Organic photovoltaic cells

1. An article, comprising:

first and second electrodes;

a photoactive layer between the first and second electrodes; and

a hole transport layer between the first electrode and the photoactive layer, the hole transport layer consisting of an ionic copolymer,

wherein the article is configured as a photovoltaic cell.

2. The article of claim 1 , wherein some of the copolymer is present in the photoactive layer.

3. The article of claim 1 , wherein the photoactive layer comprises an electron acceptor material and an electron donor material, and some of the copolymer is in contact with the electron acceptor material and the electron donor material beneath a surface of the photoactive layer.

4. The article of claim 3 , wherein the electron donor material comprises a polymer and the electron acceptor material comprises a fullerene.

5. The article of claim 1 , wherein the ionic copolymer comprises a tetrafluoroethylene backbone.

6. The article of claim 5 , wherein a structural unit of the ionic copolymer comprises a perfluorovinyl ether group.

7. The article of claim 6 , wherein the perfluorovinyl ether group is terminated with a sulfonyl group.

8. The article of claim 1 , wherein the ionic copolymer has the chemical structure

wherein x, y, and z are integer values of one (1) or greater than one (1).

9. The article of claim 1 , wherein the hole transport layer has a thickness of at most 50 microns.

10. The article of claim 1 , wherein the hole transport layer has a thickness of at most 30 microns.

11. The article of claim 1 , wherein the hole transport layer has a thickness of at most 10 microns.

12. The article of claim 1 , wherein the hole transport layer has a thickness of at least 0.01 micron.

13. The article of claim 1 , wherein the hole transport layer has a thickness of at least 0.5 micron.

14. The article of claim 1 , further comprising an electron injection layer between the first and second electrode.

15. The article of claim 14 , wherein the electron injection layer has a thickness of 10 nm to 300 nm.

16. The article of claim 1 , wherein the photoactive layer comprises an electron donor material and an electron acceptor material.

17. The article of claim 16 , wherein the electron donor material comprises a polymer.

18. The article of claim 17 , wherein the polymer is selected from the group consisting of polythiophenes, polyanilines, polycarbazoles, polyvinylcarbazoles, polyphenylenes, polyphenylvinylenes, polysilanes, polythienylenevinylenes, polyisothianaphthanenes, polycyclopentadithiophenes, polysilacyclopentadithiophenes, polycyclopentadithiazoles, polythiazolothiazoles, polythiazoles, polybenzothiadiazoles, poly(thiophene oxide)s, poly(cyclopentadithiophene oxide)s, polythiadiazoloquinoxaline, polybenzoisothiazole, polybenzothiazole, polythienothiophene, poly(thienothiophene oxide), polydithienothiophene, poly(dithienothiophene oxide)s, polytetrahydroisoindoles, and copolymers thereof.

19. The article of claim 18 , wherein the electron donor material comprises a polymer selected from the group consisting of polythiophenes, polycyclopentadithiophenes, and copolymers thereof.

20. The article of claim 19 , wherein the electron donor material comprises poly(3-hexylthiophene) or poly(cyclopentadithiophene-co-benzothiadiazole).

21. The article of claim 16 , wherein the electron acceptor material comprises a material selected from the group consisting of fullerenes, inorganic nanoparticles, oxadiazoles, discotic liquid crystals, carbon nanorods, inorganic nanorods, polymers containing CN groups, polymers containing CF 3 groups, and combinations thereof.

22. The article of claim 21 , wherein the electron acceptor material comprises a substituted fullerene.

23. The article of claim 22 , wherein the substituted fullerene comprises PCBM.

24. An article, comprising:

a hole transport layer having first and second sides, the first side of the hole transport layer contacting an electrode, the second side of the hole transport layer contacting a photoactive layer, and the hole transport layer consisting of an ionic copolymer,

wherein the article is configured as a photovoltaic cell.

25. A system, comprising:

a plurality of photovoltaic cells according to claim 1 ,

wherein the plurality of photovoltaic cells are configured as a photovoltaic system.

26. The system of claim 25 , wherein at least some of the plurality of photovoltaic cells are electrically connected in series.

27. The system of claim 25 , wherein at least some of the plurality of photovoltaic cells are electrically connected in parallel.

28. A system, comprising:

a plurality of photovoltaic cells according to claim 24 ,

wherein the plurality of photovoltaic cells are configured as a photovoltaic system.

29. The system of claim 28 , wherein at least some of the plurality of photovoltaic cells are electrically connected in series.

30. The system of claim 28 , wherein at least some of the plurality of photovoltaic cells are electrically connected in parallel.