionally substituted naphthyl, optionally substituted phenyl, optionally substituted pyridinyl, optionally substituted quinolinyl, optionally substituted cyclohexyl, or optionally substituted cyclopentyl. In one embodiment, R is indene, napthyl, phenyl, pyridinyl, quinolinyl, cyclohexyl, or cyclopentyl. In one embodiment, R is optionally substituted indene. In one embodiment, R is indene. In one embodiment, n is from 1 to 6. In one embodiment, n is from 1 to 3. In one embodiment, R is indene and n is 1. In one embodiment, R is indene and n is 2. In one embodiment, R is indene and n is 3. In one embodiment, R is indene, n is from 1 to 20. In one embodiment, R is indene, n is from 1 to 10. In one embodiment, the first ring is optionally substituted with at least one substituent selected from the group consisting of hydroxy, acyl, acylamino, acyloxy, alkyl, substituted alkyl, alkoxy, substituted alkoxy, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, amino, substituted amino, aminoacyl, aryl, substituted aryl, aryloxy, substituted aryloxy, cycloalkoxy, substituted cycloalkoxy, carboxyl, carboxyl esters, cyano, thiol, thioalkyl, substituted thioalkyl, thioaryl, substituted thioaryl, thioheteroaryl, substituted thioheteroaryl, thiocycloalkyl, substituted thiocycloalkyl, thioheterocyclic, substituted thioheterocyclic, cycloalkyl, substituted cycloalkyl, halo, nitro, heteroaryl, substituted heteroaryl, heterocyclic, substituted heterocyclic, heteroaryloxy, substituted heteroaryloxy, heterocyclyloxy, or substituted heterocyclyloxy, or combination thereof. In one embodiment, R is covalently bonded to the endohedral metallofullerene by [4+2] cycloaddition. In one embodiment, R is covalently bonded to the endohedral metallofullerene by one or two covalent bonds. In one embodiment, R is covalently bonded to the endohedral metallofullerene by two bonds. In one embodiment, R is covalently bonded to the endohedral metallofullerene by two carbon-carbon bonds. In one embodiment, R is covalently bonded to the endohedral metallofullerene by two carbon-carbon bonds at a endohedral metallofullerene [6,6] position. In one embodiment, said endohedral monofullerene has a surface with 60, 68,70, 78, 80, 82, 84, 86, 90, or 92 carbons. In one embodiment, the endohedral metallofullerene comprises at least one derivative group bonded to the surface of the endohedral metallofullerene besides R. In one embodiment, the p-type material comprises a conjugated polymer. In one embodiment, the p-type material comprises a conjugated polymer soluble or dispersible in organic solvent or water. In one embodiment, the p-type material comprises a polythiophene. In one embodiment, the p-type material comprises a regioregular polythiophene. In one embodiment, the n-type and p-type materials are present in a ratio of from about 0.1 to 4.0 p-type to about 1 n-type, based on weight. In one embodiment, the p-type material comprises polythiophene and the R group is optionally substituted indene, and the composition is in the form of a film having a film thickness of about 10 nm to about 300 nm. In one embodiment, the p-type material comprises regioregular polythiophene and the R group is indene. In one embodiment, the p- type material comprises regioregular polythiophene and the R group is indene and the composition further comprises at least two solvents.

In another embodiment, a composition comprises a mixture comprising: (i) at least one p-type material, (ii) at least one n-type material, wherein the n-type material comprises at least one endohedral metallofullerene derivative comprising at least one [6,6] endohedral metallofullerene bonding site wherein both carbon atoms of the [6,6] bonding site are covalently bonded to a group R. In one embodiment, the group R comprises a first ring bonded directly to the [6,6] endohedral metallofullerene bonding site. In one embodiment, the group R comprises a first ring bonded directly to the [6,6] endohedral metallofullerene bonding site and a second ring fused to the first ring. In one embodiment, the group R comprises a first five-membered carbocyclic ring bonded directly to the [6,6] endohedral metallofullerene bonding site and a second six-membered carbocyclic ring fused to the first ring. In one embodiment, the group R comprises optionally substituted indene. In one embodiment, the group R comprises indene. In one embodiment, the p-type material comprises a conjugated polymer. In one embodiment, the p-type material comprises a polythiophene. In one embodiment, the p-type material comprises a regioregular polythiophene. In one embodiment, the p-type material comprises a regioregular polythiophene and the group R is optionally substituted indene. In one embodiment, a composition comprises a mixture comprising: (i) at least one p- type material, (ii) at least one n-type material, wherein the n-type material comprises an endohedral metallofullerene derivative comprising at least one endohedral metallofullerene covalently bonded by [4+2] cycloaddition to at least one derivative moiety. In one embodiment, the derivative moiety comprises a first ring bonded directly to the endohedral metallofullerene. In one embodiment, the derivative moiety comprises a first ring bonded directly to the endohedral metallofullerene and a second ring fused to the first ring. In one embodiment, the derivative moiety comprises a first fϊve-membered carbocyclic ring bonded directly to the endohedral metallofullerene bonding site and a second six-membered carbocyclic ring fused to the first ring. In one embodiment, the derivative moiety comprises optionally substituted indene. In one embodiment, the derivative moiety comprises indene. In one embodiment, the p-type material comprises a conjugated polymer. In one embodiment, the p-type material comprises a polythiophene. In one embodiment, the p-type material comprises a regioregular polythiophene. In one embodiment, the p-type material comprises a regioregular polythiophene and the derivative moiety is optionally substituted indene.

In one embodiment, a photovoltaic device comprises at least one anode, at least one cathode, and at least one active layer, wherein the active layer comprises a composition comprising a mixture comprising: (i) at least one p-type material, (ii) at least one n-type material, wherein the n-type material comprises an endohedral metallofullerene derivative represented by:

E*-(R)n

and solvates, salts, and mixtures thereof, wherein n is at least one, E* comprises an endohedral metallofullerene having a surface which comprises six-membered and five- membered rings; and R comprises at least one optionally substituted, unsaturated or saturated, carbocyclic or heterocyclic first ring, wherein the first ring directly bonds the surface of the endohedral metallofullerene. In one embodiment, the device demonstrates an increase of efficiency of at least 5% compared to a substantially analogous device comprising an active layer of P3HT-PCBM. In one embodiment, the device demonstrates an increase of efficiency of at least 15% compared to a substantially analogous device comprising an active layer of P3HT-PCBM. In one embodiment, the device further comprises at least one hole injection layer. In one embodiment, the device further comprises at least one hole injection layer comprising a polythiophene. In one embodiment, the device further comprises at least one hole injection layer comprising a regioregular polythiophene. In one embodiment, the R group comprises an optionally substituted indene group. In one embodiment, the R group comprises an indene group. In one embodiment, the R group comprises an optionally substituted indene group, the p-type material comprises at least one regioregular polythiophene. In one embodiment, the R group comprises an optionally substituted indene group, the p-type material comprises at least one regioregular polythiophene, and the device further comprises a hole injection layer comprising a regioregular polythiophene.

