Engineering all-polymer planar photonic crystals as aegises against sunlight overheating

Abstract

Reducing heating by sunlight is of paramount interest for sustainability and energy efficiency. Solar heating causes harmful CO2 emissions related to the cooling of buildings and vehicles cooling and causes a reduction in greenhouse crop yields during hot seasons. Therefore, reducing the absorption of sunlight with low-cost passive systems could play a major role in energy saving and human sustainability from an environmental standpoint. In this work, dielectric mirrors (aegises) are designed to reflect near-infrared radiation and fabricated out of different polymer pairs ranging from commodity to specialty polymers. Structurally similar tandem structures are designed using a quantitative rationale that allows for predicting thermal shielding efficiency that could be used to design optimized reflectors. As a proof-of-concept, structures are designed via the presented rationale and then fabricated out of different polymer pairs and tested. This allowed to study the influence of materials’ dielectric contrast on the efficiency in heat reduction. Thanks to the new rationale and the improved materials, although coming at the cost of an increase of reflectance of visible light, an efficiency of 27 % is achieved with the polymer pair providing the higher dielectric contrast, namely the Aquivion-poly(N-vinylcarbazole) one.