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Chlorination of Side Chains: A Strategy for Achieving a High Open Circuit Voltage Over 1.0 V in Benzo[1,2-b:4,5-b']dithiophene-Based Non-Fullerene Solar Cells

Journal Article · · ACS Applied Energy Materials
 [1];  [2];  [2];  [2];  [2];  [3];  [4];  [2]
  1. Southern Univ. of Science and Technology, Shenzhen (People's Republic of China); Peking Univ., Shenzhen (China)
  2. Southern Univ. of Science and Technology, Shenzhen (People's Republic of China)
  3. Peking Univ., Shenzhen (China)
  4. Argonne National Lab. (ANL), Lemont, IL (United States); The Univ. of Chicago, Chicago, IL (United States)
+ Show Author Affiliations

Here, a benzo[1,2-b:4,5-b']dithiophene-based donor material with chlorine atoms substituted on its side chains, named PBClT, was designed and developed for application in non-fullerene solar cells to enhance the open-circuit voltage (Voc) without decreasing charge carrier transfer in the corresponding blend films. The results demonstrated that the chlorinated PBClT polymer was an efficient donor in non-fullerene polymer solar cells (PSCs) and exhibited a blue-shifted absorbance, resulting in more complementary light absorption with non-fullerene acceptors, such as ITIC. In addition, the chlorine substitution decreased the HOMO level of PBClT, and as a result, the Voc of the corresponding solar cell increased dramatically to 1.01 V, which is much higher than that of the non-chlorine analog, PTB7-Th, with a Voc of approximately 0.82 V. The 2D-GIWAX results illustrated that the PBClT/ITIC blend film exhibited a “face-on” orientation, which suggested that the chlorine substituents on the side chains favored π-π stacking in the direction perpendicular to the electron flow in photovoltaic devices. Furthermore, the PBClT/ITIC blend film showed a π-π stacking distance of 3.85 Å, which was very close to that of its non-chlorine analog blend film with a distance of approximately 3.74 Å. Based on this result, the introduction of multiple chlorine atoms on the conjugated side chains not only adjusted the energy level of the low-band-gap polymer through the electron withdrawing ability of the chlorine atoms but also subtly avoided obvious morphological changes that could result from strong steric hindrance in the main chain of the polymers. The PBClT/ITIC-based PSCs exhibited a maximum PCE of 8.46% with a Voc of 1.01 V, which is an increase in the PCE of approximately 22% compared to the PTB7-Th-based device based on our parallel experiments.

Research Organization:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Organization:
National Natural Science Foundation of China; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
Grant/Contract Number:
AC02-06CH11357
OSTI ID:
1440758
Journal Information:
ACS Applied Energy Materials, Journal Name: ACS Applied Energy Materials Journal Issue: 5 Vol. 1; ISSN 2574-0962
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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Cited By (5)

Design Principles and Synergistic Effects of Chlorination on a Conjugated Backbone for Efficient Organic Photovoltaics: A Critical Review journal February 2020
A Benzo[1,2‐ b :4,5‐ c ′]Dithiophene‐4,8‐Dione‐Based Polymer Donor Achieving an Efficiency Over 16% journal January 2020
Effect of chlorination and fluorination of benzothiadiazole on the performance of polymer solar cells journal February 2020
Carbon–oxygen-bridged hexacyclic non-fullerene acceptors with chlorinated end groups journal January 2019
Halogenation on benzo[1,2- b :4,5- b ′]difuran polymers for solvent additive-free non-fullerene polymer solar cells with efficiency exceeding 11% journal January 2020

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Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
charge transfer
chlorination
high open circuit voltage
nonfullerene acceptor
polymer solar cells
side-chain engineering