TY - JOUR
T1 - Solution Aggregate Structures of Donor Polymers Determine the Morphology and Processing Resiliency of Non-Fullerene Organic Solar Cells
AU - Khasbaatar, Azzaya
AU - Cheng, Andrew
AU - Jones, Austin L.
AU - Kwok, Justin J.
AU - Park, Sang Kyu
AU - Komar, Jessica K.
AU - Lin, Oliver
AU - Jackson, Nicholas E.
AU - Chen, Qian
AU - DeLongchamp, Dean M.
AU - Reynolds, John R.
AU - Diao, Ying
N1 - This work was primarily supported by the Office of Naval Research under grant numbers N00014-19-1-2146 (Y.D.), N00014-22-1-2202 (Y.D.), N00014-21-1-2087 (J.R.R), and N00014-22-1-2185 (J.R.R). A.K. acknowledges the Parr fellowship and 3 M Corporate fellowship. J.J.K. and Y.D. acknowledge support by the NSF CAREER award under Grant No. 18-47828. O.L. and Q.C. acknowledge support from Air Force Office of Scientific Research grant AFOSR FA9550-20-1-0257. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility, operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357 and the Advanced Light Source, a U.S. DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. The research also used facilities of the Materials Research Laboratory Central Research Facilities, University of Illinois. Extraordinary facility operations were supported in part by the DOE Office of Science through the National Virtual Biotechnology Laboratory, a consortium of DOE national laboratories focused on the response to COVID-19, with funding provided by the Coronavirus CARES Act. The authors thank beamline scientists Joseph W. Strazalka of the Advanced Photon Source (Beamline 8-ID-E), Argonne National Laboratory, Cheng Wang of the Advanced Light Source (Beamline 11.0.1.2), Eliot Gann of the National Institute of Standards and Technology, and Xiaobin Zuo for facilitating the GIWAXS, RSoXS, NEXAFS, and SAXS measurements, respectively. We are also grateful to the Diao group members Kyung Sun Park for training on freeze-drying experiments and providing helpful discussions on analyzing GIWAXS results and Jong-Hoon Lee for assistance in troubleshooting device measurements. The authors also appreciate Peter J. Dudenas and Bijal Patel from the National Institute of Standards and Technology for the helpful discussions related to RSoXS analysis.
PY - 2023/4/11
Y1 - 2023/4/11
N2 - The solution-state aggregation of conjugated polymers is critical to the morphology and device performance of bulk heterojunction (BHJ) organic solar cells (OSCs). However, the detailed structures of polymer solution-state aggregates and their impact on the morphology and device performance of OSCs remain largely unexplored. Herein, we utilize a benzodithiophene-based donor polymer (PM7) and its ester-functionalized derivatives (PM7 D1 and D2) with reduced backbone rigidity as our model systems to demonstrate how a polymer solution-state aggregate structure impacts the morphology and processing resiliency of OSCs. Using X-ray scattering and microscopic imaging techniques, we ascertain that PM7 solution forms a combination of semi-crystalline fiber aggregates and amorphous polymer chain network aggregates, whereas PM7 D1 and D2 solutions primarily form amorphous network aggregates through sidechain associations. Interestingly, when the solution temperature is increased, the fiber aggregates of PM7 break down while the polymer network aggregates remain stable. Due to this temperature-dependent behavior of the fiber aggregates, blade-coated devices fabricated from the PM7 donor polymer and non-fullerene acceptor, ITIC-4F, lead to highly processing temperature-sensitive performance, whereas PM7 D1 and D2 polymers exhibit improved processing temperature resiliency. More importantly, we report that amorphous, network-like aggregates are conducive to superior device performance in blade-coated OSCs owing to the formation of blend films with short π-π stacking distance, small domain spacing, and face-on preferred molecular orientation. In contrast, we find that fiber-like aggregates lead to large π-π stacking distance, large domain spacing, and isotropic molecular orientation in the blend film, which deteriorate the device performance.
AB - The solution-state aggregation of conjugated polymers is critical to the morphology and device performance of bulk heterojunction (BHJ) organic solar cells (OSCs). However, the detailed structures of polymer solution-state aggregates and their impact on the morphology and device performance of OSCs remain largely unexplored. Herein, we utilize a benzodithiophene-based donor polymer (PM7) and its ester-functionalized derivatives (PM7 D1 and D2) with reduced backbone rigidity as our model systems to demonstrate how a polymer solution-state aggregate structure impacts the morphology and processing resiliency of OSCs. Using X-ray scattering and microscopic imaging techniques, we ascertain that PM7 solution forms a combination of semi-crystalline fiber aggregates and amorphous polymer chain network aggregates, whereas PM7 D1 and D2 solutions primarily form amorphous network aggregates through sidechain associations. Interestingly, when the solution temperature is increased, the fiber aggregates of PM7 break down while the polymer network aggregates remain stable. Due to this temperature-dependent behavior of the fiber aggregates, blade-coated devices fabricated from the PM7 donor polymer and non-fullerene acceptor, ITIC-4F, lead to highly processing temperature-sensitive performance, whereas PM7 D1 and D2 polymers exhibit improved processing temperature resiliency. More importantly, we report that amorphous, network-like aggregates are conducive to superior device performance in blade-coated OSCs owing to the formation of blend films with short π-π stacking distance, small domain spacing, and face-on preferred molecular orientation. In contrast, we find that fiber-like aggregates lead to large π-π stacking distance, large domain spacing, and isotropic molecular orientation in the blend film, which deteriorate the device performance.
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U2 - 10.1021/acs.chemmater.2c02141
DO - 10.1021/acs.chemmater.2c02141
M3 - Article
AN - SCOPUS:85151388557
SN - 0897-4756
VL - 35
SP - 2713
EP - 2729
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 7
ER -