Tips & Tricks for a successful HORIZON-CL5-2027-07-D3-16 proposal
Opening
4 August 2027
Deadline
Keywords
Tandem photovoltaics
EUPI-PV Partnership
TRL 6-7
Innovation Action
Interface engineering
Thin films
Scalable manufacturing
competitive energy supply
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HORIZON-CL5-2027-07-D3-16: Industrial processes and equipment for innovative, reliable and scalable tandem technologies (EUPI-PV Partnership)
What does it take to industrialise reliable, high-efficiency tandem solar cells?
Industrialising tandem solar cells requires combining high efficiency with long-term reliability, uniform thin films over large areas and scalable production equipment. Perovskite/silicon devices illustrate one research route: Liu et al. (2024), Nature, reported a certified stabilised efficiency of 33.89% using bilayer interface passivation to reduce electrical losses at material interfaces. Artuk et al. (2025), Nature Communications, demonstrated a certified efficiency of 28.9% over a 60 cm² active area. These research-cell results illustrate progress in efficiency and larger-area fabrication. In this manufacturing context, HORIZON-CL5-2027-07-D3-16 calls for tandem technologies with efficiencies beyond silicon limits and lifetimes comparable to silicon, alongside demonstrations of interface engineering, thin films and production equipment suitable for large-scale deployment.
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Administrative facts: what do we know about the HORIZON-CL5-2027-07-D3-16 call?
Which call is it, and when is the opening and the deadline?
- Call: ENERGY, HORIZON-CL5-2027-07.
- Destination: Sustainable, secure and competitive energy supply.
- Topic: HORIZON-CL5-2027-07-D3-16.
- Scheduled opening: 4 August 2027.
- Scheduled deadline: 1 December 2027, 17:00 Brussels time.
- Type of action: Innovation Action (IA).
What about the budget and estimated size of the project?
- Total indicative call budget: EUR 179 million.
- Topic budget: EUR 28.50 million.
- Indicative number of funded projects: 3.
- Budget per project: around EUR 9.50 million
What are the key eligibility and evaluation conditions?
- Eligibility: General Annex B applies. Legal entities established in China are ineligible under this destination.
- Evaluation: General Annex D applies; no specific thresholds are stated in the topic.
- Target maturity: TRL 6 to 7 at completion; any starting TRL.
- Reporting: results contributing to EUPI-PV partnership indicators.
- Results: the granting authority may object to ownership transfers or exclusive licensing up to four years after project completion.
Scientific range: what does the Commission expect from the HORIZON-CL5-2027-07-D3-16 grant?
What outcomes are expected?
Your results should strengthen European industrial know-how and improve the prospects for commercialising tandem photovoltaics. They must also support the EU Solar PV Industry Alliance and the joint solar energy research and innovation agenda. We read this as a manufacturing opportunity (keep the eventual buyer visible).
What is within scope?
- Tandem technologies with lifetimes comparable to silicon and efficiencies beyond silicon limits.
- Interface engineering and thin films at large scale.
- Production processes and equipment ready for large-scale deployment.
What are the specifically proposed research directions?
- The programme leaves material chemistry and device architecture open.
- Our reading: select the technical bottleneck that prevents your tandem technology from reaching industrial production. Then show how your process and equipment address it, with evidence spanning device performance and durability. You will need to explain what transfers between laboratory samples and the intended production format.
Scientific strategy: how can you enhance your chances of being funded through HORIZON-CL5-2027-07-D3-16?
What scientific choices matter most?
- Define the manufacturing demonstration first.
- Make lifetime claims testable. The programme asks for silicon-like lifetimes, but that wording alone gives you no acceptance protocol. We would specify ageing conditions and failure criteria early, then explain how accelerated tests support the lifetime claim. Independent verification belongs in the work plan (budget for it).
- Show efficiency across representative areas and repeated production runs. Our recommendation: report variation alongside your best result.
- Treat production yield as a scientific question. Track defects against processing conditions, and set decision points for changing the process.
- Cost the next production step. Include throughput assumptions and equipment costs in the business case, with potential financing sources, particularly the Innovation Fund.
Consortium & proposal-writing plan: what works best with this type of call?
- Give the industrial demonstration a named owner.
- For planning, somewhere around eight to twelve partners could work; this is a suggested range. Cover tandem device research and manufacturing equipment, alongside independent reliability testing and commercial deployment. If two partners offer the same capability, explain why both need funded work (access to different equipment might justify it).
