Novel D-π-A carbazole sensitizers with 4-phenyl-2-(thiophen-2-yl)thiazole as π-bridge for dye-sensitized solar cells

• Three novel carbazole sensitizers were synthesized.
• 4-Phenyl-2-(thiophen-2-yl) thiazole is used as π-bridge of these sensitizers.
• The photovoltaic performance of carbazole sensitizers was investigated.
• The optimal η of these carbazole dyes reaches 4.72%.

A class of novel carbazole sensitizers was synthesized with carbazole derivatives as the electron donor, 4-phenyl-2-(thiophen-2-yl) thiazole as π-bridge and cyanoacetic acid as the electron acceptor. Their absorption spectra, photovoltaic performance and electrochemical properties were evaluated. These carbazole sensitizers share the same π-bridge and electron acceptor and display the similar absorption spectra. However, the differences in link mode and substituent bring about the absorptivity variation. It is observed that the link mode of π-bridge at the benzene ring instead of N atom of the carbazole unit favors improving the light absorptivity and lowering the charge recombination. Those carbazole sensitizers show the optimal photovoltaic performance with a Jsc of 10.01 mA/cm2, Voc of 0.66 V, and ff of 0.72, corresponding to an overall conversion efficiency η of 4.72% under standard AM 1.5G irradiation.