Fabrication of high transmittance and low sheet resistance dual ion doped tin oxide films and their application in dye-sensitized solar cells

In this work, low resistivity and high transmittance fluorine doped tin oxide (FTO) and Li doped FTO (LIFTO) films are prepared by spray pyrolysis and the effect of hazes of FTO and LIFTO on the performance of dye-sensitized solar cells (DSSCs) is studied. Influences of different parameters such as molar ratio of F/Sn, Li⁺ and F^- dual ion doping, substrate temperature and carrier gas on the optical, electrical, grain structural and surface morphological characteristics of the LIFTO films are evaluated in detail. It is found that with the increase of dual ion doping concentrations of Li⁺ and F^- from 0.0 to 0.05 M, the resistivity of the LIFTO film increases from 4.4 × 10^{- 4} to 7.8 × 10^{- 4} Ω·cm, the transmittance enhances from 60% to 70% (500 nm) and the haze decreases from 30% to 10% respectively, which may be correlated with the changes in the grain size of the LIFTO. Performance of the DSSCs with the LIFTO substrates having a haze value of ca. 25% shows the best photocurrent and solar cell conversion efficiency.