Tandem solar cells (TSCs) are lauded for their potential to surpass the efficiency limitations of conventional single-junction solar devices by stacking two subcells with different bandgaps. Each subcell absorbs distinct segments of the solar spectrum, enabling more effective harnessing of sunlight. In the realm of all-perovskite tandem solar cells, however, practical implementation has faced formidable hurdles. Central among these challenges is the mismatched crystallization kinetics between the wide-bandgap (WBG) and narrow-bandgap (NBG) perovskite layers. This imbalance often leads to phase segregation and defect proliferation, detracting significantly from device efficiency and operational longevity.

To overcome these intrinsic difficulties, Professors GE Ziyi and LIU Chang, along with their research team, have devised a unified colloidal chemistry strategy that strikes a delicate balance in crystallization dynamics between the WBG and NBG perovskite subcells. This breakthrough leverages a meticulously designed modulation system based on graded carboxylate anions—specifically tartrate (Ta-) and citrate (Cit-) ions—that exert precise control over nucleation and crystal growth pathways in both subcells.

In the WBG subcell, the introduction of tartrate anions proves instrumental by stabilizing the coordination environment of Pb2+ ions. This stabilization suppresses unwanted phase segregation, fostering a more uniform and controlled crystalline lattice arrangement. Such uniformity is vital because it minimizes defect sites that can act as recombination centers for charge carriers, thus preserving the solar cell’s photovoltaic performance.

Conversely, in the NBG subcell—which typically suffers from Sn2+ defect states that act as non-radiative recombination centers—citrate anions play a dual role. They optimize Sn-I bonding within the colloidal precursor environment, effectively passivating the vulnerable Sn2+ defects. This passivation enhances the charge transport properties of the NBG layer, which is fundamental to maximizing the overall current output of the tandem device.

Amplifying the stabilizing effect, choline cations are introduced as synergistic agents, passivating undercoordinated metal ions at the interfaces between the crystal and colloid phases. This interface passivation is crucial for constructing a robust stabilization matrix that maintains heterojunction integrity during the critical nucleation and growth phases. The tailored colloidal precursor solution thus orchestrates a harmonized crystallization process across the tandem structure, ensuring optimized electronic and structural properties.

The resultant tandem solar cells demonstrate a phenomenal power conversion efficiency (PCE) of 29.76%, a value that is among the highest recorded for all-perovskite tandem architectures. Notably, this outstanding performance was independently certified with a measured PCE of 29.22%, underscoring the reproducibility and credibility of the method. The devices also showcase remarkable operational stability, sustaining over 90.2% of their initial efficiency after more than 700 hours of continuous exposure under maximum power point tracking—a rigorous test indicative of commercial viability.

Scaling up from lab-scale testing, the team fabricated a 1 cm² large-area tandem cell using their colloidal chemistry methodology. This larger device achieved a commendable PCE of 28.87%, demonstrating the strategy’s potential for practical deployment in industrial-scale photovoltaic manufacturing processes. The scalability factor is particularly significant because it addresses a fundamental bottleneck in transitioning high-efficiency perovskite technology from academic laboratories to accessible green energy solutions.

Beyond immediate performance gains, this research contributes a universal framework for tuning multijunction crystallization kinetics via chemical modulation. By aligning nucleation rates and mechanisms between the dissimilar perovskite layers, the approach mitigates deleterious defects while enhancing crystallinity and charge carrier dynamics. Such control at the colloidal precursor level marks a paradigm shift in perovskite processing, offering a path toward commercial all-perovskite tandem cells that can consistently deliver high efficiency with long-term stability.

The implications of this work resonate through the broader field of optoelectronics and renewable energy. With theoretical efficiencies for all-perovskite tandem solar cells predicted to exceed 40%, strategies like those pioneered here are vital stepping stones to surpassing current photovoltaic technology thresholds. Moreover, the chemical insight gained through the interplay of tartrate and citrate anions, coupled with choline cation synergy, reveals a new dimension of colloid chemistry manipulation that may inspire innovations beyond photovoltaics, potentially touching other areas such as light-emitting diodes and photodetectors.

Financial support for this landmark study was provided by prominent Chinese national initiatives, including the National Key Research and Development Program, the Young Scientists Fund of the National Natural Science Foundation of China, and the National Natural Science Foundation of China. This backing underlines the strategic importance attributed to cutting-edge energy materials research in addressing global energy challenges.

In summary, the integrated colloidal chemistry approach to tuning nucleation kinetics in all-perovskite tandem solar cells embodies a significant technological leap. By resolving the crystallization mismatches that have historically hampered tandem device performance, the team’s work not only pushes conversion efficiencies near the 30% mark but also lays the foundation for stable, scalable, and commercially viable perovskite photovoltaics. This development signals a hopeful horizon for next-generation solar technology poised to deliver affordable, high-efficiency renewable energy worldwide.

