Triple-junction solar cells are designed to capture a broader portion of sunlight than conventional single-junction devices. Instead of relying on one absorber to convert all usable photons, the architecture stacks three sub-cells with different bandgaps. A wide-bandgap perovskite at the top absorbs higher-energy visible photons, a second perovskite layer converts a different part of the solar spectrum, and a crystalline silicon bottom cell captures lower-energy near-infrared light. When these sub-cells are connected in series, the voltages generated by each junction add together. However, the current is limited by the sub-cell producing the lowest current, making both electronic quality and optical design critical to overall performance.

The researchers focused first on the top wide-bandgap perovskite, where defects at or near the surface can severely reduce the voltage of a solar cell. These defects create electronic states inside the material’s bandgap. Photogenerated electrons and holes can become trapped at these states and recombine before they contribute to an external current. This process, known as non-radiative recombination, releases energy as heat rather than light and lowers the quasi-Fermi-level splitting, a key measure of the maximum voltage that a photovoltaic absorber can generate under illumination.

To suppress these losses, the team introduced a passivating molecule known as 4F-POEABr. The molecule contains an ammonium group that can interact with the perovskite surface and an electron-deficient molecular structure designed to influence the local electronic environment. According to the researchers, these features provide two complementary forms of protection. Chemical passivation reduces the activity of defect sites, while field-effect passivation changes the distribution of electrical charge near the surface, making it more difficult for electrons and holes to encounter one another and recombine.

The effect was reflected in the electronic quality of the treated wide-bandgap perovskite. The material reached a quasi-Fermi-level splitting of 1.53 electron volts, indicating a substantial reduction in voltage loss under illumination. When incorporated into a sub-cell, it produced an open-circuit voltage of 1.413 volts. Open-circuit voltage is measured when no current is drawn from the device, and in high-efficiency solar cells it provides a direct indication of how effectively the absorber preserves photogenerated charge. Achieving a high voltage in a wide-bandgap perovskite is especially important because the top cell must generate substantial voltage while transmitting suitable light to the sub-cells beneath it.

The study also tackles a less visible but equally important problem: how light travels through the stack. In a triple-junction device, photons pass through multiple transparent electrodes, transport layers, perovskite absorbers and interconnection layers before reaching the silicon cell. At every boundary, light can be reflected, transmitted or absorbed. Because the thicknesses and refractive indices of these layers determine how waves interfere with one another, even nanometre-scale changes in a layer can alter the amount of light reaching a particular sub-cell.

The researchers used systematic interference management to increase the current generated by the middle perovskite sub-cell, which limited the current of the series-connected device. Their approach involved tailoring a bilayer made from tin oxide and indium zinc oxide. These transparent conducting and electron-transport components were selected and arranged to modify the optical field inside the stack. By controlling reflection and transmission at the interfaces, the redesigned structure delivered an additional 0.5 milliamperes per square centimetre from the current-limiting middle junction. In a triple-junction device, such a gain can be decisive because excess current from one sub-cell cannot compensate for a shortage in another when all junctions operate in series.

The reported efficiencies show the importance of combining chemical and optical engineering rather than treating them as separate challenges. A device can have excellent material quality yet lose performance if its layers prevent sunlight from reaching the correct absorber. Conversely, sophisticated light management cannot recover voltage lost through severe non-radiative recombination. In the new architecture, molecular passivation improves the voltage contribution of the wide-bandgap top cell, while the tin oxide/indium zinc oxide structure improves current balance through the stack. The two strategies reinforce one another, allowing more of the incident solar energy to be converted into electrical power.

The researchers further report negligible hysteresis, meaning that the measured efficiency showed little dependence on whether the voltage was scanned upward or downward. This behavior is important because hysteresis can make photovoltaic performance difficult to evaluate and may signal charge accumulation or unstable ionic movement within perovskite layers. The devices also incorporated robust interconnection layers and engineered interfaces between the perovskite components. These design elements were intended to improve operational stability and reduce variation from one device to another, two requirements that become increasingly demanding as laboratory-scale cells expand toward commercial dimensions.

The larger-area result is particularly notable because performance often declines when devices grow. Defects, non-uniform coating, resistance in transparent electrodes and alignment errors can all become more consequential over a wider surface. The certified 26.97% steady-state efficiency measured across 15.62 square centimetres therefore suggests that the approach is not limited to a small demonstration area. Although further work will be required to establish long-term outdoor durability, manufacturing compatibility and large-module performance, the study presents a clear roadmap for improving sophisticated tandem architectures: protect the perovskite interfaces, control the electrical environment at defect-rich surfaces and design every transparent layer with both photons and charges in mind. Together, these advances move perovskite/perovskite/silicon triple-junction solar cells closer to the high efficiencies promised by multi-junction photovoltaics.

Subject of Research: Perovskite/perovskite/silicon triple-junction solar cells, molecular defect passivation and optical interference management.

