High-efficiency heterojunction crystalline Si solar cell and optical splitting structure fabricated by applying thin-film Si technology

Thin-film Si technology for solar cells has been developed for over 40 years. Improvements in the conversion efficiency and industrialization of thin-film Si solar cells have been realized through continuous research and development of the thin-film Si technology. The thin-film Si technology covers a wide range of fields such as fundamental understanding of the nature of thin-film Si, cell/module production, simulation, and reliability technologies. These technologies are also significant for solar cells other than the thin-film Si solar cells. Utilizing the highly developed thin-film Si solar cell technology, we have achieved ∼24% efficiency heterojunction crystalline Si solar cells using 6-in. wafers and >26% efficiency solar cells with an optical splitting structure. These results indicate that further improvement of thin-film Si technology and its synergy with crystalline Si solar cell technology will enable further improvement of solar cells with efficiencies above 26%.