Competition among global corporations to set an international standard for "tandem cells," cited as next-generation solar cells, is intensifying. A tandem cell is a solar cell that dramatically boosts power conversion efficiency compared with conventional silicon cells, but no international standard has yet been established to prove its validity and safety.
According to the energy industry on the 12th, from the 20th to the 24th of next month (local time), a regular meeting of the International Electrotechnical Commission (IEC) "Technical Committee on Photovoltaic Energy Systems (IEC TC 82)" is scheduled to be held in Washington, D.C. in the United States. The event will be attended by solar power corporations and research institutes from around the world, as well as government officials.
At this meeting, attendees from each country are expected to engage in heated debate over how to establish an international standard for tandem cells.
A tandem cell is a high-efficiency cell that layers the next-generation material perovskite on top of an existing silicon solar cell. Its hallmark is maximizing efficiency by having the two layers absorb different parts of the solar spectrum. With power conversion efficiency improved by about 50% over a single silicon cell, tandem cells are expected to be commercialized around 2027.
The biggest weakness of tandem cells is poor durability. Solar power plants typically operate outdoors for more than 20 years. Conventional silicon panels are warranted for 25 years, but perovskite is vulnerable to heat and humidity, making the warranty period much shorter. In response, IEC TC 82 is devising methods to measure lifespan to determine whether tandem cells can withstand actual outdoor environments for more than 20 years.
Creating a standard at IEC TC 82 means defining rigorous test methods for product durability, efficiency measurement, and safety. Because IEC standards are global guidelines agreed upon worldwide, once a standard is established, corporations around the world produce products to meet it. In other words, obtaining IEC certification is like getting a pass to enter markets worldwide.
Until now, the solar industry has focused competition on how high the power conversion efficiency of tandem cells can be. China is in the lead on efficiency. LONGi, a Chinese solar company, said in April last year that a tandem cell achieved 34.8% efficiency. However, it did not disclose the cell area, and the industry views it as testing on a small, lab-scale cell (1 ㎠).
Chinese corporations argue that higher power conversion efficiency should become the standard. Their logic is that the most advanced technology should set the standard. Backed by massive capital, Chinese corporations are already building dedicated tandem production lines. They are also dispatching many technical Commissioners to reflect process specifications arising in mass production into IEC standards.
In contrast, corporations in Korea, Japan, and the United Kingdom are focusing on how large they can make the cell area rather than on the efficiency figure alone. At the commercialization stage, it is crucial whether high efficiency is achieved over a large area and whether the product can be used reliably over time. These companies already assess that tandem cell efficiency has neared 30%, securing sufficient economics.
Qcells released that it recorded 28.6% efficiency on an M10 (330 ㎠) tandem cell, the size of a single silicon cell. Oxford PV in the United Kingdom achieved 26.9% efficiency on a 170 ㎠ tandem cell, half the size of a silicon cell. Corporations in several countries, excluding China, say performance verification standards should be set for commercially sellable areas.
Professor Lee Jun of Sungkyunkwan University said, "Development to raise tandem cell efficiency has wrapped up for now, and what matters is which corporations commercialize first," adding, "Steering the international standard-setting in a favorable direction is most important, but China's offensive is formidable."
Professor Park Jong-seong of Gyeongsang National University noted, "For the commercialization of tandem cells, the government needs to provide full support," pointing out, "The government is carrying out national projects, but compared with China, the reality is a shortage of personnel."