10/12/2025
JingAo Solar (JingAo), one of the largest solar panel manufacturers in the world and a member of the Silicon Module super league, has recently concluded a significant patent litigation against its competitor Astronergy and its European subsidiary Chint, based on two European Patents EP2787541 “Solar Cell” and EP4092759 “Solar Cell Panel”. The parallel EPO Opposition and Appeals processes running alongside the hearings at the UPC make this an interesting series of decisions to unpick.
The European Patents
EP2787541 relates to photo-voltaic solar cell and a corresponding method of manufacture. EP4092759 claims a corresponding solar cell module. Both solar cells involve an innovative cell-structure and utilize advanced materials to achieve considerably higher energy conversion efficiencies than existing designs.
The patents were originally filed in the name of the Korean giant LG Electronics in 2014 and were assigned to the Chinese manufacturer Jinko Solar when LG exited the solar panel business in 2022, and subsequently to JingAo Solar in 2024. Both patents relate to n-type TOPCon (Tunnel Oxide Passivated Contact) Cell Technology.
N-type TOPCon technologies, use n-type monocrystalline silicon doping for the base material, and have a thin oxide layer and a polycrystalline layer which form the tunnel oxide passivated contact on the rear side of the cell. Compared to their (PERC) passivated emitter rear contact solar cell counterparts they can achieve a considerably higher conversion efficiency (of around 25%) and are expected to account for an increasingly large share of worldwide sales of solar panels over the next 10 years, some estimates say approximately 70-80% of the market.
Opposition And Appeal at the EPO (EP4092759)
On 7 November 2025, the Opposition Division of the EPO declared EP4092759 invalid due to added subject matter. Astronergy withdrew their opposition in December 2025 following settlement with JingAo. However, the patent remains opposed by the Conseil European de l’Industrie Solaire, and JingAo must now file an Appeal if they are to prevent the patent from being revoked.
The added subject matter decision was based on the presence in the claim of three features not considered to be directly and unambiguously derivable from the application as filed.
The granted claims defined “finger electrode lines (42a)” and “bus bar electrode lines (42b)” crossing the finger electrode lines. The expressions “finger electrode lines” and “bus bar electrode lines” were not present verbatim in the application as filed, although separate expressions like finger lines, electrodes, ad bus bar lines were.
However, the more significant issue was that the claim did not further define how the bus bar electrode lines and finger electrode lines related to one another. Although, the proprietor tried to argue that claim required the two features to be part of the same electrode, the Opposition Division rejected this argument.
[2.4.7.4] The description discloses a connection between the bus bar lines and the finger lines, for example in the first sentence of paragraph [0092], claim 1 is however silent as to how the finger electrode lines and bus bar electrode lines cross, and is silent as to whether let alone how they are connected.
The granted claims of EP4092759 also defined a “plurality of pad sections (422) formed on the bus bar lines”, while the description presented these features as “included in” the bus bar not “formed on it”. The Opposition Division argued that “It is immediately apparent that both the linguistic and technical meaning of “formed on” in feature 1.4 of claim 1 is different to that of “include” in paragraph [0093] of the parent application”.
The EPO takes a strict interpretation of the requirement to not add subject matter by amendment to claims during examination of the application.
Opposition And Appeal at the EPO (EP2787541)
In October 2024, EP2787541 was found to be valid in separate Opposition Proceedings at the EPO, launched originally by CARBON and SEMCO SMARTECH France in May 2023. Astronergy GmbH joined as an Intervener (and second opponent) in the Opposition proceedings in September 2024, with Astronergy BV and Chint new Energy joining as second and third interveners (third and fourth opponents) in November 2024.
During the Opposition JingAo were able to defend the patent arguing against the sufficiency, added subject matter, and inventive step attacks. Separate proceedings at the UPC Local division in 2025 also upheld the patent and led to the local division of the UPC in Munich issuing an order for injunctions in Germany, France, the Netherlands and Italy on 28 November 2025. Following this order, JingAo and Astronergy have now reached an agreement, and Astronergy have withdrawn as Opponent on both EP4092759 and EP2787541.
An Appeal is pending against the decision of the Opposition Division and was accelerated in view of the pending UPC infringement action. The provisional opinion of the Board of Appeal looks positive with respect to the enforceability of the patent but raised interesting questions around the admissibility of the second and third interveners (acting as Opponents 3 and 4), and the possibility of remitting the case back to the Opposition Division to hear the newly filed evidence.
Intervention of the Assumed Infringer (Astronergy BV and Chint New Energy) in the EPO Proceedings
JingAo’s argument that the second and third interveners had filed their submissions at the EPO outside of the three month period to do so set by Rule 89 (1) EPC and Article 105(1) EPC does not look likely to succeed. JingAo had argued that the start of the three month intervention period should start from either of the deemed commencement date that their claim at the UPC, or on the date that the defendants (opponents 3 and 4) had been served with the notice of the claim (in which cases both intervention would be inadmissible), rather than within the three months from the notional or backdated fictitious date of service set out by the UPC. The preliminary opinion of the Appeal Board however is that:
The board should also recognise the fictitious service date of 28 August 2024 as the “institution of proceedings for infringement” within the meaning of Article 105(1) (a) EPC and as such the relevant date for the purpose of the time limit under Rule 89(1).
Consequently, it would seem that the interventions were filed in time. Now that Astronergy has withdrawn the Opposition, the point is perhaps no longer of consequence.
The UPC Action (EP2787541)
The decision of the Munich Local Division was handed down on 28 November 2025 in favour of the patentee. The claim had been amended according to Rule 30 RoP to allow for additional infringing product of Astronergy to be included in the proceedings. For assessing inventive step, the approach taken in Amgen V Sanofi 25 November 2025 is adopted (see page 33 of the decision). The patent was held valid and infringed.
For relief, the patentee was entitled to an injunction to refrain the defendant from making, offering, placing on the market, using or importing or storing for those purposes, the invention within the territory of Germany, France, Netherlands and Italy. The patentee was also entitled to an interim award of costs of 50% of the applicable ceiling of representation costs (Art 69 UPCA) to cover the fees that it had incurred. The cost award amounted to €124 000. The defendant had not made a case that enforcement of the injunction should depend on an order of security against the patentee, and consequently no order was made by the court.
Conclusions
Patent enforcement in Europe can move quickly and can involve different strategies at both the EPO and the UPC. At the UPC, the patentee may have first-mover advantage following from taking the initiative and planning ahead for the short deadlines set by the court. Although the opposition against the EP2787541 patent began in 2023, the patentee initiated and concluded patent litigation against Astronergy over a period of 16 months, between July 2024 and the end of November 2025.
The EPO offers an opportunity for the defendant to subject the patents enforced against them to a high level of scrutiny, in addition to any invalidation action or arguments filed at the court. The opinion of the Opposition Division in EP4092759 shows the dangers of filing claim amendments without paying due attention to the EPO’s high bar on added subject matter.
If you would like to discuss any of the procedural aspects of this matter with our UPC team or European Opposition teams, please contact us here. Our electronics team is available to take any enquiries in connection with the technology of the case, including n-type TOPCon solar panels.
This article is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.