Article Title: Defect passivation and optical management of triple-junction solar cells

Article References: Xu, Y., Wang, Z., Deng, C. et al. Defect passivation and optical management of triple-junction solar cells. Nature (2026). https://doi.org/10.1038/s41586-026-11010-8

Image Credits: AI Generated

DOI: 10.1038/s41586-026-11010-8

Keywords: Perovskite solar cells, triple-junction photovoltaics, silicon solar cells, defect passivation, 4F-POEABr, wide-bandgap perovskites, non-radiative recombination, optical management, interference engineering, solar-cell efficiency.

Organic-based hole transport layers are pivotal in perovskite solar cells, acting as conduits for extracted positive charge carriers and determining the overall device efficiency and longevity. Their vulnerability to thermal degradation and interfacial deterioration under high-energy conditions restricts their application in next-generation photovoltaic devices, especially where durability and reliability are paramount. The latest work led by Yun, Lee, and Kim extensively investigates how these HTLs respond to thermally induced stresses that mimic extraterrestrial conditions, shedding light on mechanisms previously overlooked in terrestrial testing environments.

Delving deep into the molecular architecture of the HTLs, the research team employed a combination of spectroscopic analyses, microscopic imaging, and electronic characterization to map out changes in material properties at the interface with perovskite layers. These techniques revealed nuanced degradation pathways involving morphological instabilities and chemical reactions accelerated by thermal cycling, including bond breakage and molecular reconfiguration, which compromise charge extraction and polymer integrity.

One pivotal finding centers on the role of interfacial defects that proliferate during repetitive exposure to temperature cycles ranging from sub-zero to several hundred degrees Celsius. Such variations trigger physical stress and generate localized hotspots at the HTL/perovskite junction, increasing the likelihood of trap states that hamper charge transport and facilitate non-radiative recombination losses. These phenomena cumulatively diminish both power conversion efficiency and operational lifespan.

To counteract these detrimental effects, the researchers explored the integration of novel additive compounds into the organic HTL matrix. These additives function as stabilizers at the molecular level, enhancing thermal resilience by forming stronger intermolecular bonds and promoting uniform morphology. Their inclusion improved the adhesion and cohesion properties of the HTL films, mitigating delamination and maintaining intimate contact with the perovskite layers even after prolonged thermal stress.

The team also evaluated different polymer architectures, comparing conventional doped polymers with newly engineered conjugated polymers specifically designed to resist thermolytic breakdown. Their investigations identified structural motifs that inherently resist bond scission and oxidation, suggesting pathways to customize HTL materials that combine high conductivity with unparalleled stability for space-like operation.

Importantly, the research underscores the critical influence of the deposition and annealing processes on interfacial quality. Variations in processing parameters were shown to alter the microscopic arrangement and crystallinity of HTL films, which in turn affected thermal tolerance. Optimized processing yielded smoother interfaces, reduced defect densities, and enhanced mechanical robustness, providing vital guidelines for scalable manufacturing.

The implications of this study extend far beyond terrestrial applications. As humanity ventures toward lunar bases, Mars missions, and orbital infrastructures requiring autonomous, long-lasting energy sources, solar technologies must endure the punishing thermal swings and radiation environments of space. The durability insights gained here pave the way for perovskite photovoltaics that not only survive but thrive in such scenarios, offering lightweight, flexible, and highly efficient alternatives to heavy, rigid silicon panels.

Moreover, the advanced understanding of interfacial phenomena could impact the design of terrestrial photovoltaic modules facing extreme climates, from scorching deserts to Arctic regions, where temperature gradients continuously challenge device integrity. The cross-disciplinary techniques employed set a benchmark for future stability studies across various thin-film solar cell technologies.

This research also challenges the preconceived notion that organic materials cannot match the resilience required for demanding operational contexts. By unraveling the molecular dynamics at play and tailoring the chemical environment, organic HTLs demonstrate untapped potential to revolutionize solar energy harvesting.

Looking toward commercialization, the study highlights essential criteria for material selection and device fabrication that industry players must meet to achieve space-grade quality. The balance between electronic performance, mechanical strength, and thermal stability will be central themes in the next wave of perovskite solar cell development.

Furthermore, the integration of machine learning algorithms with experimental data promises accelerated discovery and optimization of HTL compounds and processing regimes. Predictive modeling based on the reported findings could usher in a new era of targeted molecular engineering for photovoltaics.

In summary, the work by Yun, Lee, Kim, and colleagues represents an inspiring convergence of fundamental science and applied engineering addressing one of the grand challenges in renewable energy technology. By overcoming interfacial instabilities in organic-based hole transport layers, the door opens to deploying perovskite solar cells in environments previously deemed inhospitable, propelling humanity closer to sustainable off-world energy solutions.

With ongoing efforts to refine material formulations and scale up fabrication methods, perovskite photovoltaics with robust organic HTLs stand on the cusp of transforming the energy landscape, both on Earth and beyond.

Subject of Research: Interfacial stability of organic hole transport layers in perovskite photovoltaics under space-like thermal environments

Article Title: Interfacial stability of organic-based hole transport layers in perovskite photovoltaics for space-like thermal environments

Article References:
Yun, D., Lee, H., Kim, H. et al. Interfacial stability of organic-based hole transport layers in perovskite photovoltaics for space-like thermal environments. Commun Eng (2026). https://doi.org/10.1038/s44172-026-00695-4

Image Credits: AI Generated