Novel D–A–π–A carbazole dyes containing benzothiadiazole chromophores for dye-sensitized solar cells

New D–A–π–A carbazole dyes containing benzothiadiazole chromophores were designed and synthesized for application in dye-sensitized solar cells (DSSCs). The light-harvesting capabilities and photovoltaic performance of these dyes were investigated systematically through comparison of different π-bridges and acceptors. Compared with thiophene bridge, benzene bridge provides improved IPCE and VOC, which leads to better photoelectricity conversion efficiency. Dyes with cyanoacetic acid acceptor display superior photovoltaic properties though with shorter absorption maximum and lower molar absorption coefficient compared with dyes with rhodanine acetic acid acceptor. Therefore, dye with benzene bridge and cyanoacetic acid acceptor shows the most efficient photoelectricity conversion efficiency and has the maximum η value of 5.40% (VOC = 710 mV, JSC = 10.99 mA/cm2, and ff = 0.71) under simulated AM 1.5 irradiation (100 mW/cm2).