Synthesis and photovoltaic properties of phthalocyanine end-capped copolymers with conjugated dithienylbenzothiadiazole–vinylene side chains

Two phthalocyanine end-capped copolymers with conjugated dithienylbenzothiadiazole–vinylene side chains, PHY1 and PHY2, have been synthesized according to the Stille–Coupling polymerization method. The structures, thermostability, optical and electrochemical properties of the copolymers were characterized via NMR, GPC, TGA, DSC, UV–vis, photoluminescence (PL) spectroscopy, and cyclic voltammetry (CV), respectively. The two copolymers exhibit excellent film-forming ability and good thermostability in a wide temperature range. PHY1 and PHY2 end-capped with different phthalocyanines showed broad absorption bands ranging from the ultraviolet to the red/near-infrared (IR) region of the solar spectrum and deep HOMO energy levels. Bulk heterojunction polymer solar cells were fabricated based on PHY1 and PHY2 with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as the electron acceptor and showed power conversion efficiencies (PCE) of 1.56% and 1.26%, respectively, under the illumination of AM 1.5, 100 mW/100 cm2.