Title: 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

Abstract

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 (V_oc) 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 V_oc 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 V_oc 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 atomsmore » 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 V_oc 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.« less

Authors:

Chao, Pengjie ^[1]; Mu, Zhao ^[2]; Wang, Huan ^[2]; Mo, Daize ^[2]; Chen, Hui ^[2]; Meng, Hong  ^[3];

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Chen, Wei  ^[4];

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He, Feng  ^[2]

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+ Show Author Affiliations

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)

Publication Date:

2018-04-23

Research Org.:

Argonne National Lab. (ANL), Argonne, IL (United States)

Sponsoring Org.:

National Natural Science Foundation of China (NSFC); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division

OSTI Identifier:

1440758

Grant/Contract Number:  

AC02-06CH11357

Resource Type:

Accepted Manuscript

Journal Name:

ACS Applied Energy Materials

Additional Journal Information:

Journal Volume: 1; Journal Issue: 5; Journal ID: ISSN 2574-0962

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

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