Site Specific In3⁺‐Alloying Unlocks Intense Photoluminescence and High Stability in Antimony Halide Hybrids for WLED and Anticounterfeiting Applications

Abstract While metal doping strategies have proven effective in regulating the bandgap and enhancing the photophysical properties of hybrid metal halides, site‐specific atom alloying by mixing metals of different elements offers a new route for material modification. Here an antimony halide hybrid material with the formula of (C₄H₁₂N₂)₅[(SbCl₅)₂(SbCl₆)Cl₄] ( Py‐SbCl ) is shown with crystallographically independent alternating square pyramidal [SbCl₅] and octahedral [SbCl₆] sites sandwiched by organic layers. Interestingly, the octahedral site of the [SbCl₆] can be fully replaced by the In 3+ ions, forming the alloyed compound (C₄H₁₂N₂)₅[(SbCl₅)₂(InCl₆)Cl₄] ( Py‐SbInCl ). More importantly, the latter shows a near‐unity photoluminescence quantum yield of 97%, which is ≈7 times of enhancement compared to the pristine Py‐SbCl compound. This is mainly due to the much‐enhanced Young's modulus, higher radiative decay rates and longer electron transient rates, presumably stemming from shorter In─Cl bond distances and higher dipole moments, as revealed by a cocktail study of X‐ray single‐crystal crystallography, density functional theory, femtosecond transient absorption spectroscopy and so on. In addition, it is shown that Py‐SbInCl is an excellent yellow phosphor that can be used for white light‐emitting diodes and other applications such as counterfeiting. Therefore, making site‐specific alloying compounds may open a new design approach for functional bimetallic hybrid materials.