Carbazole based A-π-D-π-A dyes with double electron acceptor for dye-sensitized solar cell

• Double electron acceptor dyes were synthesized and used as sensitizer for DSSCs.
• Three different spacers linked to the donor carbazole unit.
• Dye structure with benzene linker showed better photovoltage compared to N719.
• Dye with thiophene linker showed better overall efficiency compare to other two.
• LUMO levels of CSG dyes are favorable for efficient electron injection.

Three novel carbazole-based A-π-D-π-A-featured dyes (CSG1–CSG3) have been designed, synthesized for applications in dye-sensitized solar cells and fully characterized with NMR, MS, IR, UV–vis and electrochemical measurements. These dyes share the same donor (N-hexylcarbazole) and acceptor/anchoring group (cyanoacrylic acid), but differs in conjugated linkers incorporated, such as benzene, furan or thiophene, to configure the novel A-π-D-π-A framework for effective electron flow. The power conversion efficiencies were observed to be sensitive to the π-bridging linker moiety. The photovoltaic experiments showed that dye with a benzene linker exhibited a higher open-circuit voltage (0.699 V) compared to thiophene and furan linker. Among all dyes, CSG2 containing a thiophene linker exhibited the maximum overall conversion efficiency of 3.8% (JSC = 8.90 mA cm−2, VOC = 584 mV, FF = 0.74) under standard global AM 1.5 G solar condition. Under similar fabrication conditions, champion dye N719 exhibited the maximum overall conversion efficiency of 6.4% (JSC = 14.74 mA cm−2, VOC = 606 mV, FF = 0.716).

Three novel carbazole-based A-π-D-π-A-featured dyes with different linkers (CSG1–CSG3) have been designed, synthesized, characterized and successfully applied for dye solar cells. The photovoltaic experiments showed that dye CSG1 (benzene linker), exhibited a higher open-circuit voltage (0.699 V) compared to CSG2 (thiophene linker), CSG3 (furan linker) and N719. The power conversion efficiency was shown to be sensitive to the structural modifications of the sensitizer on π-bridging linker. Among the three organic dyes, CSG2 containing a thiophene linker exhibited the maximum overall conversion efficiency of 3.8% (JSC = 8.90 mA cm−2, VOC = 584 mV, FF = 0.74) under standard global AM 1.5 G solar condition.Figure optionsDownload as PowerPoint slide