Effect of solvent volume on the optical properties of SnO2:F films deposited by a simplified spray technique

Transparent conducting fluorine doped tin oxide (FTO) films are fabricated onto glass substrates using a simplified spray pyrolysis technique at a substrate temperature of 340 degrees C. The optical constants such as refractive index, absorption coefficient, extinction coefficient are estimated using the Swanepoel method and the solvent volume dependence of these optical constants are investigated in detail and reported. The refractive index (n(f)) of the film is found to be in the range of 1.671-1.675. It is observed that the refractive index increases sharply near the optical absorption edge and the n(f) decreases with the increase in the solvent volume which may be mainly attributed to the increase in the carrier concentration. The optical band gap (3.62 - 3.70 eV) and the band edge sharpness of the films are found to be increased with the solvent volume.