Influence of the chemical composition in SiNx films on silver paste contact formation at silicon surface

• Rs of Ag paste to Si depended on the chemical composition of SiNx film.
• Small Ag particles embedded in the frits causing contact resistance decreased.
• Si–Si bond in SiNx film suppressed the silver paste penetrating the SiNx film.

We have studied the contact formation of silver (Ag) paste at the silicon surface as a function of chemical composition of silicon nitride films (SiNx) on the front side of crystalline Si solar cell. By tuning silicon (Si) to nitrogen (N) atomic ratio in the SiNx films deposited by PECVD, the contact resistance between Ag paste and Si surface was observed to decrease from N-rich to Si-rich condition then increase again as the chemical composition further into Si-rich. Microstructure analysis via scanning electron microscopy (SEM) imaging revealed the number and diameter of Ag particles embedded in frits are found to be responsible for the behavior of contact resistance. On the other hand, limited number of Ag crystallites on Si surface is also affecting the contact resistance on the highly Si-rich regime. We suggested SiNx films affected silver paste contact formation by modifying chemical composition and properties of interfacial frits.