Back contact solar PV technology has moved from niche to mainstream, and into the utility-scale segment, as highlighted at the TaiyangNews Special Webinar
LONGi said that its flagship Hi-MO 9 BC module now delivers up to 670 W output and 24.8% efficiency at a lower LCOE than TOPCon modules
TÜV Rheinland compared BC and TOPCon modules in an LCOE case study, which indicated measurable differences in yield and LCOE under specific test conditions
Once seen as a niche, high-cost product, back contact (BC) technology has quickly become mainstream. This was clear at the 2025 solar shows – The smarter E / Intersolar Europe in Munich and SNEC in Shanghai – where commercial BC modules were prominently displayed.
LONGi, a key player in BC technology and a pioneer in the space, has refined it through GW-scale production facilities and is working on improving its bifacial performance. The manufacturing giant from China, along with global PV testing and certification firm TÜV Rheinland, joined the TaiyangNews Special Webinar Unlocking the Utility Potential of BC Technology on September 30, 2025, to highlight commercial advances making BC a strong option for utility-scale PV installations.
The one striking feature that differentiates BC from other competing technologies is that all electrical contacts are present on the rear of the cell, which eliminates front-side shading, thereby improving efficiency. TaiyangNews Head of Technology Shravan Chunduri, in his presentation during the event, shared that the top 3 commercial solar module efficiencies on the TOP SOLAR MODULES Listing are represented by BC, all exceeding 24%, ahead of HJT & TOPCon.
Having proven its value in residential projects, BC is now increasingly used in utility-scale solar due to its high efficiency, which helps lower overall costs.
LONGi Advances Back Contact with Hi-MO 9
Dr. Alex Li, Senior Director of Global Products at LONGi Green Energy’s Product Management Center, presented an overview of the manufacturer’s back contact technology and its efforts towards its refinement with its flagship Hi-MO 9 module. Equipped with the company’s proprietary Hybrid Passivated Back Contact (HPBC) 2.0 and TaiRay wafer, along with a zero busbar (ZBB) structure, the Hi-MO 9 offers up to 670 W output and 24.8% conversion efficiency. These features help bring down its LCOE by 3.9% to 6.8%, stressed Li.
He noted that the Hi-MO 9 back contact module can generate 6.5% to 8.0% more power under the same land area compared with TOPCon. It also substantially reduced the hotspot temperature by 60°C in comparison to TOPCon, when it does occur during its 30-year outdoor operation lifecycle.
With further improvements, it has the potential to lead TOPCon by 25-30 Wp in terms of PMAX under the same module dimensions at all times, which is an untouchable ceiling for TOPCon.
Li added that LONGi plans to enhance metallization and optical layers to continuously improve the bifaciality of Hi-MO 9 in order to be comparable to conventional TOPCon, which enables increased deployment of back-contact technology in utility application scenarios.
TÜV Rheinland compares BC and TOPCon
Dr. Christos Monokroussos, Global Segment Coordinator for Solar at TÜV Rheinland Group, presented a detailed analysis based on the institute’s lab and field-testing data. He centered his discussion on a specific comparative case study to illustrate how performance differences translate into economic value.
Presenting a comparative case study of two specific types of PV module—BC and TOPCon modules installed in the UK’s Southampton, Monokroussos said the evaluation covered key parameters of nameplate power (STC), temperature coefficient (PMAX, VOC, ISC), low-light performance (100 W/m² to 800 W/m²), incidence angle modifier (IAM), nominal module operating temperature (NMOT), and reverse current coefficient (Arev).
According to product datasheets of the 2 products combined with TÜV Rheinland's own measurements, the BC modules offered higher efficiency at STC, a slightly better temperature coefficient of PMAX, but a lower bifaciality coefficient.
At a 75° incidence angle, IAM of BC modules was about 5.12% higher, and NMOT was roughly 0.5°C lower compared to TOPCon.
The economic modeling for this specific scenario revealed a clear advantage for the BC module. The study found that, compared to TOPCon, the BC model's LCOE was 2.1% lower for the same DC capacity and 3.2% lower for the same installation area. Furthermore, its internal rate of return (IRR) was 2.6% higher for the same DC capacity and 4.7% higher for the same installation area. These outcomes reflect the Southampton case inputs, including system design, cost assumptions, and site conditions.
Overall, the results suggested a modest, but measurable energy yield advantage for BC modules in this study, according to Dr. Monokroussos. However, he stressed that accurate yield assessment should be done on a case-by-case basis for different module types.
Panel Discussion
Following individual presentations from the 2 speakers, they joined a panel discussion with TaiyangNews’ Shravan Chunduri on scaling up BC technology for large-scale deployments.
LONGi’s Alex Li explained that patented production tool advancements, ultra-fast high-precision manufacturing methods, and solar cell architectural innovations now allow LONGi to produce 250,000 back-contact solar cells per day from a single production line, which is 10 times more than 10 years ago, enabling its mass-production feasibility. BC modules also deliver around 30 Wp more power and bifaciality, which pitches them as the better option for utility solar projects worldwide.
Market adoption is rising quickly, according to Li, as he shared that LONGi is expanding its BC production capacity from 20 GW in early 2024 to 50 GW by the end of 2025.Developers and installers also report higher yield and improved long-term reliability performance with BC modules installed in the field, especially during high-temperature periods and low-light hours, which makes BC attractive for utility projects, he stressed.
TÜV Rheinland’s Dr. Christos Monokroussos added that, in certain project scenarios, higher efficiency combined with advanced trackers has been a key factor in making BC more economically viable for large-scale projects. Together, these changes have helped BC gain stronger market acceptance.
Looking ahead, Li expects BC to dominate utility markets by 2028, while Monokroussos sees the technology steadily improving in efficiency and reliability over the next decade, with strong potential to pair with tandem structures. Both speakers agreed that BC is no passing trend, but a lasting part of the solar industry’s future.
Block your date for the next TaiyangNews event on October 17, 2025 as it returns with the Advanced Solar Module Applications Conference 2025, which will bring together industry leaders to explore design innovations in modules that address the needs of solar beyond traditional applications. Register for free here.
