Preparation and characteristics of aluminum back electrodes on flexible substrates

Al thin films were deposited on flexible polyimide substrates by radio frequency magnetron sputtering method to make aluminum back electrode for Si-thin film solar cells.The effects of sputtering power and working pressure on the properties of Al electrodes were carried out.Atomic force microscope(AFM) was used to examine the surface morphology and roughness of the films.The electrical and optical properties of the films were characterized by four-probe meter and UV/VIS near-IR spectrophotometer,respectively.The results show that,with the increasing of the sputtering power,the root mean square surface roughness of Al thin films is improved greatly,and the higher the sputtering power is,the higher the diffuse reflectivity and conductivity of Al thin films are.The average diffuse reflectance of the film reaches to 70%.The films deposited at 0.5 Pa perform lower resistivity and higher reflectivity.As concern to the electrical and optical properties of the films,the Al thin films prepared at 300-450 W and 0.5 Pa have excellent comprehensive performance.