Building Double Branch Dyes with Acetylenic Bonds: An Effective Strategy to Enhance the Efficiency of Dye‐Sensitized Solar Cells

Double branch (DB) dyes could reduce intermolecular interactions and realize good photovoltaic performances. Herein, symmetric DB dyes (FSDD‐1 and FSDD‐2) featuring with one and two acetylenic bonds as the isolation groups are reported. The corresponding single branch (SB) dye FSSD‐EH is synthesized for comparison. For the adsorption spectra, bathochromic shifts and higher ε are observed for DB dyes FSDD‐1 and FSDD‐2 compared with SB dye FSSD‐EH, which suggests better light‐harvesting capabilities for the DB dyes. Dye‐sensitized solar cells (DSSCs) sensitized by DB dyes FSDD‐1 and FSDD‐2 exhibit significant increases for the Jsc and Voc compared with SB dye FSSD‐EH, so much better η are achieved by the DB dyes (5.34, 7.14, and 2.46% for FSDD‐1, FSDD‐2, and FSSD‐EH, respectively). FSDD‐2 with a diyne unit exhibits higher η compared with FSDD‐1 with an yne unit as the isolation groups. The research shows that a much better photovoltaic performance of DSSCs can be achieved after connecting two dye molecules to be a DB dye by adopting acetylenic bonds as the isolation group. A longer distance between the two branches realized by a diyne unit is beneficial and effective to achieve better photovoltaic performance. A significant increase in photovoltaic performance is observed by connecting two dye molecules to be double branch (DB) dyes with acetylenic bond(s) as the isolation groups. Nearly 3‐fold power conversion efficiency is achieved for the DB dye FSDD‐2 with a diyne as the isolation group compared with the single branch dye FSSD‐EH.