WANG Lifu ^{1, 2}, FU Shaojian ², ZENG Tao ^{1, 3}, DU Zhiyu ¹, CHEN Yunxia ^{1, 3}
(1. Jingdezhen Ceramic University, Jingdezhen 333403, Jiangxi, China; 2. Shangrao Jietai New Energy Tech Co., Ltd, Shangrao 334100, Jiangxi, China; 3. Jingdezhen Key Laboratory of Environmental Ceramics, Jingdezhen 333403, Jiangxi, China)

Abstract:  In this work, we report a highly efficient 9-busbars bifacial PERC mono-silicon cells with a dimension of 158.75 mm×158.75 mm, which is suitable for large-scale production. In contrast to the traditional consecutive linear pattern, the selective-dash pattern on the rear-side of these optimizing solar cells can promote the full discharge of the air from the laser-groove along the direction of the blade movement during screen printing of the Al electrode paste, resulting in satisfactory filling effects. After the post co-firing process, micromorphological characterization results revealed that the well-filled Al paste can form a low-temperature eutectic compound with Si, facilitating the formation of local Al back surface field and effectively reducing the voids under the Al grid lines. Furthermore, relying on electroluminescence imaging-position, quantum efficiency spectrum inspection, focusing on the regions with color difference of the traditional Si solar cells that can often serve as an effective indicator of the corresponding defects, was conducted. It was found that the formation of local Al-BSF is beneficial to improve the utilization of long-wavelength photons. Finally, optimized bifacial Si solar cells, with the front and rear efficiencies of 22.502% and 14.777% (AM1.5 G, 1000 W/m2, 25 ℃), were achieved, which are much higher than those of their traditional patterned counterparts.
Key words:  bifacial PERC; solar cells; rear-pattern design; Al-BSF; efficiency