Subject of Research: Not applicable
Article Title: Tailoring Colloidal Precursor Chemistry for Tunable Nucleation Kinetics in All-Perovskite Tandem Solar Cells​
News Publication Date: 27-Mar-2026
Web References: 10.1016/j.joule.2025.102381
References: Provided in the article DOI and journal publication
Image Credits: NIMTE

The exceptional performance realized by this triple-junction architecture is particularly notable considering its scalability and cost-effectiveness compared to traditional high-efficiency cells. Kerem Artuk, the lead author of the study and an EPFL alumnus now at CSEM, emphasizes that this design mirrors the performance of the most advanced space-grade III-V multi-junction solar cells, which typically achieve efficiencies near 37% yet demand materials and manufacturing processes that are prohibitively expensive for terrestrial applications. By contrast, this perovskite-silicon hybrid approach offers a promising path toward high-efficiency photovoltaics at a fraction of the cost.

Achieving this milestone was anything but straightforward. Conventional triple-junction cells are often constrained by low voltage output in the upper cell and insufficient current in the middle cell, limitations that historically capped their overall performance. To address these challenges, the EPFL-CSEM team implemented three innovative modifications to the cell’s material and optical structure. First, they introduced a specialized molecule during perovskite formation, effectively guiding crystal growth and eradicating defects that typically hinder voltage enhancement. This led to a remarkable boost in the top cell’s voltage, reaching 1.4 volts under sunlight—a significant leap forward in perovskite cell technology.

The second breakthrough involved a novel three-step fabrication process tailored for the middle perovskite cell, meticulously engineered to augment light harvesting in the near-infrared domain, a spectral region previously underserved in multi-junction devices. This refinement dramatically enhances the cell’s current generation capabilities, directly impacting the overall power conversion efficiency. Complementing this, the third innovation strategically positioned nanoparticles between the bottom silicon layer and the middle perovskite cell. These nanoparticles act as reflective agents, redirecting otherwise lost photons back into the middle layer, thereby elevating its absorption efficiency and current output.

Beyond the technical marvels, this advancement signals a paradigm shift toward making high-efficiency solar technology accessible and practical for everyday use. Both perovskite materials and silicon substrates benefit from mature, cost-effective manufacturing routes, especially when contrasted with the specialized, costly III-V semiconductor processes which dominate in aerospace applications. With this scalable, low-cost fabrication blueprint, the door opens for multi-junction photovoltaics to transition from satellite-exclusive solutions to mainstream commercial and residential energy systems.

The project, spearheaded by Christian Wolff and his team at EPFL, is not merely a demonstration of power conversion efficiency but a holistic illustration of integrating fundamental science with cutting-edge engineering. Their ongoing roadmap includes pursuing scale-up strategies in partnership with CSEM, alongside rigorous durability assessments crucial for real-world deployment. The researchers aim to ensure these high-performing cells can maintain their stability and performance over extended operational lifetimes, addressing one of the most significant barriers facing perovskite technologies.

This breakthrough also rekindles enthusiasm for multi-junction solar cells’ potential, which theoretically can exceed 40% efficiency by optimizing material combinations and photon management strategies. The silicon-perovskite system, bolstered by tailored crystallization techniques and photonic enhancements, brings this optimistic projection within tangible reach. Notably, this achievement represents a five-fold improvement over the group’s 2018 prototype, which initially demonstrated a modest 13% efficiency, underscoring rapid advancements in materials science and device engineering over a relatively short period.

Fundamentally, the triple-junction design capitalizes on the complementary absorption spectra of each semiconductor layer. The top perovskite tuned for high voltage, the middle perovskite maximizing near-infrared capture, and the silicon bottom cell harvesting the remaining longer-wavelength light—together, this stratified architecture efficiently converts a broader segment of the solar spectrum. The strategic deployment of nanoparticles further refines the internal light environment, exemplifying how photon and carrier management synergistically elevate device performance.

This research heralds an era where perovskite-based multi-junction solar cells do not merely rival but surpass existing terrestrial photovoltaics in both performance and cost-efficiency. Moreover, the potential to fine-tune these cells for specialized applications—including space missions where weight, efficiency, and cost are critically balanced—positions this innovation at the confluence of academic inquiry and industrial transformation.

Refining the fabrication process to be scalable and integrating robustness into these cells will be the next critical milestones. The collaboration between EPFL and CSEM is actively exploring these avenues, envisioning seamless incorporation of the technology into commercial products. The team’s multidisciplinary approach—merging materials chemistry, optical physics, and precision engineering—embodies the Swiss tradition of excellence and innovation in renewable energy technologies.

In conclusion, this triple-junction solar cell breakthrough is more than a record in energy conversion efficiency—it symbolizes a transformative advance in photovoltaic science. By harnessing perovskite materials’ versatility and silicon’s reliability, combined with innovative optical engineering, this research sets a new paradigm for cost-effective, high-performance solar energy solutions that are scalable for widespread adoption. As the push for sustainable energy intensifies globally, innovations such as these catalyze the transition toward cleaner, more affordable power sources for the planet’s future.

Subject of Research: Advancement in triple-junction perovskite-silicon solar cells achieving record efficiency through novel material and photonic engineering.

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

News Publication Date: 17-Mar-2026

Web References:

• Nature Article DOI: 10.1038/s41586-026-10385-y
• EPFL PV-Lab
• CSEM

Image Credits: © Kerem Artuk

Keywords

Triple-junction solar cell, perovskite photovoltaics, silicon solar cell, multi-junction efficiency, photon management, carrier management, scalable manufacturing, high-efficiency solar energy, renewable energy technology, photovoltaic innovation