Sb ³⁺ ‐Doping Induced Self‐Trapped Excitons and Ultrafast Carrier Dynamics in 0D Hybrid Indium Halides

Abstract Organic‐inorganic metal halides (OIMH) doped with Sb ³⁺ often exhibit excellent optoelectronic properties, however, their photoluminescence (PL) mechanisms, especially after Sb ³⁺ doping, require a deeper understanding of their excited states and optical transitions. Through synergistic analysis of temperature‐dependent PL and femtosecond transient absorption (fs‐TA） spectroscopic study, the coexistence of dual polaronic states and their temperature‐dependent transient bipolaronic state absorption processes in 0D Sb ³⁺ :(C ₂ H ₈ N) ₄ InCl ₇ system have been identified: (1) Sb ³⁺ ‐site polaron or self‐trapped exciton(STE) emission originating from spin‐allowed ( ³ P ₁ → ¹ S ₀ ) and ( ¹ P ₁ → ¹ S ₀ ) in SbCl ₆ octahedra) is favorably formed first, giving emission at 615 nm at room temperature; (2) In ³⁺ ‐Sb ³⁺ donor‐acceptor pair (DAP) STE (In ³ P ₁ → Sb ¹ S ₀ ) can be produced under 111.2 cm ⁻¹ Longitudinal Optical (LO) phonon assistance at 160 K and giving emission 700 nm at room temperature. Both polaronic states can collaborate to give the broad emission with a photoluminescence quantum yield (PLQY) of 98.4%. Though 0D structure, close energy span between Sb(III) and In(III) can cause such DAP behavior for Sb ³ ⁺ with 5s ² electrons in the In‐Cl matrix, this provides key insights into the radiation synergy effects with the host via short and long‐range phonons. This model paves the way for developing novel high‐performance luminescent materials for optoelectronic applications.