Photoluminescence and photocatalytic properties of Er3+-doped In2O3 thin films prepared by sol–gel: application to Rhodamine B degradation under solar light

Abstract

The effect of Er3+ doping (1%) on the structural, optical and photocatalytic properties of In2O3 thin films deposited on quartz substrates by spin coating was investigated. The In2O3:1% Er3+ films, annealed in the temperature range 800–1000 °C, were characterized by X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy, UV–Vis spectroscopy, ellipsometry and photoluminescence (PL). The films are polycrystalline with a cubic structure and the lattice parameter increases with the incorporation of Er3+ owing to its larger radius. The SEM images of the film show a granular morphology with large grains (~ 200 nm). The doped In2O3 film exhibits less transparency than In2O3 in the UV–visible region with band gaps of 3.42 and 3.60 eV, respectively. PL shows strong lines at 548 and 567 nm, assigned to Er3+ under direct excitation at 532 nm. The energy diagram of the junction In2O3:1% Er3+/Na2SO4 (0.1 M) solution plotted from physical and photoelectrochemical characterizations shows the feasibility of the films for Rhodamine B (RhB) degradation under solar light. The conduction band at 2.22 V deriving from the In3+:5s orbital is suitably positioned with respect to the O2/O 2 · level (~ 1.40 VSCE), leading to oxidation of 32% of 10 ppm RhB within 40 min of solar irradiation.