Dithieno[2,3‐d:2′,3′‐d′]naphtho[2,1‐b:3,4‐b′]dithiophene based medium bandgap conjugated polymers for photovoltaic applications

Three novel medium band gap (MBG) conjugated polymers (CPs) (named as P1, P2, and P3, respectively) were developed by copolymerizing 2,7‐dibromo‐10,11‐di(2‐hexyldecyloxy)dithieno[2,3‐d:2′,3′‐d′]naphtho[2,1‐b:3,4‐b′]dithiophene (NDT‐Br) with three different units: 2,5‐bis(tributylstannyl)thiophene, 2,5‐bis(trimethylstannyl)thieno[3,2‐b]thiophene and trans −1,2‐bis(tributylstannyl)ethene, respectively. The thermal, optical, and electrochemical properties of the polymers were investigated. All of the polymers have good thermal stability and medium band gap (∼ 1.9 eV). Prototype bulk heterojunction photovoltaic cells based on the blend P1/P2/P3 and [6, 6] phenyl‐C61 butyric acid methyl ester (PC 61 BM) were assembled and the photovoltaic properties were assessed. Power conversion efficiencies (PCEs) of 1.61% ∼ 2.43% have been obtained under 100 mW cm −2 illumination (AM1.5). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133 , 43288.