Bi and Yb Codoped Cs2Ag0.6Na0.4InCl6 Microcrystals: Visible to Near-Infrared Fluorescence for Thermometry

The optical and thermometric properties of bismuth (Bi) and ytterbium (Yb) codoped double perovskite Cs2Ag0.6Na0.4InCl6 microcrystals (MCs) are investigated, which possess high photoluminescence quantum yield and stable broadband spectra from visible to near-infrared (NIR) region. Thermal quenching and dynamic properties are shown using temperature-dependent steady-state photoluminescence (PL) and time-resolved PL (TRPL) techniques, which reveal the transition mechanism from self-trapped excitons (STEs) to Yb dopants. Taking advantage of the diverse thermal quenching of distinct PL between STEs and Yb3+ emissions, an optical thermometer based on the fluorescence intensity ratio is designed in the visible and NIR region, which can provide a self-referenced temperature with high sensitivity. The maximum absolute and relative sensor sensitivities are 0.113 K-1 and 1.66% K-1, respectively. These characteristics all demonstrate that Bi/Yb codoped Cs2Ag0.6Na0.4InCl6 MCs can be excellent and novel luminescent materials for non-contact temperature measurement.