Intrinsic defect of electronic structure for the chlorine-type porphyrin 1, which was synthesized for use in dye-sensitized solar cell (DSSC), is found by theoretical calculation including density functional method (DFT), time-dependent DFT, and C+/C− function. It is believed that the limited cell performance obtained by using dye 1 as the sensitizer is due to the existence of this electronic defect. To avoid this defect, a series of novel molecules with electron deficient π bridge were designed. The subsequent theoretical calculation indicated that the electron deficient π bridge in the newly designed molecule is quite effective in offsetting the electronic defect observed for dye 1. The parameters for the designed molecules closely associated with open-circuit voltage and short-circuit current density including dipole moment of dye vertical to the surface of semiconductor and light-harvesting efficiency were then evaluated. By comparing these parameters of designed dyes with those of dye 1, we can predict that the DSSC based on dye 4 (2, 6-cyan benzoic acid as anchoring group) should possess enhanced performance, which would be a valuable theoretical guidance for the practical work. © 2013 Wiley Periodicals, Inc.