Tm3+-Mediated Energy Bridge in Lead-Free Double Perovskites: Suppressing Multiphonon Relaxation for Multifunctional Photonic Applications

Abstract

The growing demand for efficient and sustainable photonic materials has spurred significant interest in eco-friendly lead-free double perovskites, which exhibit exceptional photoluminescence properties for next-generation sensing and display technologies. However, the emission performance of the material is limited by multiphonon relaxation, which leads to low energy efficiency under complex operating conditions. In this study, the ³H₅ energy level of Tm³⁺ is strategically engineered as an energy bridge within lead-free double perovskites, effectively overcoming the constraints imposed by inefficient multiphonon relaxation in Er3+ (4I11/2 → 4I13/2). This targeted modulation of energy transfer pathways results in a significant 50-fold enhancement in the red-to-green (R/G) emission ratio of Er³⁺, increasing from 0.09 to 4.58, accompanied by a pronounced chromaticity shift from green (0.278, 0.709) to red (0.678, 0.320). This tunable emission behavior is further modulated by laser power density and excitation wavelength (808 or 980 nm). Moreover, GMTO: Er3+, Tm3+ demonstrates excellent temperature-measuring ability based on the luminescence intensity ratio (2H11/2/4F9/2→4I15/2), achieving a maximum relative sensitivity of 1.03% K-1 at 313 K. This work not only demonstrates a generalizable strategy to suppress multiphonon relaxation via lanthanide energy bridges but also paves the way for multifunctional photonic devices tailored to emerging applications in smart sensing, secure communication, and next-generation optoelectronics.