Effect of film thickness on the structural, optical and electrical properties of SnO_2: F thin films prepared by spray ultrasonic for solar cells applications

摘要

In this work, undoped tin dioxide (SnO_2) and fluorine doped tin dioxide (SnO_2: F) thin films were deposited on 480 ℃ heated glass using spray ultrasonic technique. SnCl_2 and NH_4F were used as sources of SnO_2 and fluorine doping respectively. Effects of films thickness on the optical, structural and opto-electrical properties of undoped and 6 wt.% fluorine doped SnO_2 (FTO) thin films were investigated. Optical transmittance spectra of the films showed high transparency of about 76-84% in visible region. The optical gap, for SnO_2 and 6 wt.% F doped SnO_2 thin films, were found to be in 3.77-3.93 eV range. X-ray diffraction (XRD) patterns showed that both SnO_2 and SnO_2: F films were polycrystalline with cassiterite tetragonal crystal structure. The preferential orientation for undoped SnO_2 was along (211) plane whereas F doped SnO_2 preferential orientations were along (200) planes. The calculated grain sizes were in 25.63-33.53 nm average. Figure of merit for FTO thin films revealed maximum value about 9.04 × 10~(-3) (Ω~(-1)) at λ = 800 nm. The high conducting and transparent elaborated FTO thin films are promising to be used as window layer in solar cells.