Comprehensive Analysis and Process Optimization for Wet Chemical Alkaline Edge Isolation for Industrial TOPCon Solar Cells

Tunnel oxide passivated contact (TOPCon) solar cells are on their way to becoming the next leading cell concept in industrial solar cell manufacturing. However, the efficiency gain compared to state‐of‐the‐art PERC cells comes at the cost of additional processes in the manufacturing route. Therefore, it is of utmost importance to increase the profitability of the TOPCon cell architecture by reducing the capital and operating costs as much as possible. In addition to the development of production machines with high throughput and small footprint, the main lever for wet chemical processes is to reduce the consumption of expensive chemicals while maintaining a high process quality. In this work, this goal is pursued with a focus on wet chemical edge isolation. This process is industrially mainly performed in a combination of an inline process for single‐sided glass removal followed by a batch process for rear‐side emitter removal (cluster process). This paper presents our approach to reduce the inline process time without increasing the HF concentration. Furthermore, the rear surface morphology after the alkaline etching at different KOH concentrations with and without a new generation of polishing additive is characterized, and the effect on the implied open‐circuit voltages is shown. The influence of dissolved potassium silicate is also investigated in order to increase the lifetime of the KOH bath. Based on the results, we present TOPCon cell results with efficiencies of about 23.5%, as well as cost of ownership calculations for the most promising approaches and discuss cost of ownership calculations for a US manufacturing scenario.