In one embodiment, a method of making a composition is provided comprising a mixture comprising: (i) providing at least one p-type material, (ii) providing at least one n- type material, wherein the n-type material comprises a endohedral metallofullerene derivative represented by:

E*-(R)n

and solvates, salts, and mixtures thereof, wherein n is at least one, E* comprises an endohedral metallofullerene having a surface which comprises six-membered and fϊve- membered rings; and R comprises at least one optionally substituted, unsaturated or saturated, carbocyclic or heterocyclic first ring, wherein the first ring directly bonds to the surface of the endohedral metallofullerene, (iii) combining the p-type and n-type materials to form the mixture, wherein the mixture further comprises at least one solvent. In one embodiment, the mixture comprises at least two solvents. In one embodiment, the method further is comprising removing solvent and forming the mixture into a film. In one embodiment, R comprises optionally substituted indene. In one embodiment, R comprises indene.

In one embodiment, a composition comprises at least one endohedral metallofullerene derivative represented by:

E*-(R)_n

and solvates, salts, and mixtures thereof, wherein n is at least one, E* comprises an endohedral metallofullerene having a surface which comprises six-membered and five- membered rings; and R comprises at least one optionally substituted, unsaturated or saturated, carbocyclic or heterocyclic first ring, wherein the first ring directly bonds to the surface of the endohedral metallofullerene.

In one embodiment, a composition comprises at least one endohedral metallofullerene derivative comprising at least one [6,6] endohedral metallofullerene bonding site wherein both carbon atoms of the [6,6] bonding site are covalently bonded to a group R.

In one embodiment, a composition comprises at least one endohedral metallofullerene derivative comprising at least one endohedral metallofullerene covalently bonded by [4+2] cycloaddition to at least one derivative moiety.

One or more advantages for at least one or more embodiments include, for example, substantially better photovoltaic efficiency, versatility with a variety of active layer systems which can be tuned to particular applications, improved device lifetime, and/or improved material and device processability.

BRIEF DESCRIPTION OF DRAWING

Figure 1 shows a typical conductive polymer photovoltaic (solar cell).

DETAILED DESCRIPTION INTRODUCTION & DEFINITIONS

"Optionally substituted" groups refers to functional groups that may be substituted or unsubstituted by additional functional groups. When a group is unsubstituted by an additional group is may be referred to as a group name, for example alkyl or aryl. When a group is substituted with additional functional groups it may more generically be referred to as substituted alkyl or substituted aryl.

"Carbocyclic" refers to a cyclic arrangement of carbon atoms forming a ring including for example benzene or cyclohexane. Carbocyclic includes both cycloalkyl and aryl groups. The term "cycloalkyl" refers to cyclic alkyl groups of from 3 to 20 carbon atoms having single or multiple condensed cyclic rings which condensed rings may or may not be aromatic provided that the point of attachment is not at an aromatic carbon atom. "Aryl" refers to an aromatic carbocyclic group of from 6 to 20 carbon atoms having a single ring (e.g., phenyl) or multiple condensed rings (e.g., naphthyl or anthryl) which condensed rings may or may not be aromatic provided that the point of attachment is at an aromatic carbon atom. Preferred aryls include phenyl, naphthyl, and the like.

"Heterocyclic" refers to a saturated, unsaturated, or hetero aromatic group having a single ring or multiple condensed rings, from 1 to 20 carbon atoms and from 1 to 4 heteroatoms, selected from nitrogen, oxygen, sulfur, -S(O)- and -S(O)₂-- within the ring. Such heterocyclic groups can have a single ring (e.g., pyridyl or furyl) or multiple condensed rings (e.g., indolizinyl or benzothienyl) wherein the condensed rings may or may not be aromatic and/or contain a heteroatom provided that the point of attachment is through an atom of the aromatic heteroaryl group. Heterocyclic groups can be for example, pyridine, or thiophene, or furan or tetrahydrofuran, pyrrole, tetrahydropyrrole, pyran, and the like. The term heterocyclic includes heteroaryl groups where "heteroaryl" refers to an aromatic group of from 1 to 20 carbon atoms and 1 to 4 heteroatoms selected from the group consisting of oxygen, nitrogen, sulfur, -S(O)-, and -S(O)₂- within the ring. Heteroaryls include pyridyl, pyrrolyl, indolyl, thiophenyl, and furyl.

"Alkyl" refers to straight chain and branched alkyl groups having from 1 to 20 carbon atoms, or from 1 to 15 carbon atoms, or from 1 to 10, or from 1 to 5, or from 1 to 3 carbon atoms. This term is exemplified by groups such as methyl, ethyl, n-propyl, ώo-propyl, n- butyl, t-butyl, n-pentyl, ethylhexyl, dodecyl, isopentyl, and the like.

"Substituted alkyl" refers to an alkyl group having from 1 to 3, and preferably 1 to 2, substituents selected from the group consisting of alkoxy, substituted alkoxy, acyl, acylamino, acyloxy, amino, substituted amino, aminoacyl, aryl, substituted aryl, aryloxy, substituted aryloxy, cyano, halogen, hydroxyl, nitro, carboxyl, carboxyl esters, cycloalkyl, substituted cycloalkyl, heteroaryl, substituted heteroaryl, heterocyclic, and substituted heterocyclic.

The terms "Substituted carbocyclic," "substituted aryl," "substituted cycloalkyl," "substituted heterocyclic," and "substituted heteroaryl refer to carbocyclic, aryl, cycloalkyl, heterocyclic, or heteroaryl groups with from 1 to 5 substituents, or optionally from 1 to 3 substituents, or optionally from 1 to 2 substituents, selected from the group consisting of alkoxy, substituted alkoxy, acyl, acylamino, acyloxy, amino, substituted amino, aminoacyl, aryl, substituted aryl, aryloxy, substituted aryloxy, cyano, halogen, hydroxyl, nitro, carboxyl, carboxyl esters, cycloalkyl, substituted cycloalkyl, heteroaryl, substituted heteroaryl, heterocyclic, and substituted heterocyclic.

"Alkoxy" refers to the group "alkyl-O-" which includes, by way of example, methoxy, ethoxy, n-propyloxy, ώo-propyloxy, n-butyloxy, t-butyloxy, n-pentyloxy, 1-ethylhex-l- yloxy, dodecyloxy, isopentyloxy, and the like.

