Optimizing the molecular structure to adjust the properties of photosensitizer is one of the crucial means to improve the power conversion efficiency of dye-sensitized solar cells (DSSCs). In this paper, four aromatic fused rings were selected as electron donor units to construct photosensitizers PBT-series. The effects of structural differences in the donor moiety on the photophysical and photochemical properties of the molecules were investigated in detail. The results show that the devices based on the dyes with triphenylene or fluoranthene as electron donor can yield higher short-circuit photocurrent densities (J(sc)) and open-circuit voltages (V-oc) than the devices based on the reference dyes with pyrene or phenanthrene as electron donor, and the power conversion efficiency (PCE) is increased by 37% and 23%, respectively. PBT-2 and PBT-4 sensitizers have better light absorption properties due to stronger intramolecular charge transfer (ICT) charge transitions, which helps to increase the photocurrent of devices, while they also exhibit significantly lower charge recombination rates. Eventually, PBT-2-based devices showed the best power conversion efficiency of 7.67% under the standard global AM 1.5 solar conditions.