A dual-mode self-cleaning film for durable passive radiative cooling and solar heating

Abstract

Solar heating and radiative cooling offer sustainable pathways to address fossil energy demand. However, their single-mode operation and susceptibility to contamination restrict performance under varying daily and seasonal conditions. Herein, a superhydrophobic dual-mode thermal management film with combined cooling and heating features was developed. The cooling side (CS) exhibits high visible light reflectance (87%) and high infrared emissivity (95%), allowing a cooling effect of about 5.9 °C under 72 mW cm⁻². Furthermore, the heating side (HS) generates coral-like black micro-nanostructures on the polyimide tape surface by a femtosecond laser one-step approach. It has exceptionally high solar absorption (98%) and can yield a temperature rise of about 40 °C at one-sun intensity. In addition, the material possesses excellent superhydrophobicity and chemical stability over a wide pH range. It exhibits favorable self-cleaning performance with a contact angle of more than 155°. This thermal management film holds significant application potential in building energy efficient devices, giving new insights for realizing passive temperature regulation.