Single-Junction Silicon Solar Cell Technology Enters Large-Scale Application Phase

On April 27, during a release event in Beijing, Li Zhengguo, the founder and president of Longi Green Energy (601012.SH), announced that the maturity level of Back Contact (BC) technology has reached approximately 80%. He expressed confidence that while there is still room for optimization, the major obstacles have been overcome, allowing for true large-scale promotion within the industry.

This announcement coincided with the launch of the “White Paper on the Development of Back Contact (BC) Battery Technology”, co-authored by the China Electricity Council, the German Rheinland TV Group, the Jianheng Certification Center, Aiko Solar, and Longi Green Energy. This document marks the first comprehensive overview of the BC technology in the photovoltaic sector, indicating that this “ultimate form of single-junction silicon solar cells” is now entering a new stage of large-scale application.

BC batteries are a type of photovoltaic technology that features both positive and negative electrodes placed entirely on the back, eliminating any shading from grid lines on the front. Currently, TOPCon technology dominates the domestic photovoltaic battery market, while BC technology remains relatively niche, primarily produced by companies like Longi Green Energy, Aiko Solar (600732.SH), and TCL Zhonghuan (002129.SZ).

Proponents of BC technology argue that it offers higher efficiency and power generation capabilities, along with superior temperature coefficients and reduced degradation, leading to greater reliability. As market competition intensifies, more companies are venturing into BC technology development and production. Even JinkoSolar (688223.SH), previously a staunch supporter of TOPCon technology, has indicated plans to establish a pilot line for BC technology.

The White Paper reports that the current mass production efficiency of BC technology has surpassed 27%, exceeding the mass production efficiency of TOPCon by 1.6%. The technology’s maturity and cost competitiveness are now comparable to traditional methods, with a theoretical efficiency limit of 29.1%, nearing the ceiling of crystalline silicon efficiency.

Starting in 2024, major component manufacturers are expected to unveil their BC component products, demonstrating their commitment to this technology. Companies such as GCL-Poly Energy, Chint New Energy, Trina Solar (688599.SH), Yida New Energy, and Huayao Optoelectronics have showcased BC components at various exhibitions, with Tongwei Co. (600438.SH), JA Solar (002459.SZ), and LONGi Solar also planning high-profile releases by 2025.

Though companies may have slightly different approaches to BC technology, the White Paper emphasizes that investment in BC has become a primary focus for photovoltaic manufacturers, signaling the beginning of BC as a mainstream technology in production.

During the release event, Li Zhengguo cautioned against repeating the mistakes made with TOPCon technology, which experienced rapid oversupply due to low entry barriers. He stressed that Longi and Aiko have been proactive in establishing technological safeguards, including patent applications, R&D partnerships with key suppliers, and more effective personnel management strategies.

Li expressed strong confidence that BC technology will become the mainstream and transformative technology for single-junction batteries, unless there is a significant shift to stacked layers or other solutions. He noted that without utilizing the BC platform, it will be challenging for any product to remain competitive in the industry.

The White Paper indicates that the current mass production efficiency of BC batteries is around 27%, with component efficiency at approximately 24.4%, significantly surpassing that of bifacial contact photovoltaic technologies. However, there remains a 2% efficiency gap to reach the theoretical limit of BC technology. With ongoing optimization, BC battery efficiency is projected to rise to about 28.5%, with overall component efficiency exceeding 26% within the next 3-5 years.

Wang Yongqian, chief scientist at Aiko Solar, believes that the next generation of battery technology expected to achieve mass production will likely build on the BC battery’s structure and features. Notable avenues include photon multiplication and perovskite/BC stacking.

Zhang Tao, former director of the Industry Association Chamber of Commerce at the State-owned Assets Supervision and Administration Commission, highlighted the necessity of social collaboration for the deep development and maturation of BC technology. He emphasized that as the photovoltaic industry increasingly contributes to the energy structure, the role of BC technology as a key support mechanism becomes more prominent. However, its large-scale promotion requires coordinated development across the industrial chain and supply chain, collaborative innovation between academia and industry, enhanced standard systems, a more scientific patent layout, and optimized digital intelligent manufacturing processes to accelerate cost reduction and efficiency enhancement.

Wu Jinhua, executive president of the Solar Power Branch of the China Electricity Council, stated that BC technology has transitioned from the laboratory to large-scale application, marking the beginning of a dual revolution in photovoltaic efficiency and scenarios. He offered three recommendations for advancing BC technology: first, merge BC with TOPCon, HJT, and other technologies for optimal efficiency and cost configurations; second, collaborate with more domestic and international experts and institutions to refine the component recognition system and establish an outdoor empirical database to enhance market trust; and third, promote respect for patents, orderly competition, and prevent unlimited capacity expansion.