Hexagonal Halide Perovskite Cs₂LiInCl₆: Cation Ordering, Face‐Shared Octahedral Trimers and Mn²⁺ Luminescence

Abstract

The In‐based double perovskite halides have been widely studied for promising optical‐electric applications. The halide hexagonal perovskite Cs2LiInCl6 was isolated using solid‐state reactions and investigated using X‐ray diffraction and solid‐state NMR spectra. The material adopts a 12‐layered hexagonal structure (12R) consisting of layered cationic orders driven by the cationic charge difference and has Li+ cations in the terminal site and In3+ in the central site of face‐shared octahedron trimers. Such a cationic ordering pattern is stabilized by electrostatic repulsions between the next‐nearest neighboring cations in the trimers. The LiCl6 octahedron displays large distortion and is confirmed by 7Li SSNMR in the Cs2LiInCl6. The Cs2LiInCl6 material has a direct bandgap of ~ 4.98 eV. The Cs2LiInCl6: Mn displays redshift luminescence (centered at ~610 ‐ 622 nm) from the substituted Mn2+ emission in octahedron with larger PLQY (17.8%‐48%) compared with that of Cs2NaInCl6: Mn2+. The Mn‐doped materials show luminescent concentration quenching and thermal quenching. The composition Cs2Li0.99In0.99Mn0.02Cl6 exhibits the highest PL intensity, a maximum PLQY of 48%, and high luminescent retention rate of ~ 86% below 400 K and is suitable for application for pc‐LED. These findings contribute to our understanding of the chloride perovskites and hold potential for widespread optical applications.