Benzotriazole and benzothiadiazole containing conjugated copolymers for organic solar cell applications

2-Dodecyl benzotriazole (BTz) and benzothiadiazole (BTd) containing copolymers poly(4-(2-dodecyl-2H-benzod]1,2,3]triazol-4-yl)benzoc]1,2,5]thiadiazole (P1), poly(4-(5-(2-dodecyl-7-(thiophen-2yl)-2H-benzod]1,2,3]triazol-4-yl)thiophen-2-yl)benzoc]1,2,5] thiadiazole (P2) and poly(4-(5-(2-dodecyl-7-(4-hexylthiophen-2-yl)-2H-benzod] 1,2,3]triazol-4-yl)-3-hexylthiophen-2-yl) benzoc]1,2,5] thiadiazole (P3) were synthesized via Suzuki polycondensation. We report the application of conjugated copolymers in bulk heterojunction photovoltaic devices. When the copolymers were blended with 6,6]phenyl-C₆₁-butyric acid methyl ester (PCBM), P2 showed the best performance with an open circuit voltage (V_oc), a short-circuit current density (J_sc) and a power conversion efficiency (PCE) of 0.45 V, 3.48 mA cm^?2 and 0.45%, respectively, under AM 1.5G illumination conditions (100 mW cm^?2). The hole mobilities of the devices were calculated from J–V curves using Space Charge Limited Current (SCLC) method and the maximum mobility value was found to be 3.15 × 10^?5 cm² V^?1 s^?1 for the P2:PCBM blend.