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

Tunnel Oxide Passivated Contacts (TOPCon) solar cells are on the way to becoming the next leading cell concept in industrial solar cell manufacturing. However, the efficiency gain in relation to state of the art PERC cells comes with higher expenses for additional processes in the manufacturing route. To further increase the profitability of the TOPCon cell architecture it is therefore of utmost importance, to lower the capital and operational expenses as far as possible. Next to the development of high throughput and low footprint manufacturing machines the main lever for wet chemical processes is to reduce the consumption of costly chemicals whilst maintaining a high process quality. In this work, this goal is pursued with a focus on the wet-chemical edge isolation. This process is industrially predominantly performed in a combination of an inline process for single side glass removal followed by a batch process for rear side emitter removal (cluster process). This manuscript shows our approach to reduce the inline process duration 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 impact on implied open circuit voltages will be shown. In an analogous way we will investigate the influence of dissolved potassium silicate aiming for an increase of KOH-bath lifetime. Based on the findings we will present TOPCon cell results with efficiencies of about 23.5% as well as cost of ownership calculations for the the US.