Star-Shaped Fused-Ring Electron Acceptors with a C3 h-Symmetric and Electron-Rich Benzotri(cyclopentadithiophene) Core for Efficient Nonfullerene Organic Solar Cells

Xiaofu Wu; Weijie Wang; Hao Hang; Hua Li; Yonghong Chen; Qian Xu; Hui Tong; Lixiang Wang

doi:10.1021/acsami.9b08017

Star-Shaped Fused-Ring Electron Acceptors with a C_{3 h}-Symmetric and Electron-Rich Benzotri(cyclopentadithiophene) Core for Efficient Nonfullerene Organic Solar Cells

ACS Appl Mater Interfaces. 2019 Aug 7;11(31):28115-28124. doi: 10.1021/acsami.9b08017. Epub 2019 Jul 24.

Authors

Xiaofu Wu¹, Weijie Wang^{1

2}, Hao Hang^{1

3}, Hua Li^{1

2}, Yonghong Chen^{1

3}, Qian Xu⁴, Hui Tong^{1

2}, Lixiang Wang^{1

2}

Affiliations

¹ State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry , Chinese Academy of Sciences , Changchun 130022 , P. R. China.
² University of Science and Technology of China , Hefei 230026 , PR China.
³ University of Chinese Academy of Sciences , Beijing 100039 , P. R. China.
⁴ School of Chemistry and Environmental Engineering , Changchun University of Science and Technology , Changchun 130022 , P. R. China.

PMID: 31296002
DOI: 10.1021/acsami.9b08017

Abstract

Classical fused-ring electron acceptors (FREAs) with a linear acceptor-donor-acceptor (A-D-A) architecture continuously break records of power conversion efficiency (PCE) in nonfullerene organic solar cells. In contrast, the development of star-shaped FREAs still lags behind. Herein, a new C_3h-symmetric and electron-rich core, benzotri(cyclopentadithiophene) (BTCDT) in which the central benzo[1,2-b:3,4-b':5,6-b″]trithiophene fused with three outer thiophenes via three cyclopentadienyl rings, is synthesized and used for the construction of star-shaped FREAs (BTCDT-IC and BTCDT-ICF). Owing to the strong electron-donating ability of the BTCDT unit, both acceptors exhibit the effective intramolecular charge transfer, leading to the strong absorption in the region of 500-800 nm with narrow band gaps below 1.70 eV as well as suitable highest occupied molecular orbital and lowest unoccupied molecular orbital levels. Compared with nonfluorinated BTCDT-IC, fluorinated BTCDT-ICF red-shifts the absorption peak to 688 nm and reduces the band gap to 1.62 eV, which induces a broader external quantum efficiency (EQE) response ranging from 300 to 800 nm and a higher maximum EQE of 70% while blending with a wide band gap polymer donor J61. The J61:the BTCDT-ICF blend film exhibits more suitable phase morphology compared with the J61:BTCDT-IC blend film, which is responsible for the enhanced EQE value, increased short-circuit current density (J_SC), and fill factor (FF) in organic solar cell devices. As a result, the J61:BTCDT-ICF-based device yields a best PCE of 8.11% with a high J_SC of 16.93 mA cm^-2 and a high FF of 65.6%, demonstrating that the BTCDT-based star-shaped FREAs hold great potential for nonfullerene organic solar cells.

Keywords: -symmetry; benzotri(cyclopentadithiophene); donor−acceptor; nonfullerene organic solar cells; star-shaped fused-ring electron acceptors.