Addressing these constraints, a pioneering team of researchers has unveiled an innovative approach centered around the development of a solution-processed interconnecting layer crafted from surface-engineered indium oxide (In₂O₃) nanocrystals. Distinguished by exceptional optical transparency, this novel recombination layer is meticulously engineered to facilitate smooth interfacial contact and optimize energy level alignment through precise control over nanocrystal morphology and tailored ligand chemistry. By circumventing the optical losses associated with gold-based layers, the In₂O₃ nanocrystal film stands to significantly enhance device performance and stability in all-perovskite tandem solar modules.

A crucial facet of this breakthrough lies in the strategic incorporation of a phosphonic acid additive into the lead-tin (Pb–Sn) perovskite precursor solution. This additive serves multiple synergistic purposes: it improves electronic contact between the perovskite absorber and the In₂O₃ recombination layer, thereby facilitating efficient hole extraction, and regulates the crystallization kinetics of the perovskite film. The result is a notable mitigation of residual strain within the film matrix during deposition, fostering the formation of high-quality large-area perovskite layers with enhanced structural integrity and homogeneity.

The innovative synthesis and integration methodologies underpinning this approach collectively tackle pivotal interfacial and bulk material challenges that have limited tandem perovskite solar modules to laboratory-scale prototypes. By augmenting carrier recombination efficiency at the interconnection layer, the researchers effectively reduce non-radiative recombination losses, while simultaneous improvements in carrier extraction streamline charge transport dynamics. These advances culminate in the realization of large-area films exhibiting exceptional uniformity, a critical prerequisite for scalable manufacturing.

Demonstrating the broader utility of this technology, the researchers fabricated a 65 cm² all-perovskite tandem solar module that achieved a certified power conversion efficiency (PCE) of 26.2%, verified by the Japan Electrical Safety and Environment Technology Laboratories (JET). The module showcased an impressive open-circuit voltage (Voc) of 2.182 V, a fill factor (FF) of 77.4%, and an average short-circuit current density (Jsc) of 15.6 mA/cm² across the subcells. These metrics not only signify a substantial leap forward compared to previous records but also underscore the feasibility of translating high-performance tandem perovskite solar technologies from benchtop demonstrations to commercial-scale production.

Beyond performance metrics, the strategic use of solution-processed In₂O₃ nanocrystals as an interconnecting layer addresses long-standing challenges linked to interfacial instability. Traditional gold-based TRJs are susceptible to degradation mechanisms such as ion migration and interfacial chemical reactions, which degrade device longevity. In contrast, the oxide-based recombination junction introduced here exhibits enhanced chemical robustness and mitigates adverse interfacial phenomena, thereby extending the operational lifespan of tandem modules under real-world conditions.

The design ingenuity is further exemplified by the modulation of nanocrystal surface chemistry through ligand engineering. By optimizing ligand length and binding affinity, the team achieved a delicate balance between colloidal stability during synthesis and effective electronic coupling post-deposition. Such precise molecular control is critical for ensuring minimal interfacial traps and seamless charge recombination, which collectively boost overall device efficiency.

Moreover, the phosphonic acid additive’s role extends beyond facilitating electronic coupling. Its influence on perovskite crystallography is profound — it promotes the growth of larger crystalline grains, reduces grain boundary defects, and minimizes residual strain that can adversely impact charge carrier dynamics. These microstructural refinements are instrumental in achieving smooth, defect-free films that are essential for tandem devices, where interlayer coherence critically affects performance.

This research also exemplifies an escalating trend toward employing solution-based processes in photovoltaics, heralding a shift from energy-intensive vacuum deposition techniques toward more sustainable and scalable manufacturing. The compatibility of this approach with large-area module fabrication signifies its potential to accelerate the deployment of perovskite tandem photovoltaics in commercial applications, bridging the gap between experimental breakthroughs and market realities.

By elucidating the intricate interplay between nanocrystal morphology, ligand chemistry, and perovskite film crystallization, this work provides a comprehensive framework for interfacial engineering that could be adapted across various multijunction solar architectures. Such adaptability is especially pertinent as the solar industry seeks to continuously push the envelope on efficiency, cost reduction, and device stability.

