Luminescence chromaticity regulation and dual-mode temperature sensing of Sb3+/Ln3+ (Ln3+ = Er3+, Ho3+) doped Cs2NaLuCl6

All-inorganic lead-free halide double perovskites (HDPs) with unique soft lattice structure have attractive photoluminence (PL) from self-trapping excitons (STEs). However, pristine HDPs suffer from low PL quantum yiled and narrow color gamut, collectively hindering their applications. Here, heavy metal ion Sb 3+ is introduced into rare-earth-based Cs 2 NaLuCl 6 HDPs to enhance the blue emission intensity of STEs and the mechamism is illustrated through DFT calulation. Then lanthanide ions (Ln 3+  = Er 3+ , Ho 3+ ) are added in blue light emissive Cs 2 NaLuCl 6 : Sb 3+ and typical green and red light emission can be obtained via the energy transfer (ET) from STEs to Er 3+ and Ho 3+ , respectively. Luminescence chromaticity modulation and white emission is achieved by adjusting the doping content of Ln 3+ . Leveraging the distinct thermal responses of STEs and Er 3+ emissions in Cs 2 NaLuCl 6 : Sb 3+ , Er 3+ , a dual-mode fluorescence intensity ratio (FIR) thermometer is proposed by integrating non-thermally coupled energy levels (NTCL) and thermally coupled energy levels (TCL) of STEs and Er 3+ . The dual-mode FIR thermometer exhibits pronounced chromaticity variation (CIE Δy = 0.072) with temperature range from 294 to 473 K, elevated sensitivity (S r  = 1.24 %) at 293 K and better repeatability test, demonstrating its application for high-precision visualized optical temperature sensing.