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.

124