Influence of the terminal group on optoelectronic properties of fused-ring nonfullerene acceptors with ethylhexyl side chain. (October 2021)

• Record Type: Journal Article
• Authors: Zhang, Qian; Adil, Muhammad Abdullah; Wang, Zhongke; Zhao, Guangtao; Wang, Tao; Jiang, Ruibin; Zhang, Jianqi; Wang, Qiang
• Is Part Of: Dyes and pigments. Volume 194(2021)
• Publication Date: 2021-10
• Subjects: Organic solar cell -- Nonfullerene acceptor -- Side chain -- Power conversion efficiency; Dyes and dyeing -- Periodicals; Pigments -- Periodicals; 667.2
• DOI: 10.1016/j.dyepig.2021.109635
• Languages: English
• ISSNs: 0143-7208

Abstract

Abstract: Three fused-ring nonfullerene electron acceptors are designed and synthesized by combining side chain effect and terminal group modification. The 2-ethylhexyl substituent is employed to replace the commonly used n-hexyl or n -hexylphenyl side chains. Three acceptor units, 2-(3-oxo-2, 3-dihydroinden-1-ylidene) malononitrile (IC), 2-(6-oxo-5, 6-dihydro-4H-cyclopenta [ c ]thiophen-4-ylidene) malononitrile (CPTCN), and 2-(5, 6-dichloro-3-oxo-2, 3-dihydro-1 H -inden-1-ylidene)malononitrile (IC–2Cl) are used as the terminal groups and the three fused-ring nonfullerene acceptors, IDTC8 -IC, IDTC8 -Th, and IDTC8 -4Cl are developed, respectively. The thermal, photophysical, electrochemical and photovoltaic properties of the three acceptors are systematically studied in view of the influence of the side chain and the terminal group. The three acceptors exhibit strong absorption ranging from 500 nm to 720 nm in solution with high molar extinction coefficients. The large bandgap polymer PM6 is chosen as the donor to blend with the acceptors, due to the complementary absorption bands and well-matched energy levels. The optimized organic solar cell based on PM6:IDTC8 -IC exhibits a power conversion efficiency (PCE) of 8.56% with an open-circuit voltage ( V OC ) of 0.98 V, a short-circuit current density ( J SC ) of 13.93 mA cm −2, and a fill factor (FF) of 62.42%. The PM6:IDTC8-4Cl device demonstrates the best performance with a PCE of 9.79%, a V OC of 0.82 V, a J SC of 17.40 mA cm −2, and a FF of 68.67%. The impacts of carrier mobility, film morphology, and molecular packing properties of the blend films on photovoltaic performances are systematically investigated. The results imply that the synergistic effect of alkyl chains on the central core and modification of the terminal groups yields improved photovoltaic performance of nonfullerene acceptors. Highlights: Three fused-ring small-molecule electron acceptors with different terminal groups are developed. A high power conversion efficiency of 9.79% is realized in organic solar cells based on IDTC8 -4Cl. The synergistic effect of alkyl chains and modification of the terminal groups yields improved photovoltaic performance.