Tm3+-doped Cs2Ag0.6Na0.4In0.9Bi0.1Cl6 microcrystals for thermometry

Lead-free double perovskites have superb luminescence properties for broad applications. However, increasing or improving near-infrared (NIR) photoluminescence (PL) is still a challenge. In this paper, a high-performance microcrystal is designed based on Tm 3+ heavily doped Cs 2 Ag 0.6 Na 0.4 In 0.9 Bi 0.1 Cl 6 (CANIBC), which realize both the self-trapped excitons (STEs) and Tm 3+ NIR emission. The emission mechanism and energy transfer (ET) process are studied by steady-state and time-resolved PL spectra. The ET efficiency from STEs to Tm 3+ can reach 38.3 %, and the NIR PL quantum yield of Tm 3+ can reach 22.7 %. Meanwhile, the PL spectra of Tm 3+ -doped CANIBC microcrystals (MCs) with different concentrations are used to investigate their temperature sensing properties based on both fluorescence intensity ratio (FIR) and lifetime. Based on the FIR, relative sensitivity ( S r ) can reach 2.93 % K −1 at 303 K. Moreover, based on lifetimes, S r can maintain more than 1.55 % K −1 from 303 to 453 K, and maximum S r can also achieve 2.38 % K −1 at 360 K. These excellent luminescence and sensing properties offer greater development potential in the field of NIR phosphor and thermometry.