"Substituted alkoxy" refers to the group "substituted alkyl-O-." "Alkenyl" refers to alkenyl group preferably having from 2 to 6 carbon atoms and more preferably 2 to 4 carbon atoms and having at least 1 and preferably from 1-2 sites of alkenyl unsaturation. Such groups are exemplified by vinyl, allyl, but-3-en-l-yl, and the like.

"Substituted alkenyl" refers to alkenyl groups having from 1 to 3 substituents, and preferably 1 to 2 substituents, selected from the group consisting of alkoxy, substituted alkoxy, acyl, acylamino, acyloxy, amino, substituted amino, aminoacyl, aryl, substituted aryl, aryloxy, substituted aryloxy, cyano, halogen, hydroxyl, nitro, carboxyl, carboxyl esters, cycloalkyl, substituted cycloalkyl, heteroaryl, substituted heteroaryl, heterocyclic, and substituted heterocyclic with the proviso that any hydroxyl substitution is not attached to a vinyl (unsaturated) carbon atom.

"Aryloxy" refers to the group aryl-O- that includes, by way of example, phenoxy, naphthoxy, and the like.

"Alkoxy" refers to the group "alkyl-O-" which includes, by way of example, methoxy, ethoxy, n-propoxy, ώo-propoxy, n-butoxy, t-butoxy, sec-butoxy, n-pentoxy and the like.

"Substituted alkoxy" refers to the group "substituted alkyl-O-".

"Acyl" refers to the groups H-C(O)-, alkyl-C(O)-, substituted alkyl-C(O)-, alkenyl- C(O)-, substituted alkenyl-C(O)-, alkynyl-C(O)-, substituted alkynyl-C(O)- cycloalkyl-C(O)-, substituted cycloalkyl-C(O)-, aryl-C(O)-, substituted aryl-C(O)-, heteroaryl-C(O)-, substituted heteroaryl-C(O), heterocyclic-C(O)-, and substituted heterocyclic-C(O)- wherein alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, cycloalkyl, substituted cycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, heterocyclic and substituted heterocyclic are as defined herein.

"Acylamino" refers to the group -C(O)NRR where each R is independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, cycloalkyl, substituted cycloalkyl, heteroaryl, substituted heteroaryl, heterocyclic, substituted heterocyclic and where each R is joined to form together with the nitrogen atom a heterocyclic or substituted heterocyclic ring wherein alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, cycloalkyl, substituted cycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, heterocyclic and substituted heterocyclic are as defined herein.

"Acyloxy" refers to the groups alkyl-C(O)O-, substituted alkyl-C(O)O-, alkenyl- C(O)O-, substituted alkenyl-C(O)O-, alkynyl-C(O)O-, substituted alkynyl-C(O)O-, aryl- C(O)O-, substituted aryl-C(O)O-, cycloalkyl-C(O)O-, substituted cycloalkyl-C(O)O-, heteroaryl-C(O)O-, substituted heteroaryl-C(O)O-, heterocyclic-C(O)O-, and substituted heterocyclic-C(O)O- wherein alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, cycloalkyl, substituted cycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, heterocyclic and substituted heterocyclic are as defined herein.

"Alkynyl" refers to alkynyl group preferably having from 2 to 6 carbon atoms and more preferably 2 to 3 carbon atoms and having at least 1 and preferably from 1-2 sites of alkynyl unsaturation.

"Substituted alkynyl" refers to alkynyl groups having from 1 to 3 substituents, and preferably 1 to 2 substituents, selected from the group consisting of alkoxy, substituted alkoxy, acyl, acylamino, acyloxy, amino, substituted amino, aminoacyl, aryl, substituted aryl, aryloxy, substituted aryloxy, cyano, halogen, hydroxyl, nitro, carboxyl, carboxyl esters, cycloalkyl, substituted cycloalkyl, heteroaryl, substituted heteroaryl, heterocyclic, and substituted heterocyclic.

"Amino" refers to the group -NH₂.

"Substituted amino" refers to the group -NR 'R" where R' and R" are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, cycloalkyl, substituted cycloalkyl, heteroaryl, substituted heteroaryl, heterocyclic, substituted heterocyclic and where R' and R" are joined, together with the nitrogen bound thereto to form a heterocyclic or substituted heterocylic group provided that R' and R" are both not hydrogen. When R' is hydrogen and R" is alkyl, the substituted amino group is sometimes referred to herein as alkylamino. When R' and R" are alkyl, the substituted amino group is sometimes referred to herein as dialkylamino.

"Aminoacyl" refers to the groups -NRC(O)alkyl, -NRC(O)substituted alkyl, -NRC(O)cycloalkyl, -NRC(O)substituted cycloalkyl, -NRC(O)alkenyl, -NRC(O)substituted alkenyl, -NRC(O)alkynyl, -NRC(O)substituted alkynyl, -NRC(O)aryl, -NRC(O)substituted aryl, -NRC(O)heteroaryl, -NRC(O)substituted heteroaryl, -NRC(O)heterocyclic, and -NRC(O)substituted heterocyclic where R is hydrogen or alkyl and wherein alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, cycloalkyl, substituted cycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, heterocyclic and substituted heterocyclic are as defined herein. "Carboxyl" refers to -COOH or salts therof.

"Carboxyl esters" refers to the groups -C(O)O-alkyl, -C(O)O-substituted alkyl, - C(O)Oaryl, and -C(O)O-substituted aryl wherein alkyl, substituted alkyl, aryl and substituted aryl are as defined herein. "Cycloalkoxy" refers to -O-cycloalkyl groups.

"Substituted cycloalkoxy" refers to -O-substituted cycloalkyl groups.

"Halo" or "halogen" refers to fluoro, chloro, bromo and iodo.

"Heteroaryloxy" refers to the group -O-heteroaryl and "substituted heteroaryloxy" refers to the group -O-substituted heteroaryl.

"Heterocyclyloxy" refers to the group -O-heterocyclic and "substituted heterocyclyloxy" refers to the group -O-substituted heterocyclic.

"Thiol" refers to the group -SH.

"Thioalkyl" or "alkylthio ether" or "thioalkoxy" refers to the group -S-alkyl.

"Substituted thioalkyl" or "substituted alkylthioether" or "substituted thioalkoxy" refers to the group -S-substituted alkyl.

"Thiocycloalkyl" refers to the groups -S-cycloalkyl and "substituted thiocycloalkyl" refers to the group -S-substituted cycloalkyl.

"Thioaryl" refers to the group -S-aryl and "substituted thioaryl" refers to the group -S- substituted aryl.

"Thioheteroaryl" refers to the group -S-heteroaryl and "substituted thioheteroaryl" refers to the group -S-substituted heteroaryl.

