Triphenylamine-based starburst dyes with carbazole and phenothiazine antennas for dye-sensitized solar cells

Two new triphenylamine-based starburst dyes (WD-2 and WD-3) are designed, in which the carbazole/phenothiazine groups are used as secondary electron donor and the rhodanine-3-acetic acid moiety as the acceptor. We report the synthesis, photophysical and electrochemical properties of the dyes as well as their applications in dye-sensitized solar cells (DSSCs). Under standard global AM 1.5 solar condition, the WD-2 sensitized cell gives a short circuit photocurrent density Jsc = 6.4 mA cm−2, an open circuit voltage Voc = 600 mV, a fill factor ff = 0.8, corresponding to an overall conversion efficiency of 3.1%. Under the same conditions, the WD-3 sensitized cell gives Jsc = 4.7 mA cm−2, Voc = 570 mV, and ff = 0.78, corresponding to an overall conversion efficiency of 2.1%. The conversion efficiency is increased about 47% from WD-2 sensitized cell to WD-3 sensitized cell. The research results show that the inefficient electron injection from the excited dyes into the conduction band of TiO2 results in the low efficiencies of DSSCs based on the two dyes.

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► The phenothiazine group as secondary electron donor was introduced into organic dyes.
► The dyes with the starburst conformations can reduce aggregation between molecules and avoid the charge recombination processes of injected electrons with triiodide in the electrolyte.
► Power conversion efficiency of 3.1% was obtained for the DSSCs based on WD-2 without deoxycholic acid.