Color tunable emission from CaS:Cu+,Mn2+ rare-earth-free phosphors prepared by a simple carbon-thermal reduction method

Photoluminescence properties of CaS:Cu+,CaS:Mn2+ and CaS:Cu+,Mn2+ rare-earth -free phosphors prepared by a carbon-thermal reduction method were investigated. The emission spectrum of Cu+-doped CaS consists of two overlapped bands peaking at 415 nm (attributed to isolated Cu+ activator) and 475 nm (attributed to aggregated Cu+ center). The influence of Cu+ doping concentration on the emission spectrum is discussed. The emission spectrum of Mn2+-doped CaS exhibits a band emission peaking at 568 nm under 250 nm excitation. The emission spectra of the doubly activated CaS:Cu+, Mn2+ phosphors consist of Cu+ and Mn2+ emissions simultaneously, and their shapes depend strongly on the Mn2+ concentration. Based on the emission and excitation spectra of the CaS:0.15 mol%Cu+, xMn(2+) phosphors, the energy transfer from Cu+ to Mn2+ takes place. The emitting colors of the doubly activated phosphors can also be tuned. In particular, the emitting color of CaS:0.15 mol% Cu+, 0.6 mol % Mn2+ sample is close to white light. (C) 2018 Elsevier B.V. All rights reserved.