Influence of triple bonds as π-spacer units in metal-free organic dyes for dye-sensitized solar cells

Four metal-free org. sensitizers (TC101-TC104) with triple bonds in π-spacers and 5 ref. dyes (TC, TC105, TPC1, D5, and TH208) without triple bonds were applied in dye-sensitized solar cells to study the influence of triple bonds as π-spacer units on their photoelectrochem. properties and dye-sensitized solar cells (DSCs) performance. The introduction of triple bond could red shift the dye's absorption spectrum due to the enhancement of the π-spacer. However, the spectrum red shift is much less than that of the introduction of double bond because of more electronegativity of triple bond. The incident photon-to-current conversion efficiency reveals that the electron transfer yield (Φ(ν)ET) of DSCs becomes larger with the introduction of triple bond. Electrochem. impedance spectroscopy anal. reveals that the introduction of triple bond almost does not change the electron lifetimes in TiO2 films but decreases the effective diffusion lengths.