Twin-Perovskite\nStructured Ba<sub>8</sub>Ti<sub>3</sub>Nb<sub>4</sub>O<sub>24</sub>: Pr<sup>3+</sup>: A Fast Photochromics\nwith Millisecond-Level Response Speed for Optical Storage

Photochromism (PC) involves profound and complex optoelectronic\nprocesses and the interplay of color centers and the host matrix.\nTo date, achieving a fast PC response speed remains a challenge. Here,\na new fast PC “twin-perovskite” niobate ceramic, Ba<sub>8</sub>Ti<sub>3</sub>Nb<sub>4</sub>O<sub>24</sub>: Pr<sup>3+</sup> (BTN:Pr<sup>3+</sup>), exhibiting a remarkable PC response time\ndown to 20 ms and a record PC contrast of 42.3% among niobate-based\nPC materials, is identified. Experimental and theoretical approaches\nreveal the key role of the oxygen vacancy in the PC reaction. It is\nproposed that the fast PC response is related to the short time spent\nredistributing charge carriers due to a single type of color center\nand the quick transport of charge carriers within the densely packed\ncrystal framework featuring a face-sharing twin-plane structure. Finally,\nwe present demo experiments of real-time write-display of information\nin a repeatable manner and demonstrate bit-by-bit information optical\nstorage at high write speeds that could be read in dual modes.