Dual‐mode reversible photoluminescence tuning in rare‐earth doped scheelite thin films via mechanical strain

Flexible optoelectronic technology has shown great application prospects in various fields. The appealing aspect of this technology lies in the reversible regulation of the luminescent properties of materials through external stimuli. Epitaxial CaWO 4 :Er 3 ⁺/mica heterostructures fabricated by van der Waals epitaxy exhibit record photoluminescence modulation under mechanical strain. Under an in‐plane compressive strain of −0.15%, a unprecedented photoluminescence enhancement of Δ I / I = 1286% is realized, accompanied by a strain‐photoluminescence efficiency of ΔI/I·Δε −1 = 6429. This all‐inorganic platform enables dual‐mode optical responses (intensity modulation and color shift), outperforming in sensitivity. Our approach establishes a universal paradigm for strain‐engineered luminescent films, enabling flexible displays with dynamic spectral control under stress.