- Include an innovative SME with responsibility for a specific process or instrument.
- Agree exploitation rights early.
- Build the required exploitation and dissemination plan around a feasibility study and business plan, covering scalability, commercialisation and deployment. Assign EUPI-PV reporting explicitly.
How would microfluidics contribute to this topic?
Manual formulation can make systematic comparisons slow. Microfluidic platforms offer controlled mixing and automated experiments using small material volumes. Research on perovskite nanocrystals demonstrates this experimental approach. We see a possible application to solution-processed tandem materials, subject to validation for your chosen architecture.
- Say your precursor mixture changes during preparation. You could use a flow platform to vary composition and residence time systematically, then compare the resulting materials. Your consortium would still need to coat and test actual devices, including ageing, before choosing a recipe for the production line.
- Check solvent compatibility and clogging early.
- For suitable nanocrystal routes, automated synthesis with optical feedback could help your team narrow down candidate formulations. This is a proposed contribution to the project.
- Connect each screening result to a manufacturing decision.
For suitable tandem technologies, microfluidics could help your consortium compare formulations and control material preparation. Your proposal should connect these experiments to measurable improvements in device performance or manufacturing consistency.
The MIC already brings its expertise in microfluidics to Horizon Europe:
H2020-NMBP-TR-IND-2020
Microfluidic platform to study the interaction of cancer cells with lymphatic tissue
H2020-LC-GD-2020-3
Toxicology assessment of pharmaceutical products on a placenta-on-chip model
FAQ – HORIZON-CL5-2027-07-D3-16
Why can perovskite/silicon tandem solar cells exceed the efficiency limit of single-junction silicon?
Perovskite/silicon tandem solar cells can exceed silicon’s single-junction efficiency limit by dividing sunlight between two absorbers, reducing energy losses. Each absorber has a different bandgap, the minimum energy needed to excite an electron across the semiconductor’s energy gap. The perovskite top cell absorbs higher-energy photons; the silicon bottom cell uses lower-energy photons transmitted through it.
Richter, Hermle and Glunz (2013) calculated a limiting efficiency of 29.43% for an idealised, 110 µm-thick undoped silicon cell under one-sun illumination at 25 °C. This is a theoretical silicon benchmark under defined assumptions, rather than the efficiency of a commercial panel.
A tandem can exceed that benchmark because its two absorbers use sunlight differently. The benefit still depends on controlling optical losses and extracting electrical charge efficiently from both subcells. Adding a second absorber alone does not guarantee an efficiency improvement.
Scientific reference: Richter, Hermle and Glunz (2013). Reassessment of the Limiting Efficiency for Crystalline Silicon Solar Cells. IEEE Journal of Photovoltaics. DOI: 10.1109/JPHOTOV.2013.2270351.
How should certified tandem solar-cell efficiencies be compared across different device areas?
A meaningful comparison of perovskite/silicon tandem efficiencies must include the measured area, measurement method and device format. Power conversion efficiency is electrical output divided by incident light power. Active-area measurements focus on the designated active region; aperture-area measurements use the illuminated opening; total-area measurements include the entire device footprint.
Artuk et al. (2025) reported certified efficiencies of 31.6% on a 1 cm² device and 28.9% on a 60 cm² active-area device in Nature Communications. The measurements were certified by JRC-ESTI and Fraunhofer ISE CalLab, respectively. These are different devices within one study, so the difference should not be treated as a universal scaling penalty.
The practical lesson is to report efficiency together with area and certification details. A 60 cm² tandem cell also remains distinct from an interconnected, encapsulated module. Repeated-device statistics help establish whether the reported performance is reproducible beyond the best sample.
Scientific reference: Artuk et al. (2025). 60 cm² perovskite-silicon tandem solar cells with an efficiency of 28.9% by homogeneous passivation. Nature Communications. DOI: 10.1038/s41467-025-63673-y.
How does interface passivation improve the efficiency of perovskite/silicon tandem solar cells?
Interface passivation reduces electronic defects where the perovskite absorber meets neighbouring layers. These defects can allow electrons and holes to recombine before their energy becomes useful electrical output. A successful interface treatment must suppress this loss while preserving charge extraction through the device.
Liu et al. (2024) demonstrated this balance using bilayer interface passivation in a Nature study. Their perovskite/silicon tandem achieved an independently certified stabilised efficiency of 33.89%, a fill factor of 83.0% and an open-circuit voltage close to 1.97 V. Open-circuit voltage is measured when no current flows; fill factor describes how effectively the current–voltage curve supports useful power output.
