Effects of ethynyl unit and electron acceptors on the performance of triazatruxene-based dye-sensitized solar cells

Metal-free organic dyes JY43-JY46 based on the triazatruxene donor were synthesized for dye-sensitized solar cells (DSSCs), where the effects of ethynyl unit and electron acceptor/anchor were systematically investigated. Compared to dyes JY45 and JY46, JY43 and JY44 containing an additional ethynyl unit in the molecular structure showed higher molar absorption coefficients, respectively. The strongly electron-withdrawing cyanoacrylic acid seemed helpful for dyes to achieve better light harvesting ability compared with dyes having carboxylic acid groups, resulting in the enhancement of the dyes' photocurrents. Notably, dyes JY43 and JY45 incorporating carboxylic acid anchors exhibited more effective suppression of charge recombination and longer lifetimes of excited electrons, therefore delivering higher photovoltages. Under standard light irradiation (AM 1.5G), the dye JY43 with an ethynyl unit and carboxylic acid in its skeleton gave the highest power conversion efficiency of 7.51% in the iodine electrolyte.