At the core of this development lies the intricate manipulation of two-dimensional (2D) and three-dimensional (3D) perovskite phases within the solar cell architecture. Traditionally, 2D perovskite layers have been introduced at either the bulk or surface of 3D perovskite films by adding long-chain ammonium salts during fabrication. While these 2D structures are recognized for enhancing device stability and passivating surface defects, the challenge has been to precisely localize them exclusively at the buried bottom interface without adversely affecting the bulk properties of the perovskite layer.

The team tackled this challenge by exploiting a novel approach involving sequential grafting of thioglycolic acid and oleylamine onto SnO₂ nanoparticles—the commonly used electron transport layer in n–i–p configured solar cells. The ligand chemistry was meticulously designed to anchor the oleylamine tightly via strong chemical bonds with thioglycolic acid. This chemistry effectively controls the interfacial cation exchange with formamidinium iodide (FAI), a crucial perovskite precursor, ensuring that 2D phase formation occurs selectively and only after thermal annealing during device processing.

This selective in situ formation of the 2D perovskite layer creates a well-defined buried 2D/3D heterojunction at the interface between SnO₂ and the 3D FA-based perovskite absorber. The presence of this localized 2D layer catalyzes the crystallization kinetics of the 3D perovskite phase, yielding larger grains and a more uniform film morphology. Such improved crystallinity is pivotal for reducing recombination losses, enhancing charge carrier mobility, and ultimately boosting the device’s photovoltaic performance.

Moreover, this buried heterojunction substantially diminishes defect densities at the electron transport interface. Defects typically act as nonradiative recombination centers that degrade performance and accelerate device aging. By achieving over a tenfold reduction in defect concentration at this critical juncture, the researchers effectively curtailed interfacial recombination pathways, thereby extending both the efficiency and operational stability of the solar cells.

The benefits of this interfacial engineering are reflected in the impressive power conversion efficiencies achieved by the resulting perovskite solar cells. Devices fabricated on a small active area (0.09 cm²) reached an outstanding certified efficiency of 26.04%, a benchmark competitive with the highest-performing perovskite architectures to date. Notably, this method scales favorably, maintaining robust efficiencies of 23.44% and 22.22% on larger aperture areas of 21.54 cm² and 64.80 cm², respectively, demonstrating promising prospects for commercial viability and large-scale deployment.

This advancement also underscores a vital understanding of the interfacial chemistry in perovskite solar cells. The utilization of a solid-state ligand-exchange reaction for interfacial modification diverges from conventional solution-processed routes, offering enhanced control and stability. The thermal annealing step triggers the cation exchange precisely, enabling the formation of reproducible, high-quality 2D/3D heterostructures that resist decomposition and ion migration under operational stresses.

The approach opens new frontiers in perovskite interface research, where chemical tailoring of transport layers and their interactions with perovskite precursors can be harnessed for optimized device architectures. By integrating chemically robust ligands and leveraging solid-state reactions, the strategy holds promise for overcoming key barriers that have dogged perovskite solar cells, particularly regarding long-term durability and consistent high performance.

In practical terms, the buried 2D layer serves as an energy cascade or passivation buffer layer, minimizing energetic disorder at the interface and facilitating efficient extraction of photogenerated electrons into the SnO₂ layer. This design mitigates interfacial energy barriers and suppresses charge carrier recombination, which are critical for achieving maximal photocurrent and fill factor in perovskite solar cells.

Furthermore, since SnO₂ is widely recognized for its excellent electron transport properties and chemical stability, the functionalization approach demonstrated here can be seamlessly integrated into existing manufacturing processes. Such compatibility accelerates the potential translation of this technology from laboratory-scale innovations to industrial-scale photovoltaic module production.

The researchers’ methodology also sparks possibilities for customizing interface chemistry for various perovskite compositions beyond formamidinium-based systems. Fine-tuning ligand identities and processing conditions could unlock similar buried heterojunction benefits for mixed-cation or mixed-halide perovskites, thereby expanding the versatility of this technique across the perovskite family.

