Down-shifting emission of Yb3+ ions sensitized by broad charge transfer band of V-O and Yb-O in Ca2V2O7 phosphors

Yb3+ singly doped pyrovanadate Ca2V2O7 phosphors were prepared by conventional solid state reaction. The crystal structure of the powders was investigated by X-ray diffraction. The diffuse reflection spectrum, photoluminescence excitation, emission spectra were investigated. The intense near infrared down-shifting emission of Yb3+ ions were demonstrated upon excitation of ultraviolet (UV) photon in a wide range of 250-450 nm. The broad excitation band in UV is attributed to the overlap of Yb3+-O2− and V5+-O2− charge transfer band. With the combination of wide Yb-O charge transfer band, which is seldom reported to sensitize the down-shifting emission of Yb3+ ion, the spectral response of the spectral converting materials is greatly extended. The energy transfer process from V-O and Yb-O charge transfer band to Yb3+ ions and involved mechanism have been discussed.