Near-infrared luminescence spectroscopy in yttrium oxide phosphor activated with Er3+, Li+ and Yb3+ ions for application in photovoltaic systems

Abstract Near-infrared emission from phosphors Y2O3 doped with Er3+, Li+ and Yb3+ ions under continuous excitation at 523 nm is reported. The downshifting emissions from 950 to 1090 nm correspond to transitions 4I11/2 → 4I15/2 of Er3+ ions and 2F5/2 → 2F7/2 of Yb3+ ions; the emissions from 1500 to 1600 nm correspond to transitions 4I13/2 → 4I15/2 of Er3+. The role of Yb3+ ions in phosphors of Y2O3 doped with 4 at.% of Er, 2 at.% of Li and 2 at.% of Yb was to enhance the 950–1090 nm emissions around 3.5 times in comparison with Yb3+ free samples, through an energy transfer from the erbium 4I11/2 level to the ytterbium 2F5/2 level. Li+ plays an important role in such energy transfer process. With addition of Li+ an erbium 4I13/2 and ytterbium 2F5/2 level decay time increasing is also observed. A peak intensity increase in XRD patterns of the sample tri-doped revealed that the incorporation of lithium increases the phosphor crystallinity. FT-IR and SIMS studies confirmed that Li+ ions are incorporated into the Y2O3 host. According to the optical and structural properties of these phosphors, they could be used to increase the photon absorption in photovoltaic systems.