Fabrication of dc sputtered Ag/Al:Si bilayers with improved optical reflectance

Highly textured Ag/Al:Si bilayers were developed on flexible stainless steel substrates by dc magnetron sputtering to improve light scattering properties. The evolution of the surface texture of the back reflectors was examined by changing the deposition temperature of the Al:Si bottom layers, followed by the deposition of highly reflective Ag top layers to increase the reflectance of the bilayers. With increasing deposition temperatures from room temperature to 500 °C, the surface roughness of the Al:Si films increased from 11.2 nm to 87.8 nm by abnormal grain growth according to the structure zone model, while that of the pure Ag films increased from 6.6 nm to 46.6 nm under the same deposition conditions. While the pure Al:Si layers had larger surface feature dimensions in comparison to the pure Ag films, these films exhibited poor light scattering properties due to their low reflectivity and reflection losses on the highly textured surface. After depositing 100-nm-thick Ag films on textured Al:Si films prepared at 300 °C, the diffuse reflectance of the Ag/Al:Si bilayers was found to be vastly superior to that of the pure Ag films at 500 °C throughout the 500–1000 nm range. The relationship between surface features and the light scattering properties of the Ag/Al:Si bilayers fabricated under various deposition conditions was investigated in detail.

► Highly textured Ag/Al:Si bilayers by sputtering. ► Improved reflectance and light scattering properties of the textured Ag/Al:Si bilayers. ► The evolution of the surface texture of back reflectors by changing the deposition temperature.