Key takeaways:
ISC Konstanz sees back-contact as the logical successor to TOPCon, arguing that further efficiency gains require eliminating front-side shading and redesigning cell architecture
Industry roadmaps and performance rankings show BC technologies leading at the module level, with cell efficiencies projected beyond 26% under crystalline silicon limits
Regional market dynamics in China and exploratory shifts in India and Europe could accelerate a transition from TOPCon to BC if economic conditions align
Back-contact (BC) technology is often described as a promising pathway to push crystalline silicon cell efficiency to its theoretical limit. With growing improvements in efficiency and bifaciality, BC modules are gaining industry focus.
At the TaiyangNews High Efficiency Solar Technologies Conference 2025, Radovan Kopecek from ISC Konstanz presented his views on why BC technology represents the next evolutionary step after TOPCon. His keynote was not limited to cell efficiency alone; it also connected technology development to broader market dynamics, cost trends, and the long-term trajectory of the global energy transition.
He began by placing PV growth in context citing projection that suggest that renewables will overtake coal in electricity generation by 2026. Currently, the combination of solar and storage can push the levelized cost of electricity (LCOE) to record lows, even challenging wind in certain regions. According to Kopecek, this cost dynamic fundamentally changes the energy debate.
From a technology standpoint, he positioned BC as a natural continuation of the n-type journey. The industry transitioned from Al-BSF to PERC, then to TOPCon and heterojunction (HJT). Now, with TOPCon dominating the n-type bifacial era, the next efficiency jump requires structural innovation. While front-side polysilicon concepts are technically possible, they are difficult to scale to large wafers. Moving the ‘magic’ to the rear side – where both polarities are handled without front metallization shading – is, in his assessment, the more practical path forward.
The efficiency charts from TaiyangNews support his argument. BC modules rank at the top of performance rankings, with leading products approaching or surpassing 24-25% module efficiency. Industry roadmaps estimate BC to exceed 26% at the cell level, pushing toward the practical crystalline silicon limits. While tandem technologies promise even higher efficiencies, Kopecek expressed skepticism about their ability to scale to TW levels due to complexity. He sees crystalline silicon back-contact as the technology that can realistically drive large-scale deployment.
Another important signal, according to Kopecek, is structural convergence. Earlier BC concepts differed significantly, where some used only one passivated contact, others relied on different metallization or structuring approaches. Today, however, most major players are working toward similar BC architectures, even if deposition methods vary. When the industry aligns around a common structure, it often indicates that a technology is entering mainstream territory.
He also highlighted regional dynamics. In the US, PERC still plays a role, partly due to simplicity and the patent landscape. Europe has seen setbacks, with some HJT-focused manufacturers struggling. India remains largely TOPCon-driven but is already exploring BC upgrades. In China, where new factory approvals are restricted, manufacturers seeking competitiveness must upgrade existing lines to higher efficiencies. This creates strong incentives to transition from TOPCon to BC.
Beyond efficiency, Kopecek emphasized additional advantages of BC designs. With all metallization on the rear, front shading is eliminated, enabling higher performance and better reverse-bias behavior; copper metallization becomes more feasible, reducing silver dependency. Module design flexibility also improves, including support for overlap concepts and zero-busbar (0BB) approaches. Bifaciality, once a concern for BC, is steadily improving and now reaches levels suitable for utility-scale deployment.
He also underlined the growing importance of semiconductor-grade material quality, precise laser structuring, and advanced interconnection methods in BC manufacturing. Workshops and summits over the past year have shown rapid progress, with pilot lines already implementing 0BB BC modules and increasing bifacial factors.
Kopecek concluded that TOPCon will remain dominant in the near term, but BC is gaining momentum quickly. If the industry decides to shift – as it did from PERC to TOPCon – the transition could happen faster than current forecasts suggest. In his outlook, BC-based crystalline silicon will play a central role in driving PV toward the multi-TW scale, contributing significantly to the global energy supply by mid-century.
The full video presentation, titled Taking Back-Contact to the Next Level, can be accessed here.