Tailor‐Made Host–Guest Organic–Inorganic Hybrid Antimony Halide Enables Efficient Light‐Emitting Diodes

Abstract Organic–inorganic antimony (Sb) halides are garnering increasing interest for lead‐free perovskite light‐emitting diodes (LEDs), but the non‐radiative recombination and poor charge transport are hard‐treat case to restrict their electroluminescent performance. Here we developed efficient Sb halide LEDs based on the tailor‐made host‐guest (Ph 4 P) 2 SbCl 5 (Ph 4 P = tetraphenylphosphonium) emitters that enable good luminescence and charge transport properties simultaneously. Experimental and theoretical studies reveal that the self‐trapped excitons triggered by excited‐state structural deformation were localized in spatial‐confined [SbCl 5 ] 2− polyhedrons, generating a high photoluminescence quantum yield (96.8%). The host–guest (Ph 4 P) 2 SbCl 5 emitter with 35DCzPPy (3,5‐bis(3‐(carbazol‐9‐yl)phenyl) pyridine) host shows an enhanced radiative recombination, rooting in the type‐I energy level configuration and efficient energy transfer between 35DCzPPy and (Ph 4 P) 2 SbCl 5 . The 35DCzPPy with delocalized molecular orbital enhances the electrical properties of emitters, which balances the charge transport/injection in devices. These benefits result in efficient Sb halide LEDs with a record‐high luminance of 6689 cd m −2 and external quantum efficiency of 6.47%. Moreover, large‐area LEDs with an emitting area up to 900 mm 2 were demonstrated with uniform emission. This work provides meaningful insights into reaching high‐performance metal halide LEDs towards future practical applications.