Beyond Silicon Limits: TaiyangNews Conference Maps Commercialization Path For Perovskite Tandems

Solar technology is advancing at a pace where the gap between commercial products and practical efficiency limits is narrowing faster than ever before. The latest example comes from back-contact (BC) technology, where the architecture behind the world’s most efficient single-junction silicon solar cell is already finding its way into commercial production. While the current world-record single-junction silicon cell stands at 28.13%, commercial module efficiencies have already crossed the 25% threshold, as featured in the latest TaiyangNews TOP SOLAR MODULES feature. 

Against this backdrop, the industry is increasingly looking beyond the theoretical efficiency ceiling of single-junction silicon devices. Among the next-generation approaches under evaluation, perovskite-silicon tandem technology has emerged as the leading contender to push efficiencies to the next level. TaiyangNews organized the Next-Generation PV Technology: Perovskite Tandem Solar Technology Status & Outlook – Assessing Commercialization Roadmaps conference to provide a comprehensive perspective on the status of the technology, commercialization readiness, manufacturing challenges, and industry roadmaps. 

Several Open Questions 

In his opening remarks, TaiyangNews Managing Director Michael Schmela pointed out that despite rapid progress, the perovskite-silicon tandem is still, to a large extent, a laboratory technology. At the same time, he underscored that the transition toward commercialization has already begun, with the first commercial modules even being sold. However, it is well known that there are quite a few challenges, including long-term stability, reliability, large-area processing, and manufacturing yield. The major challenge here is to scale this lab-champion technology to GW scale, which is obviously not simple. Schmela reiterated the conference goal: to provide as close to a 360° perspective by bringing together stakeholders from across the value chain to discuss the path from record laboratory cells to industrial-scale deployment. 

HZB: Retaining Reliability is Key 

In his keynote at the conference, Rutger Schlatmann of Helmholtz-Zentrum Berlin outlined the role of perovskite tandems in the next phase of PV development. While today’s mainstream technologies, such as TOPCon, heterojunction (HJT), and interdigitated back-contact (IBC), continue to improve, their pace of progress has slowed. 

All these technologies are hitting inherent limits. One among these is not being able to fully harness the wide spectrum of sunlight. This can be addressed using the so-called tandem structure, which stacks 2 PV devices with complementary absorption. Here, a wide-bandgap top cell absorbs high-energy photons, while the bottom silicon cell captures the lower-energy portion. 

Among the available options, perovskites are emerging as the most suitable partner for silicon. This is due to their tunable bandgap, high optoelectronic quality, and low-cost processing. HZB and partners have demonstrated tandem efficiencies above 30% using both HJT and TOPCon bottom cells. For perovskites, stability remains a key challenge. Devices deployed in 2019 are still running, offering early signs of durability. Even so, several degradation mechanisms remain under investigation. Ion migration, phase segregation, and delamination are among the key concerns, particularly at the module scale. Schlatmann emphasized that efficiency is no longer the main hurdle; the next phase will depend on improvements in measurement, scaling, and long-term reliability. 

GCL: 4T Architecture Positioned as Practical Path for Tandem 

Bin Fan of GCL Technology focused on module-level implementation of tandem technologies. While several companies follow 2-terminal (2T) architectures, GCL bets on 4-terminal (4T) designs. In 2T, the sub-cells are electrically connected in series, requiring current matching and limiting operation to a narrow bandgap range around ~1.7 eV. In contrast, 4T designs allow the top and bottom cells to operate independently, enabling a wider bandgap window and theoretical efficiencies above 40%, emphasized Fan. His presentation highlighted that real-world conditions, such as spectral variation and temperature changes, introduce mismatch losses in 2T, leading to an estimated ~7% annual energy yield penalty.  

From a manufacturing perspective, 4T was presented as more flexible. Perovskite layers can be processed on flat substrates and combined with any silicon bottom cell at the module level. This primarily circumvents the process-coupling challenges seen in monolithic 2T designs, Fan highlights. GCL reported a tandem module efficiency of 29.51% on a 2,048 cm² device and 27.06% on a 1.71 m² near-commercial module. The company has also built and is operating a 500 MW production line. Demonstration projects using 4T tandem modules are underway, and the company indicated readiness to integrate with multiple silicon technologies, including BC architectures. In summary, GCL’s Fan outlines that the 4T offers broader material flexibility, simpler manufacturing, and better real-world performance for scaling tandem PV. 

Leadmicro: Equipment Pathways Focus on Stability and Scalable Perovskite Manufacturing 

Representing the equipment wing of the ecosystem was Jerry Liao from Leadmicro. His talk was focused on the transition of perovskite technologies from lab-scale efficiency records to industrial production. While record efficiencies have reached ~35% for perovskite-silicon combinations, most results are still based on small-area devices. Liao highlighted that industrialization depends on 3 key factors: efficiency, cost, and stability. Equipment cost was identified as a major contributor, alongside challenges in scaling and lifetime performance. 

