Lead-free broadband orange-emitting zero-dimensional Sb3+-doped indium-based organic–inorganic metal halides

Abstract

Low-dimensional organic–inorganic metal halides have shown great application potential and new opportunities for use in solid-state lighting due to their excellent optical and electronic properties. However, the most studied hybrid compounds contain lead, which limits their application environments. The preparation of organic–inorganic metal halides with high luminous efficiency, long-term stability, and a lead-free composition for environmental protection has become an important goal for the design of materials. Here, novel Sb³⁺-doped indium-based metal halides, (CH₃NH₃)₄InCl₆·Cl, have been designed and synthesized via a simple mechanical ball milling method; in the lead-free zero-dimensional (0D) halide (CH₃NH₃)₄InCl₆·Cl, isolated [InCl₆]³⁻ octahedra are separated by methylamine cations. Under UV excitation, the bulk-phase powder exhibits broadband orange-yellow emission peaking at 607 nm with a full width at half-maximum of ∼160 nm upon incorporating Sb³⁺ into the (CH₃NH₃)₄InCl₆·Cl matrix. The photoluminescence quantum yield (PLQY) of Sb³⁺-doped (CH₃NH₃)₄InCl₆·Cl is as high as 67.72%. The effects of the Sb₃⁺-doping concentration on the crystal structure and optical characteristic have been investigated. The indirect band gap characteristics of (CH₃NH₃)₄InCl₆·Cl were demonstrated via density functional theory (DFT) calculations, and the relatively wide band gaps of 3.83 eV and 2.99 eV of (CH₃NH₃)₄InCl₆·Cl and (CH₃NH₃)₄ClInCl₆:Sb³⁺ were experimentally determined. These experimental results suggest that the as-prepared Sb³⁺-doped (CH₃NH₃)₄InCl₆·Cl has potential applications in solid-state lighting devices.