Thieno[2,3-a]carbazole-based donor-π-acceptor organic dyes for efficient dye-sensitized solar cells

New donor-π-acceptor organic dyes K-1 and K-2 containing thieno[2,3-a]carbazole as an electron donor were designed and synthesized for dye-sensitized solar cells (DSCs). Photophysical and electrochemical properties of K-dyes were investigated. DSCs based on K-dyes showed a high conversion efficiency of 6.6-6.7% with a Jsc of 12.40-12.49 mA cm−2 and a Voc of 0.70-0.71 V. The molecular geometry calculation indicated that the existence of thienocarbazole donor in K-dyes enhanced the molecular planarity compared to the carbazole analogue dye MK-3. As a result, DSCs based on K-dyes showed high IPCEs, perhaps due to efficient intramolecular charge transfer and electron injection from excited dye to TiO2 conduction band.

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