In summary, this landmark study introduces a nanocrystal-tailored recombination strategy that decisively overcomes key bottlenecks in all-perovskite tandem solar modules. With the combination of surface-engineered indium oxide nanocrystals and phosphonic acid-modulated perovskite crystallization, the team demonstrates unprecedented performance and stability in scalable devices. Their findings mark a transformative advance, positioning perovskite tandems closer than ever to widespread commercial adoption and reshaping the future of high-efficiency solar energy harvesting.

As perovskite photovoltaic technologies march toward maturity, innovations such as this highlight the critical importance of interface design and chemical precision in optimizing device architectures. The prospect of facile, low-cost fabrication coupled with record-setting efficiency metrics sets a compelling precedent for next-generation tandem solar modules that could dramatically accelerate the global energy transition.

Looking forward, further investigations into the long-term operational stability under varied climatic stressors, integration with complementary photovoltaic technologies, and cost-benefit analyses of large-scale manufacturing will bolster the pathway to commercial viability. The versatile nature of the nanocrystal-based interconnection layer invites exploration into hybrid materials systems, potentially unlocking new paradigms in tandem cell design and functional performance.

This breakthrough not only paves the way for scalable, high-efficiency perovskite tandem solar modules but also inspires a new paradigm in nanomaterials engineering — one where molecular precision meets device architecture to unlock unprecedented energy conversion capabilities. The solar community will keenly anticipate subsequent iterations and refinements spurred by this seminal work, underscoring the relentless quest for sustainable energy solutions.

Subject of Research: Development of nanocrystal-engineered interconnecting layers to enhance performance and stability of all-perovskite tandem solar modules.

Article Title: Nanocrystal-tailored recombination for all-perovskite tandem solar modules.

Article References:
Xiao, K., Sun, H., Kong, X. et al. Nanocrystal-tailored recombination for all-perovskite tandem solar modules. Nature (2026). https://doi.org/10.1038/s41586-026-10768-1

Image Credits: AI Generated

The impressive feat was accomplished with a 16 cm² triple-junction cell that boasts an independently certified steady-state power conversion efficiency of 23.3 percent. This figure represents the highest efficiency achieved for any large-area cell of its kind, highlighting the substantial progress made by the research team. Meanwhile, at a smaller scale, a 1 cm² cell recorded an astounding efficiency of 27.06 percent, setting new benchmarks for thermal stability. These remarkable efficiency levels underscore the potential of perovskite materials to outperform traditional silicon-based solar technologies when engineered properly.

Published in the esteemed journal Nature Nanotechnology, the team’s findings also contain a historical precedent, as the 1 cm² cell became the first in the world to pass the rigorous Thermal Cycling test conducted by the International Electrotechnical Commission (IEC). This intense test subjects devices to extreme temperature fluctuations ranging from -40 to 85 degrees Celsius over 200 cycles. Remarkably, this prototype retained 95 percent of its efficiency even after over 400 continuous hours of operation under light, highlighting its impressive durability and capability to perform under challenging conditions.

The design and engineering of the triple-junction solar cell feature a complex interplay of three interconnected semiconductors, each tailored to absorb specific parts of the solar spectrum. By capturing a larger portion of solar energy, the design maximizes the conversion efficiency, a crucial factor in the performance of solar panels. The incorporation of advanced materials and innovative engineering strategies has enabled the team to push the limits of efficiency and stability for these advanced solar technologies.

Professor Ho-Baillie, who is also involved with the University of Sydney’s Net Zero Institute, explains that the recent breakthroughs stem from an innovative re-engineering of the chemistry underlying the perovskite material and the overall architecture of the triple junction cell. By replacing methylammonium—often used in high-efficiency perovskite configurations—with rubidium, the research team improved the stability of the perovskite lattice. This substitution minimizes defects and degradation and is a key factor in enhancing overall performance.

Alongside this change, less stable lithium fluoride has been replaced with piperazinium dichloride as a new surface treatment. This alternative treatment has played a pivotal role in improving the longevity and robustness of the solar cells, making them more viable for real-world applications. The team’s approach not only enhances the operational lifespan of the cells but also opens new avenues for optimizing performance through material engineering.

