Stretch‐Assembled Flexible Circularly Polarized Luminescence Films for Multifunctional Anti‐Counterfeiting

ABSTRACT Circularly polarized luminescence (CPL) perovskite materials attract significant research attention due to their excellent optoelectronic performance. However, existing materials suffer from intrinsically weak CPL intensity and poor signal tunability, severely limiting practical applications. Herein, a novel flexible and stretchable two‐layer composite film is fabricated via mechanical stretch‐assisted assembly. It adopts a stacked structure composed of a CsPbBr 3 ‐based linearly polarized luminescence film and a pure ethylene‐vinyl acetate (EVA) film, delivering a high luminescence dissymmetry factor of g lum = 0.307. Specifically, CsPbBr 3 nanowires (NWs) are aligned in an EVA matrix via mechanical stretching to construct a linearly polarized luminescent layer. A pure EVA film is stretched to align the quarter‐wave phase retardation with the emission wavelength of CsPbBr 3 NWs. Assembling the two layers at ±45° enables left‐handed CPL and right‐handed CPL, respectively. The excellent flexibility, structural stability, and dynamically tunable CPL performance (where g lum can be modulated by the stretch ratio) of this composite film, together with the demonstrated potential in curved‐surface anti‐counterfeiting and encrypted information recognition, provides a new paradigm for the development of high‐performance flexible CPL devices.