Ultraviolet-Adaptive Transparent Films with Electromagnetic Interference Shielding for Smart Window Applications

The increasing demand for smart buildings calls for transparent window films that can integrate electromagnetic interference (EMI) shielding with reversible light-responsive functionality. However, integrating stable photochromic functionality with high transparency, efficient EMI shielding, and functional coupling between these properties remains challenging. Herein, a multifunctional transparent composite film was developed by incorporating phosphotungstic acid (PWA) into a poly(methyl methacrylate) (PMMA) matrix, followed by spray-coating silver nanowire (AgNWs) network and hot pressing to construct a sandwich structure. In this architecture, the PWA/PMMA layers provide ultraviolet (UV) irradiation-responsive photochromism and encapsulation protection, while the embedded AgNWs network serves as both a transparent conductive pathway for EMI shielding and a Joule heating element. Owing to the enhanced AgNWs interjunction contact and effective encapsulation, the film exhibits an EMI shielding effectiveness of 24.1 dB in the X-band with a high optical transmittance of 79.7% at 550 nm at an AgNWs areal density of 0.56 mg/cm 2 . Under UV irradiation, the composite film undergoes a reversible color change from colorless to blue, with an initial photoresponse observed within 3 s and a saturated coloration reached within 20 min, corresponding to an absorbance of 0.58 at 730 nm at a UV dose of 120 kJ/m 2, and maintains 96.97% of its initial colored-state absorbance at 730 nm after 100 coloration–bleaching cycles. The film also maintains stable EMI shielding performance after prolonged exposure, demonstrating its promise for smart window applications.