Fuelling IP: The 11 Year Odyssey – Hanwha’s solar cell patent opposition

One of the most effective ways to maintain the integrity of the European patent framework is through post-grant opposition proceedings. An opposition allows one or more third parties to challenge the validity of a European patent within nine months of its grant. This window of time is relatively short but, as will be discussed in this case study, the consequences can be long lasting.

Oppositions serve as an important quality-control mechanism, helping to ensure that only patents satisfying the EPO’s strict requirements relating to patentability, sufficiency of disclosure and added matter are maintained. Opposition proceedings are a relatively swift procedure, but complex cases can stretch far beyond the typical timeframe. It is in this context that the dispute surrounding Hanwha’s solar cell patent EP 2 220 689 occurred. What started as a routine opposition transformed into an 11-year journey. This case is an example of how opposition proceedings can influence an industry’s technological and commercial landscape.

The Patent

Hanwha’s patent involved a solar cell design using two surface-passivating dielectric layers on a silicon substrate, with the purpose of the invention to reduce recombination losses and improve conversion efficiency, which was central to Hanwha QCells’ Q.ANTUM technology.

Timeline of the 11‑Year Opposition Procedure

In 2015, ten parties challenged the validity of Hanwha’s patent before the EPO’s Opposition Division, arguing that the patent lacked an inventive step. The Opposition Division decided to uphold the patent in amended form.

The patent was originally filed by the German Institute for Solar Energy Research, before being acquired by SolarWorld, and subsequently transferred to Hanwha Solutions. The insolvency of SolarWorld resulted in various procedural delays, leading the EPO to suspend and later retroactively set aside the Opposition Division’s decision to uphold the patent in amended form. Hanwha, as the new proprietor, appealed this decision.

In 2020, due to the appeal lodged by Hanwha Solutions, the EPO’s Board of Appeal ruled that the first-instance opposition proceedings were to be continued. The opposition was effectively restarted and these proceedings culminated in oral proceedings in 2022, in which the Opposition Division maintained the patent in limited form. This decision led both Hanwha and REC Solar, the only remaining opponent, to lodge appeals. Over the course of the proceedings, all other opponents either withdrew or did not appeal.

In July 2026, the EPO Board of Appeal decided to revoke the patent in its entirety on the grounds of lack of inventive step . The EPO found that the double layer passivation structure did not meet the inventive step requirement, concluding that the claimed configuration was an obvious combination of known technical features.

The decision reinforces a clear trend towards stricter scrutiny of inventive step in the renewable energy sector, particularly for photovoltaic process technologies that combine known technical features. This is especially relevant in the current competitive landscape of the global solar manufacturing industry.

Industry Impact

Hanwha’s patent was central to the company’s litigation strategy against competing manufacturers in Europe, the United States and Australia.

Hanwha had sued JinkoSolar, Longi, and REC Solar for infringement of the patent. In 2020, the Düsseldorf Regional Court ruled in Hanwha’s favour, granting injunctions, recalls, and destruction orders, with the judges concluding that the parties had infringed the intellectual property rights of Hanwha. The Hague Court of Appeal upheld a cross-border injunction against Longi in 2022 covering eleven European countries. However, in 2023, the Australian Federal Court found several claims of the corresponding Australian patent invalid and ruled that REC Solar did not infringe.

The revocation of the European patent undermines the legal basis of the court judgments founded on the patent in Hanwha’s favour, and may have broader implications for the enforcement and defence of related family patents. Although a European revocation for lack of inventive step is not binding on foreign courts, it may be persuasive. As a result, Hanwha may face greater challenges in supporting inventive step arguments in jurisdictions beyond Europe.

Competitors that were previously excluded from parts of the European market for certain passivated-cell products are now free to compete following the patent’s revocation. The decision also removes Hanwha’s licensing and enforcement leverage, weakening the foundations of agreements and settlements reached in reliance on the patent. In some cases, affected parties may even explore avenues for recovering losses.
This case illustrates how the revocation of a patent can destabilise years of litigation and enforcement across multiple jurisdictions.

Future PV patents

This case may be an important benchmark for assessing inventive step in future opposition proceedings relating to high-efficiency silicon cell technologies. The decision suggests that, for high-efficiency silicon cell technologies, combining known features may not be sufficient to support an inventive step unless the combination delivers an unexpected technical benefit. Consequently, patents directed to incremental improvements may be more vulnerable to opposition.

Conclusion

Oppositions should not simply be viewed as administrative formalities. Oppositions can be strategic battlegrounds, as a single opposition can overturn years of national litigation, licensing agreements, and commercial strategy. The timeline of this case, although a rare example, is indicative of how parties must be ready for procedural endurance as delays and external factors may prevent a quick resolution.

In an industry that is led by rapid innovation and intense competition, oppositions are not merely part of the patent system, they can be one of its most useful tools.

HGF has extensive experience in patent opposition proceedings. We work closely with clients across a wide range of technologies and our team provides strategic advice on both offensive and defensive opposition matters, helping to secure and maintain strong patent protection.

This article was prepared by Trainee Patent Attorney Rindai Machokoto.

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