Significant enhancement of visible up-conversion emissions of Y2O2S:Er3+ phosphors by Mn2+ sensitizing under 1550 nm excitation

Abstract

A novel up-conversion (UC) emission route of Er³⁺ by Mn²⁺ sensitizing in a Y₂O₂S:Er³⁺ phosphor prepared via a high-temperature solid-state reaction method is reported here. This methodology resulted in a significant enhancement of visible up-conversion emission by 1550 nm laser diode excitation. By co-doping Mn²⁺, the visible (red and green) UC emission intensity, which is assigned to the transitions of ⁴F_9/2 → ⁴I_15/2 (670 nm), ⁴S_3/2 → ⁴I_15/2 (547 nm), ²H_11/2 → ⁴I_15/2 (528 nm) of Er³⁺, was 2 to 3 times higher than that of the Mn²⁺-free one. As the concentration of Mn²⁺ was increased, the visible UC emission intensity was enhanced and then reduced. The phosphor powders were well crystallized in a hexagonal shape with an average size of ca. 2 μm. Based on the results of the luminescence spectra, energy matching conditions and three-photon process dependence on excitation power, a possible UC mechanism is proposed. The proposed sensitizing route may lead to a promising step towards high-intensity UC emissions of rare-earth ion doped phosphors.