In a remarkable advancement in photovoltaic technology, researchers have unveiled an innovative approach to enhance the efficiency and durability of silicon-based solar cells through the development of bifacial tunnel oxide passivating contacts (TOPCon). This breakthrough, reported by Gao, Mao, Yang, and their colleagues in a 2026 publication in Nature Energy, marks a transformative step forward in the pursuit of higher power conversion efficiencies (PCE) and longer-lasting photovoltaic devices, tackling fundamental bottlenecks inherent to traditional TOPCon designs.
Conventional silicon solar cells employing tunnel oxide passivating contacts have long been recognized for their ability to reduce recombination losses at the interfaces between silicon and metal contacts. However, these cells face intrinsic limitations, notably from front-side recombination occurring both in the contact regions and at non-contact areas, which restricts the achievable power conversion efficiency. This new research pioneers a bifacial architecture that strategically modifies the front and rear side contacts, enabling a substantial leap beyond these limits. Employing a patterned front n-type TOPCon finger array, integrated with a full-area rear p-type TOPCon emitter, the research team has demonstrated solar cells reaching a certified efficiency of 26.34%, a notable improvement over standard configurations.
The bifacial design is not merely a superficial modification but a meticulously engineered system that leverages the unique advantages of both n-type and p-type doping on opposite facets of the silicon wafers. This dual-contact structure facilitates enhanced charge carrier collection and minimized recombination across the active areas of the cell. Crucial to achieving this performance was the precise control of the polycrystalline silicon crystallinity and dopant concentrations within the tunnel oxide layers. These parameters were optimized to ensure robust passivation qualities and electrical conductivity, addressing the delicate balance required for maintaining tunnel oxide integrity while allowing efficient charge transport.
A pivotal aspect of the breakthrough lies in the tailored tunnel oxide properties. The researchers fine-tuned the thickness and uniformity of these ultrathin oxide layers, which act as essential barriers preventing direct recombination between the silicon wafer and the metal contacts. Stabilizing these oxide layers under operational conditions is indispensable for achieving both high efficiency and long-term device stability. By combining this with an optimized silver paste formulation for the metallization process, the team ensured excellent electrical contact quality without compromising the passivation layers, thereby minimizing resistance losses and contact-induced recombination.
Beyond efficiency gains, the new bifacial TOPCon solar cells exhibit exceptional operational resilience. Extended testing under damp-heat conditions, which simulate real-world aging environments, revealed outstanding stability in performance metrics. These cells showed negligible degradation induced by light exposure (known as light-induced degradation) and, notably, resisted detrimental effects caused by simultaneous exposure to light and elevated temperatures, which often plague silicon solar cells by causing irreversible performance drops. Such robustness is vital for commercial viability, especially for installations subjected to harsh climates.
The implications of these durable bifacial TOPCon cells are further amplified by their integration into tandem solar cell architectures. By pairing the silicon-based bifacial bottom cell with a wide-bandgap perovskite top cell in a monolithic structure, the team achieved a certified power conversion efficiency of 32.73%. This surpasses the efficiency plateau of single-junction silicon cells, opening avenues for next-generation photovoltaics that marry the stability and mature fabrication infrastructure of silicon with the high absorption efficiencies of perovskite materials. With an impressive open-circuit voltage of 1.961 volts, these tandem cells manifest the synergistic potential of hybrid photovoltaic architectures.
This integration exemplifies a scalable and industry-compatible strategy, leveraging refined fabrication techniques and materials engineering to push the boundaries of solar energy conversion. The precise engineering of the bilayer p-type TOPCon contacts on the rear side played a critical role in enabling this tandem architecture, improving charge selection and carrier extraction, which are essential for tandem cell efficiency. The combination of high-quality passivation, optimized doping profiles, and careful metallization culminates in a device architecture poised for both high performance and manufacturability.
This milestone also provides significant insights into the underlying physics of recombination mechanisms in TOPCon devices. By systematically studying and manipulating the crystallinity of the polysilicon layers, the researchers illuminated how grain boundaries and dopant distributions influence carrier lifetimes and transport properties. Such mechanistic understanding is vital for guiding future designs and further efficiency enhancements beyond the current benchmarks.
Moreover, the work addresses long-standing challenges related to the scalability of advanced contact architectures. Unlike past efforts that relied on complex, costly fabrication methods, these bifacial TOPCon cells are amenable to established silicon solar cell manufacturing processes. The compatibility with large-area wafers and standard metallization techniques underscores the potential for widespread adoption in commercial photovoltaic production lines, a crucial requirement for meaningful impact in the global renewable energy landscape.
The comprehensive approach combining materials science, device engineering, and tandem integration underscores a paradigm shift in solar cell development. It strategically balances the intricate requirements of solar cell interfaces while pushing the envelope of achievable efficiencies and long-term operational stability. With renewable energy adoption accelerating worldwide, such innovations are indispensable for reducing costs and enhancing the performance of photovoltaic systems deployed across diversified environmental conditions.
Future research inspired by this study is expected to further probe the optimization landscape, including exploration of alternative dopants, interface passivation chemistries, and metallization schemes tailored for bifacial cell configurations. In tandem, perovskite materials are rapidly evolving, and their integration with silicon substrates offers a fertile ground for further efficiency breakthroughs and cost reductions through tandem architectures.
As the photovoltaic research community digests these findings, the bifacial TOPCon model may become a standard bearer for next-generation silicon solar cells, combining unmatched efficiency potential with proven environmental robustness. The promise of over 32% efficiency tandem cells delivered through industry-compatible processes heralds an exciting era in solar energy technology development, carving pathways to more sustainable and economically viable clean energy solutions globally.
In conclusion, this research marks a serious leap forward, not only in numerical efficiency metrics but in the holistic optimization of solar cell design for both performance and durability. It exemplifies how concerted interdisciplinary innovation in materials, interface science, and device architecture can overcome entrenched limitations, setting the stage for a new generation of photovoltaic technologies that meet the ambitious demands of future energy systems.
Subject of Research: Bifacial tunnel oxide passivating contacts (TOPCon) in silicon solar cells and perovskite/silicon tandem solar cells to improve power conversion efficiency and device stability.
Article Title: Bifacial tunnel oxide passivating contacts for silicon and perovskite/silicon tandem solar cells with improved efficiency.
Article References:
Gao, K., Mao, J., Yang, Z. et al. Bifacial tunnel oxide passivating contacts for silicon and perovskite/silicon tandem solar cells with improved efficiency. Nat Energy (2026). https://doi.org/10.1038/s41560-026-02007-8
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41560-026-02007-8
