Deformation‐Tolerant Functional Elastomer Overlayers for Haze‐Assisted Light Extraction and Color Conversion in Stretchable Mechanoluminescent Films

ABSTRACT Mechanoluminescence (ML), which converts mechanical stimuli into light without an external power supply, offers opportunities for self‐powered optical sensing, wearable displays, soft robotics, and adaptive light‐emitting systems. ZnS:Cu particles embedded in a poly(dimethylsiloxane) matrix (ZnS:Cu‐PDMS) represent an attractive stretchable ML platform because they generate strong emission under mechanical deformation. However, most strategies for improving ML performance rely on modifying the emissive composite itself, limiting independent control over postemission photon extraction and spectral conversion. Here, a modular functional elastomer overlayer strategy is presented to decouple ML generation from photon extraction and color conversion in ZnS:Cu‐PDMS composite films. Polyurethane (PU), nematic liquid crystal (NLC)‐loaded PU (NLC‐PU), 4‐(dicyanomethylene)‐2‐methyl‐6‐(p‐dimethylaminostyryl)‐4H‐pyran (DCM)‐doped PU, and DCM‐ and NLC‐loaded PU (DCM‐NLC‐PU) overlayers are integrated as independently tunable optical layers. NLC‐PU forms birefringent NLC‐rich domains that provide visible‐range haze, strain‐responsive optical anisotropy, and broadband, nonresonant photon redistribution. When applied to ZnS:Cu‐PDMS films, NLC‐PU enhances outwardly collected green ML while preserving the intrinsic emission spectrum. DCM‐containing overlayers enable green‐to‐yellow‐orange color conversion, while DCM‐NLC‐PU combines spectral conversion with scattering‐assisted outward emission enhancement. This overlayer architecture provides a deformation‐tolerant route for controlling brightness and color in stretchable ML platforms.