Tailoring Self-Trapped Exciton Emission in 0D Indium-Based Perovskites by Solvent-Induced Crystal Structure Engineering

Abstract

0D indium-based all-inorganic metal halide perovskites offer great potential for multifunctional applications but face the challenges of poor structural adjustability and an incomplete dynamic picture of self-trapped exciton (STE) emissions. Here, a novel 0D Cs₄InCl₇ single crystal is developed as a solvation bridge for phase transformations to either 0D Cs₂InCl₅·H₂O via water or into 0D Cs₃InCl₆ by methanol. The diversified crystal structures not only enrich the emission colors but also the difference in the coordination number and symmetry of Cs⁺, laying foundations for comprehending the influence of A-site on STE emissions. Steady-state and transient spectroscopy together with density functional theory simulations, reveal that low coordination geometry and charge symmetry of octahedron facilitate excited state distortions, leading to strong second-order Jahn-Teller (SOJT) effect for large Stokes shift of STE emissions. Multicolor tuning in Sb³⁺-doped Cs₄InCl₇ under solvent and heat stimuli enables the extended optical applications in anti-counterfeiting, temperature sensing, and solvent sensors. The work offers an improved understanding of SOJT manipulation via atomic engineering of A-site in 0D lead-free perovskites and sheds light on their broad practical applications.