Improvement of Light Trapping in Bifacial PERC Silicon Solar Cells by Optimizing the Rear Surface Morphology

Currently, a bifacial passivated emitter and rear cell (bi-PERC) is the mainstream solar cell technology in the photovoltaic industry. In this paper, we studied the influence of rear pyramid morphologies with different slope angles on the overall optical and electrical properties of bi-PERC solar cells. With the help of simulations, we first obtained a macro understanding of the influence of rear surface morphologies on the absorbed and lost photon current density of bi-PERC solar cells. In practice, both the optical and passivation properties of solar cells were affected by the rear surface morphology. A smoother rear surface was proven to be favorable for rear passivation and unfavorable for rear-side light trapping. Rear surface morphologies also contributed to back-reflection and back-scattering effects that influenced the front-side light trapping. Consequently, the highest front-side average efficiency of 22.86%, with an average bifaciality factor of 76.02%, was achieved for the bi-PERC solar cells using a modified acidic polishing process. Furthermore, the calculated equivalent bifacial efficiency showed that a maximum value of 29.82% could be obtained at an albedo value of 40%. Finally, we further evaluated the optical performances of the corresponding single-cell modules.