Diyne unit containing organic dyes coded as FSD105 and FSD106 were designed and synthesized to investigate their light harvesting capabilities and the DSSC performances. Through tuning the geometrical structures of dye molecules by introducing an extra ethynylene, FSD105 and FSD106 showed an obviously improved coplanar geometry, and thus the significantly bathochromic shifted absorption spectra, IPCE spectra and larger Gamma values, leading to the enhancement of J(sc) which guaranteed the highest eta (3.82%) for FSD106-based DSSC. In order to avoid the dye aggregation, CHCl3/EtOH was adopted as the sensitizing solvents instead of CHCl3 only or CDCA as coadsorbent was added to reduce the Gamma value of FSD106-based DSSC. As a result, the J(sc) and the eta value increased significantly. Finally, FSD106/CDCA-based DSSC showed the highest eta value (4.76%), which is 1.53-fold as the previous reported FSD101-based DSSC (3.12%) by introducing an extra ethynylene to improve the molecular coplanarity. (C) 2017 Elsevier Ltd. All rights reserved.