Enhancing Polymer Photovoltaic Performance via Optimized Intramolecular Ester-Based Noncovalent Sulfur···Oxygen Interactions

Year: 2018

Type: article

Abstract: Head-to-head (HH) bithiophenes are typically avoided in polymer semiconductors since they engender undesirable steric repulsions, leading to a twisted backbone. While introducing electron-donating alkoxy chains can lead to intramolecular noncovalent S···O interactions, this comes at the cost of elevating the HOMOs and compromising polymer solar cell (PSC) performance. To address the limitation, a novel HH bithiophene featuring an electron-withdrawing ester functionality, 3-alkoxycarbonyl-3′-alkoxy-2,2′-bithiophene (TETOR), is synthesized. Single crystal diffraction reveals a planar TETOR conformation (versus highly twisted diester bithiophene), showing distinctive advantages of incorporating alkoxy on promoting backbone planarity. Compared to first-generation 3-alkyl-3′-alkoxy-2,2′-bithiophene (TRTOR), TETOR contains an additional planarizing (thienyl)S···O(carbonyl) interaction. Consequently, TETOR-based polymer (TffBT-TETOR) has greatly lower-lying FMOs, stronger aggregation, closer π-stacking, and better miscibility with fullerenes versus the TRTOR-based counterpart (TffBT-TRTOR). These characteristics are attributed to the additional S···O interaction and electron-withdrawing ester substituent, which enhances backbone planarity, charge transport, and PSC performance. Thus, TffBT-TETOR-based PSCs exhibit an increased PCE of 10.08%, a larger V oc of 0.76 V, and a higher J sc of 18.30 mA cm –2 than the TffBT-TRTOR-based PSCs. These results demonstrate that optimizing intramolecular noncovalent S···O interactions by incorporating electron-withdrawing ester groups is a powerful strategy for materials invention in organic electronics.

Source: Macromolecules

DOI: 10.1021/acs.macromol.8b00161

Authors: Jianhua Chen, Qiaogan Liao, Gang Wang, Zhenglong Yan, Hang Wang, Yulun Wang, Xianhe Zhang, Yumin Tang, Antonio Facchetti, Tobin J. Marks, Xugang Guo

Institutions: Nankai University, Southern University of Science and Technology, State Key Laboratory of Medicinal Chemical Biology, Northwestern University

Language: English

Topic: Organic Electronics and Photovoltaics

Subfield: Electrical and Electronic Engineering

Field: Engineering

Domain: Physical Sciences

SDG: Affordable and clean energy

Open Access status: green

Funders: U.S. Department of Energy, Northwestern University, National Natural Science Foundation of China, Natural Science Foundation of Guangdong Province, South University of Science and Technology of China, University of Science and Technology of China, Office of Science, Shenzhen Peacock Plan, Basic Energy Sciences, Air Force Office of Scientific Research, Argonne National Laboratory

OpenAlex ID: W2801418252