"Thioheterocyclic" refers to the group -S -heterocyclic and "substituted thioheterocyclic" refers to the group -S-substituted heterocyclic.

"Salts" are derived from a variety of organic and inorganic counter ions well known in the art and include, by way of example only, sodium, potassium, calcium, magnesium, ammonium, tetraalkylammonium, and the like; and when the molecule contains a basic functionality, salts of organic or inorganic acids, such as hydrochloride, hydrobromide, tartrate, mesylate, acetate, maleate, oxalate and the like.

"Solvate" refers to those forms of the compounds which form, in the solid or liquid state, a complex by coordination with solvent-molecules. Hydrates are a specific form of solvates in which the coordination takes place with water.

"Conjugated polymer" refers to polymers comprising at least some conjugated unsaturation in the backbone.

"A polythiophene" or "polythiophene" refers to polymers comprising a thiophene in the backbone including polythiophene, derivatives thereof, and copolymers and terpolymers thereof. "Regioregular polythiophene" refers to polythiophene having high levels of regioregularity including for example at least 80%, or at least 90%, or at least 95%, or at least 98%, or at least 99%.

It is understood that in all substituted groups defined above, polymers arrived at by defining substituents with further substituents to themselves (e.g., substituted aryl having a substituted aryl group as a substituent which is itself substituted with a substituted aryl group, etc.) are not intended for inclusion herein. In such cases, the maximum number of such substituents is three. That is to say that each of the above definitions is constrained by a limitation that, for example, substituted aryl groups are limted to -substituted aryl-(substituted aryl)-substituted aryl.

Similarly, it is understood that the above definitions are not intended to include impermissible substitution patterns (e.g., methyl substituted with 5 fluoro groups or a hydroxyl group alpha to ethenylic or acetylenic unsaturation). Such impermissible substitution patterns are well known to the skilled artisan.

Other terms used herein are defined as follows, unless the context makes clear otherwise.

All references cited herein are incorporated by reference in their entirety.

Solar cells are described in for example Hoppe and Sariciftci, J. Mater. Res., Vol. 19, No. 7, July 2004, 1924-1945, which is hereby incorporated by reference including the figures..

Figure 1 illustrates some components of a conventional solar cell. See also for example Dennler et al., "Flexible Conjugated Polymer-Based Plastic Solar Cells: From Basics to Applications," Proceedings of the IEEE, vol. 93, no. 8, August 2005, 1429-1439, including Figures 4 and 5 therein. Various architectures for the solar cell can be used, including inverted solar cells. Important elements include the active layer, an anode, a cathode, and a substrate to support the larger structure. In addition, a hole injection layer can be used, and one or more conditioning layers can be used. The active layer can comprise a P/N composite including a P/N bulk heterojunction.

The following references describe photovoltaic materials and devices:

US Patent Publication 2006/0076050 to Williams et al., "Heteroatomic Regioregular Poly(3-Substitutedthiophenes) for Photovoltaic Cells," (Plextronics) which is hereby incorporated by reference including working examples and drawings. US Patent Publication 2006/0237695 (Plextronics), "Copolymers of Soluble Poly(thiophenes) with Improved Electronic Performance," which is hereby incorporated by reference including working examples and drawings.

US Patent No. 7,147,936 to Louwet et al.

In addition, US Patent Publication 2006/0175582 "Hole Injection/Transport Layer Compositions and Devices" describes hole injection layer technology, (Plextronics) which is hereby incorporated by reference including working examples and drawings.

ENDOHEDRAL METALLOFULLERENES

Endohedral metallofullerenes are related to fullerenes. Fullerenes can be described as spheroidal carbon compounds. For example, the fullerene surface can present [6,6] bonding and [6,5] bonding as known in the art. The fullerene can have a surface comprising six- membered and five-membered rings. Fullerenes can be for example C60, C70, or C84, and additional carbon atoms can be added via derivative groups. See for example Hirsch, A.; Brettreich, M., Fullerenes: Chemistry and Reactions, Wiley-VCH Verlag, Weinheim, 2005, (including pages 12-17 on generation of endohedral fullerenes) which is hereby incorporated by reference including teachings for fullerene nomenclature and synthesis, derivatization, reduction reactions (Chapter X), nucleophilic additions (Chapter 3), cyclo additions (Chapter 4), hydrogenation (Chapter 5), radical additions (Chapter 6), transition metal complex formation (Chapter 7), oxidation and reactions with electrophiles (Chapter 8), halogenation (Chapter 9), regiochemistry (Chapter 10), cluster modification (Chapter 11), hetero fullerenes (Chapter 12), and higher fullerenes (Chapter 13). Methods described herein can be used to synthesize fullerene derivatives and adducts.

As used herein, "endohedral" refers to the encapsulation of atoms inside the fullerene cage network. Accepted symbols for elements and subscripts to denote numbers of elements are used herein. Further, all elements to the right of an @ symbol are part of the fullerene cage network, while all elements listed to the left are contained within the fullerene cage network. Under this notation, Sc₃N@C8o(R) indicates that the Sc₃N trimetallic nitride is situated within a Cso fullerene cage and the R group is situated on the exterior of the Cso fullerene cage and bonded to carbon of the fullerene cage.

U.S. Pat. No. 6,303,760, hereby incorporated by reference in its entirety, describes a family of endohedral metallofullerenes where a trimetallic nitride is encapsulated in a fullerene cage. The endohedral metallofullerenes have the general formula A₃__rX_rN@C_m (n=0-3) where A is a metal, X is a second trivalent metal, r is an integer from 0 to 3, and m is an even integer from about 60 to about 200, including, but not limited to, about 60, about 68, about 70, about 78, about 80, about 82, about 84, about 86, about 90, and about 92. The metals A and X may be an element selected from the group consisting of a rare earth element and a group IIIB element and may be the same or different. In some embodiments, A and X may be selected from the group consisting of Scandium, Yttrium, Lanthanum, Gadolinium, Holmium, Erbium, Thulium, and Ytterbium, where A and X may be the same or different. Such endohedral metallofullerenes are commercially available from Luna nano Works, a division of Luna Innovations Inc., as TRIMETASPHERE® carbon nanomaterials. See also US Patent Publication 2007/0295395 to Phillips et al. for uses of trimetaspheres.

DEVICE ELEMENTS OTHER THAN THE ACTIVE LAYER

Electrodes, including anodes and cathodes, are known in the art for photovoltaic devices. See, for example, Hoppe et al. article cited above. Known electrode materials can be used. Transparent conductive oxides can be used. Transparency can be adapted for a particular application. For example, the anode can be indium tin oxide, including ITO supported on a substrate. Substrates can be rigid or flexible.

If desired, hole injection and hole transport layers can be used. An HIL layer can be for example PEDOT :PSS as known in the art. See, for example, Hoppe et al. article cited above.

