A first-principles study on improvement of photoinjection in organic dyes

First principles methods are implemented in order to design new metal free organic dyes with motivation to improve photoinjection in dye sensitized solar cell (DSSC). The simulated structures obey general D-pi-A structure and various structural modifications are made in pi-bridge as well as donor assembly of the dyes. The addition of benzothiadiazole and pyridine in pi-bridge caused shifting of absorption spectrum of dyes shifted toward lower energies. The analysis of structural and photoelectric properties of the dyes revealed that the dyes containing triarylamine in donor assembly show largest light harvesting efficiencies. The process of photoinjection was modeled by adsorbing the series of dyes on surface of (TiO2)(n) particles to investigate the injection and recombination kinetics. The dyes having benzothiadiazole in pi-bridge exhibited smallest injection energies while the dyes having pyridine in the in pi-bridge shown highest recombination energies. The detailed investigation of UV-visible spectra of dye-semiconductor complex was carried out to explore suitability of the dyes for practical applications in DSSC.