Carbazole-bridged double D–A dye for efficient dye-sensitized solar cell

• We synthesized an A–π–D–D′–D–π–A organic dye with a secondary donor (D′) instead of a π spacer.
• The secondary donor increases η and Jsc values of DSSCs.
• Arylamino groups as primary donors prevent the formation of the dye aggregates.
• Two anchoring functionalities including two different donors increase the DSSC efficiencies.

A di-anchoring organic dye based on an acceptor–π spacer–donor–secondary donor–donor–π spacer–acceptor structural motif has been synthesized and used as a sensitizer for dye-sensitized solar cells (DSSCs). The new synthetic approach uses two π spacers, two acceptors and two different donors such as arylamino and carbazole units. The double donor–acceptor dye CBZ-3 is linked by a carbazole unit as a secondary donor which increases the donor–acceptor strength of the dye and proved to increase the η and Jsc values of the photovoltaic cell compared to the corresponding mono-anchoring system CBZ-2 and the monodonor dye CBZ-1. With the non-planar structure of the arylamino group and the alkyl chains which efficiently prevent the formation of the dye aggregates, the dye exhibited a high open-circuit photovoltage (Voc) of 650 mV, a short-circuit photocurrent density (Jsc) of 7.20 mA cm−2 and the solar energy-to-electricity conversion efficiency (η) of 3.23%.

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