Insertion of double bond π-bridges of A–D–A acceptors for high performance near-infrared polymer solar cells

Abstract

Double bond π-bridges were introduced into an A–D–A structured n-type organic semiconductor (n-OS) IDT-IC and a new n-OS acceptor SJ-IC was synthesized. In comparison with IDT-IC, the SJ-IC film shows significantly red-shifted absorption, improved electron mobility and tuned crystallinity, which make its blend film with a polymer donor easier to form appropriate phase separation. The polymer solar cells with polymer J61 as a donor and SJ-IC as an acceptor demonstrated a higher PCE of 9.27% with a higher J_sc of 16.99 mA cm⁻², while the device based on J61/IDT-IC only delivered a PCE of 6.95% with a J_sc of 13.70 mA cm⁻², which should be ascribed to the red-shifted and broadened absorption of SJ-IC. Therefore, inserting double bond π-bridges into n-OS acceptor molecules is a simple and effective way to broaden and red-shift their absorption to improve their photovoltaic performance. In addition, the near-infrared absorption of the SJ-IC acceptor should be beneficial to its future application in semitransparent and tandem PSCs.