Insulation and diffusion barrier characteristics of spin-on-glass layer on a stainless steel substrate

The efficiency of CIGS (Copper Indium Gallium diSelenide) solar cells fabricated on stainless steel foil is lower than that on soda-lime glass substrates due to the lack of sodium incorporation and metal impurity diffusion. A dielectric barrier is necessary to prevent metal impurity diffusion for stainless steel substrates. Spin-on-glass (SOG) coatings are characterized by their lower cost and larger area than other vacuum deposition methods. By using spin coating SOG to deposit SiO _x barrier layers, this study investigates the characteristics of their insulation and impurity barrier. For insulation property, a higher curing temperature is preferred. The insulation does not further improve when the curing temperature exceeds 400 °C. The SiO _x film resistance can be as high as 10 ⁸Ω when the voltage is smaller than 10 V. For impurity barrier characteristics, although thick thickness is preferred, it easily incurs thermal cracking. To effectively barricade metal impurity diffusion, the influence of SiO _x thickness is larger than that of curing SOG temperature.