Rear side dielectrics choices in PERC solar cells

Characterization of SiO_x and Al₂O₃ passivation film and the effect on PERC cells performance were studied in details. Due to >2×10¹¹ 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 J₀₂. 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, Al₂O₃ film with >2×10¹² cm^-2 negative fixed charge show total different properties and excellent passivation on PERC cells. Deposited by Al₂O₃/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.