The result shows why interface engineering deserves attention alongside absorber composition. For manufacturing development, our recommendation is to assess whether the treatment produces consistent electrical improvements across the coated area and repeated batches, while remaining compatible with subsequent processing.
Scientific reference: Liu et al. (2024). Perovskite/silicon tandem solar cells with bilayer interface passivation. Nature. DOI: 10.1038/s41586-024-07997-7.
What changes when perovskite deposition moves from spin-coating to blade-coating on textured silicon?
Moving a perovskite formulation from spin-coating to blade-coating changes how the liquid spreads, loses solvent and crystallises. Spin-coating spreads solution by rotating a substrate. Blade-coating draws a liquid meniscus across the surface. Textured silicon adds another challenge: the coating must cover microscopic pyramids without leaving gaps or strongly uneven regions.
Er-raji et al. (2025) investigated a hybrid evaporation/blade-coating process in EES Solar. They identified wet-film thickness and solvent evaporation rate as central controls. Their blade-coating step used one-eighth of the solution volume used in the spin-coating comparison, and fully textured tandem cells achieved efficiencies approaching 28% and open-circuit voltages above 1.9 V.
These figures describe the study’s experimental process, rather than a factory-wide saving. The manufacturing implication is that formulation and coating equipment need joint optimisation: a successful spin-coated recipe requires renewed control of drying and film formation when transferred to a moving meniscus.
Scientific reference: Er-raji et al. (2025). Coating dynamics in two-step hybrid evaporated/blade-coated perovskites for scalable fully-textured perovskite/silicon tandem solar cells. EES Solar. DOI: 10.1039/D5EL00073D.
Why must mixed-halide perovskite absorbers be tested under illumination rather than only after fabrication?
Mixed-halide perovskite absorbers need testing under illumination because light can redistribute iodide and bromide, changing local composition and electronic properties. These materials combine different halides to adjust the bandgap, the energy threshold governing light absorption. This tunability makes them useful candidates for a tandem solar cell‘s upper absorber, but measurements taken before illumination may miss light-induced changes.
Hoke et al. (2015) reported a clear example in Chemical Science. Under one-sun illumination, the mixed-halide materials they studied developed a new photoluminescence peak at 1.68 eV in less than one minute. Photoluminescence is light re-emitted after optical excitation. The researchers associated the reversible changes with segregation into iodide-rich and bromide-rich domains.
This early study identifies a mechanism to investigate; it does not establish identical behaviour for every modern perovskite composition. Its practical implication is that measurements on freshly prepared films should be complemented by measurements during illumination, including checks for changes in emission, voltage and composition.
Scientific reference: Hoke et al. (2015). Reversible photo-induced trap formation in mixed-halide hybrid perovskites for photovoltaics. Chemical Science. DOI: 10.1039/C4SC03141E.
What does T80 measure, and how does it relate to perovskite tandem solar-cell lifetime?
T80 is the time required for a solar cell’s efficiency to fall to 80% of its stated initial value under a specified test (Khenkin et al., 2020). For example, a device beginning at 30% efficiency reaches that threshold at 24% efficiency: a 20% relative loss, or six percentage points. This is an illustrative calculation, not a reported experimental result.
The consensus published by Khenkin and colleagues in Nature Energy in 2020 sets out stability assessment and reporting procedures based on ISOS, the International Summit on Organic Photovoltaic Stability. Meaningful reporting includes illumination, temperature, atmosphere, encapsulation and electrical operating conditions, together with the baseline used to calculate degradation.
Consequently, 1,000 hours of testing cannot independently establish a 25-year outdoor lifetime. Such a projection requires evidence connecting the imposed stresses and observed degradation mechanisms to field operation. For a tandem device, the measurement must also establish the stability of the complete stack, including both absorbers and their interfaces.
Scientific reference: Khenkin et al. (2020). Consensus statement for stability assessment and reporting for perovskite photovoltaics based on ISOS procedures. Nature Energy. DOI: 10.1038/s41560-019-0529-5.
What published evidence supports using microfluidics to accelerate materials research for tandem photovoltaics?
Microfluidic platforms can automate controlled synthesis and connect each experiment to rapid measurements, helping researchers investigate how processing conditions affect materials. A relevant example is PoLARIS, an autonomous microfluidic laboratory described in Nature Communications. It combines continuous-flow synthesis, optical measurements and machine-learning-guided experiment selection for double-perovskite nanoplatelets.
