Synthesis of novel sensitizers with a linear conjugated di(1-benzothieno)[3,2-b:2′,3′-d]pyrrole unit for dye-sensitized solar cells

Abstract

Three novel D−π−A structural metal-free organic sensitizers (DBTP−1∼3) are designed, in which a linear planar aromatic group, the di(1-benzothieno)[3,2-b:2′,3′-d]pyrrole is first introduced as the π-bridge for dye-sensitized solar cells. Triphenylamine, 9,9-dimethyle-9H-fluorene and carbazole serve as the electron donor, respectively, while cyanoacrylic acid is used as an electron acceptor and anchoring unit. The photophysical, electrochemical, theoretical calculations have been employed to apprehend the correlation between the structures of DBTP−1∼3 and their photovoltaic performances. Further, co-adsorption studies are used to investigate the electronic recombination of the target dyes. As a result, the maximum power conversion efficiency of 6.50% (short-circuit current of 14.66 mA cm−2, open-circuit voltage of 0.67 V, and fill factor of 66%) for the 2 mM chenodeoxycholic acid co-adsorbed device based on DBTP−1 is obtained, while without any co-adsorbent it gives efficiency of 4.55%. The standard dye N719 gives 8.54% power conversion efficiency.