A pentacyclic building block containing an azepine-2,7-dione moiety for polymer solar cells

Abstract

A pentacyclic building block containing an azepine-2,7-dione moiety, TTA, was developed. Two D–A copolymers (PTTABT and PTTABDT) using TTA as the acceptor unit were synthesized, showing good solubility and medium bandgaps. The PTTABT film exhibits a broad absorption with a FWHM of 205 nm, while PTTABDT:PC₇₁BM solar cells gave a higher PCE of 5.46%, resulting from its higher V_oc and ideal phase separation in the active layer.