In the relentless pursuit of next-generation photovoltaic technologies, perovskite/silicon tandem solar cells have garnered significant attention due to their exceptionally high power conversion efficiencies. These tandem structures leverage the complementary spectral absorption properties of perovskite and silicon, facilitating unprecedented energy harvesting capabilities far surpassing traditional single-junction solar cells. However, as research advances towards more flexible and lightweight designs vital for wearable and portable applications, mechanical durability becomes a pressing concern. The cyclic environmental stresses imposed on flexible devices induce mechanical strain, often provoking interfacial delamination and ensuing performance degradation that threatens the longevity and commercial viability of these cutting-edge solar cells.
A recent breakthrough study spearheaded by a collaboration of researchers, including Fang, Ding, Yang, and colleagues, introduces an innovative dual-buffer-layer strategy designed to fundamentally address these mechanical challenges. This pioneering approach utilizes a composite buffer system comprising two distinct tin oxide (SnO_x) layers, each engineered with precise structural and functional characteristics to synergistically alleviate mechanical stress and preserve the electrical integrity essential for efficient charge extraction. Central to this design is the controlled modulation of the atomic layer deposition purging time, which tailors the microstructure of the buffer layers and thereby optimizes their stress dissipation and electrical contact capabilities.
The first component of this dual-buffer system is a deliberately engineered loose SnO_x layer. Characterized by a less dense structure, this layer operates as a strain energy dissipation medium, effectively cushioning the delicate interfaces from the recoiling forces induced during subsequent sputtering deposition processes. By absorbing and redistributing mechanical stresses generated during thermal and mechanical cycling, the loose SnO_x buffer acts as a protective cushion, substantially mitigating the risk of cracks and delamination that conventionally plague flexible solar modules under repeated bending and environmental fluctuations.
Complementing this stress-relieving cushion is a tightly packed, compact SnO_x layer optimally designed to ensure strong electrical contact and effective charge transport pathways. This dense layer maintains the critical electrical interfacial coupling between the perovskite absorber and silicon substrates, enabling sustained high carrier mobility and reducing recombination losses. The dual-buffer-layer construct cleverly balances mechanical flexibility with electronic functionality through this sequential layering, providing a durable yet high-performance interface previously unattainable in flexible tandem solar architectures.
Implemented on an ultrathin silicon bottom cell just 60 microns thick, this dual-buffer-layer strategy culminated in a flexible tandem solar cell boasting an extraordinary certified power conversion efficiency of 33.4% on a 1-cm^2 active region. Notably, when scaled up to a wafer-sized 260-cm^2 module, the device maintained a robust certified efficiency of 29.8%, demonstrating remarkable scalability without sacrificing performance. This feat underscores the potential for widespread commercial viability and integration into diverse form factors where lightweight and flexible power sources are paramount.
A defining strength of these advanced tandem cells extends beyond efficiency into their impressive power-per-weight ratio, reaching up to 1.77 W/g. This metric signals a transformative advancement for portable and aerospace photovoltaic applications, where maximizing energy output relative to mass is a critical criterion. The ultrathin silicon base combined with the mechanically resilient dual-buffer interface manifests in devices lightweight enough for emerging sectors without compromising electrical robustness.
Durability assessments further validated the mechanical and operational resilience conferred by the dual-buffer design. The flexible tandem cells retained over 97% of their initial performance metrics after enduring an arduous 43,000 bending cycles, executing these deformations with a minimum curvature radius of approximately 40 millimeters—conditions that far exceed everyday mechanical stress scenarios in wearable electronics. Such endurance signals a paradigm shift towards solar cells that can withstand repetitive strain without succumbing to failure modes that have hampered flexible photovoltaics historically.
Thermal stability likewise benefitted significantly, with the tandem solar cells exhibiting around 97% retention of original power conversion efficiency following 250 cycles of rigorous thermal fluctuations between -40 °C and 85 °C. This wide thermal endurance window simulates practical operating environments ranging from extreme cold to high heat, underscoring the buffer layers’ crucial role in mitigating thermal expansion mismatch and preventing interfacial cracking under such stresses.
This novel dual-buffer-layer engineering thus addresses a fundamental bottleneck in the flexible solar cell domain: the tradeoff between mechanical flexibility and functional stability. By strategically managing interfacial strain while solidifying electronic coupling, the approach bridges the gap between flexible form factor demands and the uncompromising efficiency standards of photovoltaic technologies reserved traditionally for rigid substrates.
The implications of these findings extend well beyond the laboratory. As the global community intensifies efforts for clean energy transition and portable power solutions, perovskite/silicon tandem solar cells equipped with robust stress mitigation mechanisms open avenues for integrated power sources in automotive, aerospace, wearable, and architectural applications. This technology promises not only enhanced energy yield but also mechanical resilience essential for the widespread adoption of flexible photovoltaics.
Looking ahead, the research team anticipates that further refinement in buffer layer material chemistry and deposition techniques could unlock even higher efficiency thresholds and durability milestones. Moreover, integrating this dual-buffer concept with evolving perovskite compositions and encapsulation strategies could amplify device longevity and environmental stability, propelling flexible tandem solar cells closer to mass-market realities.
This work stands as a landmark achievement, exemplifying how nuanced interface engineering grounded in atomic layer deposition dynamics can dramatically advance the field of sustainable energy materials. As the solar industry increasingly calls for adaptability, efficiency, and longevity, the dual-buffer-layer framework marks a critical step towards realizing durable, high-performance flexible photovoltaic platforms capable of powering a more sustainable and connected future.
Subject of Research: Development of mechanically robust, high-efficiency flexible perovskite/silicon tandem solar cells through innovative dual-buffer-layer interface engineering.
Article Title: Flexible perovskite/silicon tandem solar cell with a dual buffer layer.
Article References:
Fang, Z., Ding, L., Yang, Y. et al. Flexible perovskite/silicon tandem solar cell with a dual buffer layer. Nature (2025). https://doi.org/10.1038/s41586-025-09835-w
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Tags: atomic layer deposition techniquesdual-buffer-layer strategyenergy harvesting advancementsFlexible Solar Technologyhigh power conversion efficiencyinterfacial delamination in photovoltaicslightweight solar cellsmechanical durability in solar devicesperovskite silicon tandem solar cellsphotovoltaic performance optimizationtin oxide buffer layerswearable solar applications
