The role of Wafer Enhancements in Solar Technology

With a direct impact on the efficiency, cost effectiveness and scalability of photovoltaic (PV) systems, advances in wafer technology are critical to the solar industry. Significant improvements in solar cell performance have been achieved through advances such as increasing wafer size. Larger wafers enable higher performing solar cells to be produced, reducing the overall cost per watt and making solar energy more competitive. Furthermore, innovations in wafer manufacturing processes, including developing thinner and more flexible wafers, help save materials and open up new solar applications. These developments are all crucial in order to meet the growing global demand for renewable energy and achieve sustainability goals.

However, evolutions in wafer technology go beyond the thickness of the wafer itself. Infact, though the use of thinner wafers in the solar industry offers material savings and potentially lower costs, it also comes with significant challenges that could limit its adoption. A key concern is the increased fragility of thinner wafers, making them more prone to breakage when manufactured, transported and installed. This increases manufacturing costs due to higher defect rates and limits scalability. In addition, thinner wafers have reduced mechanical strength, which can compromise long-term durability under environmental stresses such as wind or snow loads.

In 2024, LONGi introduced a wafer and an underlying technology that formed the basis of our Hi-MO X16 Max series, as well as the brand new Hi-MO X10 - TaiRay Inside technology and the TaiRay wafer were born. But unlike many competitors in the market, they did not focus on reducing thickness. Instead, LONGi focused on improving on a discovery made by Polish chemist Jan Czochralski in 1915. By accidentally dipping a pen into a molten tin instead of an inkwell, he discovered single crystal pulling. The chemist went on to develop the technique and use it to measure how quickly different metals crystallise. It was the birth of the so-called Czochralski method and Recharge Czochralski (RCZ), a state-of-the-art ingot pulling process. LONGi has now improved the ingot pulling process to make the resulting wafers more stable, robust, free of impurities and therefore more powerful.

New M11 TaiRay silicon wafers for TOPCon, heterojunction and back-contact cells

The new TaiRay silicon wafers are suitable for the currently prevailing solar technologies such as TOPCon, heterojunction (HJT) and back contact cells (BC). They show an efficiency increase of approx. 0.1% for the cell technologies mentioned. The wafers are the result of three years of intensive research and development by a LONGi R&D team of several hundred employees. LONGi has thus achieved a breakthrough in the field of silicon wafers, which has not seen any significant innovations in the last decade.

There are three key benefits of the TaiRay-silicon-wafers:

• High platform compatibility (TOPCon, heterojunction, back contact)
• More evenly distributed resistance
• Effective removal of impurities

The thickness of the TaiRay wafers used in the HPBC 2.0 evolutionary back contact technology is 140 μm, while the average thickness of n-type silicon wafers used in TOPCon cells is currently 130 μm.

TaiRay wafers offer a 16 percent higher bending strength

In addition to the technological benefits, the TaiRay wafers also have improved mechanical properties. The tested bending strength of LONGi TaiRay silicon wafers is 16% higher than that of conventional wafers, ensuring a higher break resistance while producing thinner wafers with a lower probability of cell breakage during production.

Monocrystalline silicon wafers have always been LONGi's pioneer product, with the producer achieving the world's largest shipment volume for nine consecutive years. In recent years, the wafer segment has been upgraded to mono-crystalline, large-size and thin wafers, and LONGi has made significant contributions to each technological shift.

Silicon ingots have better and uniform resistance distribution

The new TaiRay wafers and their benefits are the result of an improved Recharge Czochralski (RCz) process used in the production of monocrystalline silicon ingots.

The longer the conventional silicon ingots are, the greater the difference in resistance across the entire ingot. Thanks to the improved RCz process, LONGi TaiRay silicon wafers can achieve a more uniform axial resistance distribution without having to shorten the ingot length. For the same ingot length, the resistance ratio between the ends is halved, resulting in more efficient cells.

In addition, metal impurities in LONGi's TaiRay silicon wafers can be removed more easily. Compared to conventional products, there is also more scope for improving efficiency. The more contaminants that can be removed, the greater the potential for improved cell efficiency.

Improving silicon wafers is indispensable for the enhancement of solar cells

Over the last decade, the solar industry has made significant breakthroughs in terms of technology and cost. As a result, solar power generation has become the fastest growing renewable energy source in the world. Global solar power generation entered the "terawatt era" in 2023. Zhenguo Li, founder and president of LONGi, said that the rapid development of the PV industry is mainly due to the continuous reduction of electricity costs. Reducing the cost and improving the efficiency of power generation are always the driving factors of the PV industry.

The accelerated development of the PV industry has also accelerated the development of silicon wafers which are essential for the enhancement of solar cells. The quality of the silicon wafer determines the conversion efficiency of the cell. However, in recent years, the continuous improvement of silicon wafer production technology has slowed down the progress of improving the performance of silicon wafers. The homogenization of silicon wafer products has become increasingly evident.