Design of anti-thermal quenching Pr3+-doped niobate phosphors based on a charge transfer and intervalence charge transfer band excitation-driven strategy

Abstract

Thermal quenching limits further large-scale applications of Pr³⁺-doped phosphors. Research shows that intervalence charge transfer (IVCT) can be used as both the quenching luminescence channel and the red-emitting compensation channel for Pr³⁺-doped phosphors due to its unique dual-function mechanism. The problem of how to reduce quenching and improve compensation effects through IVCT has become an important issue. In this contribution, a dual compensation mechanism is proposed by designing an excitation-driven strategy of charge transfer (CT) and IVCT, thus realizing anti-thermal quenching of red light. Under different excitation-driven strategies, YNbO₄:x%Pr³⁺ phosphors exhibited both single compensation and dual compensation effects in red emission. In the case of excitation of the IVCT band alone, the ³P₀ energy level electrons of Pr³⁺ were transferred to the ¹D₂ level through the IVCT state formed between Pr³⁺ and Nb⁵⁺, resulting in enhanced red emission from the ¹D₂ → ³H₄ transition of Pr³⁺. In the case of simultaneously exciting the charge transfer band (CTB) and the IVCT band, there is a charge transfer from both the host matrix and the Pr^{3+ 3}P₀ level to the ¹D₂ level, leading to higher red emission intensities in all samples within the temperature range of 303 K to 523 K compared to single compensation. Notably, the YNbO₄:0.1%Pr³⁺ sample exhibited a maximum comprehensive intensity of red emission under dual compensation, reaching 2.18 times its intensity at 303 K, significantly higher than the 1.38 times its intensity under single compensation. Furthermore, this phosphor exhibits high optical temperature sensing sensitivity and excellent thermochromic properties, allowing for both quantitative and qualitative temperature measurements. This work provided a new avenue for the development of Pr³⁺-doped niobate anti-thermal quenching luminescent materials.