Perovskite-silicon triple-junction photovoltaics represent a complex yet highly rewarding engineering feat. By stacking three sub-cells with distinct bandgaps, these devices harness a broader spectrum of sunlight more effectively than simpler architectures. However, the complexity introduced by this multilayer device structure leads to practical bottlenecks that have historically limited device performance. Two primary issues dominate the design challenges: first, the wide-bandgap perovskite top-cell suffers from reduced open-circuit voltage, undermining overall voltage output; second, the middle perovskite layer faces restricted photocurrent generation due to difficulties in fabricating thick, high-quality absorber layers that maintain structural and electronic integrity.

Addressing the voltage deficit in the wide-bandgap top-cell, researchers have innovated by incorporating a carefully selected non-volatile additive, 4-hydroxybenzylamine. This organic molecule exerts a profound influence on the crystallization dynamics of the perovskite layer, steering film formation towards preferential orientation. Such controlled crystallization not only enhances carrier transport pathways but also passivates defects that act as non-radiative recombination centers—pathways that waste photogenerated charges and reduce voltage. The result is a dramatic boost in open-circuit voltage, reaching values as high as 1.405 volts, a record performance metric for wide-bandgap perovskite top-cells.

Complementing this additive’s role, meticulous optimization of energy-level alignment within the device layers further mitigates voltage losses. By carefully tuning energy band offsets between the perovskite and charge transport layers, engineers realized improved charge extraction efficiency, minimizing recombination at interfaces. The synergy of material chemistry and electronic engineering culminates in a top-cell that not only delivers higher voltage but also manifests enhanced operational stability, a critical criterion for commercial viability of perovskite-based solar technologies.

While voltage enhancement is vital, maximizing the current output from the middle-cell is equally challenging yet essential for achieving commercially compelling efficiencies in triple-junction devices. The difficulty lies in depositing thick perovskite layers with narrow bandgaps that absorb a substantial fraction of the solar spectrum without compromising the electronic quality. To overcome this, a novel three-step deposition approach was developed. This strategy enables the growth of thick, low-bandgap perovskite films that retain exceptional microstructural integrity, avoiding issues like excessive grain boundaries or defect formations that traditionally degrade performance.

Maintaining the morphological and electronic quality of these thick absorbers is pivotal for efficient electron extraction. The refined deposition technique ensures that the perovskite layers exhibit uniform crystallinity and minimized trap state density, crucial for long carrier lifetimes and diffusion lengths. Consequently, the photocurrent generation in the middle-cell is significantly improved, translating into a more balanced current matching between the sub-cells, a prerequisite for high-performance tandem configurations.

Another ingenious aspect of the recent work is the integration of low-refractive-index silicon oxide (SiOx) nanoparticles strategically embedded in the front valleys of the textured silicon bottom-cell. This subtle optical engineering acts as a middle-reflector, exploiting photonic effects to enhance light trapping within the middle perovskite layer. By selectively reflecting longer-wavelength photons back into the intermediate absorber, these nanoparticles boost photon absorption and charge carrier generation without contributing additional parasitic absorption or scattering losses.

This sophisticated photon management approach enhances the overall light-harvesting capacity of the triple-junction stack, effectively utilizing incident solar radiation with minimal optical losses. The intimate interplay between nanoscale optical structuring and hybrid material interfaces signifies a new paradigm in multijunction solar cell design, where electronic and photonic optimizations are woven seamlessly to elevate device performance.

Critically, these two parallel advances—the voltage improvement in wide-bandgap perovskite top-cells and the photocurrent enhancement in narrow-bandgap middle-cells—were successfully integrated in practical, 1 cm² perovskite-perovskite-silicon triple-junction devices. The resulting solar cells achieved a certified power conversion efficiency of 30.02%, a milestone that firmly situates this technology at the forefront of photovoltaic research and commercial potential. Such efficiency gains represent a significant leap beyond the typical limits of silicon-based tandem cells, inching closer to the theoretical efficiency ceiling for multijunction devices.

