Influence of Plasma‐Enhanced Chemical Vapor Deposition Poly‐Si Layer Thickness on the Wrap‐Around and the Quantum Efficiency of Bifacial n‐TOPCon (Tunnel Oxide Passivated Contact) Solar Cells. Issue 16 (8th July 2021) - Grübel, Benjamin
Abstract : In typical industrial processing of tunnel oxide passivated contact (TOPCon) solar cells, poly‐Si is deposited on the entire back of the cells. During the deposition process, a wrap‐around of poly‐Si onto the edges and the front side of the cells is virtually unavoidable if chemical vapor deposition processes are used. Plasma‐enhanced chemical vapor deposition (PECVD) is used to investigate very thin poly‐Si films and their effect on wrap‐around on bifacial TOPCon solar cells fabricated without wrap‐around etching. As a result, reduction of the poly‐Si thickness down to 30 nm significantly increases the shunt resistance, reduces the reverse bias current, and thus reduces the risk of hot spots as measured by IR imaging and microcharacterization by secondary electron microscopy. Electroplated metallization proves to be a suitable candidate for contacting such thin TOPCon layers, being less sensitive than screen‐printed metallization. Abstract : Industrial tunnel oxide passivated contact (TOPCon) cells feature a limited rear side contact recombination. Poly‐Si deposition technologies typically require an etch back step due to poly‐Si wrap‐around. Decreasing the poly‐Si thickness during plasma‐enhanced chemical vapor deposition reduces the extent of the wrap‐around. Electroplating proves to be suitable for contacting such thin TOPCon layers being less sensitive than screen‐printed metallization.