Simplified process for high efficiency, self-aligned IBC c-Si solar cells combining ion implantation and epitaxial growth: Design and fabrication

Abstract Front and rear contacted wafer-based c-Si solar cells characterized by P-diffused emitter and Al-based back surface field currently constitute the dominant solar cell architecture in the photovoltaic market. The key success of this technology is based on the simple and cost effective fabrication process. However, its conversion efficiency is limited. High-efficiency c-Si solar cells architectures have been demonstrated at laboratory and industrial scale with the aim of decreasing the levelized cost of electricity (LCOE) by increasing efficiency. For this reason, high-efficiency solar cells are expected to increase their market share in next decade. In particular, interdigitated back contacted (IBC) c-Si solar cell architecture, which the current world record efficiency is based on, is expected to gain shortly relevance at industrial level. In this work, activities at TUDelft on the fabrication of IBC c-Si solar cells are reported. In particular, a novel method for realizing high-efficiency IBC c-Si solar cells based on single-side and (relatively) low-temperature doping techniques is demonstrated. In particular, epitaxial growth of B-doped Si is used to form the emitter, while P-ion implantation is deployed to form both front and back surface fields. To pattern the rear junction, a self-aligned process based on one lithographic step has been developed. In addition, metal lift-off is used to define the metal contacts of both polarities. By using this process, efficiency higher than 20% has been demonstrated.

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