Influence of oxygen micro atmosphere during contact formation

The mechanism of front side contact formation of glass containing silver thick film pastes is strongly dependent on the oxygen partial pressure po2 in the firing atmosphere. The oxygen partial pressure influences the silver dissolution and precipitation kinetics as well as the silicon surface etching at the interface. With a controlled oxygen partial pressure, it is possible to improve the cell performance. Therefore, the availability of oxygen was varied via either the glass frit composition or the addition of inorganic additives. With increasing oxidizing character of the inorganic additives interface morphology and the cell characteristics can be influenced. Comparison to the amount and size of the silver precipitations at the wafer interface confirm the correlation between oxygen partial pressure, Ag precipitation and cell performance.