In essence, this work represents a critical stride toward the long-sought goal of creating perovskite solar cells that combine efficiency, scalability, and operational longevity. The judicious engineering of a buried 2D/3D heterojunction via a solid-state ligand-exchange reaction stands as an elegant solution to interfacial challenges, paving a route toward the widespread deployment of perovskite photovoltaics in the global energy landscape.

As the solar industry advances toward a sustainable, carbon-neutral future, innovations like this herald transformative impacts, enabling low-cost, highly efficient, and durable solar technologies. Continued exploration of interface chemistry and materials engineering is poised to unlock further enhancements, bringing perovskite solar cells closer to their theoretical efficiency limits and widespread commercial success.

With this breakthrough, the collaboration of material chemists, physicists, and device engineers demonstrates the power of interdisciplinary research to solve complex challenges in renewable energy technologies. The interplay between molecular-level control and macroscopic device performance highlights the sophisticated science behind next-generation photovoltaics.

Looking ahead, the implications of buried 2D/3D heterojunctions extend beyond solar cells alone. Similar interfacial strategies could be adapted for light-emitting diodes, photodetectors, and other optoelectronic devices where controlling charge transport and defect densities at interfaces is crucial. This versatility suggests a broad impact across emerging semiconductor technologies.

Ultimately, this research embodies a visionary approach to tackling fundamental materials limitations through chemical precision and innovative processing, setting a benchmark for future explorations in perovskite and hybrid semiconductor interfaces.

Subject of Research: Perovskite solar cells, interface engineering, 2D/3D heterojunctions, solid-state ligand-exchange, SnO₂ electron transport layers, perovskite crystallization and defect passivation.

Article Title: Buried 2D/3D heterojunction in n–i–p perovskite solar cells through solid-state ligand-exchange reaction

Article References:
Zhao, Q., Zhang, B., Hui, W. et al. Buried 2D/3D heterojunction in n–i–p perovskite solar cells through solid-state ligand-exchange reaction. Nat Energy (2026). https://doi.org/10.1038/s41560-026-01980-4

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41560-026-01980-4

Yet, the advancement of inverted PSCs has been hindered by persistent issues at the microscopic level. Chief among these challenges is the poorly regulated buried interface—the critical boundary where the perovskite active layer contacts the hole-transport layer. This interface suffers from uncontrolled microstructures and the presence of electronic defects, which collectively degrade device performance and undermine long-term operational stability. Addressing these interface-related problems is essential for unlocking the full potential of inverted PSCs.

Researchers from the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) under the Chinese Academy of Sciences have pioneered an innovative crystal-solvate (CSV) pre-seeding methodology that precisely engineers this elusive buried interface. Their breakthrough approach enables unprecedented control over the bottom interface’s morphology and electronic characteristics, thereby facilitating the creation of high-efficiency, large-area perovskite photovoltaic modules. This seminal study was recently disclosed in the prestigious journal Nature Synthesis, marking a significant milestone in photovoltaic materials science.

The cornerstone of the team’s technique is the deliberate pre-deposition of low-dimensional halide crystal-solvate seeds, chemically denoted as PDPbI₄·DMSO, onto substrates modified with self-assembled monolayers (SAMs). These CSV nanocrystals serve as a meticulously designed structural scaffold that templates the crystallization of the succeeding perovskite layer. Their unique rod-shaped, anisotropic morphology significantly refines the wettability of the naturally hydrophobic SAM surface, ensuring the homogeneous spreading of the perovskite precursor solution. This modulation of surface energy is a critical enabler for uniform film formation, which is fundamental to device reproducibility and performance.

More profoundly, during the nucleation and growth phases of the perovskite film, these pre-seeded CSV nanocrystals act as abundant heterogeneous nucleation centers. This nucleation density enhancement expedites perovskite crystallization kinetics, producing a more consistent and ordered polycrystalline structure. Such finely tuned crystallization dynamics mitigate defect generation and grain boundary irregularities, which are notorious for impairing charge transport and accelerating device degradation.

