In the rapidly evolving landscape of solar energy technology, the pursuit of highly efficient, scalable, and cost-effective photovoltaic solutions remains paramount. Recent advances have spotlighted all-perovskite tandem solar modules as promising candidates to surpass the efficiency limits of single-junction cells. However, the widespread commercialization of these devices encounters formidable challenges, chiefly stemming from the reliance on conventional tunnel recombination junctions (TRJs) that traditionally employ gold-based materials. While gold has been favored for its conductivity and stability, it inadvertently introduces significant near-infrared parasitic absorption, curtailing the module’s overall photocurrent generation capacity and hindering long-term operational durability.
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
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