The core focus was on stability, where degradation is driven by humidity, oxygen, temperature, light exposure, and ion migration, including metal diffusion and reactions such as AgI formation. Leadmicro positioned atomic layer deposition (ALD) as a key solution, enabling conformal layers for transport, diffusion barriers, and encapsulation. Materials such as SnO₂ and Al₂O₃ improve interface stability and protect the perovskite layer. ALD SnO₂ is also applied at sub-cell interfaces as a carrier-diffusion barrier and local encapsulation layer, reducing ion migration and improving junction stability. 

Liao outlined a full process flow for perovskite cell manufacturing, with ALD integrated across ETL, HTL, and encapsulation layers, and PVD used as an alternative for certain depositions. The perovskite absorber is deposited using slot-die coating. Liao also presented the full equipment portfolio spanning ALD, PVD, evaporation, and laser tools, covering lab, pilot, and GW-scale production. Leadmicro’s laser scribing systems support P1-P4 patterning across laboratory, pilot, and mass production lines. 

S.C New Energy: Process Control and Coating Technologies for Mass Production 

S.C New Energy was yet another equipment vendor representing this stream. Jiang Sheng of S.C New Energy focused on key process challenges in scaling perovskite-silicon tandem cells to mass production. The topics highlighted in his presentation were surface cleanliness of silicon bottom cells, high-quality film formation on textured surfaces, and control of edge effects during deposition. For cleaning, the company uses functional water containing micro- and nano-bubbles (<100 μm), which improves particle removal through enhanced surface interaction. This is particularly important for TOPCon and HJT substrates, where contamination and oxide layers affect interface quality. 

For film formation, a combination of vacuum coating technologies was presented, including PVD, evaporation, ALD, and CVD. Inkjet printing was also promoted for perovskite layer deposition, achieving film-thickness uniformity within ~3% variability and reduced edge defects. The company has established pilot production lines covering around 600 m², integrating processes such as cleaning, coating, laser patterning, and testing. These pilot setups are used to validate process integration and equipment performance. The ultimate goal here is to address key challenges in the areas of stability, efficiency, and manufacturability. 

Solamet: Low-Temperature Metallization Challenges for Perovskite Tandems 

Metallization has been a key driver of progress in solar cell architecture, and this step is equally important for perovskite-silicon tandems. Leading paste supplier Solamet focused on metallization challenges for perovskite-silicon tandem cells, where processing temperatures must remain below ~140°C. Unlike conventional high-temperature pastes, low-temperature systems rely on resin-based curing rather than full burnout, thereby limiting conductivity. This leads to higher bulk and contact resistance, especially when using screen printing on TCO layers such as ITO and IZO. Kaien Chang, VP Technology at Solamet, highlighted that achieving low resistivity at lower temperatures remains a key barrier to tandem cell scaling, with current pastes exhibiting significantly higher contact resistance than established silicon technologies. 

To address this, Solamet presented thermoplastic and thermosetting paste systems that combine silver flakes, spherical silver particles, and silver-coated copper powders to improve conductivity. Mechanisms such as particle rearrangement and diffusion during curing were highlighted as critical for forming conductive pathways at low temperatures. The company is also working with laser transfer processes to enable finer line metallization and improve print quality. Ongoing efforts focus on optimizing contact resistance across different substrates and surface textures. Another point of importance in this context, highlighted by Chang as essential, was collaboration between paste suppliers and cell manufacturers. 

Hangzhou First: Encapsulation Solutions Target Stability of Perovskite Modules 

Hangzhou First, the market leader in the encapsulation materials segment, presented encapsulation solutions tailored for perovskite and tandem solar cells, for which sensitivity to moisture, oxygen, and UV exposure remains a key challenge. Overseas Sales Manager Bo Jin represented the company at the conference, with his presentation highlighting thermoplastic polyolefin (TPO)-based encapsulants. Materials such as XUR150 are designed for low-temperature processing and high electrical insulation. These materials are positioned for use across perovskite-only, 2T, and 4T tandem module configurations. The product is also built on a modular platform that enables tweaking the melting behavior to match different lamination conditions, as required by a specific technology or manufacturer. 

In addition, high-barrier sealants such as PIB-405 were presented for edge sealing applications. Jin also presented the results of reliability testing under damp heat conditions, including 85°C and high-humidity exposure, which showed minimal power degradation and stable mechanical performance, including peel and shear strength. The materials are designed to work in combination with EVA, EPE, and POE layers, with options such as UV-cutoff encapsulation to further protect perovskite layers. The overall approach focuses on improving long-term module stability through enhanced moisture barriers and compatibility with existing encapsulation systems. 

WAVELABS: Measurement and Metrology Challenges for Perovskite Tandems 

Lukas Ziegler of WAVELABS focused on measurement challenges for perovskite and tandem solar cells. As efficiencies increase, accurate characterization becomes critical, especially since tandem devices are highly sensitive to the spectral shape of the light source. Unlike silicon, perovskite cells require preconditioning under steady illumination to reach stable operating conditions. Fast IV measurements, commonly used in production, can introduce errors due to hysteresis and metastability effects, making tandem characterization more complex than conventional silicon testing. 

