Sol-gel preparation and near-infrared emission properties of Yb3+ sensitized by Mn4+ in double-perovskite La2ZnTiO6

Yb3+/Mn4+ co-doped La2ZnTiO6 (brief as LZT:Yb3+/Mn4+) phosphors with xYb(3+) (x = 0-0.12) and yMn(4+) (y = 0-0.01) doping concentrations have been synthesized via a sol-gel method. X-ray diffraction (XRD) and photoluminescence spectra were employed to characterize the properties of final products. The LZT:Yb3+/Mn4+ material can efficiently convert the short-wavelength sunlight in wide spectral ranges (250-600 nm) into near-infrared emission around 990 nm which matches the higher photosensitivity region of Si-based solar cells. A dipole-dipole interaction plays an important role for the energy transfer process from Mn4+ to Yb3+ ions, which has been verified by Dexter's theory. Under the 390 nm excitation, the energy transfer efficiency is 38.6% in the La1.9ZnTi0.998O6:0.1Yb(3+)/0.002Mn(4+) co-doped sample. Due to the effective absorption of Mn4+ in the visible region and charge transfer transitions (O-2(-)-> Yb-3(+) and O2- -> Mn4+) in the UV region for LZT and the efficient energy transfer to Yb3+, this material can be developed as spectral convertors to improve silicon solar cell photovoltaic conversion efficiency.