Lead-Free Broadband Orange-Emitting Zero-Dimensional Hybrid (PMA)₃InBr₆ with Direct Band Gap

Low-dimensional organic-inorganic hybrid metal halides have emerged as broadband light emitters for phosphor-converted white light-emitting diodes (WLEDs). Herein, we report a new zero-dimensional (0-D) lead-free metal halide (PMA)₃InBr₆ [PMA⁺: (C₆H₅CH₂NH₃)⁺] that crystallizes in the monoclinic system with P2₁/c space group. The structure consists of slightly distorted [InBr₆]^3- octahedra surrounded by organic PMA⁺ cations. The direct band gap characteristic of (PMA)₃InBr₆ was demonstrated by density functional theory calculation, and its relatively wide band gap of 3.78 eV was experimentally determined. Upon 365 nm ultraviolet light excitation, (PMA)₃InBr₆ exhibited strong broadband orange luminescence with a full-width at half-maximum of ∼132 nm resulting from self-trapped exciton emission, and the photoluminescence quantum yield was determined to be ∼35%. A WLED fabricated by combining the orange-emitting (PMA)₃InBr₆, a green phosphor Ba₂SiO₄:Eu²⁺, and a blue phosphor BaMgAl₁₀O₁₇:Eu²⁺ exhibited a high color-rendering index of 87.0. Our findings indicate that the organic-inorganic hybrid (PMA)₃InBr₆ may have potential for luminescence-based applications.