Effect of oxygen vacancies on photoluminescence and electrical properties of (200) oriented fluorine-doped SnO2 films

Polycrystalline fluorine-doped SnO2 (FTO) films have been deposited on glass substrate by ultrasonic spray pyrolysis at 500 degrees C. The effects of F/Sn atom ratio in precursor solution on the structural, optical and electrical properties of FTO films have been investigated. The XRD results indicate that all films consist of polycrystalline cassiterite tetragonal particles with obviously (2 0 0) preferred orientations. SEM images present that all the films consist of uniform, clear and sharp edge shaped pyramid particles. The film prepared with F/Sn = 1 in precursor solution possess the UV-vis transmittance about 70%, the lowest resistivity of 3.50 x 10(-4) Omega.cm and the minimum value of [O-I]/[O-II] (oxygen atom at different condition determined by XPS) of 0.99 which can be contributed to the improved conductivity. In the room temperature photoluminescence (PL) spectra, there are four intense emission bands corresponding to defect of different oxygen vacancy states in FTO films.