ACTIVE LAYER P-TYPE MATERIAL

The active layer can comprise at least one p-type material, and the fullerene derivative n-type materials can be used in combination with various p-type materials. The advantage of some embodiments of the invention is that the substituents used to derivatize the fullerene can be chosen based on the calculated LUMO level or the calculated electron affinity. The goal in these embodiments can be to maximize the difference between the LUMO level of the n-type with the HOMO level of the p-type, while still maintaining photo carrier generation within the active layer.

The p-type material can be an organic material including a polymeric material, although other types of p-type material are known in the art. For example, the p-type material can comprise a conjugated polymer or a conducting polymer, comprising a polymer backbone having a series of conjugated double bonds. It can be a homopolymer or a copolymer including a block copolymer or a random copolymer, or a terpolymer. Examples include polythiophene, polypyrrole, polyaniline, polyfluorene, polyphenylene, polyphenylene vinylene, and derivatives, copolymers, and mixtures thereof. The p-type material can comprise a conjugated polymer soluble or dispersible in organic solvent or water. Conjugated polymers are described in for example T. A. Skotheim, Handbook of Conducting Polymers, 3^r Ed. (two vol), 2007; Meijer et al., Materials Science and Engineering, 32 (2001), 1-40; and Kim, Pure Appl. Chem., 74, 11, 2031-2044, 2002. The p-type active material can comprise a member of a family of similar polymers which have a common polymer backbone but are different in the derivatized side groups to tailor the properties of the polymer. For example, a polythiophene can be derivatized with alkyl side groups including methyl, ethyl, hexyl, dodecyl, and the like.

One embodiment comprises copolymers and block copolymers which comprise, for example, a combination of conjugated and non-conjugated polymer segments, or a combination of a first type of conjugated segment and a second type of conjugated segment. For example, these can be represented by AB or ABA or BAB systems wherein, for example, one block such as A is a conjugated block and another block such as B is an non-conjugated block or an insulating block. Or alternately, each block A and B can be conjugated. The non-conjugated or insulating block can be for example an organic polymer block, an inorganic polymer block, or a hybrid organic-inorganic polymer block including for example addition polymer block or condensation polymer block including for example thermoplastic types of polymers, polyolefϊns, polysilanes, polyesters, PET, and the like. Block copolymers are described in, for example, US Patent No. 6,602,974 to McCullough et al., and US Patent Publication No. 2006/0278867 to McCullough et al. published December 14, 2006, each incorporated herein by reference in its entirety.

In particular, polythiophenes and derivatives thereof are known in the art. They can be homopolymers or copolymers, including block copolymers. They can be soluble or dispersible. They can be regioregular. In particular, optionally substituted-alkoxy- and optionally substituted alkyl-substituted polythiophenes can be used. In particular, regioregular polythiophenes can be used as described in for example US Patent No. 6,602,974 and 6,166,172 to McCullough et al., as well as McCullough, R. D.; Tristram- Nagle, S.; Williams, S. P.; Lowe, R. D.; Jayaraman, M. J. Am. Chem. Soc. 1993, 115, 4910, including homopolymers and block copolymers. See also Plextronics (Pittsburgh, PA) commercial products. Soluble alkyl- and alkoxy-substituted polymers and copolymers can be used including poly(3-hexylthiophene). Other examples can be found in US Patent Nos. 5,294,372 and 5,401,537 to Kochem et al. US Patent Nos. 6,454,880 and 5,331,183 further describe active layers.

Soluble materials or well dispersed materials can be used in the stack to facilitate processing.

Additional examples of p-type materials and polythiophenes can be found in WO 2007/011739 (Gaudiana et al.) which describes polymers having monomers which are, for example, substituted cyclopentadithiophene moieties, and which is hereby incorporated by reference in its entirety including formulas.

ACTIVE LAYER N-TYPE MATERIAL

The active layer can comprise an n-type material comprising at least one endohedral metallofullerene structure. In particular, the active layer can comprise at least one n-type material, wherein the n-type material comprises at least one derivatized endohedral metallofullerene or endohedral metallofullerene derivative. The derivative compound can be for example an adduct. The terms "derivatized endohedral metallofullerene," "endohedral metallofullerene derivative" as used herein, can be used interchangeably and can be for example endohedral metallofullerene comprising, from 1 to 84, or 1 to 70, or 1 to 60, from 1 to 20, from 1 to 18, from one to ten, or from one to six, or from one to five, or from one to three substituents each covalently bonded to, for example, one or two carbons in the carbon compounds. The derivatized endohedral metallofullerene can comprise an endohedral metallofullerene covalently bonded by [4+2] cycloaddition to at least one derivative moiety, R.

Structures for the n-type material can be represented by:

E*-(R)n

and solvates, salts, and mixtures thereof, wherein n is at least one;

E is an endohedral metallofullerene having a surface which comprises six-membered and fϊve-membered rings; and

R comprises at least one optionally substituted, unsaturated or saturated, carbocyclic or heterocyclic first ring, wherein the first ring directly bonds to the surface of the endohedral metallofullerene. The first ring can be substituted. The first ring can be not substituted. The first ring can be an unsaturated ring. The first ring can be a saturated ring. The first ring can be a carbocyclic ring. The first ring can be a heterocyclic ring.

The first ring can be an optionally substituted four-membered, five-membered, or six- membered ring. It can in particular be an optionally substituted five-membered ring.

The R group can further comprise a second ring which is bonded to or fused with the first ring. The second ring can be optionally substituted. The second ring can be for example an aryl group which is fused to the first ring.

The first ring directly bonds to the endohedral metallofullerene. For example, the R group can covalently bond to the endohedral metallofullerene by a [4+2] cycloaddition. The R group can be covalently bonded to the endohedral metallofullerene by one or two covalent bonds, including two covalent bonds, including by two carbon-carbon bonds. The R group can be bonded to the endohedral metallofullerene surface by a covalent bond to one atom in the R group. Alternatively the R group can be bonded to the endohedral metallofullerene surface by covalent bonds to two atoms in the R group. The two atoms in the R group bonded to the endohedral metallofullerene can be adjacent to each other, or can be separated by from each other by 1 to 3 other atoms in the R group. The R group can be covalently bonded to the endohedral metallofullerene by two carbon-carbon bonds at an endohedral metallofullerene [6,6] position.

For example, endohedral metallofullerenes can be derivatized with electron withdrawing groups or electron releasing groups. Electron withdrawing groups and electron releasing groups are known in the art and can be found in Advanced Organic Chemistry, 5th Ed, by Smith, March, 2001.

The electron withdrawing group can be attached directly to the endohedral metallofullerene cage or via methano-bridges similar to the PCBM structure.

