Synthesis and photovoltaic properties of new branchlike organic dyes containing benzothiadiazole or triphenylamine-linked consecutive vinylenes units

Two novel branchlike organic dyes (WD1 and FD1) based on 4,7-bis-(4-hexylthiophen-2-yl)benzo[1,2,5]thiadiazole (DTBT) and triphenylamine, containing vinylenes and consecutive vinylenes as π-conjugated unit, respectively, were designed and synthesized for dye-sensitized solar cells (DSSCs). The photophysical, electrochemical and photovoltaic properties of the dyes were investigated. The introduction of consecutive vinylenes into two branches of the FD1 molecule leads to a remarkably red-shifted absorption and higher molar extinction coefficient compared with the reference dye D2. The DSSCs based on FD1 and WD1 dyes exhibited the power conversion efficiency of 7.04% and 2.18% under AM1.5G irradiation (100 mW/cm2).

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► Two branchlike organic dyes have been designed and synthesized.
► The introduction of consecutive vinylenes leads to high molar extinction coefficient.
► The DSSCs based on FD1 dye exhibited the maximum power conversion efficiency of 7.04%.