Efficient photochromic self-recovery behavior in Tm/Yb co-doped K0.5Na0.5NbO3 thick films

Photochromic (PC) materials have potential applications in the fields of memory, anti-counterfeiting due to their reversible writable/erasable properties. The common organic PC films are restricted during applications owing to the strict requirements of thermal stability and waterproof of devices. Additionally, most of the PC materials strongly rely on external conditions (irradiation/heat) to realize reversible PC regulations, which may cause irreversible damage to devices (reduce the performance and service life). Hence, it is imperative to develop new inorganic membrane materials with PC self-recovery behavior. Here, a novel strategy to achieve completely reversible PC regulation based on the K0.5Na0.5NbO3 (KNN) based thick films is reported. It is worth noting that the PC self-recovery behavior can be optimized via forming the inter-electronic-levels in the band gap via Tm/Yb co-doping in KNN, alleviating the barrier of carrier transition from valence band to conduction band and heightening the recombination efficiency of carriers. And the obtained thick films manifest a reversible PC self-recovery reaction within 6 min. This work is expected to provide the effective guidance for facilitating the further utilization of PC materials.