Overview and Future Perspective of Si Tandem Solar Cells

Silicon solar cells are the most established solar cell technology and are expected to dominate the market also in the near future. As state-of-the-art silicon solar cells are approaching the Shockley-Queisser limit (32%-33%), stacking silicon solar cells with other photovoltaic materials to form multi-junction devices is a promising pathway to raise the efficiency. However, many challenges stand in the way of fully realizing the potential of Si tandem solar cells because heterogeneously integrating silicon with other materials often degrades their qualities. Recently, promising efficiencies of 35% and 36.1% have been demonstrated for perovskite/Si 2-junction and III-V/Si 3-junction tandem solar cells, respectively. However, further efficiency improvements and cost reduction of the Si tandem solar cell modules are necessary if they are to compete with Si single-junction solar cell modules. Motivated by the potential, but also by the remaining open questions, this paper presents an overview of recent research endeavors and challenges in the field of Si tandem solar cells. The first part of this review focuses on the integration of silicon with III-V compound semiconductor, perovskites and other materials to form multi-junction solar cells. The second part presents perspectives for Si-based tandem solar cells and modules. Finally, the paper presents an analytical model to compare the material qualities of different types of Si-based tandem solar cells and project the practical efficiency limits, which are found to be more than 39% and 44% for 2-junction and 3-junction Si-based tandem solar cells, respectively. In this paper, cost and reliability issues for Si tandem cells and modules are discussed.