Effect of Pb-Te-O glasses on Ag thick-film contact in crystalline silicon solar cells

In the paper, the influences of Pb-Te-O (PTO) glasses with different Pb/Te ratios on silver screen-printed contact formation in crystalline silicon solar cells were investigated. Thermal properties of PTO glasses such as crystallization behavior, liquidus temperature and viscosity-temperature features are determined by Pb/Te ratio. Glass etching reaction, Ag dissolution-precipitation process and all key processes of Ag thick-film contact to crystalline silicon solar cells, are closely related to glass chemistry and Pb/Te ratio of PTO glasses. The dissolution process of Ag in PTO glasses with different Pb/Te ratio was studied. XPS measurement shows that Ag+ is the dominant form of silver dissolved in PTO glass melts. TG and XRD results reveal that the formation of a new B-rich liquid glassy-phase, induced by the crystallization of glass, accelerates the dissolution of Ag at lower temperature. Glass with higher Pb/Te ratio has a weaker glass etching reaction ability and is expected to have a high high-temperature viscosity, resulting in higher Ag-precipitate density in the glassy-phase. The observed microstructures, I-V electrical performance and contact resistance maps lead to a better understanding of the relationship between glass properties and contact resistance.