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Title: Fine-Tuning Semiconducting Polymer Self-Aggregation and Crystallinity Enables Optimal Morphology and High-Performance Printed All-Polymer Solar Cells

Abstract

Polymer aggregation and crystallization behavior play a crucial role in the performance of all-polymer solar cells (all-PSCs). Gaining control over polymer self-assembly via molecular design to influence bulk-heterojunction active-layer morphology, however, remains challenging. Herein, we show a simple yet effective way to modulate the self-aggregation of the commonly used naphthalene diimide (NDI)-based acceptor polymer (N2200), by systematically replacing a certain amount of alkyl side-chains with compact bulky side-chains (CBS). Specifically, we have synthesized a series of random copolymer (PNDI-CBSx) with different molar fractions (x = 0–1) of the CBS units and have found that both solution-phase aggregation and solid-state crystallinity of these acceptor polymers are progressively suppressed with increasing x as evidenced by UV–vis absorption, photoluminescence (PL) spectroscopies, thermal analysis, and grazing incidence X-ray scattering (GIWAXS) techniques. Importantly, as compared to the highly self-aggregating N2200, photovoltaic results show that blending of more amorphous acceptor polymers with donor polymer (PBDB-T) can enable all-PSCs with significantly increased PCE (up to 8.5%). The higher short-circuit current density (Jsc) results from the smaller polymer phase-separation domain sizes as evidenced by PL quenching and resonant soft X-ray scattering (R-SoXS) analyses. Additionally, we show that the lower crystallinity of the active layer is less sensitive tomore » the film deposition methods. Thus, the transition from spin-coating to solution coating can be easily achieved with no performance losses. On the other hand, decreasing aggregation and crystallinity of the acceptor polymer too much reduces the photovoltaic performance as the donor phase-separation domain sizes increases. The highly amorphous acceptor polymers appear to induce formation of larger donor polymer crystallites. These results highlight the importance of a balanced aggregation strength between the donor and acceptor polymers to achieve high-performance all-PSCs with optimal active layer film morphology.« less

Authors:
ORCiD logo [1];  [2];  [1];  [3];  [3]; ORCiD logo [1]; ORCiD logo [3]; ORCiD logo [2]; ORCiD logo [1]
  1. Stanford Univ., CA (United States)
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
  3. South Dakota State Univ., Brookings, SD (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1605364
Grant/Contract Number:  
N00014-17-1-2214; AC02-76SF00515; ECCS-1542152; MRI-1428992; ED18DEN3030025
Resource Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 142; Journal Issue: 1; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Polymer morphology; Crystallinity; Aggregation; Scattering; Polymers

Citation Formats

Wu, Yilei, Schneider, Sebastian, Walter, Christopher, Chowdhury, Ashraful Haider, Bahrami, Behzad, Wu, Hung-Chin, Qiao, Qiquan, Toney, Michael F., and Bao, Zhenan. Fine-Tuning Semiconducting Polymer Self-Aggregation and Crystallinity Enables Optimal Morphology and High-Performance Printed All-Polymer Solar Cells. United States: N. p., 2019. Web. https://doi.org/10.1021/jacs.9b10935.
Wu, Yilei, Schneider, Sebastian, Walter, Christopher, Chowdhury, Ashraful Haider, Bahrami, Behzad, Wu, Hung-Chin, Qiao, Qiquan, Toney, Michael F., & Bao, Zhenan. Fine-Tuning Semiconducting Polymer Self-Aggregation and Crystallinity Enables Optimal Morphology and High-Performance Printed All-Polymer Solar Cells. United States. https://doi.org/10.1021/jacs.9b10935
Wu, Yilei, Schneider, Sebastian, Walter, Christopher, Chowdhury, Ashraful Haider, Bahrami, Behzad, Wu, Hung-Chin, Qiao, Qiquan, Toney, Michael F., and Bao, Zhenan. Tue . "Fine-Tuning Semiconducting Polymer Self-Aggregation and Crystallinity Enables Optimal Morphology and High-Performance Printed All-Polymer Solar Cells". United States. https://doi.org/10.1021/jacs.9b10935. https://www.osti.gov/servlets/purl/1605364.
@article{osti_1605364,
title = {Fine-Tuning Semiconducting Polymer Self-Aggregation and Crystallinity Enables Optimal Morphology and High-Performance Printed All-Polymer Solar Cells},
author = {Wu, Yilei and Schneider, Sebastian and Walter, Christopher and Chowdhury, Ashraful Haider and Bahrami, Behzad and Wu, Hung-Chin and Qiao, Qiquan and Toney, Michael F. and Bao, Zhenan},
abstractNote = {Polymer aggregation and crystallization behavior play a crucial role in the performance of all-polymer solar cells (all-PSCs). Gaining control over polymer self-assembly via molecular design to influence bulk-heterojunction active-layer morphology, however, remains challenging. Herein, we show a simple yet effective way to modulate the self-aggregation of the commonly used naphthalene diimide (NDI)-based acceptor polymer (N2200), by systematically replacing a certain amount of alkyl side-chains with compact bulky side-chains (CBS). Specifically, we have synthesized a series of random copolymer (PNDI-CBSx) with different molar fractions (x = 0–1) of the CBS units and have found that both solution-phase aggregation and solid-state crystallinity of these acceptor polymers are progressively suppressed with increasing x as evidenced by UV–vis absorption, photoluminescence (PL) spectroscopies, thermal analysis, and grazing incidence X-ray scattering (GIWAXS) techniques. Importantly, as compared to the highly self-aggregating N2200, photovoltaic results show that blending of more amorphous acceptor polymers with donor polymer (PBDB-T) can enable all-PSCs with significantly increased PCE (up to 8.5%). The higher short-circuit current density (Jsc) results from the smaller polymer phase-separation domain sizes as evidenced by PL quenching and resonant soft X-ray scattering (R-SoXS) analyses. Additionally, we show that the lower crystallinity of the active layer is less sensitive to the film deposition methods. Thus, the transition from spin-coating to solution coating can be easily achieved with no performance losses. On the other hand, decreasing aggregation and crystallinity of the acceptor polymer too much reduces the photovoltaic performance as the donor phase-separation domain sizes increases. The highly amorphous acceptor polymers appear to induce formation of larger donor polymer crystallites. These results highlight the importance of a balanced aggregation strength between the donor and acceptor polymers to achieve high-performance all-PSCs with optimal active layer film morphology.},
doi = {10.1021/jacs.9b10935},
journal = {Journal of the American Chemical Society},
number = 1,
volume = 142,
place = {United States},
year = {2019},
month = {12}
}

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