A particularly novel aspect of this strategy lies in the entrapment of dimethyl sulfoxide (DMSO) solvent molecules within the CSV crystalline lattice. Upon thermal annealing—a critical post-deposition process—these solvent molecules are gradually liberated in a spatially confined, bottom-interface microenvironment. This creates a transformative “lattice-confined solvent annealing” effect, wherein the controlled release of solvent vapors promotes grain reorganization and growth selectively at the interface without compromising the integrity of the entire perovskite layer. This gentle solvent atmosphere works synergistically with the seed-induced crystallization, culminating in a robust, defect-suppressed grain architecture.

The integrated control of crystallization and interfacial stabilization manifests dramatically in the film morphology. The CSV pre-seeding approach effectively eliminates interfacial voids and smooths grain boundary grooves, which are typical sites of electronic traps and recombination centers. The resulting perovskite “bottom layer” is densely packed and highly oriented, exhibiting significantly enhanced electronic properties and superior photothermal stability. These improvements directly translate into better charge carrier mobility, prolonged operational lifespan, and minimized performance deterioration under real-world conditions.

To bridge the gap between laboratory-scale innovation and practical manufacturing, the research team incorporated the CSV pre-seeding method into a slot-die coating process, a scalable and industry-relevant technique. This hybrid manufacturing approach enabled the fabrication of a perovskite solar mini-module with an active aperture area of nearly 50 cm²—a size relevant for commercial application. Remarkably, this mini-module achieved a power conversion efficiency (PCE) of 23.15%, with a negligible efficiency loss of less than 3% compared to smaller-area cells. Such scaling performance retention outpaces many previously reported perovskite photovoltaic systems and is pivotal for real-world deployment.

Professor Pang Shuping, a leading figure in this research, underscored the significance of overcoming the longstanding scaling bottleneck attributed to size effects by harmonizing induced crystallization with buried interface restoration. Beyond the immediate application to perovskite photovoltaics, this crystal-solvate pre-seeding paradigm represents a versatile materials platform. By tuning the organic cations and solvent molecules comprising the CSV seeds, an extensive library of bespoke CSV compounds can be crafted. This tunability paves the way for customizable interface engineering strategies tailored for a broad spectrum of soft-lattice semiconductors and optoelectronic devices beyond solar cells.

This pioneering work redefines the roadmap for interface engineering by demonstrating that precision crystal nucleation control combined with controlled interfacial solvent modulation can surmount previously intractable barriers to device efficiency and stability. The implication is clear: such molecular-level design and process integration will propel perovskite photovoltaic technologies closer to commercial realization, while simultaneously expanding the foundational understanding of crystal growth mechanisms in complex thin-film systems.

As solar energy continues to assume a central role in global renewable energy portfolios, innovations like the CSV pre-seeding method promise to drive the next generation of high-performance, scalable photovoltaic technologies. The amalgamation of fundamental materials chemistry with applied device engineering showcased in this study represents a beacon of progress, illuminating pathways toward cleaner, more sustainable energy futures.

Subject of Research: Advancement of buried interface engineering in inverted perovskite solar cells through crystal-solvate pre-seeding for enhanced crystallization and stability.

Article Title: Crystal-Solvate Pre-Seeding Strategy Enables Precise Buried Interface Regulation for High-Efficiency, Scalable Inverted Perovskite Solar Cells

News Publication Date: February 27, 2026

Web References:
http://dx.doi.org/10.1038/s44160-026-00993-x

Image Credits: Image by SUN Xiuhong, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences

Keywords

Perovskite Solar Cells, Crystal-Solvate Pre-Seeding, Buried Interface, Inverted PSC, Crystallization Control, Photovoltaics, Interface Engineering, Dimethyl Sulfoxide, Thermal Annealing, Slot-Die Coating, Power Conversion Efficiency, Large-Area Solar Modules

The allure of TPSCs lies not only in their non-toxic composition but also in their theoretically remarkable performance. These materials exhibit an ideal bandgap conducive to high power conversion efficiencies (PCEs), theoretically capable of exceeding 33%. However, translating this potential into practical devices has been significantly hampered by several technical challenges. Current TPSCs lag behind their lead-based counterparts in both efficiency and operational stability, principally due to issues related to charge transport and interface engineering. In particular, the hole transport layers and the buried interfaces in inverted device configurations have remained persistently problematic, impeding the efficient extraction of photogenerated holes and curtailing device longevity.

