Highly transparent and thermally stable near-infrared shielding films

Background: Sunlight not only provides illustration but also brings a lot of heat indoors. It is highly desired to develop a single material to shield near infrared (NIR) but allow visible light to pass through. Although tungsten bronze is one of the most promising materials for NIR shielding, it still retains a challenge to increase the transmittance in the visible range.Methods: Cs0.33WO3 is designed for the primary material of NIR shielding, and a cheap, nontoxic, water-borne polyvinylpyrrolidone (PVP) is used as an auxiliary one. We are the first to provide a facile way to incorporate PVP into the Cs0.33WO3 layer to fabricate the NIR shielding films with high transparency in the visible region.Findings: The PVP incorporation significantly enhanced transmittance in the visible region of films from 80.9 to 91.3% at the threshold of 10% transmittance in the NIR region, being a 12.9%-fold enhancement compared to the pristine Cs0.33WO3 layer. The enhancement may arise from reflection reduction inside the Cs0.33WO3 layer caused by the PVP incorporation. The PVA incorporation also displayed good protection for Cs0.33WO3 against thermal stimulation at 180 degrees C owing to the interaction of the pyrrole unit of PVP with Cs.

Automated summary

By incorporating PVP into the Cs0.33WO3 layer, a NIR shielding film with high transparency in the visible region was successfully fabricated, resulting in significantly enhanced transmittance. The reduction of internal reflection in the Cs0.33WO3 layer caused by the incorporation of PVP, along with the protective effect of PVA at high temperatures, contributed to the improvements.