Upconversion red emission and near-infrared quantum-cutting persistent luminescence of Nd³⁺-activated Ca₂SnO₄ induced by Yb³⁺

Abstract

In this work, we have investigated the near-infrared (NIR) photoluminescence, upconversion (UC), and long-lasting phosphorescence properties of Nd³⁺/Yb³⁺-doped Ca₂SnO₄ phosphors. Two-photon NIR quantum cutting (QC) luminescence is observed when the Nd³⁺-O²⁻ charge-transfer band in Ca₂SnO₄:Nd³⁺, Yb³⁺ phosphors was excited, and the theoretical quantum yield is found to be close to 200%. More interestingly, the unique two-photon UC red emission under 808 nm laser diode excitation and NIR QC persistent luminescence can be realized only in Nd³⁺-Yb³⁺ codoped samples. The energy-transfer mechanism between Nd³⁺ and Yb³⁺ is revealed from the energy level structure and decay measurements. Different cross-relaxation schemes related to ²F₅/₂-²F₇/₂ of Yb3+ and f-f transition of Nd³⁺ are proposed. The results show that multifunctional luminescence properties are achieved in Nd³⁺-doped Ca₂SnO₄ with the introduction of Yb³⁺.