Abstract
In the back-side metallization process of the passivated emitter and rear cell (PERC), the contact between the Ag rear electrode and Al rear electrode is an important factor for cell efficiency. In this paper, we report on the effect of Ag paste containing two types of oxide glass frit, V-B-Te and Pb-B-Si, on the Ag/Al contact, owing to their remarkable contrast with regard to the Ag/Al contact resistance. By combining the observation of the Ag/Al interface structure with the investigation on the interaction between glass and Al, glass transition temperature, and the distribution of glass phase in the Ag electrode, the influence of the glass phase on the contact resistance between rear Ag and Al electrodes was clearly elucidated.
Highlights
A passivated emitter and rear cell (PERC) concept with rear surface passivation and local aluminum (Al) rear contacts was first proposed in 1989 [1]
In the currently exemplified Ag paste for rear-side metallization of crystalline silicon (c-Si) PERC solar cells, In the currently exemplified Ag paste for rear-side metallization of c-Si PERC solar cells, the the content of the glass frit is 1.2% of the total mass, while the Ag powder accounts for nearly content of the glass frit is 1.2% of the total mass, while the Ag powder accounts for nearly 60%
Both the two glass frits can meet the requirement of the rear Ag paste for PERC
Summary
A passivated emitter and rear cell (PERC) concept with rear surface passivation and local aluminum (Al) rear contacts was first proposed in 1989 [1]. Different from the conventional crystalline silicon (c-Si) solar cells, PERC solar cells demand that the rear SiNx /Al2 O3 passivation layer not be corroded by silver (Ag) paste during the sintering process. The firing of this Ag paste results in etching of the SiNx passivation layer and formation of Ag/Si ohmic contact by a glass-phase medium [4,5]. The glass frit used in rear Ag paste for PERC solar cells is expected to not corrode the SiNx passivation layer. The PbO-containing glass frit has been employed in the majority of rear Ag pastes, there is a potential risk of degrading the cell efficiency due to the corrosion effect of PbO on the SiNx passivation layer. The Ag/Al contact resistance is discussed with respect to the dependence of the contact interface structure on the glass frit composition
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