Beyond raw performance, the reported devices exhibit promising stability characteristics under operational conditions, addressing one of the long-standing concerns hindering the adoption of perovskite materials. The role of 4-hydroxybenzylamine in defect passivation and film stabilization is critical here, ensuring that the device maintains performance integrity over extended periods. This stability is fundamental for transitioning these high-efficiency laboratory prototypes into reliable products fit for market deployment.

This breakthrough also underscores the importance of interdisciplinary approaches in photovoltaic research, blending chemistry, materials science, optical physics, and device engineering. The precisely orchestrated control over perovskite crystallization chemistry, deposition protocols, energy band alignments, and nanophotonic design exemplifies how holistic innovation can overcome entrenched material and device limitations.

Looking ahead, the roadmap for perovskite-silicon triple-junction solar cells is now enriched with practical design guidelines and scalable fabrication techniques demonstrated by this work. Future research will likely explore further improvements in long-term durability, manufacturability at scale, and integration into real-world photonic and energy systems. Moreover, the conceptual insights into additive-assisted crystallization and nanostructured photon management may extend to other optoelectronic applications beyond photovoltaics, such as photodetectors and light-emitting devices.

In conclusion, the confluence of advanced material additives, novel deposition methodologies, and sophisticated nanophotonic engineering presents a paradigm shift for next-generation solar technologies. The achievement of over 30% certified efficiency in triple-junction perovskite-perovskite-silicon cells offers a compelling vision for high-performance, cost-effective renewable energy solutions. As the global energy landscape demands cleaner and more efficient technologies, such innovations pave the way for perovskite-based multijunction photovoltaics to become a cornerstone of sustainable energy infrastructure in the coming decade.

Subject of Research: Perovskite-silicon triple-junction solar cells and advanced carrier/photon management strategies for enhanced photovoltaic efficiency.

Article Title: Triple-junction solar cells with improved carrier and photon management.

Article References:
Artuk, K., Turkay, D., Kuba, A., et al. Triple-junction solar cells with improved carrier and photon management. Nature (2026). https://doi.org/10.1038/s41586-026-10385-y

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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

Central to optimizing tandem solar cells is the seamless spectral matching between the top and bottom absorber layers. Achieving this requires the perovskite top cell to possess a wide bandgap, which is effectively attained through a mixed-halide composition rich in bromide. Bromide-rich perovskites tune the absorption onset to higher energies, thus complementing the narrower bandgap CIGS bottom cell and allowing for better utilization of the solar spectrum. Nonetheless, incorporating high bromide content has historically been fraught with difficulties, particularly related to the inhomogeneous distribution of halides during the film formation process, which severely undermines the electronic quality and reproducibility of the resultant perovskite films.

One of the most critical obstacles in scalable manufacturing of these bromide-rich perovskite layers is the tendency for halide segregation and phase heterogeneity, especially when using commonly adopted film deposition techniques. These phenomena cause the formation of regions with varying halide compositions, which adversely affect the perovskite’s optoelectronic properties and, by extension, the overall performance of the tandem solar cells. Addressing this issue demands innovative approaches to control the crystallization dynamics and intermediate phases during film growth to preserve halide homogeneity throughout.

Drawing inspiration from coordination chemistry, Zhang and colleagues employed 2-pyrrolidinone as a coordinating solvent in the perovskite precursor solution. This strategic solvent choice acts to complex with halide and lead ions, thereby suppressing premature crystallization of halide intermediates—a key step that often triggers heterogeneity. By moderating the kinetics of precursor crystallization under ambient blade-coating conditions, this approach ensures a uniform halide distribution and smooth film morphology over large areas, marking a pivotal step towards industrially relevant fabrication methods.

Blade coating, a scalable and cost-effective technique compatible with roll-to-roll processing, was utilized to deposit the perovskite layers. Conventionally challenging for bromide-rich compositions due to rapid crystallization and non-uniformity, the introduction of 2-pyrrolidinone dramatically enhanced film quality by prolonging intermediate phase stability. This allowed for controlled nucleation and growth, resulting in dense and pinhole-free films exhibiting exceptional compositional homogeneity, critical for high-performance tandem devices.

