Perovskite Solar Cells, the Future of Renewable Energy

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On November 26, the City of Yokohama and Toin Gakuen co-hosted the Perovskite Solar Cell Forum. Professor Tsutomu Miyasaka of the Faculty of Biomedical Engineering at Toin University of Yokohama delivered the keynote address. Miyasaka is widely regarded as the father of perovskite solar cells.

In his presentation, Professor Miyasaka highlighted recent research advancements. He reported that the conversion efficiency of perovskite solar cells now rivals that of crystalline silicon cells. The professor stressed the need to accelerate mass production initiatives in the private sector. 

Additionally, he commended the favorable environment created by government policies. Specifically, he expressed support for the Japanese government's target of deploying 20 gigawatts of perovskite solar cells by 2040.  

Latest Developments in Perovskite Technology

According to Professor Miyasaka's report, the latest conversion efficiency of perovskite solar cells is just under 27%. This efficiency matches that of crystalline silicon cells, which dominate 95% of the market. For tandem cells that combine silicon and perovskite technologies, efficiencies exceeding 30% have been achieved.

He also highlighted several unique features of perovskite solar cells:

1. The ability to generate power under low indoor light.
2. Simpler manufacturing processes compared to silicon cells.
3. Production using printing methods, resulting in lightweight, flexible, film-like structures.

These advantages open the door to new applications that differ from those of traditional silicon cells.

The Miyasaka Research Group, in collaboration with JAXA, was the first in the world to demonstrate that perovskite solar cells are resistant to cosmic radiation. Their research also showed that these cells can generate power even in low temperatures at high altitudes. Miyasaka Research Group continues to explore the material's immense potential for applications in space exploration.

In 2012, Professor Miyasaka's team became the first to incorporate perovskite into a solid-state solar cell, successfully proving the material's capabilities. Since then, they have actively collaborated with private companies to advance research and development for mass production. Their goal is to drive its widespread adoption in society.

Domestic Raw Material Advantages

Perovskite solar cells primarily rely on lead and iodine as their key raw materials. Japan, as the world's second-largest producer of iodine, can source nearly all these materials domestically. This presents a major national security advantage over silicon-based cells, which rely heavily on China for their raw materials.

The simplified manufacturing process of perovskite solar cells also holds the potential for significantly lower production costs. These cells are also more environmentally friendly, considering both the production process and waste management.

In Japan, the limited availability of flat land restricts the growth potential of silicon-based solar cells. Moreover, silicon-based panels, which were rapidly adopted following the 2011 Great East Japan Earthquake, are nearing the end of their lifespan. This is likely to mark the beginning of a mass disposal era.

China has surpassed Japan as the global leader in silicon-based solar panels. In early November, Beijing enacted its first comprehensive Energy Law during the National People's Congress. This legislation underscores the competition Japan faces in advancing renewable energy initiatives.

On November 26, the Japanese government unveiled its ambitious goal to deploy a total of 20 gigawatts of domestically developed perovskite solar cells by 2040. This target is equivalent to the output of 20 nuclear power stations and represents around 10% of household electricity demand. The government's policy has created a favorable environment for accelerating perovskite research and development. 

Private Sector Tackles Challenges

At the forum, Kaneka, a leader in solar innovation, presented on tandem cells. These cells combine silicon-based and perovskite technologies for improved efficiency. Kaneka's representative projected that conversion efficiencies could exceed 40% in the future. The company is also advancing research on modules integrated into construction materials, such as building wall panels.

Sekisui Chemical, a leader in film-based perovskite solar cells, aims to commercialize its technology by 2025. Similarly, EneCoat Technologies, a Kyoto University startup, plans to open a mass-production facility as early as 2026. Companies such as Toyota Motor Corporation will support the initiative. Panasonic Holdings (HD) is also targeting aiming to commercialize glass-integrated solar panels for building materials by 2026.

Key challenges for companies include:

• Scaling up production to accommodate large surface areas.
• Enhancing durability and lifespan.
• Recycling waste materials, including lead recovery.
• Reducing production costs.

In terms of societal applications, various possibilities are under consideration. These include integrating perovskite solar cells into building exteriors, indoor spaces, vehicles, trains, ships, agricultural facilities, and security power supplies. Such advancements highlight perovskite solar cells' potential beyond the flat land applications of traditional silicon-based cells.

Yokohama City is championing perovskite solar cells as a technology "born in Yokohama." As part of a project commissioned by the Ministry of the Environment, a range of perovskite solar cells have been installed at Osanbashi Pier in Yokohama Port for demonstration purposes. Trials are being conducted under challenging natural conditions, such as sea breezes and high humidity, and include efforts to develop monitoring and support systems.

Seizing Opportunities

Professor Miyasaka highlighted China's aggressive national investments, which have enabled it to dominate the global silicon solar cell market. He emphasized that for Japan to gain a competitive edge in domestically produced perovskite solar cells, forming a consortium of companies is essential. 

Moreover, he stressed the need for swift research and development, bold infrastructure investments, and the courage to establish mass production systems.

In addition, he called on businesses to shift their focus from university-led basic research to the practical and commercial applications of perovskite technology. Reflecting on Japan's setback in losing its leadership in silicon solar cells to China, he encouraged businesses to embrace an optimistic outlook and forge ahead with determination. 

For Japan, a country with limited energy self-sufficiency, innovation in perovskite solar cells offers an opportunity for transformation.

International research and development in perovskite solar cells gained momentum after the Miyasaka Group achieved conversion efficiencies exceeding 10%. Notably, researchers who trained with the Miyasaka Group have also contributed to these advancements.

As the commercialization of perovskite solar cells approaches, the stage is set for Japanese companies to demonstrate their technological innovations and corporate commitment.

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(Read the article in Japanese.)

Author: Hidemitsu Kaito

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