Synthesis and characterization of a new solution-processable star-shaped small molecule based on 5,6-bis(n-octyloxy)-2,1,3-benzoselenadiazole for organic solar cells

A new star-shaped small molecule ( M1 ) with triphenylamine as electron donor (D) unit and 4,7-dithienyl-5,6-bis( n -octyloxy)[2,1,3]benzoselenadiazole as electron acceptor (A) unit was designed and synthesized. The relationship between the structure and properties was well investigated. M1 shows excellent solubility in common organic solvents, broad absorption (300–650 nm), good optical band gap ( E g ) (1.96 eV), and proper energy level. Meanwhile, we also investigated the performance of the organic solar cells (OSCs) based on M1 and PC 61 BM or PC 71 BM with different weight ratios, under the illumination of AM 1.5G, 100 mW/cm 2 . The OSCs based on the blend of M1 and PC 71 BM (1:2, w/w) exhibited the best device performance with a power conversion efficiency of 1.54 %, an open-circuit voltage of 0.91 V, a short-circuit current density of 4.54 mA/cm 2 , and a fill factor of 37.2 %.