A multilayer structure with high Vis-absorption based on ultrathin NiCr film

High vis-absorption materials were widely used in solar cells and light detectors. Here, we achieved an Al/SiO₂/NiCr/Si₃N₄/NiCr multilayer structure with high vis-absorption based on ultrathin NiCr film. The Al and NiCr layers were deposited through DC magnetron sputtering, and the SiO₂ and Si₃N₄ layers were prepared through Plasma Enhanced Chemical Vapor Deposition (PECVD). The average absorption of the multilayer structure was beyond 83% in the range of 400-1100 nm and the maximum absorption was 99.34% at 530nm when the thicknesses of Al, SiO₂, middle NiCr, Si₃N₄ and top NiCr layers were 80 nm, 40 nm, 4.6 nm, 30 nm and 4.6nm, respectively. Moreover, the absorption peak, along with color change of the multilayer structure from deep blue to light blue, could be adjusted by changing the thickness of Si₃N₄ layer from 30 nm to 50 nm. X-ray photoelectron spectroscopy (XPS) analyses revealed that the concentration ratio of Ni and Cr in the ultrathin NiCr films was very close to that of NiCr alloy target, and that the dielectric layers (SiO₂ and Si₃N₄) have completely covered the metal layers. Atomic force microscopy (AFM) patterns have indicated the ultrathin NiCr film has a smooth surface with the root-mean-square (RMS) roughness of 0.883 nm. The multilayer structure based on ultrathin NiCr film could be promising for building highly-efficient solar collectors.