Polymers with low band gaps and high charge mobility
View Patent ↗This disclosure relates to a polymer containing a first comonomer repeat unit and a second comonomer repeat unit different from the first comonomer repeat unit. The first comonomer repeat unit includes a cyclopentadithiophene moiety. The polymer can be used as a photoactive material in a photovoltaic cell. This disclosure also relates to such photovoltaic cells, as well as modules containing such photovoltaic cells.
1. A photovoltaic cell, comprising:
a first electrode,
a second electrode, and
a photoactive material disposed between the first and second electrodes, the photoactive material comprising a polymer including a first comonomer repeat unit and a second comonomer repeat unit, the first comonomer repeat unit comprising a cyclopentadithiophene moiety of formula (I):
and the second comonomer repeat unit comprising a benzothiadiazole moiety of formula (II):
wherein each of R 1 and R 2 in formula (I), independently, is H, C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl; and each of R 1 and R 2 in formula (II), independently, is H, C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl.
2. The photovoltaic cell of claim 1 , wherein the cyclopentadithiophene moiety is substituted with at least one substituent selected from the group consisting of C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, and C 3 -C 20 heterocycloalkyl.
3. The photovoltaic cell of claim 2 , wherein the cyclopentadithiophene moiety is substituted with hexyl, 2-ethylhexyl, or 3,7-dimethyloctyl.
4. The photovoltaic cell of claim 1 , wherein each of R 1 and R 2 in formula (I), independently, is hexyl, 2-ethylhexyl, or 3,7-dimethyloctyl.
5. The photovoltaic cell of claim 1 , wherein each of R 1 and R 2 in formula (II) is H.
6. The photovoltaic cell of claim 1 , wherein the polymer comprises a moiety selected from the group consisting of:
7. The photovoltaic cell of claim 1 , wherein the polymer further comprises a third comonomer repeat unit, the third comonomer repeat unit comprising a thiophene moiety or a fluorene moiety.
8. The photovoltaic cell of claim 7 , wherein the thiophene or fluorene moiety is substituted with at least one substituent selected from the group consisting of C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, and C 3 -C 20 heterocycloalkyl.
9. The photovoltaic cell of claim 1 , wherein the photoactive material further comprises an electron acceptor material.
10. The photovoltaic cell of claim 9 , wherein the electron acceptor material comprises a fullerene.
11. The photovoltaic cell of claim 10 , wherein the electron acceptor material comprises PCBM.
12. The photovoltaic cell of claim 9 , wherein the polymer and the electron acceptor material each has a LUMO energy level, the LUMO energy level of the polymer is at least about 0.2 eV less negative than the LUMO energy level of the electron acceptor material.
13. A polymer, comprising:
a first comonomer repeat unit comprising a cyclopentadithiophene moiety of formula (I):
a second comonomer repeat unit comprising a benzothiadiazole moiety of formula (II):
wherein each of R 1 and R 2 in formula (I), independently, is H, C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl; and each of R 1 and R 2 in formula (II), independently, is H, C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl.
14. The polymer of claim 13 , wherein the cyclopentadithiophene moiety is substituted with at least one substituent selected from the group consisting of C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, and C 3 -C 20 heterocycloalkyl.
15. The polymer of claim 14 , wherein the cyclopentadithiophene moiety is substituted with hexyl, 2-ethylhexyl, or 3,7-dimethyloctyl.
16. The polymer of claim 13 , wherein each of R 1 and R 2 in formula (I), independently, is hexyl, 2-ethylhexyl, or 3,7-dimethyloctyl.
17. The polymer of claim 13 , wherein each of R 1 and R 2 in formula (II) is H.
18. The polymer of claim 13 , wherein the polymer comprises a moiety selected from the group consisting of:
19. The polymer of claim 13 , wherein the polymer further comprises a third comonomer repeat unit, the third comonomer repeat unit comprising a thiophene moiety or a fluorene moiety.
20. The polymer of claim 19 , wherein the thiophene or fluorene moiety is substituted with at least one substituent selected from the group consisting of C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, and C 3 -C 20 heterocycloalkyl.