Self-Trapped Exciton Emission in Highly Polar 0D Hybrid Ammonium/Hydronium-Based Perovskites Triggered by Antimony Doping

Various monovalent cations are employed to construct metal halide perovskites with various structures and functionalities. However, perovskites based on highly polar A-site cations have seldom been reported. Here, a novel hybrid 0D (NH₄)_x(OH₃)_3-xInCl₆ perovskite with highly polar hydronium OH₃⁺ cations is introduced in this study. Upon doping with Sb³⁺, hybrid 0D (NH₄)_x(OH₃)_3-xInCl₆ single crystals exhibited highly efficient broadband yellowish-green (550 nm) and red (630 nm) dual emissions with a PLQY of 86%. The dual emission arises due to Sb³⁺ occupying two sites within the crystal lattice that possess different polarization environments, leading to distinct Stokes shift energies. The study revealed that lattice polarity plays a significant role in the self-trapped exciton emission of Sb³⁺-doped perovskites, contributing up to 25% of the Stokes shift energy for hybrid 0D (NH₄)_x(OH₃)_3-xInCl₆:Sb³⁺ as a secondary source, in addition to the Jahn-Teller deformation. These findings highlight the potential of Sb³⁺-doped perovskites for achieving tunable broadband emission and underscore the importance of lattice polarity in determining the emission properties of perovskite materials.