Investigation of the Defect Distribution of Laser Contact Opening Applied to Poly‐Si/SiN_xStacks

Abstract

Herein, an analysis on the impact of laser contact opening of TOPCon/SiNx stacks is presented. By etching in tetramethylammonium hydroxide (TMAH), the defect distribution in the interfacial tunnel oxide is accessed and analyzed. The defect density is significantly increased in areas where adjacent laser contact openings (LCO) overlap. Using microscopic photoluminescence (μ‐PL) spectroscopy, it is verified that correlates with an increase in the local recombination rate and thus an increase in the J0,Met. Therefore, overlapping LCO of SiNx in TOPCon/SiNx stacks should be avoided as much as possible. Furthermore, the investigations indicate that defects in the interfacial oxide are dominantly created along exposed structures like tips and edges of (etched‐back) pyramids. A comparison of TOPCon/SiNx stacks with a variation of TOPCon thicknesses indicate that etch pits, and thus the defect density, related to LCO become more significant at lower thicknesses.

Lithography‐free fabrication of a local contact interlayer for Si‐based tandem solar cells

“…The LCO process is one of the most mature technologies in p-PERC mass production, and its application to TOPCon cells and back contact structures has recently been reported. [25][26][27] On the other hand, the LIFT process has not yet been applied to solar cell mass production, but research and development activities are underway to commercialize the LIFT technology for low-temperature metallization processes or microscale electrode formation. 28,29 We applied our proposed approach to Al BSF and PERC bottom cells and showed increased V oc values compared to the ITO-full contact cells.…”

“…For commercial p ‐PERC solar cells, the full‐area back passivation stack, which typically consists of an Al 2 O 3 passivation layer covered by a hydrogenated SiN x capping layer, 22 is removed locally via a laser contact opening (LCO) process, 23,24 followed by Al screen printing. The LCO process is one of the most mature technologies in p ‐PERC mass production, and its application to TOPCon cells and back contact structures has recently been reported 25–27 . On the other hand, the LIFT process has not yet been applied to solar cell mass production, but research and development activities are underway to commercialize the LIFT technology for low‐temperature metallization processes or microscale electrode formation 28,29 …”