SiN(x)/Cu Spectral Beam Splitting Films for Hybrid Photovoltaic and Concentrating Solar Thermal Systems

[Image: see text] Spectral beam splitting (SBS) films are crucial for the development of hybrid systems based on photovoltaic (PV) and concentrating solar thermal (CST) technologies. In this study, a novel double-layer SiN(x)/Cu SBS film was prepared via magnetron sputtering. This film was developed based on the linear Fresnel solar thermal technology used in PV/CST hybrid systems. The as-deposited film exhibited superior SBS properties, with a high transmittance of 72.9% and a reflectance of 89.7%. To optimize the optical properties, the thicknesses of the metal and SiN(x) layers were precisely controlled. The optimal thicknesses of the Cu and SiN(x) layers were determined to be 17 and 67 nm, respectively. Furthermore, the thermal stability of the SBS film was evaluated. When annealed at 50 °C, the surface of the SBS film became more uniform and smooth, and with increasing annealing time, the film became denser. No strong diffraction peaks of Cu were observed in the X-ray diffraction patterns because of the low content and poor crystallization of Cu. Atomic force microscopy investigations revealed the formation of a textured surface and a decrease in the root-mean-square roughness with an increase in the annealing time from 0 to 360 h. As a key component with considerable application potential in PV/CST hybrid systems, SBS films are currently an important research topic.