New triarylamine organic dyes containing the 9-hexyl-2-(hexyloxy)-9H-carbazole for dye-sensitized solar cells

•9-hexyl-2-(hexyloxy)-9H-carbazole (HHCBZ) was synthesized for organic dyes.•Three new triarylamine sensitizers based on the HHCBZ unit were synthesized.•The HHCBZ unit outperforms the HCBZ when used as an electron donor.•An efficiency of 8.67% was achieved by M92 with the HHCBZ donor.

Developing carbazole derivatives as the electron donor for organic dyes have attracted extensive interest recently. Three organic dyes M92-94 based on the 9-hexyl-2-(hexyloxy)-9H-carbazole (HHCBZ) electron donor have been successfully designed and synthesized for dye-sensitized solar cells. M95 with the 9-hexyl-9H-carbazole (HCBZ) unit has also been synthesized for comparison. An introduction of the HHCBZ unit in triarylamine brings several advantages: (i) red shifting the absorption peak and increasing the maximum molar absorption coefficient of absorption bands; (ii) decreasing the charge recombination in cobalt cells as well as iodine cells; (iii) enhancing photocurrent/photovoltage and thus the power conversion efficiencies of cobalt cells as well as iodine cells. Devices prepared with M92 show consistently higher light-to-electric energy conversion efficiencies, with the champion device reaching 8.67%, surpassing M93-95.

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