Synthesis And Properties Of Benzoselenadiazole-based Organic Photovoltaic Materials

Abstract:A series of new conjugated polymers and small organic molecule were designed and synthesized in this paper. Organic solar cells were fabricated using them blended with PCBM as active layers, and the relationship between structure and properties were characterized. The main results are as follows:(1) A series of new5,6-bis(tetradecyloxy)-2,1,3-benzoselenadiazole-based copolymers (PBDT-DTBSe, PC-DTBSe and PF-DTBSe) have been firstly synthesized by Stille or Suzuki coupling polymerization reaction. The synthesized copolymers show good solubility in common organic solvents, such as chloroform, tetrahydrofuran and chlorobenzene with excellent film forming properties. The molecular weight was determined by GPC and the thermal properties were investigated by TGA. All the copolymers exhibited broad absorption from350nm to700nm. The preliminary results showed the device based on the structure of ITO/PEDOT:PSS/PC-DTBSe:PC61BM(1:2,w/w)/Ca/Al displayed the best photovoltaic performance with a PCE of1.35%, a Voc of0.87V, a Jsc of3.84mA/cm2and a FF of40.4%, under illumination of AM1.5G (100mW/cm2).(2) Two new D-A conjugated polymers containing benzo[1,2-b:4,5-b’]dithiophene (BDT), benzo[1,2-b:4,5-b’]difuran (BDF) donor units and4,7-di(thiophen-2-yl)-5,6-bis(n-octyloxy)[2,1,3]benzoselenadiazole (DTBSe) acceptor unit, PBDTDTBSe and PBDFDTBSe have been synthesized by Stille coupling polymerization. The two polymers show good solubility in common organic solvents, excellent film forming properties, broad absorption (350-700nm), low optical band gaps (about1.60eV) and relatively high hole mobility (1.22×10-2cm2/(V·s)). The devices based on the blend of PBDFDTBSe and PC71BM (1:1,w/w) exhibited the best device performance with a PCE of3.28%, a Voc of0.71V, a Jsc of10.37mA/cm2and a FF of44.6%under illumination of AM1.5G(100mW/cm2).(3) A novel TPA-based star-shaped small molecule (Ml) with TPA as electron-donor (D) unit and4,7-dithienyl-5,6-bis(n-octyloxy)[2,1,3]benz-oselenadiazole as electron-acceptor (A) unit was designed and synthesized. The relationship between the structure and properties was well investigated. It shows good solubility in common organic solvents, broad absorption (300-700nm) and low optical band gap (Eg)(1.98eV), meanwhile, we investigated the performance of the OSCs based on M1and PC61BM or PC71BM with different weight ratios, under the illumination of AM1.5G,100mW/cm2. The OSCs based on the blend of M1and PC71BM (1:2, w/w) exhibited the best device performance with a PCE of1.54%, a Voc of0.91V, a Jsc of4.54mA/cm2and a FF of37.2%under illumination of AM1.5G,100mW/cm2.