Self-trapped exciton luminescence of tellurium doped zero-dimensional tetraethyl tin chloride for optical thermometry

Abstract

To reduce the toxicity of lead and improve the photoluminescence (PL) quantum yield (PLQY), organic–inorganic hybrid perovskites garner widespread attention. In this work, a novel Te⁴⁺ doped Sn^(IV)-based hybrid metal halide (TEA)₂SnCl₆ (TEA = tetraethylammonium) is successfully synthesized via a solvothermal method. The spectroscopic characteristics of various samples are investigated by temperature-dependent PL and Raman methods. The (TEA)₂SnCl₆:5%Te exhibits a broad emission peaked at 597 nm with a full width at half maximum (FWHM) of 0.41 eV and a maximum PLQY of 62.8%. The [TeCl₆]²⁻ octahedron exhibits a greater propensity for lattice distortion compared to the [SnCl₆]²⁻ octahedron, in which distortion leads to the electrons being localized around the Te⁴⁺ ion, resulting in the formation of self-trapped excitons (STEs). Upon photoexcitation, these excitons undergo a transition from their ground state to an excited state. Following deexcitation, they recombine and produce orange light emission. The band gap, density of states and charge distribution are analyzed via first-principle calculations, which agree well with the experimental results. The fluorescence lifetime of (TEA)₂SnCl₆:5%Te is performed in optical thermometry and the maximum values for relative sensitivity (S_R) and absolute sensitivity (S_A) reach up to 0.57% K⁻¹ and 1 × 10⁻² K⁻¹ in the range of 100 to 340 K, respectively. (TEA)₂SnCl₆:5%Te demonstrates excellent luminous performance and optical thermometric capabilities, making it a promising material for advanced optoelectronic applications.