Investigation of the mechanism of the Ag/SiNx firing-through process of screen-printed silicon solar cells

Abstract

The mechanism of a Ag/SiN_x firing-through process in the manufacture of multi-crystalline silicon solar cells has been studied. The effect of firing temperature on the electrical performance of screen printed multi-crystalline silicon solar cells, with a conversion efficiency of up to 17.2%, has been investigated. It is revealed that with an increase in firing temperature both the series resistance and shunting resistance of the solar cells decrease monotonically, while the reverse leakage current rises gradually. SEM and EDX are used to study cross-sections of the Ag/Si interface under the fingers. It is revealed that hexagonal like silver crystallites are formed due to the chemical reaction between SiN_x and Ag₂O in the Ag paste during the firing process, through which the direct interconnection between the emitter and silver particles contained in the paste is achieved. The physical process of the firing-through is discussed. Moreover, the diffusion coefficients at different temperatures are obtained by fitting the diffusion profiles.