Novel dithieno[3,2-b:2′,3′-d]pyrrole-based organic dyes with high molar extinction coefficient for dye-sensitized solar cells

• Three dithienopyrrole-based dyes are synthesized for DSSCs.
• They exhibit high molar extinction coefficient and high Jsc.
• Phenyl group as a side chain reduces dye aggregates and charge recombination.
• One of the DSSCs shows conversion efficiency of 6.36%.

Three new metal-free organic dyes FD1–3 with a planar dithieno[3,2-b:2′,3′-d]pyrrole unit as linker were synthesized and used for dye-sensitized solar cells with high molar extinction coefficients. In this work, dithieno[3,2-b:2′,3′-d]pyrrole was employed as π-conjugated bridge to construct A–π–d–π–A organic dyes, where 9,9-dihexyl-9H-fluorene was used as a donor, and cyanoacrylic acid as an electron acceptor. For a typical device, a solar energy conversion efficiency (η) of 6.36% based on FD2 was achieved under simulated AM 1.5 solar irradiation (100 mW cm−2) with a short-circuit photocurrent density (Jsc) of 13.76 mA cm−2, an open-circuit voltage (Voc) of 669 mV, a fill factor (ff) of 0.691. The results suggest that the organic dye with a functionalized dithienopyrrole unit is a promising candidate for DSSCs due to its high molar extinction coefficients.

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