Fundamental reactions during the formation of fired silver contacts and solar cell results

The contact formation on high efficiency solar cells using a high temperature process is the subject of this research. Thermal gravimetric analyses were used to study the chemical reactions between ink components and solar cell during the firing process. The mechanism behind the etching process and the opening of the dielectric layer are explained and the influence of the glass concentration on the contact quality is given. Based on these studies, a seed layer ink was developed, optimized and tested on silicon solar cells. The developed ink was applied on high efficiency solar cells with printed and fired front contacts and compared with photolithographically defined and evaporated front contacts. At the rear side, we used a firing stable passivation layer consisting of Al2O3 and SiOx. After evaporation of aluminum and applying laser fired contacts at the rear and light induced silver plating at the front, cell efficiencies of η = 21.5% and fill factors of 81% could be measured.