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

Abstract

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 cm² 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.