Window-film-integrated, near-infrared (NIR) absorption-based nanomaterials are of great interest in terms of numerous demands to reduce energy consumption, especially in buildings and vehicles. However, the question of how to effectively manage thermal energy generated from NIR harvesting in light-absorbing materials, rather than being wasted or causing negative effects, remains challenging. Herein, hollow copper sulfide (Cu2-xS) on colorless polyimide (PI) films, enabling them to be well-dispersed and robustly adhered, underwent in situ growth fabrication and were utilized as NIR-thermal-shielding and organic-pollutant-removal dual-function window films. Due to strong NIR absorbance, arising from the heavy hole-doping (copper cation deficiency), the Cu2-xS/PI composite film exhibited great promise for use in the filtration of the NIR spectrum. By monitoring Cu2-xS densities, its NIR-shielding efficiency reached 69.4%, with hundred-percent UV blocking and consistent performance within the reliability (85 °C/85%RH) tests over one week as well as 5000 bending cycles. The integration of the films into model cars and building windows exhibited excellent thermal-shielding performance upon exposure to direct sunlight. Moreover, benefiting from the distinctive distribution of Cu2-xS, the additional thermal energy (holes) generated in NIR absorption was successfully utilized. The densely surface-confined hollow structure of Cu2-xS on PI significantly endowed good formaldehyde catalytic capacity, with removal efficiency reaching approximately 72% within 60 min and a negligible decline after quartic reuse. These integration methodologies enable the promising fabrication of a high-performance, bifunctional window film combining thermal shielding and indoor organic pollutant removal.
Keywords: dual-function window film; formaldehyde degradation; hollow Cu2−xS/PI composite film; in situ growth; near-infrared thermal shielding.