The long-expected move by cell manufacturers into n-type technologies appears to be gaining pace in 2022, and while some of the largest manufacturers focus on TOPCon as a simpler progression from the PERC cells in production today. Another cell type, heterojunction (HJT) is also at the center of the move, with big plans in place – for European manufacturing projects in particular. HJT holds most of the records for silicon solar cell efficiency, and bringing its costs down has been a key focus for researchers in recent years. This week saw the publication of new analysis from scientists led by Saudi Arabian university KAUST discussing the technical and economic factors and challenges remaining in the way of mass production for HJT. Their full analysis is published in Joule. As previous studies have noted, they find that higher initial investment for production equipment and high silver consumption are among the biggest concerns, alongside wafer quality, process control, dependence on indium, and processes for low-temperature cell interconnection.
Further HJT analysis came from Australia’s University of New South Wales, which examined the possible adoption of transition metal oxide layers, deposited using atomic layer deposition. “Using a bottom-up cost and uncertainty model with equipment cost data and process experience in the lab, we find that the production cost of these variations will likely be lower per wafer than standard HJT, with the main cost drivers being the cost of the ALD precursors at high-volume production,” the group explained.
The analysis is published in full in Progress in Photovoltaics. While the group finds that lower per-cell production cost would likely be possible with this approach, whether it can really amount to a cost reduction would depend on the cell efficiency that can be achieved with the as-yet uncommercialized transition metal oxide technology. They note that one part of their approach – replacing indium tin oxide with aluminum zin oxide as the transparent conducting layer – has particular potential as it would eliminate the need for rare and costly indium.
