High performance polymer solar cells based on a two dimensional conjugated polymer from alkylthienyl-substituted benzodifuran and benzothiadiazole

A new low bandgap D-A copolymer PBDFTDTBT containing 4,8-bis(2-(2-ethylhexyl)thiophen-2-yl)-benzo [1,2-b;3,4-b']difuran (BDFT) and 4,7-di(thiophen-2-yl)-5,6-dioctyloxybenzo[c][1,2,5]thiadiazole (DTBT) units was synthesized and characterized for application as a donor material in polymer solar cells (PSCs). The PBDFTDTBT film showed a broad absorption band from 300 nm to around 730 nm in the visible light region and the hole mobility of the blend of PBDFTDTBT and PC71BM reached up to 0.36 cm(2) V-1 s(-1) by using the space charge limited current (SCLC) method. The PSCs based on PBDFTDTBT:PC71BM (1 : 1.5, w/w) exhibited a promising power conversion efficiency (PCE) of 6.0% under the illumination of AM 1.5 G, 100 mW cm(-2) with a high short circuit current density (J(sc)) of 12.04 mA cm(-2) and an open circuit voltage (V-oc) of 0.76 V.