A breakthrough conceptual strategy has recently been introduced, tackling the hidden challenges within the buried interface of TPSCs through meticulous molecular engineering. By employing a carefully designed molecule—(E)-(2-(4′,5′-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-[2,2′-bithiophen]-5-yl)-1-cyanovinyl)phosphonic acid—the research presents a novel interfacial film that optimizes hole transport layers in inverted TPSCs. This molecular film serves as a homogeneous and uniform interfacial modifier, finely tuning the energy level alignment at the buried interface to substantially enhance hole extraction. The formation of such a well-defined molecular layer is pivotal for improving charge carrier dynamics, thereby boosting overall device efficiency.

Beyond its role in charge extraction, the molecular film exhibits an intriguing influence on the perovskite film morphology itself. The study reveals that this interfacial layer acts as a “superwetting” underlayer, effectively guiding the crystallization process of tin-based perovskite films. The improved wetting properties foster greater uniformity and grain quality within the perovskite layer, which directly correlates with reduced defect density. These high-quality films suppress non-radiative recombination, a notorious efficiency killer in perovskite photovoltaics. Consequently, the remarkable synergy between interfacial chemistry and film morphology emerges as a cornerstone for advancing TPSC performance.

This integrative approach bears fruit in the form of inverted small-area TPSCs with record-breaking power conversion efficiencies. Devices optimized with the phosphonic acid molecular film have reached a certified PCE of 17.71% under reverse scanning mode, with peak performances hitting 17.89%. These achievements represent a substantial leap forward, as previous efficiencies in TPSCs of comparable architecture hovered below this mark. The advancement underscores the crucial role played by molecular-level interface engineering in bridging the gap between theoretical potential and practical realization for tin-based perovskite photovoltaics.

Stability remains a critical benchmark for any emergent photovoltaic technology’s viability. Remarkably, devices constructed using this molecular interfacial strategy demonstrate enhanced endurance under real-world conditions. Encapsulated TPSCs maintained over 95% of their initial PCE after 1344 hours of storage in ambient conditions, showcasing resilience against environmental degradation. Additionally, continuous illumination tests under 1-sun equivalent intensities for over 1550 hours revealed that devices retained more than 94% of their performance. These stability metrics represent significant progress in addressing one of the most persistent limitations of tin-based perovskites—their tendency toward rapid oxidation and deterioration.

Crucially, the molecular interface modification also signals promise for device scalability. The study reports a record PCE of 14.40% in 1 cm² TPSCs, an area-management milestone demonstrating the technology’s potential for practical application beyond laboratory-scale devices. Scaling is essential for commercial viability, requiring solutions that maintain efficiency and reliability as device area expands. By harnessing the ability to engineer the buried interface homogeneously across larger substrates, this research lays foundational work toward viable, large-area, tin-based photovoltaics that could be integrated into commercial solar modules.

The development of this molecular film stands as a model for the power of interface chemistry in advancing the photovoltaic field. It reveals that meticulous control over buried interfaces can substantially alleviate hole extraction bottlenecks and simultaneously modulate perovskite crystallization dynamics. This dual functionality is critical in unlocking high performance and durability in lead-free perovskite solar technologies. Such achievements represent a paradigm shift that could catalyze further innovations, not only in tin-based systems but across broader perovskite and hybrid solar cell research.

Moreover, the underlying chemistry of (E)-(2-(4′,5′-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-[2,2′-bithiophen]-5-yl)-1-cyanovinyl)phosphonic acid, with its tailored phosphonic acid group and electronic properties, exemplifies molecular design principles that interface scientists could leverage in varied optoelectronic devices. The selective binding affinity and energy level tunability suggest future applications in other types of charge transport interfaces beyond TPSCs, potentially influencing organic electronics and light-emitting devices. Thus, this research not only forwards the photovoltaic frontier but also enriches the conceptual toolbox for interface engineering at large.

In a broader sustainability context, the transition from lead to tin in perovskite photovoltaics remains crucial for mitigating environmental health risks linked to heavy metal contamination. By demonstrating competitive efficiencies and improved stability, this work brings TPSCs closer to industrial acceptance and mass production. The confluence of environmental safety with high performance may provide a compelling narrative to accelerate policy and market support for perovskite-based solar technologies that are truly sustainable and scalable globally.

