Rear side dielectrics choices in PERC solar cells

Characterization of SiO
_x
and Al
₂
O
₃
passivation film and the effect on PERC cells performance were studied in details. Due to >2×10
¹¹
cm
^-2
positive fixed charge in SiO
_x
film, inversion layer is formed on PERC rear side, so that pseudo-FF of cells decreases because of large J
₀₂
. Additionally, it leads to bad low-light performance because the rear surface recombination velocity (RSRV) increases with the injection level decrease under inversion status. On the contrary, Al
₂
O
₃
film with >2×10
¹²
cm
^-2
negative fixed charge show total different properties and excellent passivation on PERC cells. Deposited by Al
₂
O
₃
/SiN
_x
stack film, PERC cells achieved to 19.8% batch average efficiency. With selective emitter technology, the average efficiency can increase up to 20.0%. Additionally, the low light output and temperature coefficient of PERC cell are also improved comparing to conventional Al-BSF cell. PERC module made by 60 cells shows power output larger than 280W.