Photonic Multilayer Structure Induced High Near‐Infrared (NIR) Blockage as Energy‐Saving Window

Abstract Energy‐saving window that selectively blocks near‐infrared (NIR) is a promising technology to save energy consumption. However, it is hard to achieve both high transmittance in visible light and high reflectance in NIR for the energy‐saving windows. Here, a TiO 2 /Ag/TiO 2 /SiO 2 /TiO 2 multilayer is demonstrated on a glass substrate to selectively block NIR while maintaining high transmittance to visible light. The thickness of a TiO 2 /Ag/TiO 2 structure is first design and optimized; the metal layer reflects NIR and the dielectric layers increase transmittance of visible light with zero reflection condition. To further enhance NIR‐blocking capability, a TiO 2 back reflector is implemented with a SiO 2 spacer to TiO 2 /Ag/TiO 2 structure. The back reflector can induce additional Fresnel reflection without sacrificing transmittance to visible light. The optimal TiO 2 (32 nm)/Ag (22 nm)/TiO 2 (30 nm)/SiO 2 (100 nm)/TiO 2 (110 nm)/glass shows solar energy rejection 89.2% (reflection 86.5%, absorption 2.7%) in NIR, visible transmittance 69.9% and high long‐wave (3 ≤ λ ≤ 20 µm) reflectance > 95%. This proposed visible‐transparent, near‐infrared‐reflecting multilayer film can be applied to the windows of buildings and automobiles to reduce the energy consumption.