High-efficiency black silicon tunnel oxide passivating contact solar cells through modifying the nano-texture on micron-pyramid surface

Abstract

Optical loss is a significant factor restricting the conversion efficiency of conventional bifacial tunnel oxide passivating contact (TOPCon) solar cells. Black silicon structure is commonly used to enhance the photogenerated current density ( J ph ) of crystalline solar cells due to its excellent light-trapping capability. However, the photogenerated current gain is cancelled by the increased emitter recombination current originated from the black silicon structure with a high enhanced surface area ratio. In this work, we used a buffered oxide etching solution to modify the surface morphology of nanopore/micron-pyramid composite (NPP) structure silicon. Further, we studied the effects of NPP structures with different enhanced surface area ratio on front-side reflection, boron atom doping, emitter passivation, and cell performance. By identifying the appropriate surface modification processing, we fabricated the large-scale (158.75 mm × 158.75 mm) bifacial TOPCon solar cells using industrial equipment and processes with an average short-circuit current density of 41.12 mA/cm 2 and average conversion efficiency of 23.08%. Through adequately widening nanostructure size and depositing high-quality Al 2 O 3 /SiN x stacked passivation films on NPP structure surface, we achieved lower carrier recombination while maintaining high J ph . • Conversion efficiency of 23.2% achieved by b-Si TOPCon solar cells. • Surface modification of b-Si improves emitter passivation using buffer etching. • Medium specific area of b-Si achieve a balance of light-trapping and electrical loss.