Conjugated polymer zwitterions and solar cells comprising conjugated polymer zwitterions

1. A conjugated polymer zwitterion comprising repeating units having structure (I), (II), or a combination thereof,

wherein

Ar is independently at each occurrence a divalent substituted or unsubstituted C 3-30 arylene or heteroarylene group;

L is independently at each occurrence a divalent C 1-16 alkylene group, C 6-30 arylene or heteroarylene group, or alkylene oxide group; and

R 1 is independently at each occurrence a zwitterion having the structure -A-B-X;

wherein

A is a center of permanent positive charge or a center of permanent negative charge;

B is a divalent group comprising a C 1-12 alkylene group, a C 6-30 arylene or heteroarylene group, or an alkylene oxide group; and

X is a center of permanent positive charge or a center of permanent negative charge, provided that the zwitterion has an overall net charge of zero.

2. The conjugated polymer zwitterion of claim 1 , wherein each occurrence of L is a hexamethylene group.

3. The conjugated polymer zwitterion of claim 1 , wherein each occurrence of R 1 is a sulfobetaine zwitterion having the structure

wherein

R 2 is independently at each occurrence a substituted or unsubstituted C 1-12 alkyl group; and

p is independently at each occurrence an integer from 1 to 12.

4. The conjugated polymer zwitterion of claim 3 , wherein

each occurrence of R 2 is methyl; and

p is 3.

5. The conjugated polymer zwitterion of claim 1 , wherein Ar is independently at each occurrence

or a combination thereof, wherein y is 1, 2, 3, or 4.

6. The conjugated polymer zwitterion of claim 1 , wherein the conjugated polymer zwitterion has a number average molecular weight of about 1,000 to about 100,000 Daltons.

7. The conjugated polymer zwitterion of claim 1 , further comprising repeating units derived from thiophene, benzothiadiazole, fluorene, isoindigo, benzene, carbazole, thienothiophene, benzodithiophene, quinoxaline, or a combination thereof.

8. The conjugated polymer zwitterion of claim 1 ,

wherein

the conjugated polymer zwitterion comprises repeating units having structure (I)

each occurrence of L is a divalent hexamethylene group;

each occurrence of R 1 is a sulfobetaine zwitterion having the structure

wherein

each occurrence of R 2 is methyl; and

p is 3;

each occurrence of Ar is a divalent heteroarylene group having the structure

 and

the conjugated polymer zwitterion has a number average molecular weight of about 10,000 to about 50,000 Daltons.

9. The conjugated polymer zwitterion of claim 1 ,

wherein

the conjugated polymer zwitterion comprises repeating units having structure (II)

each occurrence of L is a divalent hexamethylene group;

each occurrence of R 1 is a sulfobetaine zwitterion having the structure

wherein

each occurrence of R 2 is methyl; and

p is 3; and

Ar is a divalent heteroarylene group having the structure

wherein y is 2; and

the conjugated polymer zwitterion has a number average molecular weight of about 10,000 to about 50,000 Daltons.

10. A polymer solar cell comprising the conjugated polymer zwitterion of claim 1 .

11. The polymer solar cell of claim 10 , comprising

an anode substrate;

a photoactive layer;

a metal cathode layer; and

an interlayer disposed between the photoactive layer and the metal cathode layer;

wherein the interlayer comprises the conjugated polymer zwitterion of claim 1 .

12. The polymer solar cell of claim 11 , wherein the interlayer has a thickness of about 1 to about 100 nanometers.

13. The polymer solar cell of claim 11 , wherein the metal cathode layer comprises silver.

14. The polymer solar cell of claim 11 , wherein the anode substrate comprises indium tin oxide.

15. The polymer solar cell of claim 11 , wherein the photoactive layer comprises an electron-donating material and an electron-accepting material.

16. The polymer solar cell of claim 15 , wherein

the electron-donating material comprises poly(3-hexylthiophene), poly(p-phenylenevinylene), poly[2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene vinylene], poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene), poly(2,7-(9-(2′-ethylhexyl)-9-hexyl-fluorene)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)), poly(2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta(2,1-b;3,4-b′)dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)), poly(p-phenylene-ethynylene)-alt-poly(p-phenylene-vinylene), poly((2,7-(9-(2′-ethylhexyl)-9-hexyl-fluorene)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole))-co-(2,7-(9-(2′-ethylhexyl)-9-hexyl-fluorene)-alt-2,5-thiophene)), poly(4,8-bis-alkyloxybenzo(1,2-b:4,5-b′)dithiophene-2,6-diyl-alt-(alkylthieno(3,4-b)thiophene-2-(2-ethyl-1-hexanone)-2,6-diyl)), poly(4,8-bis-alkyloxybenzo(1,2-b:4,5-b′)dithiophene-2,6-diyl-alt-(thieno(3,4-b)thiophene-2-carboxylate)-2,6-diyl), poly(N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)), 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], poly [(4,4′-bis(2-ethylhexyl)dithienol [3,2-b:2′,3′-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4, 7-diyl], or a combination thereof; and

the electron accepting material comprises (6,6)-phenyl-C 71 butyric acid methyl ester, (6,6)-phenyl-C 61 butyric acid methyl ester, or a combination thereof.

17. The polymer solar cell of claim 11 , further comprising a hole transport layer disposed between the anode substrate and the photoactive layer.

18. The polymer solar cell of claim 17 , wherein the hole transport layer comprises poly(ethylenedioxythiophene) and polystyrene sulfonate.

19. The polymer solar cell of claim 11 , wherein

the anode substrate comprises indium tin oxide;

the photoactive layer comprises poly(4,8-bis-alkyloxybenzo(1,2-b :4,5-b′)dithiophene-2,6-diyl-alt-(alkylthieno(3,4-b)thiophene-2-(2-ethyl-1-hexanone)-2,6-diyl) and (6,6)-phenyl-C 71 butyric acid methyl ester;

the cathode metal layer comprises silver; and

the interlayer comprises the conjugated polymer zwitterion comprising repeating units having the structure (I)

20. The polymer solar cell of claim 11 , wherein

the anode substrate comprises indium tin oxide;

the photoactive layer comprises poly(4,8-bis-alkyloxybenzo(1,2-b :4,5-b′) dithiophene-2,6-diyl-alt-(alkylthieno(3,4-b)thiophene-2-(2-ethyl-1-hexanone)-2,6-diyl) and (6,6)-phenyl-C 71 butyric acid methyl ester;

the cathode metal layer comprises silver; and

the interlayer comprises the conjugated polymer zwitterion comprising repeating units having the structure (II)