Density functional theory (DFT) and time-dependent density functional theory (TD-DFF) calculations have been carried out to explore the underlying origin of merits for rigid pi-spacer based on reference dyes C255 and C254. The results demonstrate that higher short-circuit current density (J(SC)) of C255 is primarily ascribed to the lower EBE, while the biggish short-circuit current density (V-OC) mainly originates from the larger mu(normal) compared to C254. Besides, a novel index integral of overlap between hole and electron (S) is firstly introduced to quantitatively estimate the facility of intramolecular charge transfer (ICT) and preliminarily confirmed to be effective for the research target of this work. Furthermore, three series of dyes (C-series, A-series, AC-series) have been designed and characterized to screen promising sensitizer candidates and design strategies, while delightful results have been achieved including 6 promising candidates, design stratagem on efficiently reducing the charge recombination and combinational tactics on screening new dyes with excellent spectral properties or outstanding DSSC performance. (C) 2015 Elsevier B.V. All rights reserved.