To seamlessly connect the two perovskite junctions, the researchers employed gold at the nanoscale, employing advanced techniques such as transmission electron microscopy to gain insights into how gold nanoparticles interact within the cell structure. Contrary to previous beliefs, the researchers found that gold exists in nanoparticle form rather than as a continuous film, allowing for more efficient coverage and greater control over electric charge flow and light absorption. This pivotal discovery led the team to engineer the distribution of gold nanoparticles to maximize the performance of the solar cells.

One of the most significant challenges facing the solar energy sector is the need for sustainable and economically viable alternatives to traditional energy sources. Perovskite materials, in particular, have drawn attention in recent years due to their relatively low-cost production and their ability to efficiently capture a broader spectrum of sunlight when layered with silicon. Although the potential for these materials has been recognized, the difficulty of scaling them beyond laboratory testing to meet real-world stability requirements has historically limited their adoption.

Professor Ho-Baillie’s statement reflects the significance of their achievement: “This is the largest triple-junction perovskite device yet demonstrated, and it has been rigorously tested and certified by independent laboratories.” She emphasizes that these developments furnish researchers with increased confidence in the scalability of this technology for practical use, which could have far-reaching implications for renewable energy solutions.

International collaboration among researchers from China, Germany, and Slovenia has played an integral role in this groundbreaking work. Their partnership, along with support from the Australian Renewable Energy Agency (ARENA) and the Australian Research Council, has fostered a rich environment for innovation, bringing together diverse knowledge and expertise to tackle complex challenges in solar research.

In addition to pushing boundaries in solar technology, the publication follows a period of recognition for Professor Ho-Baillie’s leadership in solar research. She was honored with the prestigious Eureka Prize for Sustainability Research at the 2025 Australian Museum Eureka Prizes, reflecting her pioneering contributions to perovskite solar technology. The recognition not only underscores her dedication to advancing solar energy solutions but also highlights the vitality of her team’s recent findings.

In light of these advancements, Professor Ho-Baillie adds a note of excitement for the future: “It is an exciting time for solar research. Perovskites are already showing us that we can push efficiencies beyond the limits of silicon alone.” Her remarks echo the broader sentiment within the scientific community regarding the potential to significantly lower energy costs and foster sustainable solutions in line with global climate initiatives. The ongoing progress in perovskite solar technology can enable forthcoming generations to transition to cleaner energy alternatives more rapidly.

In conclusion, the unprecedented advancements achieved by the University of Sydney’s research team represent a monumental step toward a future powered by sustainable solar energy. The exceptional efficiency and durability of their latest perovskite-based solar cells could pave the way for innovative and economically viable options in the quest for renewable energy solutions. As the world grapples with climate change and energy demands, the push toward harnessing triple-junction perovskite technology may well be the catalyst needed to transform solar energy into a cornerstone of global electricity supply.

Subject of Research:
Article Title: Tailoring nanoscale interfaces for perovskite-perovskite-silicon triple-junction solar cells
News Publication Date: 7-Oct-2025
Web References: Nature Nanotechnology
References: Zheng, J. et al. ‘Tailoring nanoscale interfaces for perovskite-perovskite-silicon triple-junction solar cells’
Image Credits: The University of Sydney

Keywords

Perovskite solar cells represent a revolutionary approach in the realm of photovoltaic technology. They exhibit remarkable light-absorbing capabilities, which make them a solid contender to overcome the limitations of conventional crystalline silicon solar cells. While silicon-based cells dominate the market due to their affordability and widespread manufacturing capabilities, they have begun to plateau in efficiency as they reach their theoretical limits. In contrast, tandem solar cells that pair silicon with perovskite materials have emerged as promising alternatives, significantly enhancing overall energy conversion rates.

The unique composition of tandem solar cells allows for greater versatility in application, particularly in sectors where the adaptability and lightweight properties of solar panels are essential. Traditional perovskite/silicon cells, despite achieving efficiency rates as high as 34.6%, face challenges concerning weight and damage susceptibility. These problems hinder their application in contexts such as aerospace and automotive industries, where weight considerations and structural integrity are critical.

