The role of hydrogenation and gettering in enhancing the efficiency of next‐generation Si solar cells: An industrial perspective

We discuss the importance of gettering and hydrogenation for next‐generation silicon solar cells in the context of industrial cell fabrication. Gettering and hydrogenation play a vital role for p‐type cell technologies in improving the silicon material's minority charge carrier lifetime. These mechanisms are naturally incorporated during screen‐printed cell fabrication through the phosphorus emitter diffusion, silicon nitride deposition and subsequent metallisation firing processes. While the transition towards emitters with lower dopant concentrations and/or thermal oxide passivation can reduce surface recombination, it can negatively impact the ability to getter common impurities such as iron. For cell technologies with alternative low‐temperature metallisation approaches, the ability to hydrogenate bulk defects is greatly reduced. Ultra‐high efficiency n‐type technologies tend to use heterojunction structures rather than diffused layers, but in doing so, do not benefit from phosphorus gettering. Also, particularly for amorphous silicon‐based heterojunction structures, the imposed temperature constraints strongly limit the ability to passivate bulk defects. As a result, high‐efficiency n‐type technologies rely on the use of ‘high‐quality’ wafers or would require the deliberate addition of gettering and hydrogenation processes before cell fabrication. A potential high‐efficiency hybrid homojunction/heterojunction structure is then discussed that could naturally enable gettering and bulk hydrogenation throughout cell fabrication. Calibrated implied open circuit voltage (Voc) map of a p‐type mono‐crystalline wafer highlighting the impact of pre‐hydrogenating the top half of the wafer.