The race to improve crystalline-silicon solar efficiency is increasingly moving into the microscopic world of interfaces, defects and materials engineering.
A new study published in ACS Applied Materials & Interfaces on 25 May 2026 presents an interesting approach to improving the performance of Tunnel Oxide Passivated Contact (TOPCon) solar cells. The researchers developed a TOPCon structure combining an ultrathin silicon oxide layer produced using N₂O plasma oxidation with carbon-incorporated polycrystalline silicon (poly-Si).
The results demonstrate how carefully engineered materials at the silicon/contact interface can reduce recombination while maintaining the electrical properties required for efficient carrier collection.
For the solar industry, this is an important direction for the continued evolution of TOPCon technology.
Why Passivation Is Critical in TOPCon
TOPCon has become one of the leading technologies for high-efficiency crystalline-silicon photovoltaics.
The basic concept is relatively simple: an ultrathin oxide layer sits between the crystalline silicon wafer and a doped poly-Si contact. This structure helps passivate the silicon surface while enabling charge carriers to reach the electrical contact.
But achieving the right balance is challenging.
A good TOPCon contact needs to provide:
- Excellent surface passivation
- Low recombination
- Efficient carrier transport
- Low contact resistance
- Thermal stability
- Compatibility with industrial manufacturing
Improving one property can sometimes negatively affect another. The 2026 ACS study addresses this challenge by combining chemical passivation and electric-field-effect passivation through coordinated oxide and poly-Si engineering.
The Role of N₂O Plasma Oxidation
One of the key innovations in the study is the use of N₂O plasma oxidation to create the ultrathin silicon oxide layer.
According to the researchers, this process produces a uniform, continuous and amorphous SiOₓ layer.
Why is that important?
The silicon/oxide interface contains defects that can act as recombination centres. These defects can allow photogenerated carriers to disappear before they contribute to useful electrical current.
Better interface quality means fewer recombination losses.
The N₂O-plasma approach therefore focuses on improving the quality of the oxide and the interface it creates with the silicon substrate.
Carbon-Engineered Poly-Silicon: A Second Piece of the Puzzle
The second major element of the research is the introduction of carbon into the polycrystalline silicon layer.
The researchers found that carbon incorporation can influence several properties of the poly-Si layer.
According to the study, carbon:
- Suppresses excessive poly-Si crystallization
- Promotes hydrogen accumulation at the SiOₓ/silicon interface
- Reduces the poly-Si work function
- Creates favourable energy-band bending
- Contributes to improved passivation
Together, these effects strengthen both chemical passivation and field-effect passivation.
This is particularly interesting because TOPCon performance is not controlled by a single material.
The oxide and poly-Si layers need to function as an integrated system.
A Synergy Between Chemistry and Electrical Fields
One of the most important concepts in this research is the combination of two passivation mechanisms.
Chemical passivation
The silicon oxide helps reduce electrically active defects at the silicon interface.
Field-effect passivation
The electrical properties of the poly-Si contact help repel minority carriers away from the interface, reducing the probability of recombination.
When these mechanisms work together, the interface can become significantly more effective at preventing carrier losses.
This is precisely the type of engineering required as TOPCon cells move toward increasingly high efficiency.
The Numbers Behind the Research
The optimized structure demonstrated impressive passivation characteristics.
The researchers reported:
760 mV implied open-circuit voltage (iVₒc)
0.5 fA/cm² recombination current density (J₀,s)
27.9 ms effective minority-carrier lifetime
These values indicate a highly effective passivated contact structure.
Importantly, the research did not stop at laboratory characterization.
The optimized structure was also tested in mass-produced, large-area TOPCon cells, where the researchers reported an absolute efficiency improvement of 0.05%.
That industrial validation is particularly significant.
A material innovation becomes much more valuable to the PV industry when it can survive the realities of large-scale manufacturing.
Why the 0.05% Improvement Matters
At first glance, a 0.05 percentage-point absolute efficiency gain may appear small.
In large-scale solar manufacturing, however, even small improvements can have substantial value when multiplied across millions of cells and thousands of modules.
Higher cell efficiency can contribute to:
More watts per module → higher power density → potentially fewer modules for a given project capacity → optimized balance-of-system costs.
This is one reason why modern solar R&D focuses so intensely on seemingly small improvements in recombination, resistance and optical losses.
The industry is no longer looking only for dramatic changes in cell architecture.
It is increasingly looking for small, repeatable improvements that can be scaled economically.
