Hexagonal Halide Perovskite CsLiInCl: Cation Ordering, Face-Shared Octahedral Trimers and Mn Luminescence.

The In-based double perovskite halides have been widely studied for promising optical-electric applications. The halide hexagonal perovskite CsLiInCl 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 In 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 LiCl octahedron displays large distortion and is confirmed by Li SS NMR in the CsLiInCl. The CsLiInCl material has a direct bandgap of ~4.98 eV. The CsLiInCl: Mn displays redshift luminescence (centered at ~610-622 nm) from the substituted Mn emission in octahedron with larger PLQY (17.8 %-48 %) compared with that of CsNaInCl: Mn. The Mn-doped materials show luminescent concentration quenching and thermal quenching. The composition CsLiInMnCl 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.