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Title: A Wide Band Gap Polymer with a Deep Highest Occupied Molecular Orbital Level Enables 14.2% Efficiency in Polymer Solar Cells

Abstract

To simultaneously achieve low photon energy loss ( E loss) and broad spectral response, the molecular design of the wide band gap (WBG) donor polymer with a deep HOMO level is of critical importance in fullerene-free polymer solar cells (PSCs). Herein, we developed a new benzodithiophene unit, i.e., DTBDT-EF, and conducted systematic investigations on a WBG DTBDT-EF-based donor polymer, namely, PDTB-EF-T. Due to the synergistic electron-withdrawing effect of the fluorine atom and ester group, PDTB-EF-T exhibits a higher oxidation potential, i.e., a deeper HOMO level (ca. –5.5 eV) than most well-known donor polymers. Hence, a high open-circuit voltage of 0.90 V was obtained when paired with a fluorinated small molecule acceptor (IT-4F), corresponding to a low E loss of 0.62 eV. Furthermore, side-chain engineering demonstrated that subtle side-chain modulation of the ester greatly influences the aggregation effects and molecular packing of polymer PDTB-EF-T. With the benefits of the stronger interchain π–π interaction, the improved ordering structure, and thus the highest hole mobility, the most symmetric charge transport and reduced recombination are achieved for the linear decyl-substituted PDTB-EF-T (P2)-based PSCs, leading to the highest short-circuit current density and fill factor (FF). Due to the high Flory–Huggins interaction parameter (χ), surface-directed phasemore » separation occurs in the P2:IT-4F blend, which is supported by X-ray photoemission spectroscopy results and cross-sectional transmission electron microscope images. By taking advantage of the vertical phase distribution of the P2:IT-4F blend, a high power conversion efficiency (PCE) of 14.2% with an outstanding FF of 0.76 was recorded for inverted devices. Lastly, these results demonstrate the great potential of the DTBDT-EF unit for future organic photovoltaic applications.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [1];  [3];  [1];  [4];  [1];  [2]; ORCiD logo [1]
  1. Chinese Academy of Sciences (CAS), Beijing (China); Univ. of Chinese Academy of Sciences, Beijing (People's Republic of China)
  2. North Carolina State Univ., Raleigh, NC (United States)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  4. Chinese Academy of Sciences (CAS), Beijing (China)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1470933
Grant/Contract Number:  
[AC02-76SF00515; 2014CB643501; N00141512322; N000141712204; CAS14601; 51673201; 91633301; XDB12030200; KJZD-EW-J01]
Resource Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
[ Journal Volume: 140; Journal Issue: 23]; 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

Citation Formats

Li, Sunsun, Ye, Long, Zhao, Wenchao, Yan, Hongping, Yang, Bei, Liu, Delong, Li, Wanning, Ade, Harald, and Hou, Jianhui. A Wide Band Gap Polymer with a Deep Highest Occupied Molecular Orbital Level Enables 14.2% Efficiency in Polymer Solar Cells. United States: N. p., 2018. Web. doi:10.1021/jacs.8b02695.
Li, Sunsun, Ye, Long, Zhao, Wenchao, Yan, Hongping, Yang, Bei, Liu, Delong, Li, Wanning, Ade, Harald, & Hou, Jianhui. A Wide Band Gap Polymer with a Deep Highest Occupied Molecular Orbital Level Enables 14.2% Efficiency in Polymer Solar Cells. United States. doi:10.1021/jacs.8b02695.
Li, Sunsun, Ye, Long, Zhao, Wenchao, Yan, Hongping, Yang, Bei, Liu, Delong, Li, Wanning, Ade, Harald, and Hou, Jianhui. Tue . "A Wide Band Gap Polymer with a Deep Highest Occupied Molecular Orbital Level Enables 14.2% Efficiency in Polymer Solar Cells". United States. doi:10.1021/jacs.8b02695. https://www.osti.gov/servlets/purl/1470933.
@article{osti_1470933,
title = {A Wide Band Gap Polymer with a Deep Highest Occupied Molecular Orbital Level Enables 14.2% Efficiency in Polymer Solar Cells},
author = {Li, Sunsun and Ye, Long and Zhao, Wenchao and Yan, Hongping and Yang, Bei and Liu, Delong and Li, Wanning and Ade, Harald and Hou, Jianhui},
abstractNote = {To simultaneously achieve low photon energy loss (Eloss) and broad spectral response, the molecular design of the wide band gap (WBG) donor polymer with a deep HOMO level is of critical importance in fullerene-free polymer solar cells (PSCs). Herein, we developed a new benzodithiophene unit, i.e., DTBDT-EF, and conducted systematic investigations on a WBG DTBDT-EF-based donor polymer, namely, PDTB-EF-T. Due to the synergistic electron-withdrawing effect of the fluorine atom and ester group, PDTB-EF-T exhibits a higher oxidation potential, i.e., a deeper HOMO level (ca. –5.5 eV) than most well-known donor polymers. Hence, a high open-circuit voltage of 0.90 V was obtained when paired with a fluorinated small molecule acceptor (IT-4F), corresponding to a low Eloss of 0.62 eV. Furthermore, side-chain engineering demonstrated that subtle side-chain modulation of the ester greatly influences the aggregation effects and molecular packing of polymer PDTB-EF-T. With the benefits of the stronger interchain π–π interaction, the improved ordering structure, and thus the highest hole mobility, the most symmetric charge transport and reduced recombination are achieved for the linear decyl-substituted PDTB-EF-T (P2)-based PSCs, leading to the highest short-circuit current density and fill factor (FF). Due to the high Flory–Huggins interaction parameter (χ), surface-directed phase separation occurs in the P2:IT-4F blend, which is supported by X-ray photoemission spectroscopy results and cross-sectional transmission electron microscope images. By taking advantage of the vertical phase distribution of the P2:IT-4F blend, a high power conversion efficiency (PCE) of 14.2% with an outstanding FF of 0.76 was recorded for inverted devices. Lastly, these results demonstrate the great potential of the DTBDT-EF unit for future organic photovoltaic applications.},
doi = {10.1021/jacs.8b02695},
journal = {Journal of the American Chemical Society},
number = [23],
volume = [140],
place = {United States},
year = {2018},
month = {5}
}

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Cited by: 246 works
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Figures / Tables:

Figure 1 Figure 1: (a) Schematic energy-level diagrams of PDTB-EF-T polymer derivatives and IT-4F. (b) Normalized UV-vis absorption spectra of PDTB-EF-T polymer derivatives and IT-4F in the solid film state. (c) Normalized absorption spectra of three polymers in diluted CB at 20°C, and (d) the redshift of λmax with decreasing temperature

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Works referencing / citing this record:

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