Two new organic dyes with tert-butyl-capped N-arylcarbazole as a donor, cyanoacrylic acid as an acceptor and a bithiophene unit as a π-linker (DH-11 and DH-12) have been synthesized and characterized for dye-sensitized solar cells (DSSCs). It is found that the introduction of tert-butyl-capped N-arylcarbazole as an electron donor can efficiently suppress the intermolecular aggregation and improve the photovoltaic performances. The DSSC devices based on the dyes show relatively high power conversion efficiency of 3.67 and 3.75% for DH-11 and DH-12, respectively, which reaches over 65% of the reference dye N719-based cell fabricated and measured under the same conditions. This infers that the tert-butyl-capped N-arylcarbazole unit is a promising electron-donor that can be employed to design metal-free sensitizers with a new structural skeleton.