Y2O3 thin films doped with different concentrations of erbium ions and co-doped with 10 mol% of ytterbium were synthesized by a solid state photochemical deposition method followed by a subsequent calcination process. The photo-reactivity of the thin films was monitored by Fourier transform infrared (FT-IR) spectroscopy. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV–vis spectroscopy and photo-luminescence (PL) were employed to characterize the samples. The results reveal that Y2O3:Er films under 980 nm irradiation exhibit characteristic up-conversion emissions that are focused in the green region of the spectrum; these emissions are assigned to the (2H11/2, 4S3/2)→4I15/2 transitions of the Er3+ ions. These emissions greatly increase in intensity with the addition of Yb3+ ions in the preparation of the co-doped films. This phenomenon is …