Photon avalanche assisted upconversion via customizing the green emission

The developed SnWO₄ phosphors incorporated with Ho³⁺, Yb³⁺ and Mn⁴⁺ ions have been explored under 980 nm laser irradiation. The molar concentration of dopants has been optimized to 0.5 Ho³⁺, 3.0 Yb³⁺ and 5.0 Mn⁴⁺ in SnWO₄ phosphors. The upconversion (UC) emission from the codoped SnWO₄ phosphors has been substantially amplified up to 13 times and described based on the energy transfer and charge compensation. On incorporating the Mn⁴⁺ ions in the Ho³⁺/Yb³⁺ codoped system the sharp green luminescence shifted to reddish broadband emission due to the photon avalanche mechanism. The processes accountable for the concentration quenching have been described based on critical distance. The interaction responsible for the concentration quenching in Yb³⁺ sensitized Ho³⁺ and Ho³⁺/Mn⁴⁺:SnWO₄ phosphors is considered to be dipole-quadrupole and exchange interaction type, respectively. The activation energy 0.19 eV has been determined, and the phenomenon of thermal quenching is discussed using a configuration coordinate diagram.