Japan's promotion of perovskite cells can subvert China's photovoltaic advantages?
The Chinese edition of the Wall Street Journal published an article on the 12th, "China's hegemony in the solar energy market faces a new rival: an ultra-thin film battery", saying that Japan is promoting the research and industrialization of perovskite ultra-thin film cells through subsidies and other support, trying to subvert China's advantages in the photovoltaic field with this technology.
The article mentions that Chinese companies now control more than 80% of the global silicon solar panel supply chain, and that China has a higher share of the polysilicon market, which is the core material for solar panels. According to a report published by the International Energy Agency (IEA), "By 2025, the key components of global solar panel production will be almost entirely dependent on Chinese supplies." ”
Tamotsu Horiuchi, CTO of EneCoat Japan, shows off the solar flakes developed by the company Credit: Wall Street Journal
In order to reshape the supply chain, countries such as the United States and Japan are promoting local substitution in the solar panel supply chain, and are betting on the future of perovskite solar cells that do not use any silicon.
Why do the United States and Japan intend to bet on perovskites?
The core reason why the United States and Japan are betting on perovskites is that its upper limit is far ahead of the current silicon photovoltaic cells.
Perovskite materials originate from perovskite oxide (CaTiO3), a compound discovered by German chemist Gustav in the 19th century, and later characterized by Russian mineralogist Lev A. Perovski, hence the name perovskite. In 2012, Henry Snaith of the University of Oxford discovered that perovskites could be used as the main component of solar cells. Since then, the research on the photovoltaic effect of perovskite has advanced by leaps and bounds in the past ten years.
Perovskite cells work similarly to silicon-based solar cells, with the photogenerated volt effect. But the difference is that perovskite cells have the following three characteristics: 1. High absorbance coefficient, which can capture a wider range of photon energy. 2. The band gap is adjustable: the band gap of crystalline silicon cells is fixed, about 1.1eV, while the band gap of perovskite cells can be changed between 1.4~2.3eV by adjusting the perovskite composition, so perovskite cells with different band gaps can be designed to be superimposed with crystalline silicon cells, so as to achieve higher photoelectric conversion efficiency. (Note: The band gap is the difference between the energy of the lowest point of the conduction band and the highest point of the valence band, also known as the energy gap.) The larger the band gap, the lower the conductivity) 3. Low temperature coefficient: The temperature coefficient of crystalline silicon cells is about -0.3, that is, the power will decrease by 0.3% when the temperature rises by 1°C, so its power generation efficiency is not affected by temperature in actual work.
According to relevant studies, the theoretical power conversion efficiency of perovskite single-junction cells can reach 33%, that of perovskite-crystalline silicon tandem cells can reach 43%, and that of perovskite-perovskite tandem cells can reach 45%. In contrast, the power conversion efficiency of conventional commercial silicon panels is between about 18% and 22%. For the photovoltaic industry, for every 1% increase in photovoltaic power conversion efficiency, the corresponding LCOE decreases by 5% to 7%. Behind this 1%, it may take 3-5 years of time and day of R&D investment from the industry's top talents.
Perovskite disruption to the PV industry seems to be on the way.
In July 2023, a team from the School of Engineering at the University of Toronto, Canada, published an article in Nature, announcing the preparation of all-perovskite triple junction solar cells with an open-circuit voltage of 3.21 volts and a power conversion efficiency of 24.3% (quasi-steady-state power conversion efficiency of 23.3%). The battery retains an initial efficiency of 80% after 420 hours of operation at its maximum power point.
Group photo of the team Image source: Faculty of Engineering, University of Toronto
In November, a team from Northwestern University published an article in Science, announcing that the team had successfully fabricated an inverted perovskite solar cell. The quasi-steady-state power conversion efficiency of the battery reaches 25.1%, and it can operate stably for more than 2000 hours at 65°C in ambient air. They also claim to have fabricated monolithic all-perovskite tandem solar cells with a power conversion efficiency of 28.1%.
Higher conversion efficiency and disruptive materials mean that future battery designs will be lighter and more flexible. According to the Wall Street Journal, the perovskite layer in perovskite cells that Japan is now focusing on is only 1 micron thick. The weight of the battery is only one-tenth of that of today's solar cells, and the thickness is only one-twentieth. So perovskite cells can be mounted on walls or curved surfaces to generate electricity in weak sunlight, even indoors.
Due to the above-mentioned characteristics of perovskite cells, international giants have invested heavily in promoting related research, and the United States, Japan, South Korea and other countries regard them as rule subversives.
As early as September 2020, South Korea's Ministry of Trade, Industry and Energy updated a new roadmap for the solar module industry, saying that it would invest 190 billion won (about 159.7 million U.S. dollars) in tandem photovoltaic technology research over the next five years, and eventually increase the photovoltaic power conversion efficiency of solar cells to 35% by 2030. In May 2021 and July 2022, Japan and the United States also issued policies to develop next-generation solar cell technology and commercialize perovskite photovoltaic technology.
