Unraveling the photophysical response of BaLaLiTeO6:Dy3+ double perovskites with excellent thermal stability for colour tunable LEDs and optical thermometry

Abstract

The quest for reliable phosphors has accelerated amidst a growing demand for cost-effective, high-performance multifunctional phosphors. Incorporating thermometric application into double perovskite phosphors can enhance their multifaceted features for diverse applications. The present work endeavours to develop a series of BaLaLiTeO₆:Dy³⁺ double perovskites via a solid-state reaction route, stressing their application in next-generation colour-tunable LEDs and non-contact luminescence thermometry. X-ray diffraction, Raman and FTIR spectroscopy analysis were done to make inferences about the structural modifications induced by the substitution of Dy³⁺ at the La³⁺ site of BaLaLiTeO₆. An extensive investigation of optical characteristics was carried out by diffuse reflectance spectroscopy, photoluminescence spectroscopy and decay curve analysis. Prominent photometric parameters were also evaluated to assess the commercial feasibility of the developed phosphors in photonic applications. Judd-Ofelt parameters were estimated from the photoluminescence excitation spectra of BaLaLiTeO₆:Dy³⁺ for the first time. Furthermore, the values of radiative parameters, fluorescence decay time and quantum efficiency suggested the suitability of the developed phosphor as a competent material. A comprehensive analysis of BaLaLiTeO₆:Dy³⁺ as a thermographic phosphor was done by temperature-dependent photoluminescence spectroscopy. The potential use of this material in luminescence temperature sensing was probed by estimating the thermometric figures of merit based on the fluorescence intensity ratio (FIR). An absolute sensitivity of 22.17 $\times$ 10⁻⁴ K⁻¹ was achieved at a temperature of 500 K and a remarkable maximum relative sensitivity of 2.34 %K⁻¹ was attained at 250 K, which is much higher than other Dy³⁺ substituted thermographic phosphors. All these culminated features of BaLaLiTeO₆:Dy³⁺ phosphor proved their prospective applications in thermally stable colour-tunable LEDs, wLEDs and as non-contact optical temperature sensors.