Study of multimodal light emissions from Pr3+/Yb3+ doped NaLa(MoO4)2 phosphors for optoelectronic devices and plant-growth applications†

Abstract

Recent advancements in materials design have driven the scientific community to explore phosphor materials for multifunctional applications. This study presents the multimodal light emission (downshifting – DS, quantum cutting – QC, and upconversion – UC) from Pr³⁺/Yb³⁺ activated NaLa(MoO₄)₂ phosphors for multifunctional applications. Under blue (449 nm) and NIR (980 nm) excitation, co-doped phosphors emit visible light through DS and UC processes caused by different f–f transitions of Pr³⁺ ions. Additionally, when the co-doped samples are excited with blue light, they emit a near-infrared (NIR) light band ranging from 900 to 1050 nm. This is caused by the f–f transition of Yb³⁺ resulting from energy transfer from a single Pr³⁺ ion to a pair of Yb³⁺ ions through the QC process. Concurrently, in-depth investigations were conducted to understand the concentration and thermal quenching mechanism. Firstly, the applicability of phosphors in optical thermometry using the luminescence intensity ratio (LIR) technique was explored, with the maximum relative sensitivity of 0.41% K⁻¹ (448 K). A phosphor-coated LED (pc-LED) was constructed by coupling NaLa_0.97Pr_0.03(MoO₄)₂ with a blue LED chip (InGaN). Furthermore, based on the observed optical properties of the prepared phosphor, its application in improving the photovoltaic performance of solar cells and indoor plant applications is systematically discussed.