Tandem photovoltaic perovskites Image source: Helmholtz Center Institute for Materials and Energy, Berlin
According to the relevant plan, companies such as Sekisui Chemical and Toshiba are expected to start mass production of perovskite cells as early as 2025. The Japanese government has also allocated a budget of more than US$400 million to help companies produce perovskite cells on a large scale. In April last year, the Japanese government also announced that it plans to popularize flexible solar panels with perovskite cells as the core by 2030, and increase the photoelectric power conversion efficiency of solar cells to 35%.
However, there are still three major problems hindering the development of perovskite cells: 1. Batteries are susceptible to moisture, compared with monocrystalline silicon and polycrystalline silicon, perovskite materials are ionic materials that are more susceptible to moisture or oxidative degradation, which is a huge test for batteries that need to work continuously for more than 10 years or even more than 30 years. 2. The battery is difficult to make wide, because perovskite is not a crystal, so the wider the cell, the more difficult it is to form a thin and uniform perovskite layer, which leads to the power conversion efficiency of large-area size cells is less than 20%, and problems such as short circuit inside the battery will lead to a decrease in photoelectric conversion efficiency. 3. It is still difficult to produce perovskite cells on a GW-scale scale.
In response to attempts led by the United States and Japan to use perovskite cells to change the existing photovoltaic landscape. The mainland industry is also accelerating the arms race for perovskite cell-related research.
The industrialization of perovskite cells in mainland China is accelerating
In May 2023, Professor Xu Jixian's team at the University of Science and Technology of China increased the certified power conversion efficiency of single-junction perovskite solar cells to 26.1%, breaking the world record. The record was internationally certified in July.
On November 3, 2023, mainland PV giant LONGi Green Energy said that according to the latest certification report of the National Renewable Energy Laboratory of the United States, the power conversion efficiency of crystalline silicon-perovskite tandem cells independently developed by LONGi Green Energy reached 33.9%, setting a new record for the highest power conversion efficiency of crystalline silicon-perovskite tandem cells in the world. Previously, the world record for power conversion efficiency of this battery was 33.7%, which was broken by King Saud University of Science and Technology in May 23.
LONGi Green Energy Announces Breaking World Record for Efficiency of Crystalline Silicon-Perovskite Tandem Cells Image source: China Daily
Later, on December 5, Aurora Solar announced that the steady-state power conversion efficiency of the 810.1cm² large-size perovskite module developed by Aurora Solar reached 19.5% after being certified by an international authoritative testing organization. This is the company's second time to set a new record for the power conversion efficiency of the largest perovskite module, after breaking the three-year-old world record held by Panasonic in June with a steady-state power conversion efficiency of 18.6%.
In terms of industrialization, the mainland seems to be faintly ahead of the United States and Japan.
As early as August 2022, Jidian Solar announced that it had reached an agreement with Wuxi Xishan Economic and Technological Development Zone to lay out the world's first GW-level perovskite photovoltaic module and BIPV product production line. It is expected to be completed and put into operation in the second half of 2024.
Thereafter, on December 27, 2023, the GCL Optoelectronics perovskite GW project with a total investment of 5 billion yuan was laid in Kunshan High-tech Zone, which will build the world's first large-scale (1.2 meters ×2.4 meters) 2GW perovskite production line, the foundation of the GCL Optoelectronics 2GW project is planned to be constructed in two phases, and is expected to be completed and put into operation in the second half of 2024, and the output value is expected to exceed 10 billion yuan in 2027.
On January 11 this year, Renshuo Solar, a "new photovoltaic force", held a completion and release ceremony for the 150MW perovskite photovoltaic module project in Changshu, Jiangsu, and it is expected that the production line will achieve mass production of 1.2m*0.6m perovskite modules in mid-2024, and the conversion power conversion efficiency of mass-produced modules will reach 20%.
What's more noteworthy is that the world's first commercially operated megawatt perovskite ground-mounted photovoltaic project, the 1 MW perovskite ground-mounted photovoltaic power station of Micronano Optoelectronics, has been successfully connected to the grid on November 29, 2023. This is the supporting construction of the 2 million kilowatt photovoltaic sand control project in Kubuqi, Mengxi Base, in the hinterland of the Kubuqi Desert in Hangjinqi, Ordos City, Inner Mongolia, using 11,200 perovskite α modules independently developed and manufactured by Micronano Optoelectronics.
Perovskite modules in the desert Image source: Micronano Optoelectronics
Regarding the rapid development of perovskite cells in mainland China, Zhu Gongshan, chairman of GCL Group, previously said that "from 2023, perovskite cell technology will officially enter the first year of mass production".
It is believed that with the continuous efforts of mainland researchers, it will be difficult for the United States and Japan to subvert the dominant position of the mainland in the photovoltaic field through perovskite cells.
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