The electron donating group can be attached directly to the endohedral metallofullerene cage or via methano-bridges similar to the PCBM structure.

Endohedral metallofullerenes can be derivatized to improve their absorption in the visible range, relative to C60-PCBM. Improved absorption in the visible range may increase or improve the photocurrent of a photovoltaic device comprising the derivatized fullerene.

In one embodiment^* is selected from A3__rX_rN@C6o, A3__rX_rN@C68, A_3-1X₁N(S)C₇O, A₃-_rX_rN@C₇₈, A₃._rX_rN@C₈₀, A₃._rX_rN@C₈₂, A₃._rX_rN@C₈₄, A₃._rX_rN@C₈₆, A₃._rX_rN@C₉₀, A₃__rX_rN@Cc>₂, and combinations thereof, where r can be 0, 1, 2, or 3. In one embodiment, R is selected from optionally substituted aryl and optionally substituted heteroaryl.

In one embodiment, R is selected from optionally substituted indene, optionally substituted naphthyl, optionally substituted phenyl, optionally substituted pyridinyl, optionally substituted quinolinyl, optionally substituted cyclohexyl, and optionally substituted cyclopentyl.

In one embodiment R is selected from indene, naphthyl, phenyl, pyridinyl, quinolinyl, cyclohexyl and cyclopentyl.

The value n can be an integer. In one embodiment, n can be from 1 to 84, or from 1 to 70, or from 1 to 60, or from 1 to 30, or from 1 to 10. In one embodiment n is from 1 to 6. In one embodiment n is from 1 to 3.

In one embodiment n is 1. In one embodiment n is 2. In one embodiment n is 3.

In one embodiment, the first ring is optionally substituted with at least one substituent selected from the group consisting of hydroxy, acyl, acylamino, acyloxy, alkyl, substituted alkyl, alkoxy, substituted alkoxy, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, amino, substituted amino, aminoacyl, aryl, substituted aryl, aryloxy, substituted aryloxy, cycloalkoxy, substituted cycloalkoxy, carboxyl, carboxyl esters, cyano, thiol, thioalkyl, substituted thioalkyl, thioaryl, substituted thioaryl, thioheteroaryl, substituted thioheteroaryl, thiocycloalkyl, substituted thiocycloalkyl, thioheterocyclic, substituted thioheterocyclic, cycloalkyl, substituted cycloalkyl, halo, nitro, heteroaryl, substituted heteroaryl, heterocyclic, substituted heterocyclic, heteroaryloxy, substituted heteroaryloxy, heterocyclyloxy, or substituted heterocyclyloxy, or combination thereof.

In one embodiment n is 1 and R is indene. In one embodiment n is 2 and R is indene. In one embodiment n is 3 and R is indene. In one embodiment n is 4 and R is indene. In one embodiment n is 5 and R is indene. In one embodiment n is 6 and R is indene.

In one embodiment, R can be covalently bonded to the endohedral metallofullerene by [4+2] cycloaddition, alternatively called a [4+2] cycloadduct. Reactions including [4+2] cycloaddition reactions and Diels-Alder reactions are generally known in the art. A dienophile double bond can react with a diene to produce a six membered ring. See for example Advanced Organic Chemistry, Reactions, Mechanisms, and Structure, 2ⁿ Ed., J. March, 1977, including chapters on addition to carbon-carbon multiple bonds (e.g., Chapter 15). See also, Belik et al., Angew. Chem. Int. Ed. Engl. 1993, 32, 1, 78-80 (showing reaction of C60 with a C8 o-quinodimethane compound to form a C68 compound comprising the fullerene and the derivative moiety); and Puplovskis et al., Tetrahedron Letters, 38, 2, 285- 288, 1997, 285-288 (showing reaction of C60 with C9 indene to form a C69 compound comprising the fullerene and the derivative moiety). The cycloaddition reaction can result in reaction at the [6,6] endohedral metallofullerene double bonds rather than [6,5] double bonds. Cycloaddition reactions are described in detail in Chapter 4, pages 101-183, of the Hirsch, Brettreich text, Fullerenes, Chemistry and Reactions, 2005.

One example of a endohedral metallofullerene derivative is an indene derivative. In addition, indene itself can be derivatized. Endohedral metallo fullerenes can be derivatized by methods described in for example U.S. Patent No. 7,358, 343, hereby incorporated by reference in its entirety. Additional known methods for derivitizing fullenes may be applicable to derivitizing endohedral metallofullerenes, as well. For example, Belik et al., Angew. Chem. Int. Ed. Engl, 1993, 32, No. 1, pages 78-80, which is hereby incorporated by reference. This paper describes addition to electron poor superalkene, C60, which can add radicals such as o-quinodimethane. It can be prepared in situ containing different functional groups and form very reactive dienes that can form [4 + 2] cycloadducts even with the least reactive dienophiles. This method provides good selectivity and stability.

The endohedral metallofullerene can comprise at least two derivative moieties, R, to form bis-adducts or at least three derivative moieties, R, to form tris-adducts. These substituents can be added to the endohedral metallofullerene by [4+2] cycloaddition. For example, Belik et al. show in Scheme 1, formula 3, a fullerene compound comprising two derivative moieties. In addition, two endohedral metallofullerenes can be covalently linked by one derivative moiety as shown in Scheme 2 of Belik et al.

While the various embodiments are not limited by theory, it is believed that the derivatization may disrupt the conjugation of the endohedral metallofullerene cage. Disrupting the conjugation effects the ionization potential and electron affinity of the derivatized endohedral metallofullerene.

In one embodiment, the active layer can comprise at least one polythiophene and at least one endohedral metallofullerene derivative comprising an electron withdrawing group.

DEVICE FABRICATION

Devices using the presently claimed inventions can be made using for example ITO as an anode material on a substrate. Other anode materials can include for example metals, such as Au, carbon nanotubes, single or multiwalled, and other transparent conducting oxides. The resistivity of the anode can be maintained below for example 15 Ω/sq or less, 25 or less, 50 or less, or 100 or less, or 200 or less, or 250 or less. The substrate can be for example glass, plastics (PTFE, polysiloxanes, thermoplastics, PET, PEN and the like), metals (Al, Au, Ag), metal foils, metal oxides, (TiOx, ZnOx) and semiconductors, such as Si. The ITO on the substrate can be cleaned using techniques known in the art prior to device layer deposition. An optional hole injection layer (HIL) can be added using for example spin casting, ink jetting, doctor blading, spray casting, dip coating, vapor depositing, or any other known deposition method. The HIL can be for example PEDOT, PEDOT/PSS or TBD, or NPB, or Plexcore HIL (Plextronics, Pittsburgh, PA).

