The four novel metal-free organic dyes Ref. Dye, SP-SO, SP-OS and SP-OO, containing a Triphenylamine (TPA) unit as the π-bridge were designed and the impacts of the spacer on the photovoltaic performances were studied. The Geometry structure, energy levels, light-harvesting ability and ultraviolet-visible absorption spectra were calculated by using Density Functional Theory (DFT) and Time-Dependent-DFT. The results show that incorporating spacer with moderate electron-deficient ability can extend the absorption range (400-950 nm) and adjust the molecular orbital energy levels, improving the photovoltaic performance devices. The investigated dye reveals that SP-SO sensitizers showed absorbance in the visible region (400-950 nm) with higher oscillator strength (f) (1.1178and LHE (0.9237).