In an effort to address these challenges, the innovative work by the KIER research team has led to the development of flexible thin-film perovskite/CIGS tandem solar cells. CIGS, known for being lightweight and flexible, is particularly suitable for integration into curved surfaces represented in modern architecture, vehicles, and other innovative applications. However, previous iterations suffered from lower efficiency rates and complex manufacturing processes, creating barriers to market readiness.

The KIER team’s novel approach involved a simple lift-off process. This methodology entails coating a polyimide layer onto a glass substrate before fabricating the perovskite/CIGS tandem solar cell atop the polyimide. The lift-off process allows for stable and uniform layer deposition which leads to significantly higher reproducibility and efficiency compared to traditional methods. The rigid glass substrate utilized in this process enhances the stability during fabrication and ultimately contributes to the performance improvement of the solar cells.

Moreover, the team identified a critical improvement mechanism during the fabrication process that involves managing the diffusion of alkali metals from the glass substrate into the CIGS layer. Excessive diffusion of potassium, in particular, can introduce defects in the absorber layer, negatively impacting the overall efficiency of the solar cells. To combat this issue, the researchers leveraged computational science to predict that the polyimide layer could effectively suppress potassium diffusion, resulting in fewer defects and a marked increase in performance.

Not only did the innovative fabrication process contribute to efficiency gains, but it also provided the new cells with outstanding durability. The research team undertook rigorous mechanical testing, performing 100,000 bending cycles to evaluate the resilience of the solar cells. Impressively, the cells maintained an efficiency of 97.7% post-testing, showcasing their robustness and suitability for challenging real-world applications.

Dr. Inyoung Jeong emphasized the significance of this achievement, noting that it lays the groundwork for future advancements toward a goal of achieving 30% efficiency in ultralight flexible solar cells. The implications of this work are vast, with the potential to expand applications in renewable energy, particularly in highly portable and adaptable modules.

Dr. Kihwan Kim, another prominent figure in the research, highlighted the power-to-weight ratio associated with the new solar cells, stating it is approximately ten times greater than traditional perovskite/silicon tandem solar cells. This breakthrough promises to enable innovative applications in demanding environments, such as in building exteriors and on vehicles, where every gram counts, and efficiency is paramount.

The research results were published in the prestigious journal Joule, which underscores the high impact of this discovery on the field of energy and materials science. This accomplishment was made possible through a collaborative effort involving distinguished scholars like Professor Tae Kyung Lee of Gyeongsang National University and Professor Hae-Jin Kim of Yonsei University, showcasing the strength of collaborative research in driving technological advancements.

As renewable energy solutions continue to shape a sustainable future, the ultra-lightweight flexible perovskite/CIGS tandem solar cells developed by KIER serve as a formidable step toward overcoming existing barriers in solar cell technology. Their impressive efficiency, durability, and lightweight nature present an exciting prospect for the future of energy generation, particularly as industries strive for greener alternatives in a world increasingly reliant on sustainable solutions.

With ongoing efforts to refine manufacturing processes and enhance the stability of these solar cells, the KIER research team aims to fortify the competitiveness of the renewable energy sector. This breakthrough not only contributes to advancing solar technology but also signals the potential for widespread adoption of renewable energy solutions across various industries, ensuring a sustainable energy future.

The study not only sheds light on the technical advancements in solar technology but also holds promise for spurring innovations that can lead to more efficient, adaptable, and sustainable energy practices globally. As researchers continue to explore the possibilities of combining cutting-edge materials and technologies, the future of solar energy looks bright, offering endless opportunities for innovation in the pursuit of clean energy.

Subject of Research: Development of ultra-lightweight flexible perovskite/CIGS tandem solar cells
Article Title: Flexible and lightweight perovskite/Cu(In,Ga)Se2 tandem solar cells
News Publication Date: 19-Mar-2025
Web References: DOI link
References: Joule Journal, March 2025
Image Credits: KOREA INSTITUTE OF ENERGY RESEARCH(KIER)

Keywords

solar energy, perovskite cells, CIGS, renewable energy, efficiency, lightweight technology, advanced materials, energy research, photovoltaic technology.