Full-color, time-valve controllable and Janus-type long-persistent luminescence from all-inorganic halide perovskites

Long persistent luminescence (LPL) has gained considerable attention for the applications in decoration, emergency signage, information encryption and biomedicine. However, recently developed LPL materials - encompassing inorganics, organics and inorganic-organic hybrids - often display monochromatic afterglow with limited functionality. Furthermore, triplet exciton-based phosphors are prone to thermal quenching, significantly restricting their high emission efficiency. Here, we show a straightforward wet-chemistry approach for fabricating multimode LPL materials by introducing both anion (Br-) and cation (Sn2+) doping into hexagonal CsCdCl3 all-inorganic perovskites. This process involves establishing new trapping centers from [CdCl6-nBrn](4-) and/or [Sn2-nCdnCl9](5-) linker units, disrupting the local symmetry in the host framework. These halide perovskites demonstrate afterglow duration time ( > 2,000 s), nearly full-color coverage, high photoluminescence quantum yield (similar to 84.47%), and the anti-thermal quenching temperature up to 377 K. Particularly, CsCdCl3:x%Br display temperature-dependent LPL and time-valve controllable time-dependent luminescence, while CsCdCl3:x%Sn exhibit forward and reverse excitation-dependent Janus-type luminescence. Combining both experimental and computational studies, this finding not only introduces a local-symmetry breaking strategy for simultaneously enhancing afterglow lifetime and efficiency, but also provides new insights into the multimode LPL materials with dynamic tunability for applications in luminescence, photonics, high-security anti-counterfeiting and information storage.