In the relentless pursuit of sustainable and environmentally friendly energy solutions, tin-based perovskite solar cells (TPSCs) have recently captivated the scientific community’s attention. Representing a hopeful alternative to traditional lead-based solar devices, these cells leverage the unique properties of tin to overcome toxicity concerns, marking a significant step forward for green technology. Although lead perovskites have dominated the photovoltaic landscape with high efficiencies, their inherent environmental risks drive the search for safer elements without sacrificing performance. In this context, TPSCs have emerged as promising candidates that may well bring the next generation of solar power to fruition.
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
