Three triphenylamine-based org. sensitizers with different electron-donating substituents (butoxyl chains or dimethylamine groups) were examd. to investigate the effect of bulky alkoxy donor substituents on the photovoltaic performances of dye-sensitized solar cells in the presence and absence of the coadsorbent chenodeoxycholic acid (CDCA) in dye-bath solns. The study showed that, using the D29 dye without bulky alkoxy substituents, the power conversion efficiency of dye-sensitized solar cell was significantly increased by ∼84% in the presence of CDCA as compared to that in the absence of CDCA addn. during the sensitization. However, the photovoltaic performance of D35-dye-sensitized solar cell having four bulky butoxyl substituents was not dependent on CDCA at all, probably due to the inherent structural nature of the D35 mol. The dye-sensitized solar cell based on the D37 sensitizer with only two bulky butoxyl chains displayed an expected medium performance as compared to D29 and D35. The inclusion of bulky alkoxy electron-donating substituents in dye mols. for efficient dye-sensitized solar cells suppressed the electron recombination and reduced the interactions between dye mols. This emphasizes the importance of designing novel dyes including functional groups that incorporate the properties normally needed from an external coadsorbent. The development of a coadsorbent-free system is in particular important for the future economization and simplification of the dye-sensitized solar cell assembly process.