Effect of Precursor Fluorine Concentration Optical and Electrical Properties of Fluorine Doped Tin Oxide thin Films

Abstract

We have studied effects of Fluorine (F) concentration on the structural, optical and electrical properties of Fluorine Doped Tin Oxide (FTO) thin films. The FTO films were fabricated with homemade spray pyrolysis setup and calcinated for twenty minutes at air environments. The homogeneous solution of Stannous Chloride (SnCl2.2H2O) and Ammonium Fluoride (NH4F) in distilled water was used as a precursor solution. Both the substrate and oven temperature was set to ca. (550 ± 5)℃ during the film synthesis and calcination processes. The films’ optical and electrical properties were investigated from transmittance, reflectance and resistance measurements. The transmittance of FTO film is found to be decreased for increasing F concentration from 0.28 M to1.14 M and increased for 1.14 M to 11.37 M. Also reflectance found to be significantly modulated with varying molar concentration of F. The maximum and minimum of the reflectance (Rmax and Rmin) found to vary from 49 % and 7 %, respectively). However, there was no clear dependency on the dopant F concentration; slightly enhancement may be true which is probably due to the increase in fundamental absorption as photon striking increases. Electrical measurement showed the decrease of resistance of 0.85M FTO film from 138 Ω to 17 Ω.