The fabricated flexible monolithic two-terminal perovskite/CIGS tandem solar cells demonstrated a remarkable power conversion efficiency (PCE) of 27.3%. This level of efficiency not only surpasses previous benchmarks for similar devices but also positions these tandem cells among the top contenders for commercial flexible photovoltaics. The monolithic design further minimizes mechanical and electrical losses, enhancing the device integration possibilities for lightweight and deformable photovoltaic systems suitable for portable and wearable applications.

Beyond the impressive efficiency gains, the device stability exhibited minimal degradation over 500 hours of continuous operation. Long-term operational stability has often limited the practical deployment of perovskite and tandem solar cells, so this durability milestone suggests a promising path forward for real-world application. The effective suppression of phase segregation and improved film uniformity underpin this robust operational lifetime, aligning with industry demand for reliable, sustainable solar technologies.

This study not only exemplifies the profound impact of solvent engineering on perovskite film formation but also highlights the importance of precursor solution chemistry in addressing compositional challenges associated with mixed-halide systems. The ability to finely tune crystallization behavior is paramount to unlocking high-efficiency devices with reproducibility across large areas—a fundamental requirement for commercial-scale solar module production.

The combination of perovskite layers with the well-established CIGS technology leverages the best of both worlds: the superior optoelectronic properties and tunability of perovskites alongside the mature and reliable thin-film chalcogenide bottom cell. This hybrid tandem architecture maximizes photovoltaic performance by capturing the complementary parts of the solar spectrum, providing a powerful route to push efficiencies well beyond single-junction limits.

This technological advance also paves the way for expanded investigations into flexible energy harvesting devices, where the intrinsic flexibility and light weight of perovskite/CIGS tandems can usher in new application realms—from building-integrated photovoltaics to wearable electronics and beyond. The suppression of halide crystallization intermediate phases thus stands as a paradigm-shifting approach that may influence broad perovskite fabrication strategies in the years to come.

Moreover, the demonstrated stability under ambient blade-coating conditions signifies a major stride towards environmental compatibility and manufacturing scalability. Processing under ambient conditions without the need for inert atmospheres reduces production costs and complexity, strengthening the economic viability of perovskite-based tandem solar modules.

The research underscores the critical role of molecular-level design in the precursor solution stage to circumvent fundamental material challenges. Through deep understanding and precise control of intermediate species in film formation, the path toward commercially relevant mixed-halide perovskite films becomes clearer, bridging the gap between laboratory breakthroughs and market-ready solar solutions.

In conclusion, the work led by Zhang and colleagues represents a formidable leap in perovskite/CIGS tandem solar cell technology, overcoming long-standing bottlenecks in halide distribution and device efficiency. With a record power conversion efficiency of 27.3% achieved on flexible, large-area tandem cells, alongside robust operational stability, this development signifies a new horizon for flexible photovoltaics with broad societal and environmental benefits.

As the push towards sustainable energy intensifies globally, innovations like these serve as critical enablers for next-generation solar technologies that can be seamlessly integrated into diverse environments. This research vividly illustrates the confluence of chemical engineering, materials science, and device physics driving the future of clean energy, positioning perovskite/CIGS tandem solar cells at the forefront of the photovoltaic revolution.

Subject of Research:
Perovskite/Cu(In,Ga)Se2 (CIGS) tandem solar cells; mixed-halide perovskite film fabrication; halide crystallization suppression; scalable blade-coating technique; flexible and lightweight photovoltaics.

Article Title:
Crystallization suppression of mixed-halide intermediates for perovskite/Cu(In,Ga)Se2 tandem solar cells with improved efficiency.

Article References:
Zhang, S., Bi, E., Lei, B. et al. Crystallization suppression of mixed-halide intermediates for perovskite/Cu(In,Ga)Se2 tandem solar cells with improved efficiency. Nat Energy (2026). https://doi.org/10.1038/s41560-026-01975-1

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41560-026-01975-1