Flexible and Rewritable Non‐Volatile Photomemory Based on Inorganic Lanthanide‐Doped Photochromic Thin Films

Emerging wearable electronics are spurring unprecedented enthusiasm in the pursuit of next-generation memory realizable on flexible substrates. Photochromic materials enable reversible manipulation and possess erasable/rewritable capability, which ensure them to be adequate candidates as optical memories. Nevertheless, it has been challenging to develop a flexible optical memory with organic photochromic elements that simultaneously meets the stringent thermo- and photostable requirements. Inorganic lanthanide Er3+-doped bismuth layer-structure ferroelectric Na0.5Bi2.5Nb2O9 (NBN:Er) exhibits superior photochromic performance. The coupling between lanthanide upconversion emission and photochromic effect enables rewritable and nondestructive readout characteristics. Low-dimensional complex oxide materials have superior mechanical properties and can be subject to large strain by integration with flexible substrates. Recent advances in synthesizing high-quality inorganic oxide films on flexible substrates provide new opportunities to build flexible optical memories with dramatically higher performance. Herein, NBN:Er thin films have been integrated with flexible polyimide substrates. These hybrid heterostructures demonstrate comprehensive robust characteristics that sustain well during the 10(5) bending cycles, and maintain stability over many write-read-erase cycles. This work addresses the main problems hampering the promising applications of inorganic photochromic materials and paves the way for developing more flexible and compact optical memories.