Embedding Te(IV) into a Robust Sn(IV)-Based Metal Halide for Deep-Red Emission

Organic–inorganic hybrid Sn(IV)-based metal halides have received wide attention due to their excellent structural stability. However, realizing red-emitting Sn(IV)-based metal halides with high stability and efficient photoluminescence (PL) efficiency remains challenging. Here, a stable organic–inorganic Sn(IV)-based metal halide (C₈H₁₀O₂N)₂SnCl₆ with a zero-dimensional (0D) structure has been obtained, which, however, displays poor PL properties due to the inert expression of Sn⁴⁺-4d¹⁰ electrons and the intrinsic indirect band gap feature. To address the above challenges, Te⁴⁺ with an active 5s² lone pair is embedded into the lattice of (C₈H₁₀O₂N)₂SnCl₆, and as a result, 5%Te⁴⁺-doped (C₈H₁₀O₂N)₂SnCl₆ with a direct band gap exhibits a broadband deep-red emission (∼688 nm) with a high PL efficiency (∼53%). Experimental and calculated results reveal that the embedding of Te⁴⁺ can effectively regulate the band structure of (C₈H₁₀O₂N)₂SnCl₆ to facilitate the transformation from an indirect to a direct band structure, thereby leading to efficient radiative recombination. Benefiting from the above merits, a high-efficiency white light-emitting diode (WLED) has been fabricated using Te⁴⁺-doped (C₈H₁₀O₂N)₂SnCl₆ with an ultrahigh color rendering index (CRI) of up to 94.5, suggesting the great potential of this material for solid-state lighting. This work provides significant insight into the design of highly efficient red-emitting phosphors for organic–inorganic hybrid metal halides.