Study on the influence of micro-alkali texturing and micro-alkali polishing process on the passivation and contact performance of n-TOPCon solar cells

The matching between the morphology of the backside of n-TOPCon solar cells and the tunnel oxide/n + polysilicon structure is the key to achieving high efficiency. In this work, based on the requirement of edge isolation, micro-alkali polishing and micro-alkali texturing were performed on the acid-polishing back surface. Their effects on surface morphology, passivation effect, contact resistance, and photoelectric conversion efficiency were investigated. Adding a short-time micro-alkali texturing process after acid polishing can form a surface morphology with both regional polishing and local microtexture. This can improve the contact characteristics without significantly affecting the passivation characteristics, enabling solar cells to achieve higher FF (83.30%) and average efficiency (24.15%). Compared with the acid polishing sample, the efficiency of the micro-alkali texturing sample is increased by 0.12%. The deterioration of ohmic contact caused by alkali polishing has not been eliminated by optimizing the reaction process of alkali polishing. The study of different surface morphologies-modified samples under different tunnel oxide layer growth time, also reveals the difference in the influence of tunnel oxide layer characteristics on samples with different morphologies. The acid-polishing samples show more stable FF and conversion efficiency at different thermal oxidation time, and the micro-alkali texturing samples have a significant FF advantage at shorter thermal oxidation time. These studies can be applied and validated in the photovoltaic industry.