A series of metal-free D-pi-A'-pi-A type organic dyes have been designed by inserting one or two thiophene between the (7 pi-A'-pi) -bridge and the donor and/or acceptor moieties based on BZTP-1. The influence of inserted thiophene into the (pi-A'-pi)-bridge on photovoltaic performances of sensitizer was investigated in detail using the density functional theory (DFI) and its time-dependent density functional theory (TD-DFT) methods. Calculated results show that increasing the length of the conjugated linker leads to a high planarity and very narrow HOMO-LUMO energy gap. Especially, dye T-T-BZTP-TT that forms by inserting two thiophenes into two sides of BLIP exhibits the most obvious red-shifted and the strongest absorption, which leads to a high Voc. Moreover, we find that these dyes show a good character of electron injection and dye regeneration owing to the ideal Delta G(inject), mu(normal) and Delta G(reg). Therefore, the insertion of thiophene into the (pi-A'-pi) -bridge has a better influence on photovoltaic performance of designed dyes compared with BZTP-1. We hope the present work will be helpful for future experimental synthesis of organic dyes to improve the performance of DSSCs. (C) 2017 Elsevier B.V. All rights reserved.