Kinetics-Tunable Hydrochromic Luminescence Switching in Rb₃TbF₆ : Eu³⁺ Perovskite

Hydrochromic luminescent materials that are responsive to water or moisture have attracted considerable attention owing to their extensive use in sensing and information security. However, fine-tuning hydrochromic response to water content remains unfulfilled research, posing constraints in the widespread application of hydrochromic luminescence. This study reports a 0D Rb₃TbF₆ perovskite with highly controllable hydrochromic characteristics. The Rb₃TbF₆ crystals exhibit a distinct hydrochromic luminescence switching after B-site doping with Eu³⁺, stemming from Rb₃TbF₆ to Rb₂TbF₅ transformation that triggers intra-crystal Tb³⁺-to-Eu³⁺ energy transfer. Through A-site alkaline metal alloying, the sensitivity of the perovskite to water stimuli is precisely tuned, rendering distinct responses over a wide range of humidity conditions (RH: 1–90% RH) and water levels (v/v: 0.5–55%). As an added benefit, the hydrochromic crystals also show excellent repeatability and photothermal stability. These advances on hydrochromic materials provide exciting opportunities in water detection, humidity sensing, and multi-level information encryption. © 2024 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH.