TY - JOUR
T1 - Suppressing Defect Formation Pathways in the Direct C-H Arylation Polymerization of Photovoltaic Copolymers
AU - Aldrich, Thomas J.
AU - Dudnik, Alexander S.
AU - Eastham, Nicholas D.
AU - Manley, Eric F.
AU - Chen, Lin X.
AU - Chang, Robert P.H.
AU - Melkonyan, Ferdinand S.
AU - Facchetti, Antonio
AU - Marks, Tobin J.
N1 - Funding Information:
This research was supported in part by Argonne-Northwestern Solar Energy Research (ANSER) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award DE-SC0001059, by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences under Award DE-FG02-08ER46536, AFOSR Grant FA9550-18-1-0320, and the Northwestern University Materials Research Science and Engineering Center under NSF Grant DMR-1720139. A.S.D. thanks the Camille and Henry Dreyfus Postdoctoral Program in Environmental Chemistry for a fellowship, and T.J.A. thanks the NSF for a predoctoral fellowship. F.S.M. was supported by Award 70NANB14H012 from the U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design (CHiMaD). We thank the Integrated Molecular Structure Education and Research Center (IMSERC) for characterization facilities supported by Northwestern University, National Science Foundation (NSF) under NSF CHE-1048773, Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205), the State of Illinois, and International Institute for Nanotechnology (IIN). Use of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under Contract DE-AC02-06CH11357.
Publisher Copyright:
Copyright © 2018 American Chemical Society.
PY - 2018/11/27
Y1 - 2018/11/27
N2 - Direct C-H arylation polymerization (DARP) holds great promise for the green, atom-efficient synthesis of π-conjugated copolymers for use in high-performance polymer solar cells (PSCs). However, C-H arylation regioselectivity control for monomers containing multiple reactive aryl C-H bonds is not well understood, and nonselective reactivity results in material defects with unknown effects on PSC performance. Here, the effects of reaction conditions on copolymer molecular mass, dispersity, and PSC performance as well as defect formation pathways occurring during the DARP synthesis of an archetypal benzodithiophene-alt-diketopyrrolopyrrole copolymer, PBDTT-DPP, are scrutinized. Small molecule model studies analyzed by HPLC-HRMS elucidate the effects of DARP conditions on trace chemical defect (primarily hydrodehalogenation and β-C-H arylation) formation. Copolymer branching arising from nonselective β-C-H arylation of monomers at the polymer chain end is identified as the principal photovoltaically deleterious defect. Fine-tuning the DARP reaction conditions reduces branching densities to below 1%, with an exceptional C-H regioselectivity of >110:1. The optimal copolymers achieve superior PSC performance versus defect-rich DARP-derived copolymers and rival those from Stille polycondensations.
AB - Direct C-H arylation polymerization (DARP) holds great promise for the green, atom-efficient synthesis of π-conjugated copolymers for use in high-performance polymer solar cells (PSCs). However, C-H arylation regioselectivity control for monomers containing multiple reactive aryl C-H bonds is not well understood, and nonselective reactivity results in material defects with unknown effects on PSC performance. Here, the effects of reaction conditions on copolymer molecular mass, dispersity, and PSC performance as well as defect formation pathways occurring during the DARP synthesis of an archetypal benzodithiophene-alt-diketopyrrolopyrrole copolymer, PBDTT-DPP, are scrutinized. Small molecule model studies analyzed by HPLC-HRMS elucidate the effects of DARP conditions on trace chemical defect (primarily hydrodehalogenation and β-C-H arylation) formation. Copolymer branching arising from nonselective β-C-H arylation of monomers at the polymer chain end is identified as the principal photovoltaically deleterious defect. Fine-tuning the DARP reaction conditions reduces branching densities to below 1%, with an exceptional C-H regioselectivity of >110:1. The optimal copolymers achieve superior PSC performance versus defect-rich DARP-derived copolymers and rival those from Stille polycondensations.
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U2 - 10.1021/acs.macromol.8b02297
DO - 10.1021/acs.macromol.8b02297
M3 - Article
AN - SCOPUS:85056447480
VL - 51
SP - 9140
EP - 9155
JO - Macromolecules
JF - Macromolecules
SN - 0024-9297
IS - 22
ER -
