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Impact of Noncovalent Sulfur–Fluorine Interaction Position on Properties, Structures, and Photovoltaic Performance in Naphthobisthiadiazole‐Based Semiconducting Polymers
Author(s) -
Saito Masahiko,
Fukuhara Tomohiro,
Kamimura Satoshi,
Ichikawa Hiroyuki,
Yoshida Hiroyuki,
Koganezawa Tomoyuki,
Ie Yutaka,
Tamai Yasunari,
Kim Hyung Do,
Ohkita Hideo,
Osaka Itaru
Publication year - 2020
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201903278
Subject(s) - materials science , polymer , substituent , polymer solar cell , fluorine , thiophene , solar cell , photovoltaic system , side chain , active layer , organic solar cell , copolymer , photochemistry , chemical physics , nanotechnology , layer (electronics) , organic chemistry , optoelectronics , chemistry , composite material , ecology , thin film transistor , biology , metallurgy
Controlling the energetics and backbone order of semiconducting polymers is essential for the performance improvement of polymer‐based solar cells. The use of fluorine as the substituent for the backbone is known to effectively deepen the molecular orbital energy levels and coplanarize the backbone by noncovalent interactions with sulfur of the thiophene ring. In this work, novel semiconducting polymers are designed and synthesized based on difluoronaphthobisthiadiazole (FNTz) as a new family of naphthobisthiadiazole (NTz)–quaterthiophene copolymer systems, which are one of the highest performing polymers in solar cells. The effect of the fluorination position on the energetics and backbone order is systematically studied. It is found that the dependence of the solar cell fill factor on the active layer thickness is very sensitive to the fluorination position. It is thus further investigated and discussed how the structural features of the polymers influence the photovoltaic parameters as well as the diode characteristics and bimolecular recombination. Further, the polymer with fluorine on both the naphthobisthiadiazole and quaterthiophene moieties exhibits a quite high power conversion efficiency of 10.8% in solar cells in combination with a fullerene. It is believed that the results would offer new insights into the development of semiconducting polymers.