Rear side optimization for mass production PERC solar cell with efficiency above 23%.

When LDSE (Laser Doped Selective Emitter) is applied to the front side of PERC solar cell, the low sheet resistance requirement for metal contact can be realized by laser doping. Therefore, at present the front sheet resistance has increased from 85 Ω to 140±10 Ω. The emitter saturation current density reduces from 100 fA/cm² to less than 50 fA/cm². Therefore, the rear surface optimization of PERC solar cell becomes more and more important. In this paper, three aspects about the rear surface are studied. Firstly, the effects of alkali polishing and acid polishing on the performance of LDSE PERC solar cell are compared for the improvement of rear surface polishing. Then, bilayer SiN_x:H capping film is adoped on the Al₂O₃ layer instead of monolayer SiN_x:H. The bottom layer of bilayer structure is made up of high refractive index SiN_x:H, which can improve the hydrogen passivation effect. The top layer of bilayer structure is made up of low refractive index SiN_x:H, which can improve the resistance to aluminum paste erosion. Finally, the influence of different kinds of laser ablation patterns on the cell performance is investigated, aiming to optimize the metal contact recombination. Benefiting from the three methods above, an average efficiency of 23.1% and a champion efficiency of 23.3% are achieved. [ABSTRACT FROM AUTHOR]