Keeping track of cell efficiencies with Back Contact is not straightforward. Manufacturers tend to be precise only when reporting laboratory or record efficiencies. For commercial production, however, there is no accurate characterization method commonly agreed upon, particularly when zero busbar (ZBB) designs are involved. As a result, efficiency figures at the cell level are primarily used for internal process validation rather than industry-wide benchmarking. In a way, this ambiguity offers some leeway. Otherwise, it would be surprising to see several BC proponents claim efficiencies approaching 27%, considering that the certified lab record for crystalline silicon single-junction cells achieved by LONGi using a BC architecture is not far apart, at 27.81%. Nonetheless, both ITRPV and CPIA have published the estimated efficiency progress of BC technology. According to CPIA, BC technology’s efficiency is expected to improve steadily, starting at 26% in 2024, reaching 26.3% in 2025, and progressively increasing to 27.4% by 2030. In contrast, ITRPV forecasts a more cautious trajectory, estimating 25.9% in 2025, 26.2% by 2027, and only 27.3% by 2035 – 5 years later than CPIA’s timeline for a similar performance level (see Back Contact Cells Demand Stricter Wafer Specs & Evolving Rear-Side Architectures).
Cell Processing
The manufacturing process for BC solar cells is an extension of high-efficiency cell technologies like TOPCon, but it involves additional complexity primarily due to the need for structuring interdigitated p and n regions on the rear side. SPIC’s first-generation IBC cells involved 10 process steps, while the newer TBC structure expanded the process to 14 steps. The added complexity stems from the integration of laser patterning, which is essential for forming the interdigitated rear-side contacts and creating precise isolation zones between the positive and negative electrodes. While not disclosing its complete process flow due to confidentiality, AIKO confirmed that its BC production line adds 2 extra steps compared to a standard TOPCon line. These additional steps are also attributed to laser processing required for structuring the rear-side contacts.
Laser technology plays a vital role in BC solar cell manufacturing, particularly in enabling the rear-side structuring that defines this architecture. While lasers have long been used in the solar industry, their application in BC requires addressing different needs. Across manufacturers, lasers are used for a range of tasks – from precision patterning to selective removal of masking layers.
Lasers have been very instrumental since the early days of BC architecture development. These patterning tools have achieved minimal substrate damage and, at the same time, can also attain ultra-high precision. However, accomplishing these operations at high speed to support high-throughput manufacturing at low cost was indeed a challenge back then, but not anymore. LONGi says it jointly developed BC laser technology with equipment manufacturers to solve the throughput challenge and reduce equipment and processing costs significantly. AIKO highlighted laser scribing as one of the most critical steps in its BC process. It is used to precisely separate the positive and negative regions on the rear side of the cell. If this step is not done properly, the cell can suffer from electrical leakage, leading to poor cell performance. While the company has successfully integrated laser tools into production, it acknowledged that laser-induced damage to the underlying silicon remains a point of concern. AIKO views this as an area for further optimization rather than a fundamental obstacle (see Leading Manufacturers Back BC As The Future Of High-Efficiency Solar).
At SPIC, lasers are used more selectively – primarily for removing masking layers during rear-side processing. It takes a different route to isolate the p and n regions, using insulating materials to physically separate the contacts. The company emphasizes the criticality of keeping the pulse output of these tools stable, and this aspect needs continual improvement.
In an exclusive interview with TaiyangNews Managing Director Michael Schmela during the TaiyangNews SNEC Solar Leadership Conversations 2025 at SNEC 2025, LONGi Group Vice President Dennis She highlighted the company's efforts to make back contact technology a cost-effective solution across diverse application scenarios (see SNEC 2025 Exclusive: Interview With LONGi Group VP Dennis She).
This text is an excerpt from the TaiyangNews Cell & Module Technology Trends 2025 report, which can be downloaded for free here.
