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 Tm3+ heavily doped Cs2Ag0.6Na0.4In0.9Bi0.1Cl6 (CANIBC), which realize both the self-trapped excitons (STEs) and Tm3+ 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 Tm3+ can reach 38.3 %, and the NIR PL quantum yield of Tm3+ can reach 22.7 %. Meanwhile, the PL spectra of Tm3+-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 (Sr) can reach 2.93 % K−1 at 303 K. Moreover, based on lifetimes, Sr can maintain more than 1.55 % K−1 from 303 to 453 K, and maximum Sr 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.