All Optically Switchable Active Photonics Based on the Halide Perovskite GST Platform

Abstract Halide perovskites are a class of semiconductors with strong direct interband transition and high mobility of charge carriers resulting in bright luminescence, which can be easily tuned chemically in a broad spectral range. Moreover, perovskites can be synthesized by means of simple wet chemistry approaches on arbitrary surfaces, opening new avenues for perovskites integration with a plethora of other functional materials. Here, this work reports on a versatile platform for reversible switching of halide perovskite's optical properties enabled by high‐index phase‐change materials (Ge‐Sb‐Te) serving as an active subnanolayer, which controls the perovskite film's behavior. Based on this approach, this work demonstrates micro‐QR‐coding and switchable bright emission, whose wavelength can be adjusted in the whole visible range.