Integrated Electrochromic‐Electromagnetic Shielding‐Energy Storage Smart Window Based on PEDOT@Fe ₃ O ₄ Core–Shell Functional Layer

Abstract Amid intensifying energy and electromagnetic (EM)‐pollution pressures, smart windows that couple light modulation with EM protection are urgently needed. Electrochromic (EC) windows offer low power and high contrast; however, multifunctional EC devices often suffer from structural complexity and unstable interfaces, impeding integration. Here, therefore a WO ₃ –PEDOT@Fe ₃ O ₄ composite cathode paired with a Prussian blue (PB) anode is engineered to assemble an electromagnetic‐shielding smart window (ESSW). Specifically, the ESSW delivers 53% UV–vis modulation at 611 nm, fast switching (3.1 s coloration; 4.7 s bleaching), high coloration efficiency (104.7 cm ² C ⁻¹ ), and durable cycling (93.4% of the initial current density after 600 cycles). Moreover, the ESSW cathode exhibits a capacitive contribution of 86.4% and an areal capacitance of 25.12 mF cm ⁻² at a discharge current density of 0.2 mA cm ⁻² . Owing to multiple loss pathways introduced by PEDOT@Fe ₃ O ₄ , the EMI shielding effectiveness consequently rises from 15.3 dB (WO ₃ ‐ECD) to 31.8 dB (ESSW). Furthermore, a 10 cm × 10 cm spray‐coated prototype demonstrates scalability and, in a sunroom scenario, reduces indoor EM‐radiation intensity from 108.2 to 19.2 µW cm ⁻² . Such smart windows, integrating electrochromism, energy storage, and EMI shielding, show strong application potential in aerospace, energy‐efficient buildings, and defense equipment.