Ziegler’s presentation highlighted the need for advanced metrology, including spectral adjustment based on EQE as defined in IEC 60904 standards, as well as maximum power point (MPP) tracking under stable illumination. Measurement conditions such as temperature uniformity, light stability, and bias state significantly influence results. With production tools capable of IV sweeps in ~30 ms and throughput of up to 6,000-9,000 cells per hour, maintaining accuracy remains a key challenge. Issues such as ion migration and hysteresis further complicate measurement, requiring dedicated procedures and stable testing environments to ensure reliable performance evaluation at both cell and module levels.  

Advances in Tandem Solar Cell Efficiency and Technology Roadmap 

JinkoSolar’s R&D director, Menglei Xu, also highlighted that single-junction silicon cells are approaching their theoretical efficiency limit of ~29.4%, constraining further gains. This is driving the transition toward perovskite-silicon tandem solar cells, which offer a much higher theoretical efficiency of ~43%. Xu’s presentation showed a clear shift from HJT-based tandems toward TOPCon-based bottom cells, reflecting alignment with large-scale manufacturing. 

On the technology side, Jinko reported a certified tandem efficiency of ~34.7% with an open-circuit voltage of ~2.0-2.01 V, combining a ~1.3 V perovskite top cell with a ~748 mV TOPCon bottom cell. Device improvements include sub-micron (~1 µm) texturing of the TOPCon surface to reduce reflectance below 10% and rear-side optimization delivering ~0.5 mA/cm² current gain. Stability results show ~98% efficiency retention after 1,000 hours of MPP tracking, ~91% after 1,700 hours, and >80% retention under 85°C operation for 1,000 hours. Xu also emphasized the role of additive engineering approaches such as halide-locking and potassium-based treatments to improve perovskite film quality and uniformity, while ongoing R&D is exploring multi-junction designs beyond current 2-terminal tandem architectures. 

Oxford PV: Commercialization Pathways for Perovskite-Silicon Tandems 

In his presentation, Chris Case, Chief Scientist Emeritus at Oxford PV, led a discussion on how external factors are influencing the progress of solar technology. The argument was that geopolitics and energy security now drive the transition as much as technical innovation. Global events, from past oil embargoes to recent invasions and supply chain disruptions, have forced countries and regions to rethink local manufacturing and energy sovereignty. Case also touched upon the emergence of ‘solar patent wars’. The industry is gradually moving away from largely public-domain technologies such as PERC and HJT toward more proprietary architectures like TOPCon and BC. As a result, intellectual property enforcement is increasingly becoming an important tool for market positioning, technology licensing, and competitive control. 

On the economic front, Case remarked that the industry’s reliance on ‘price per watt’ as a success metric is an important bottleneck. He advocated for a shift toward pricing based on integrated energy delivered over time, especially for tandem cells, which are inherently more expensive to manufacture due to their dual-cell architecture. Despite the current global overcapacity in silicon manufacturing, Case remains bullish on the long-term prospects, noting that the energy transition will eventually require multi-terawatt annual installation rates to meet net-zero targets. He concluded by discussing Oxford PV’s licensing strategy, revealing that the company has transitioned to licensing its patent portfolio to tier-one manufacturers – specifically citing a deal with Trinasolar – to enable mass production of tandem technology within established global markets. 

Tandem Solar Transition: Weighing Commercial Readiness and Market Dynamics 

The concluding panel of the TaiyangNews Next-Generation PV Technology conference brought together prominent experts to evaluate the commercial trajectory of perovskite-silicon tandem cells. A central theme that garnered consensus among all participants – Oxford PV’s Chris Case, Rutger Schlatmann from HZB, and Jerry Liao from Leadmicro – was that the industry must move beyond the narrow metric of ‘price per watt’. Instead, they collectively emphasized that the value proposition for tandems lies in ‘energy delivered’ and high efficiency, arguing that the market must evolve to recognize that a higher initial power output can result in a lower levelized cost of electricity (LCOE) over a 15-to-20-year period, even if the technology does not yet match the 30-year warranty of standard silicon single junction devices. 

The discussion also highlighted diverse perspectives on the immediate hurdles and opportunities for the technology. Case shared an interesting perspective on niche commercialization, noting that for applications like low-earth orbit satellites, the perovskite-silicon tandem technology is ‘as commercially ready as it needs to be’ already. That’s because these missions only require a 5-year lifetime. HZB’s Schlatmann pointed out that the perceived ‘lab-to-fab’ hurdle is often a feedback loop: if a fundamental physical law is encountered during scaling, research labs step back in to provide the atomic-scale analysis needed to develop a workaround. From an equipment standpoint, Jerry Liao observed that while the industry is currently fixated on competing with utility-scale silicon, the real breakthrough will come from exploring diverse application segments that don't mandate a 30-year lifespan, such as portable or aesthetic integration. The panel concluded that while technical records nearing 35% are impressive, a healthy, non-oversaturated market is the ultimate enabler for tandem technology to reach the GW scale by 2030.