Li et al. (2026) reported that the platform explored seven controllable synthesis variables and completed 120 experiments in 12 hours, consuming approximately 30 mL of each precursor. Its optimisation objective was photoluminescence quantum yield: the fraction of absorbed photons re-emitted as light. That optical quantity differs from photovoltaic power conversion efficiency.
Our interpretation is that the workflow offers a useful model for automated materials screening where the chemistry suits flow processing. Its application to a tandem manufacturing route would require connecting the screened material to deposited films and electrical device measurements. The published study demonstrates nanomaterial synthesis and optical optimisation; it does not demonstrate an improvement in tandem-cell efficiency.
Scientific reference: Li et al. (2026). Autonomous microfluidic experimentation for exploring reaction inference and synthesizing double perovskite nanoplatelets. Nature Communications. DOI: 10.1038/s41467-026-72765-2.
How can lead leakage from damaged perovskite solar cells be reduced, and what does the evidence establish?
For lead-containing perovskite solar cells, protective design can combine encapsulation with materials that capture lead if the device is damaged. Encapsulation limits environmental exposure during normal operation. Lead sequestration adds a chemical capture mechanism intended to reduce the amount released after protective barriers fail.
Li et al. (2020) reported an on-device sequestration approach in Nature that captured more than 96% of lead leakage following severe device damage under their experimental conditions. The design placed lead-binding materials on both sides of the device, including a transparent front-side film and a polymer layer containing lead-chelating agents at the back.
The percentage refers to lead retained in the reported damage tests. It does not mean that the absorber contains 96% less lead or that leakage is eliminated in every scenario. For a tandem product, our recommendation is to evaluate capture performance alongside optical transmission, ageing, realistic damage conditions and end-of-life recovery.
Scientific reference: Li et al. (2020). On-device lead sequestration for perovskite solar cells. Nature. DOI: 10.1038/s41586-020-2001-x.
Why does a higher laboratory tandem efficiency not automatically predict higher annual electricity production?
Annual electricity production depends on changing sunlight, temperature and degradation, so a higher laboratory efficiency alone cannot predict a tandem module’s yearly output. Annual energy yield measures electricity generated over time, commonly expressed in kilowatt-hours per installed kilowatt or per square metre. In a two-terminal perovskite/silicon tandem, both subcells carry the same current, so spectral changes can alter which subcell limits output.
Jäger et al. (2021) modelled this behaviour in Solar RRL, including bifacial operation, which collects light from both sides. They also examined luminescent coupling, where light emitted by the upper cell is absorbed by the lower cell. With these effects, their calculations shifted the preferred perovskite bandgap from around 1.71 eV towards 1.60–1.65 eV.
These are modelling results under stated assumptions, rather than universal design values. Their practical implication is to assess tandem designs using location-specific weather, spectral conditions and installation geometry, alongside temperature behaviour and degradation, instead of predicting annual output from a single efficiency percentage.
Scientific reference: Jäger et al. (2021). Perovskite/Silicon Tandem Solar Cells: Effect of Luminescent Coupling and Bifaciality. Solar RRL. DOI: 10.1002/solr.202000628.
Which manufacturing factors determine whether perovskite/silicon tandem modules can become economically competitive?
The economics of perovskite/silicon tandem modules depend on efficiency, production throughput, the silicon-cell architecture and the cost of additional processing. Higher efficiency increases rated watts produced per square metre, but extra equipment and processing steps also affect the manufacturing cost per watt.
Cordell, Woodhouse and Warren (2025) quantified these trade-offs in a Joule study. For a modelled US factory producing 3 GW per year at 25% module efficiency, they calculated minimum sustainable prices of USD 0.428/W for a two-terminal design and USD 0.423/W for a four-terminal design. These architectures connect the two absorbers in series or operate them electrically independently, respectively.
Minimum sustainable price is a modelled selling price supporting the assumed business economics. These figures are scenario results, rather than current market quotations or forecasts for a European factory. The useful lesson is to state efficiency and throughput assumptions explicitly and test their sensitivity before making a competitiveness claim.
Scientific reference: Cordell, Woodhouse and Warren (2025). Technoeconomic analysis of perovskite/silicon tandem solar modules. Joule. DOI: 10.1016/j.joule.2024.10.013.