Stepwise Unlock Full‐Spectrum Emission with Abnormal Anti‐Thermal Quenching in Indium‐Based Metal Halides by Tailoring Their Crystal Structure Engineering

Abstract Lead‐free metal halides with tunable optical properties have emerged as a class of optoelectronic materials with great application potential. The optical properties of metal halides are closely related to their crystal structures, and the diversity of crystal structures is a key factor in achieving efficient tunable emission. Herein, four different Sb 3+ ‐doped In 3+ ‐based metal halides of 3D Cs 2 KInCl 6 :Sb 3+ , 1D (DFEA) 2 KInCl 6 :Sb 3+ and (DFEA) 2 (NH 4 )InCl 6 :Sb 3+ , and 0D (DFEA) 3 InCl 6 :Sb 3+ (DFEA = 2, 2‐difluoroethylamine) are reported, all of which exhibit different crystal structures, resulting in efficient tunable emission bands shift from 495 to 605 nm. It is found that the larger [SbCl 6 ] 3− distortion is the reason for the redshift of the emission band, which allows to stepwise unlock the full‐spectrum emission with ultra‐high luminescence efficiency. Compared all‐inorganic Cs 2 KInCl 6 :Sb 3+ , the other three Sb 3+ ‐doped hybrid In 3+ ‐based metal halides exhibit abnormal anti‐thermal quenching behavior, which should be attributed to the participation of shallow trapped states caused by the structural defects. The tunable emission characteristics of Sb 3+ ‐doped metal halides make them show great application potential in solid‐state lighting, optical anti‐counterfeiting, and information encryption.