What This Means for the Future of TOPCon
The study highlights several important directions for TOPCon development.
1. Interface engineering will become increasingly important
As cell efficiencies rise, losses at interfaces become more significant. Better control of the Si/SiOₓ/poly-Si system can therefore provide another pathway to higher performance.
2. Material combinations matter
The study demonstrates that improving the oxide alone is not necessarily enough. The properties of the adjacent poly-Si layer also influence the overall passivation behaviour.
3. Thermal stability is essential
The optimized structure showed good tolerance to variations in annealing temperature and carbon content, which is valuable for industrial processing.
4. Laboratory results must translate to manufacturing
Perhaps most importantly, the researchers demonstrated an efficiency improvement in mass-produced large-area cells, connecting the material innovation to industrial applicability.
Connecting the Research to Frontier Energies
At Frontier Energies, our focus is on advanced N-type TOPCon solar technology and high-performance bifacial modules designed for real-world applications.
Our current portfolio includes the Phoenix, Fornax and Stellar series, covering commercial, industrial and utility-scale applications.
Frontier Energies’ Phoenix Series, for example, uses N-type TOPCon bifacial technology and offers power ratings from 615–645 Wp, with module efficiency up to 23.07%. The series is positioned for utility-scale and large commercial projects where power density is important.
The Fornax Series provides 565–600 Wp TOPCon bifacial dual-glass modules, with efficiency up to 23.23%, targeting commercial and industrial applications.
The Stellar Series uses N-type TOPCon bifacial technology with G12R cells and reaches up to 635 Wp and 23.51% module efficiency, according to Frontier Energies’ current specifications.
It is important to distinguish these commercial module specifications from the laboratory and cell-level metrics reported in the ACS research. The research focuses on the underlying TOPCon cell structure, while Frontier Energies’ figures describe complete commercial modules.
From Materials Science to Megawatts
Research such as this illustrates how the next generation of solar efficiency may be achieved.
The future is unlikely to depend on one single breakthrough.
Instead, progress will come from optimizing multiple components simultaneously:
Better silicon surfaces
↓
Better oxide layers
↓
Better poly-Si contacts
↓
Lower recombination
↓
Better carrier collection
↓
Higher-efficiency solar cells
↓
Higher-power solar modules
The challenge is to achieve these improvements while keeping manufacturing scalable, reliable and cost-effective.
That is where industrial validation becomes so important.
The Bigger Picture for India’s Solar Future
India’s solar industry is moving toward higher-power modules, greater efficiency and increased domestic manufacturing capability.
As module technologies evolve, advanced N-type TOPCon architectures are becoming increasingly important for delivering higher energy output from available land and infrastructure.
Frontier Energies states that its mission is to accelerate the transition toward sustainable energy through advanced solar manufacturing and energy infrastructure, with a focus on innovation, scale and long-term performance.
Research into advanced TOPCon passivation supports the broader technological ecosystem behind this transition.
The work may look microscopic—an ultrathin oxide layer, carbon atoms within poly-Si and the behaviour of carriers at an interface.
But the potential impact is measured at a much larger scale.
From nanometres at the silicon interface to gigawatts of solar generation.
Conclusion
The 2026 ACS Applied Materials & Interfaces study demonstrates a compelling approach to improving TOPCon solar-cell passivation by combining N₂O-plasma-grown SiOₓ with carbon-incorporated poly-Si.
The optimized structure achieved an iVₒc of 760 mV, J₀,s of 0.5 fA/cm² and a 27.9 ms minority-carrier lifetime, while industrial validation delivered a 0.05% absolute efficiency gain in mass-produced large-area TOPCon cells.
The key message is clear:
The next gains in solar efficiency may come from controlling the smallest details of the cell.
For TOPCon, the silicon/oxide/poly-Si interface remains one of the most important areas for innovation.
As research continues to improve these interfaces, the pathway toward more efficient, reliable and scalable solar technology becomes increasingly promising.
For companies such as Frontier Energies, these developments reinforce the importance of advanced TOPCon technology as part of India’s journey toward a higher-efficiency, more self-reliant and sustainable energy future.
Research Reference
Zunke Liu et al., “Nitrous Oxide-Plasma Silicon Oxide Coupled with Carbon-Incorporated Polycrystalline Silicon Enables Highly Passivated TOPCon Solar Cells,” ACS Applied Materials & Interfaces, 2026, 18(22), 31530–31541. DOI: 10.1021/acsami.6c06122.
