Investigation of Screen-Printed Rear Contacts for Aluminum Local Back Surface Field Silicon Wafer Solar Cells

Silicon wafer solar cells with an aluminum local back surface field (Al-LBSF) are currently intensively investigated for industrial application. One of the main challenges for the Al-LBSF solar cell is the formation of the local Al rear contacts. In our previous work, we have introduced the relative photoluminescence (PL) intensity method to study the Al-Si local contact formation. In this study, we apply this method to experimentally investigate the impact of the geometry (lines or points) of the rear contacts and compare the experimental results with theoretical results that are obtained using Fischer´s model. We find that the PL intensity strongly correlates with the p⁺ layer thickness and inversely correlates with the void density at the rear surface. Al-LBSF solar cells with different rear contact geometries are fabricated. High Rs was found, especially for those cells with narrower line widths and a large number of voids.