Pressure-Induced Distinct Self-Trapped Exciton Emission in Sb³⁺-Doped Cs₂NaInCl₆ Double Perovskite

Abstract The Cs₂NaInCl₆ double perovskite is one of the most promising lead-free perovskites due to its exceptional stability and straightforward synthesis. However, it faces challenges related to inefficient photoluminescence. Doping and high pressure are employed to tailor the optical properties of Cs₂NaInCl₆. Herein, Sb³⁺ doped Cs₂NaInCl₆ (Sb³⁺:Cs₂NaInCl₆) was synthesized and it exhibits blue emission with a photoluminescence quantum yield of up to 37.3%. Further, by employing pressure tuning, a blue stable emission under a very wide range from 2.7 GPa to 9.8 GPa is realized in Sb³⁺:Cs₂NaInCl₆. Subsequently, the emission intensity of Sb³⁺:Cs₂NaInCl₆ experiences a significant increase (3.3 times) at 19.0 GPa. It is revealed that the pressure-induced distinct emissions can be attributed to the carrier self-trapping and detrapping between Cs₂NaInCl₆ and Sb³⁺. Notably, the lattice compression in the cubic phase inevitably modifies the band gap of Sb³⁺:Cs₂NaInCl₆. Our findings provide valuable insights into effects of the high pressure in further boosting unique emission characteristics but also offer promising opportunities for development of doped double perovskites with enhanced optical functionalities.