Synthesis And Properties Of Organic Photovoltaic Small Molecules Based On Benzotriazole

Recently, bulk-heterojunction organic solar cells (BHJ OSCs) have been intensively studied due to their advantages of low-cost fabrication of large-area devices, light weight, mechanical flexibility and easy tenability of chemical properties of photovoltaic materials toward inexhaustible renewable clean energy. As far as we know, solution-processed organic small molecular solar cells have presented power conversion efficiency (PCE) up to9.02%, demonstrating that small molecular solar cells are comparable with their polymeric counterparts. However, in order to make OSCs to be marketable, their photovoltaic performance should be improved.we successfully designed and synthesized a series of D-A-D type photovoltaic materials, composing of benzotriazole (BTz) as the central electron withdrawing group, TPA as end capping units as well as single bond, vinylene and acetylene as the linkage. Density function theory were used to forcast the materials’ properties at molecular level before synthetics were created. UV-vis absorption spectroscopy and fluorescence quenching experiment were used to evaluate their photophysical properties. Cyclic voltammetry (CV) were carried out to get their electrochemical nature. In order to evaluated their photovoltaic (PV) properties, bulk-heterojunction (BHJ) solar cells were fabricated. Based the above experiments, we will investigate the relationship between molecular function and properties from the follow four aspects:1, how the different end-capping units to affect the photovoltaic properties;2, how the the properties chang by adding the methoxyl group on the triphenylamine;3, the effect of the conjugated length on the properties by adding benzene, thiophene or3-octylthiophene into molecular backbone;4, how the introduction of single baond, vinylene and acetylene as the linkage between acceptor and donor units effect the molecular properties.The molecule A9with the triphenylamine as donor, thiophenylbenzotriazole as acceptor and acetylene as the linkage showed the highest power conversion efficiency of3.6%. These results indicated that our work will likely expanded the D-A-D typed TPA-BTz based materials in the organic photovoltaic fields and give an important guide for developing higher efficiency materials in solution-processed small molecular OSCs.