TY - JOUR
T1 - Closely packed, low reorganization energy π-extended postfullerene acceptors for efficient polymer solar cells
AU - Swick, Steven M.
AU - Zhu, Weigang
AU - Matta, Micaela
AU - Aldrich, Thomas J.
AU - Harbuzaru, Alexandra
AU - Navarrete, J. Teodomiro Lopez
AU - Ortiz, Rocio Ponce
AU - Kohlstedt, Kevin L.
AU - Schatz, George C.
AU - Facchetti, Antonio
AU - Melkonyan, Ferdinand
AU - Marks, Tobin J.
N1 - Funding Information:
We thank C. Stern and Dr. G. Wang for helpful discussions. This research was supported, in part, by the Argonne−Northwestern Solar Energy Research Center, an Energy Frontier Research Center funded by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences under Award DE-SC0001059. Research at University of Málaga was supported by Ministerio de Economia y Competitividad (Grant CTQ2015-66897-P). F.S.M. was supported by Award 70NANB14H012 from the US Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design. T.J.A. and S.M.S. thank the National Science Foundation (NSF) for predoctoral fellowships. This work made use of the Electron Probe Instrumentation Center, Keck-II, and/or Scanned Probe Imaging and Development facilities of Northwestern University’s Atomic and Nanoscale Characterization Experimental Center (NUANCE) which received support from the Soft and Hybrid Nanotechnology Experimental Resource (NSF Electrical, Communications, and Cyber Systems Award 1542205). Use of the Advanced Photon Source, an Office of Science User Facility operated for the US DOE Office of Science by Argonne National Laboratory, was supported by the US DOE under Contract DE-AC02-06CH11357.
Funding Information:
ACKNOWLEDGMENTS. We thank C. Stern and Dr. G. Wang for helpful discussions. This research was supported, in part, by the Argonne−Northwestern Solar Energy Research Center, an Energy Frontier Research Center funded by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences under Award DE-SC0001059. Research at University of Málaga was supported by Ministerio de Economia y Competitividad (Grant CTQ2015-66897-P). F.S.M. was supported by Award 70NANB14H012 from the US Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design. T.J.A. and S.M.S. thank the National Science Foundation (NSF) for predoctoral fellowships. This work made use of the Electron Probe Instrumentation Center, Keck-II, and/or Scanned Probe Imaging and Development facilities of Northwestern University’s Atomic and Nanoscale Characterization Experimental Center (NUANCE) which received support from the Soft and Hybrid Nanotechnology Experimental Resource (NSF Electrical, Communications, and Cyber Systems Award 1542205). Use of the Advanced Photon Source, an Office of Science User Facility operated for the US DOE Office of Science by Argonne National Laboratory, was supported by the US DOE under Contract DE-AC02-06CH11357.
Publisher Copyright:
© 2018 National Academy of Sciences. All Rights Reserved.
PY - 2018/9/4
Y1 - 2018/9/4
N2 - New organic semiconductors are essential for developing inexpensive, high-efficiency, solution-processable polymer solar cells (PSCs). PSC photoactive layers are typically fabricated by film-casting a donor polymer and a fullerene acceptor blend, with ensuing solvent evaporation and phase separation creating discrete conduits for photogenerated holes and electrons. Until recently, n-type fullerene acceptors dominated the PSC literature; however, indacenodithienothiophene (IDTT)-based acceptors have recently enabled remarkable PSC performance metrics, for reasons that are not entirely obvious. We report two isomeric IDTT-based acceptors 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-benz-(5, 6)indanone))-5,5,11,11-tetrakis(4-nonylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]di-thiophene (ITN-C9) and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-benz(6,7)indanone))-5,5,11,11-tetrakis (4-nonylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithio-phene (ITzN-C9) that shed light on the exceptional IDTT properties vis-à-vis fullerenes. The neat acceptors and blends with fluoropolymer donor poly{[4,8-bis[5-(2- ethylhexyl)-4-fluoro-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene2,6-diyl]-alt-[2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo4H,8H-benzo[1,2-c:4,5-c′]dithiophene-1,3-diyl]]} (PBDB-TF) are investigated by optical spectroscopy, cyclic voltammetry, thermogravimetric analysis, differential scanning calorimetry, single-crystal X-ray diffraction, photovoltaic response, space-charge-limited current transport, atomic force microscopy, grazing incidence wide-angle X-ray scattering, and density functional theory-level quantum chemical analysis. The data reveal that ITN-C9 and ITzN-C9 organize such that the lowest unoccupied molecular orbital-rich end groups have intermolecular π−π distances as close as 3.31(1) Å, with electronic coupling integrals as large as 38 meV, and internal reorganization energies as small as 0.133 eV, comparable to or superior to those in fullerenes. ITN-C9 and ITzN-C9 have broad solar-relevant optical absorption, and, when blended with PBDB-TF, afford devices with power conversion efficiencies near 10%. Performance differences between ITN-C9 and ITzN-C9 are understandable in terms of molecular and electronic structure distinctions via the influences on molecular packing and orientation with respect to the electrode.
AB - New organic semiconductors are essential for developing inexpensive, high-efficiency, solution-processable polymer solar cells (PSCs). PSC photoactive layers are typically fabricated by film-casting a donor polymer and a fullerene acceptor blend, with ensuing solvent evaporation and phase separation creating discrete conduits for photogenerated holes and electrons. Until recently, n-type fullerene acceptors dominated the PSC literature; however, indacenodithienothiophene (IDTT)-based acceptors have recently enabled remarkable PSC performance metrics, for reasons that are not entirely obvious. We report two isomeric IDTT-based acceptors 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-benz-(5, 6)indanone))-5,5,11,11-tetrakis(4-nonylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]di-thiophene (ITN-C9) and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-benz(6,7)indanone))-5,5,11,11-tetrakis (4-nonylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithio-phene (ITzN-C9) that shed light on the exceptional IDTT properties vis-à-vis fullerenes. The neat acceptors and blends with fluoropolymer donor poly{[4,8-bis[5-(2- ethylhexyl)-4-fluoro-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene2,6-diyl]-alt-[2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo4H,8H-benzo[1,2-c:4,5-c′]dithiophene-1,3-diyl]]} (PBDB-TF) are investigated by optical spectroscopy, cyclic voltammetry, thermogravimetric analysis, differential scanning calorimetry, single-crystal X-ray diffraction, photovoltaic response, space-charge-limited current transport, atomic force microscopy, grazing incidence wide-angle X-ray scattering, and density functional theory-level quantum chemical analysis. The data reveal that ITN-C9 and ITzN-C9 organize such that the lowest unoccupied molecular orbital-rich end groups have intermolecular π−π distances as close as 3.31(1) Å, with electronic coupling integrals as large as 38 meV, and internal reorganization energies as small as 0.133 eV, comparable to or superior to those in fullerenes. ITN-C9 and ITzN-C9 have broad solar-relevant optical absorption, and, when blended with PBDB-TF, afford devices with power conversion efficiencies near 10%. Performance differences between ITN-C9 and ITzN-C9 are understandable in terms of molecular and electronic structure distinctions via the influences on molecular packing and orientation with respect to the electrode.
KW - Molecular modeling
KW - Or anic hotovoltaic
KW - Single crystal
KW - Small molecule acceptor
KW - Solar energy
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U2 - 10.1073/pnas.1807535115
DO - 10.1073/pnas.1807535115
M3 - Article
C2 - 30127011
AN - SCOPUS:85052755337
VL - 115
SP - E8341-E8348
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 36
ER -