From Molecular Rotor to Solid‐State Emitter: Unlocking Blue‐Light‐Excitable Narrow‐Band Green Emission in Hybrid Bismuth Halide for Backlight Display

ABSTRACT Developing blue‐light‐excitable narrow‐band green‐emitting materials is crucial for next‐generation backlight displays. Here, we designed and synthesized a novel 0D hybrid bismuth halide, (OfloH 2 ) 2 Bi 2 Cl 10 ·3H 2 O (OBCH), using optically active ofloxacin (OFL) as the organic component. Under blue excitation, it exhibits bright narrow‐band green‐emission peaks at 515 nm. Although OBCH retains the intrinsic green emission originating from protonated OFL solution, its fluorescence exhibits a narrowed FWHM of 59 nm, attributed to enhanced structural rigidity resulting from the rigid bismuth halide framework and the layered stacking of organic cations. Benefiting from its strong blue light excitation, narrow FWHM, a stable white light‐emitting diode device was fabricated by combining the 460 nm blue InGaN LED chip, green‐emitting OBCH, and red‐emitting KSF: Mn 4+ with a luminous efficiency of 92.34 lm/W and a wide color gamut of 109.2% sRGB standard. This work not only provides a universal strategy for utilizing rigid and stable metal halide lattices as “reactors” to confine and modulate the photophysical behavior of organic luminophor, thereby unlocking superior performance unattainable in their free state, but also offers new insights for designing next‐generation high‐performance luminescent materials.