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Research Highlights, III ‐ V//Si multijunction solar cells with 30% efficiency using smart stack technology with Pd nanoparticle array

Department of Energy and Environment

III ‐ V//Si multijunction solar cells with 3 0% efficiency using smart stack technology with Pd nanoparticle array

MAKITA Kikuo, OSHIMA Ryuji, SHOJI Yasushi, SUGAYA Takeyoshi
Global Zero Emission Research Center
MIZUNO Hidenori, TAYAGAKI Takeshi, SAI Hitoshi, TAKATO Hidetaka
Renewable Energy Research Center

Highly efficient and stable solar cells realized by new bonding technology

Using the "smart stack method," a unique bonding technology for fabricating multi-junction solar cells, a new InGaP/AlGaAs/Si three-junction solar cell that can convert more than 30% of the incoming solar energy into output power has been successfully fabricated. This GaAs/Si multi-junction solar cell, which is also highly durable, is expected to be put into practical use as a technology to realize highly efficient and low-cost solar power generation.

Figure of Highly efficient and stable solar cells

High-efficiency, low-cost photovoltaic power generation is key issue for achieving carbon neutrality

The amount of electricity generated from renewable energy sources is still insufficient to achieve carbon neutrality. Further cost reduction is needed to promote PV power generation, and the NEDO (New Energy and Industrial Technology Development Organization) PV Challenge strategy has also set a cost target of 7 yen/kWh for PV power generation by 2030. To achieve this target, a combination of GaAs cells (a common type of III-V semiconductor solar cell) and Si has emerged as a promising candidate. Until now, there have been a few reports of this kind of cell that achieved 30% efficiency using surface activation method for wafer bonding; however, problems with mass productivity and production cost have been pointed out.

Newly developed three-junction solar cell offers high efficiency and long-term stability

The developed InGaP/AlGaAs/Si three-junction solar cell achieved a high power generation efficiency of 30.8% by optimizing the cell structure using a unique mechanical stacking method (smart stack method) applying Pd nanoparticle-based bonding technology and introducing tunnel oxide film passivation contact (TOPCon) Si cells. In addition, no significant degradation was observed after 1,000 hours of durability testing under severe conditions of 85°C temperature and 85% humidity, showing that long-term stability can be expected.

GaAs/Si multi-junction cells fabricated by smart stack method pave way to higher efficiency

The cell combination used in this study is capable of achieving a power generation efficiency of 35% under normal solar irradiation conditions, and we will conduct R&D to further improve the efficiency and lower the cost of photovoltaic power generation using the smart stack method toward the practical application of GaAs/Si multi-junction cells.

Contact for inquiries related to this theme

Multijunction PV Team, Global Zero Emission Research Center

MAKITA Kikuo, Invited Senior Researcher

AIST Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan

Web: https://www.gzr.aist.go.jp/en/teams/multijunction-pv-team/

Photovoltaic System and Application Team, Renewable Energy Research Center

MIZUNO Hidenori, Chief Senior Researcher

2-2-9 Machiikedai, Koriyama, Fukushima 963-0298, Japan

Web: https://www.aist.go.jp/fukushima/en/unit/pvsysat_e.html

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