As the scientific community continues to push the boundaries of photovoltaic materials, the success of this molecular interface strategy invites deeper exploration into interfacial phenomena, encouraging researchers to focus on the often-overlooked buried layers within solar cells. The interplay between interface chemistry, film morphology, and charge dynamics uncovered here provides a rich set of parameters to optimize. Future investigations may well harness these insights to engineer next-generation devices that dramatically surpass current benchmarks in power output, long-term stability, and manufacturability.

In conclusion, the research conducted by Li et al. marks a milestone in the evolution of tin-based perovskite solar cells, delivering a potent interface engineering solution that reconciles performance and stability hurdles. The creation of a homogeneous, energetically matched buried interface via a novel molecular film reconciles multiple challenges endemic to TPSCs, setting new records in power conversion efficiency and operational durability. This work offers a compelling vision of how purposeful molecular design integrated with materials processing can unlock the latent potential of lead-free perovskite photovoltaics for a cleaner, sustainable energy future.

Subject of Research: Development and optimization of tin-based perovskite solar cells through molecular engineering of buried interfaces to enhance performance and stability.

Article Title: Tin-based perovskite solar cells with a homogeneous buried interface.

Article References:
Li, T., Luo, X., Wang, P. et al. Tin-based perovskite solar cells with a homogeneous buried interface. Nature (2025). https://doi.org/10.1038/s41586-025-09724-2

Image Credits: AI Generated

The fundamental challenge with antimony selenosulfide stems from the inefficiencies in charge carrier dynamics. In a photovoltaic cell, photogenerated electrons and holes must be effectively separated and collected at the respective contacts to generate current efficiently. However, in Sb₂(S,Se)₃ absorbers, charge carriers frequently recombine prematurely, especially near the interfaces and within the bulk material, leading to substantial energy losses. These recombination pathways have thwarted previous efforts to enhance device efficiency, necessitating innovative engineering at the contact and interface layers to mitigate such losses.

Dong and colleagues approached this problem by reexamining the front electrode architecture, particularly targeting the widely used fluorine-doped tin oxide (FTO) substrate. Conventional planar FTO substrates provide reliable conductivity but are limited in their ability to maximize light harvesting, especially as thickness and absorption properties of new materials evolve. By adopting a textured FTO substrate, the research team harnessed enhanced light scattering effects, which significantly increased the optical path length of incident photons within the Sb₂(S,Se)₃ absorber layer. This texture-induced scattering effectively maximizes light absorption, thus generating more charge carriers for extraction.

Yet, the introduction of a textured substrate is a double-edged sword. The very surface irregularities that give rise to enhanced light scattering also create morphological challenges. These include voids and shunt pathways at the interface between the FTO and the critical CdS electron-selective buffer layer, which are detrimental due to increased charge recombination and current leakage. To overcome this, the researchers expertly applied a thin SnO₂ layer using atomic layer deposition (ALD) directly onto the textured FTO prior to CdS deposition.

SnO₂, known for its excellent transparency and proper band alignment with CdS and the Sb₂(S,Se)₃ absorber, provided a uniform and conformal coating over the textured substrate. This conformality ensured a continuous interface without physical defects or electrical discontinuities, effectively eliminating unwanted shunt paths and facilitating better charge transport. The ALD method, renowned for its atomic-level thickness control and uniform deposition in complex geometries, was pivotal in this achievement, enabling coating of the intricate textured FTO surfaces without compromising the delicate CdS layer’s properties.

The cleverly engineered band structure resulting from this FTO/SnO₂/CdS configuration optimized charge carrier extraction by aligning energy levels to reduce interface recombination losses. Simultaneously, within the bulky antimony selenosulfide layer itself, the team refined compositional grading and defect passivation techniques that lowered recombination centers. Consequently, both interface-related and bulk charge recombination were suppressed, unlocking previously unattainable device efficiencies.

