• Mikie, Tsubasa
• Doi, Shuhei
• Saito, Masahiko
• Ohkita, Hideo
• Sato, Yuki

Abstract

<jats:title>Abstract</jats:title><jats:p>The use of noncovalent intramolecular interactions constitutes a powerful design strategy for preparing π-conjugated polymers featuring high backbone coplanarities and thereby high crystallinities. Herein, we report the design and synthesis of an alkoxythiophene-flanked benzobisthiazole (BBTz) as a new building unit for π-conjugated polymers, which was subsequently copolymerized to give a simple BBTz-bithiophene copolymer with alkyl and alkoxy groups (<jats:bold>PDBTz2</jats:bold>). Owing to the S···O noncovalent intramolecular interactions between the alkoxy oxygens and thiazole sulfurs in BBTz, <jats:bold>PDBTz2</jats:bold> showed greater coplanarity and crystallinity than its alkyl counterpart, <jats:bold>PDBTz1</jats:bold>. Interestingly, the backbone orientation was completely altered from the edge-on orientation observed for <jats:bold>PDBTz1</jats:bold> to a face-on orientation for <jats:bold>PDBTz2</jats:bold>, which is preferable for organic photovoltaics (OPVs). In addition, the electron-donating nature of the alkoxy group increased the HOMO energy level of <jats:bold>PDBTz2</jats:bold> compared to that of <jats:bold>PDBTz1</jats:bold>, which enabled photoinduced hole transfer from a nonfullerene acceptor, Y6, to the polymer. As a result, the short-circuit current density of an organic photovoltaic cell based on <jats:bold>PDBTz2</jats:bold> and Y6 was significantly greater than that of a cell based on <jats:bold>PDBTz1</jats:bold> and Y6. This study confirmed that alkoxythiophene-flanked BBTz is a promising building unit for high-performance π-conjugated polymers.</jats:p>

Topics

• density
• impedance spectroscopy
• Oxygen
• current density
• copolymer
• crystallinity