Achieving Near‐unity Photoluminescence Quantum Yields in Organic‐Inorganic Hybrid Antimony (III) Chlorides with the [SbCl₅] Geometry

Hybrid organic-inorganic antimony halides have attracted increasing attention due to the non-toxicity, stability, and high photoluminescence quantum yield (PLQY). To shed light on the structural factors that contribute to the high PLQY, five pairs of antimony halides with general formula A₂ SbCl₅ and A₂ Sb₂ Cl₈ are synthesized via two distinct methods and characterized. The A₂ SbCl₅ type adopts square pyramidal [SbCl₅ ] geometry with near-unity PLQY, while the A₂ Sb₂ Cl₈ adopts seesaw dimmer [Sb₂ Cl₈ ] geometry with PLQY≈0 %. Through combined data analysis with the literature, we have found that A₂ SbCl₅ series with square pyramidal geometry generally has much longer Sb⋅⋅⋅Sb distances, leading to more expressed lone pairs of SbIII . Additional factors including Sb-Cl distance and stability of antimony chlorides may also affect PLQY. Our targeted synthesis and correlated insights provide efficient tools to precisely form highly emissive materials for optoelectronic applications.