Maxwell Technologies has released a research paper in conjunction with a number of universities including Nanchang University, the Hong Kong Polytechnic University and Henan Normal University, introducing findings showing that strained heterojunction enables high-performance, fully textured perovskite/silicon tandem solar cells to achieve an efficiency of up to 31.5%.
The paper, entitled “Strained heterojunction enables high-performance, fully textured perovskite/silicon tandem solar cells” reports an innovative strain regulation strategy by forming a 3D/3D perovskite heterojunction at the buried interface through a vacuum-deposition method applicable to pyramidal texture, which promotes the conformal growth of high-quality perovskite films on fully textured silicon. This strained heterostructure promotes the preferred crystal growth, reduces interfacial defect-induced recombination, and facilitates charge extraction. As a result, the fully textured perovskite/silicon tandem cell achieves a certified steady-state efficiency of 31.5% and retains over 95% of its initial efficiency after 800h of continuous operation. The above experimental results were achieved on Maxwell’s full set of perovskite/HJT tandem cell R&D platforms and related equipment.
Maxwell has established a 4MW perovskite/HJT tandem solar cell experimental line and conducted the all-around development in terms of tandem process, equipment and materials. The company has achieved a tandem cell efficiency of 28.3% on a silicon wafer of 182mm*182mm, which is the maximum wafer size based on published data of perovskite/HJT tandem cells. Additionally, Maxwell has not only improved the mass production efficiency of heterojunction cells with technical advancement, but also paved the way for cost reduction, efficiency improvement, technical exploration and application expansion in the future.
Perovskite-Heterojunction tandem cells – a future trend with natural advantages
The surface of the heterojunction cell is the transparent conductive oxide (TCO) film. Its symmetrical structure allows it to be compatible with the positive/inverse perovskite cell technology, and effectively connect with perovskite in series. Additionally, due to its high open-circuit voltage and filling factor, it features great advantages as a material for base cells and perovskite tandems. The theoretical efficiency of perovskite-heterojunction tandem solar cells can be over 42%, showcasing a significant space for improvement on the efficiency of tandem cells in mass production in the future. As a result, it could be the optimized solution for the perovskite/silicon tandem cell.
Currently, perovskite/HJT tandem technology is under rapid development. There have been organisations that have achieved an efficiency of 34.6% on a small-sized tandem cell, and an efficiency of 30.1% on a 166mm*166mm tandem cell.
The efficiency of a full-size perovskite/HJT tandem solar cell is expected to reach over 32% in 2025.