The practical outcomes of these innovations were remarkable. Utilizing a sodium selenosulfate chemical bath deposition technique for the Sb₂(S,Se)₃ absorber, the research group fabricated solar cells that achieved certified power conversion efficiencies reaching 10.70%, a significant milestone that edges this technology closer to commercialization viability. This certification adds robustness to their findings, confirming reproducibility and reliability under standardized testing protocols, which are crucial benchmarks for industrial adoption.

Moreover, the researchers demonstrated the versatility and generality of their method by applying it to selenourea-based Sb₂(S,Se)₃ fabrication routes, traditionally different in chemical processing. The approach maintained the same enhancements in charge extraction and overall device performance, suggesting broad applicability across various precursor chemistries in antimony selenosulfide photovoltaics.

An important aspect of this work lies in scalability prospects. Moving beyond small lab-scale devices, the team successfully fabricated solar cells with active areas of 1 cm²—significantly larger than many prototype devices—which retained commendable efficiency and stability. Such scaling is a critical step in transitioning laboratory breakthroughs into industrial-scale manufacturing lines, where surface uniformity, process repeatability, and device longevity become paramount criteria.

The stability exhibited by these solar cells over extended periods, coupled with sustained performance metrics, addresses a frequently overlooked yet vital parameter in photovoltaic technology development. Devices must maintain efficiency over thousands of hours under realistic environmental conditions to offer compelling alternatives to existing silicon-based cells. The findings reported here bode well for the practical deployment of Sb₂(S,Se)₃ solar cells, furnishing confidence that these advances are not limited to transient experimental results.

Interfacing electron-selective layers with well-engineered electrodes elucidates a key principle emerging from this study: the convergence of material science, surface engineering, and precise atomic-scale fabrication techniques can pave the way for unlocking latent photovoltaic potential. Controlling charge carrier pathways at interfaces, which have historically proven to be bottlenecks for emerging thin-film technologies, is now demonstrably achievable with strategic multi-layered designs.

This work also underscores the importance of atomic layer deposition as a versatile tool in photovoltaics. Its ability to deposit ultra-thin, pinhole-free films with meticulous thickness control and compositional tuning on complex topographies embodies a game-changing technological lever. The successful implementation of ALD SnO₂ layers in this context could inspire further adaptations across other thin-film and emerging photovoltaic systems, enhancing interface engineering protocols industry-wide.

The implications extend beyond the laboratory, hinting at a future where earth-abundant and non-toxic materials like antimony selenosulfide can rival commercial solar absorbers in terms of efficiency and reliability. Incorporating textured substrates for enhanced light management combined with meticulously designed electron-selective layers signifies a path forward toward sustainable and economically viable solar technologies—critical components in addressing global energy and environmental challenges.

Ultimately, this breakthrough not only signifies a technical achievement but invites renewed enthusiasm for antimony-based photovoltaic research, motivating further investigations into novel contact materials, absorber optimizations, and large-area device architecture refinements. The dual emphasis on improving optical properties through substrate texturing and minimizing electronic losses via interfacial engineering sets a new paradigm for thin-film solar cell development.

As the field marches forward, questions remain regarding the long-term operational stability under varied climatic conditions, integration with encapsulation technologies, and compatibility with flexible substrates for wearable or building-integrated photovoltaics. Nevertheless, the groundwork established here lays a robust foundation for tackling these challenges systematically.

In conclusion, the work by Dong et al. represents a significant leap in antimony selenosulfide solar cell research, demonstrating that clever electrode design paired with electron-selective layer engineering can decisively overcome detrimental charge recombination hurdles. The attainment of a certified 10.70% efficiency augmented by scalability and stability considerations signals a promising horizon for this emerging photovoltaic class poised to make impactful contributions to the clean energy revolution.

Subject of Research: Charge carrier management and interface engineering in antimony selenosulfide (Sb₂(S,Se)₃) solar cells

Article Title: Carrier management through electrode and electron-selective layer engineering for 10.70% efficiency antimony selenosulfide solar cells

Article References:
Dong, J., Gao, Q., Wu, L. et al. Carrier management through electrode and electron-selective layer engineering for 10.70% efficiency antimony selenosulfide solar cells. Nat Energy (2025). https://doi.org/10.1038/s41560-025-01792-y

Image Credits: AI Generated