The thickness of the HIL layer can be for example from about 10 nm to about 300 nm thick, or from 30 nm to 60 nm , 60 nm to 100 nm , or 100 nm to 200 nm. The film then can be optionally dried/annealed at 110 to 200 ⁰C for 1 min to an hour, optionally in an inert atmosphere.

The active layer can be formulated from a mixture of n-type and p-type materials. The n- and p-type materials can be mixed in a ratio of for example from about 0.1 to 4.0 (p- type) to about 1 (n-type) based on a weight, or from about 1.1 to about 3.0 (p-type) to about 1 (n-type) or from about 1.1 to about 1.5 (p-type) to about 1 (n-type). The amount of each type of material or the ratio between the two types of components can be varied for the particular application.

The n- and p-type materials can be mixed in a solvent or in a solvent blend at for example from about 0.01 to about 0.1% volume solids. The solvents useful for the presently claimed inventions can include, for example, halogenated benzenes, alkyl benzenes, halogenated methane, and thiophenes derivatives, and the like. More specifically, solvent can be for example cholobenzene, dichlorobenzene, xylenes, toluene, chloroform, 3- methylthiophene, 3-propylthiphene, 3-hexylthiphene, and mixtures thereof. At least two solvents can be used.

Particularly useful solvent systems can be used as described in US patent application entitled "Solvent System for Conjugated Polymers," serial no. 60/915632 filed on May 2, 2007, to Sheina et al., which is hereby incorporated by reference in its entirety.

The active layer can be then deposited by spin casting, ink jetting, doctor blading, spray casting, dip coating, vapor depositing, or any other known deposition method, on top of the HIL film. The film is then optionally annealed at for example about 40 to about 250 ⁰C, or from about 150 to 180 ⁰C, for about 10 min to an hour in an inert atmosphere.

Next, a cathode layer can be added to the device, generally using for example thermal evaporation of one or more metals. For example, a 1 to 15 nm Ca layer is thermally evaporated onto the active layer through a shadow mask, followed by deposition of a 10 to 300 nm Al layer.

In some embodiments and optional interlayer may be included between the active layer and the cathode, and/or between the HTL and the active layer . This interlayer can be for example from 0.5 nm to about 100 nm, or from about 1 to 3 nm, thick. The interlayer can comprise an electron conditioning, a hole blocking, or an extraction material such as LiF, BCP, bathocuprine, endohedral metallofullerenes or endohedral metallofullerene derivatives, such as A3__rX_rN@C8o and other endohedral metallofullerenes and endohedral metallofullerene derivatives discussed herein.

The devices can be then encapsulated using a glass cover slip sealed with a curable glue, or in other epoxy or plastic coatings. Cavity glass with a getter/dessicant may also be used.

In addition, the active layer can comprise additional ingredients including for example surfactants, dispersants, and oxygen and water scavengers.

The active layer can comprise multiple layers or be multi-layered.

The active layer composition can comprise a mixture in the form of a film.

ACTIVE LAYER MORPHOLOGY

The active layer can be a p-n composite and for example can form a heteroj unction including a bulk heterojunction. See for example discussion of nanoscale phase separation in bulk heterojunctions in Dennler et al., "Flexible Conjugated Polymer-Based Plastic Solar Cells: From Basics to Applications," Proceedings of the IEEE, vol. 93, no. 8, August 2005, 1429-1439. Conditions and materials can be selected to provide for good film formation, low roughness (e.g., 1 nm RMS), and discrete, observable, phase separation characteristics can be achieved. The present invention can have phase separated domains on a scale of a about 5 to 50 nm as measured by AFM. AFM analysis can be used to measure surface roughness and phase behavior. In general, phase separated domains are not desirable so that both donor and acceptor are uniformly and continuously distributed in the active layer.

DEVICE PERFORMANCE

Known solar cell parameters can be measured including for example Jsc (mA/cm ) and Voc (V) and fill factor (FF) and power conversion efficiency (%, PCE) by methods known in the art. See for example Hoppe article cited above and references cited therein. Oriel Solar Simulators can be used to determine PV properties including for example FF, Jsc, Voc, and efficiencies. The simulator can be calibrated by methods known in the art including for example calibration with a KG5-Si reference cell.

LITERATURE

The following references can be also used as needed to practice the various embodiments described herein and are incorporated herein by reference:

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EXAMPLES

Various claimed embodiments are described further with use of non- limiting examples. Example 1 : Synthesis of Endohedral Metallofullerene -Indene Adducts

Endohedral metallofullerene-indene adducts are synthesized using the description in reference (Puplovskis, et al., "New Route for [60]Fullerene Functionalization in [4+2] Cycloaddition Reaction Using Indene." Tetrahedron Lett. 1997, 38,285-288) as starting point. Endohedral metallofullerenes are dissolved in o-dichlorobenzene at concentrations of approximately 6 mg mL^"1. Indene is added at 12-fold molar excess relative to the concentration of endohedral metallofullerenes and the resulting mixture is refluxed overnight. Most of the solvent is evaporated under reduced pressure and precipitation occurs after adding ethanol. The resulting solid is dried, re-dissolved in toluene and then analyzed by means of high-pressure liquid chromatography using a Cosmosil Buckyprep analytical column (250 x 4.6 mm, Nacalai Tesque, Inc.) mounted on an Agilent 1100 series instrument equipped with a variable wavelength detector operated at 330 nm. Toluene at a flow rate of 1 ml min^"1 is used for elution. Peaks are attributed to endohedral metallofullerene -indene mono- and bis-adducts, respectively. The presence of several peaks with very close elution times is consistent with the presence of several isomers. A pentabromobenzyl-functionalized silica phase is used for purification by means of flash chromatography. Pure toluene and toluene/cyclo-hexane mixtures are used for purification. HPLC analysis of the collected fractions shows endohedral metallofullerene -indene monoadduct and bis-adducts, both at high purity.

Example 2: Preparation of Polythiophene

Plexcore P3HT is prepared as described in Loewe, et al. Adv. Mater. 1999, 11, 250- 253 using 2,5-dibromo-3-hexylthiophene in place of 2,5-dibromo-dodecylthiophene, and using 0.0028 eq. of Ni(dppp)Cl₂ instead of 0.01 eq. The molecular weight as measured by GPC using chloroform as eluant is 69,000, 1.35 PDI.

Example 3 : Fabrication of Solar Cell Device Using Endohedral Metallofullerene-indene Adducts

Photovoltaic devices are prepared comprising (i) patterned indium tin oxide (ITO, anode, 60 Ω/square) on glass substrate purchased from Thin Film Devices (located in Anaheim, CA), (ii) a thin layer of HIL (30 nm thick) comprising PEDOT/PSS (AI4083) purchased from HC Stark), (iii) a 100 nm active layer comprising Plexcore P3HT (prepared as described in Example 3) blended with the n-type, which is either methanofullerence [6,6]- phenyl C61 -butyric acid methyl ester (PCBM) (purchased from Nano-C, located in Westwood, MA), endohedral metallofullerene-indene mono adduct, or endohedral metallofullerene-indene bis-adduct, (the endohedral metallofullerene adducts prepared as described in Example 1), and (iv) a Ca/ Al bilayer cathode.

The patterned ITO glass substrates are cleaned with detergent, hot water and organic solvents (acetone and alcohol) in an ultrasonic bath and treated with ozone plasma immediately prior to device layer deposition. The HIL solution (Baytron AI 4083) is then spin coated on the patterned ITO glass substrate to achieve a thickness of 30 nm. The film is dried at 150⁰C for 30 mins in a nitrogen atmosphere. The active layer is formulated to a 1.2:1 weight ratio P3HT:n-type blend in o-dichlorobenzene (formulation was made to 0.024% volume solids) and is then spun on the top of the HIL film with no damage to the HIL (verified by AFM).

The film is then annealed at 175°C for 30 mins in a glove box. Next, a 5 nm Ca layer is thermally evaporated onto the active layer through a shadow mask, followed by deposition of a 150 nm Al layer. The devices are then encapsulated via a glass cover slip (blanket) encapsulation sealed with EPO-TEK OGl 12-4 UV curable glue. The encapsulated device is cured under UV irradiation (80 mW/cm²) for 4 minutes and tested as follows.

The photovoltaic characteristics of devices under white light exposure (Air Mass 1.5 Global Filter) are measured using a system equipped with a Keithley 2400 source meter and an Oriel 300W Solar Simulator based on a Xe lamp with output intensity of 100 mW/cm² (AMI .5G). The light intensity is set using an NREL-certifϊed Si-KG5 silicon photodiode.

The Jsc, Voc and efficiency measured for each device are compared to a control device which was made as described above using PCBM as the n-type material. The Jsc, Voc and efficiency for devices made from the mono- and bis-indene adducts are all higher than the corresponding measurements for the control device.

Claims

WHAT IS CLAIMED IS:

1. A composition comprising a mixture comprising: (i) at least one p-type material, (ii) at least one n-type material, wherein the n-type material comprises an endohedral metallofullerene derivative represented by:

E*-(R)n

and solvates, salts, and mixtures thereof, wherein n is at least one,

E* comprises an endohedral metallofullerene having a surface which comprises six- membered and five-membered rings; and

R comprises at least one optionally substituted, unsaturated or saturated, carbocyclic or heterocyclic first ring, wherein the first ring directly bonds to the surface of the endohedral metallofullerene.

2. The composition according to claim 1, wherein the first ring is not substituted.

3. The composition according to claim 1, wherein the first ring is a carbocyclic ring.

4. The composition according to claim 1, wherein the first ring is an optionally substituted four-membered, five-membered, or six-membered ring.

5. The composition according to claim 1, wherein the ring is an optionally substituted five- membered ring.

6. The composition according to claim 1, wherein R further comprises a second ring which is bonded to or fused with the first ring.

7. The composition according to claim 1, wherein R further comprises an optionally substituted second ring which is an aryl group and is fused to the first ring.

8. The composition according to claim 1, wherein R is optionally substituted indene, optionally substituted naphthyl, optionally substituted phenyl, optionally substituted pyridinyl, optionally substituted quinolinyl, optionally substituted cyclohexyl, or optionally substituted cyclopentyl.

9. The composition according to claim 1, wherein R is indene, napthyl, phenyl, pyridinyl, quinolinyl, cyclohexyl, or cyclopentyl.

10. The composition according to claim 1, wherein R is optionally substituted indene.

11. The composition according to claim 1 , wherein R is indene.

12. The composition according to claim 1, wherein n is from 1 to 6.

13. The composition according to claim 1, wherein R is covalently bonded to the endohedral metallofullerene by [4+2] cycloaddition.

14. A composition comprising a mixture comprising: (i) at least one p-type material, (ii) at least one n-type material, wherein the n-type material comprises at least one endohedral metallofullerene derivative comprising at least one [6,6] endohedral metallofullerene bonding site wherein both carbon atoms of the [6,6] bonding site are covalently bonded to a group R.

15. A composition comprising a mixture comprising: (i) at least one p-type material, (ii) at least one n-type material, wherein the n-type material comprises an endohedral metallofullerene derivative comprising at least one endohedral metallofullerene covalently bonded by [4+2] cycloaddition to at least one derivative moiety.

16. A photovoltaic device comprising at least one anode, at least one cathode, and at least one active layer, wherein the active layer comprises a composition comprising a mixture comprising: (i) at least one p-type material, (ii) at least one n-type material, wherein the n- type material comprises an endohedral metallofullerene derivative represented by:

E*-(R)_n and solvates, salts, and mixtures thereof, wherein n is at least one,

E* comprises an endohedral metallofullerene having a surface which comprises six- membered and five-membered rings; and

R comprises at least one optionally substituted, unsaturated or saturated, carbocyclic or heterocyclic first ring, wherein the first ring directly bonds the surface of the endohedral metallofullerene..

17. A method of making a composition comprising a mixture comprising: (i) providing at least one p-type material, (ii) providing at least one n-type material, wherein the n-type material comprises a endohedral metallofullerene derivative represented by:

E*-(R)n

and solvates, salts, and mixtures thereof, wherein n is at least one,

E* comprises an endohedral metallofullerene having a surface which comprises six- membered and five-membered rings; and

R comprises at least one optionally substituted, unsaturated or saturated, carbocyclic or heterocyclic first ring, wherein the first ring directly bonds to the surface of the endohedral metallofullerene..

(iii) combining the p-type and n-type materials to form the mixture, wherein the mixture further comprises at least one solvent.

18. A composition comprising at least one endohedral metallofullerene derivative represented by:

E*-(R)n

and solvates, salts, and mixtures thereof, wherein n is at least one, E* comprises an endohedral metallofullerene having a surface which comprises six- membered and fϊve-membered rings; and

R comprises at least one optionally substituted, unsaturated or saturated, carbocyclic or heterocyclic first ring, wherein the first ring directly bonds to the surface of the endohedral metallofullerene.

19. A composition comprising at least one endohedral metallofullerene derivative comprising at least one [6,6] endohedral metallofullerene bonding site wherein both carbon atoms of the [6,6] bonding site are covalently bonded to a group R.

20. A composition comprising at least one endohedral metallofullerene derivative comprising at least one endohedral metallofullerene covalently bonded by [4+2] cycloaddition to at least one derivative moiety.