A recent study published in Small highlights how incorporating the metal-organic framework (MOF) UiO-66 can significantly enhance both the efficiency and stability of tin halide perovskite solar cells (TPSCs). Researchers detail the structural and chemical benefits of UiO-66 that contribute to these improvements.
Image Credit: Audio und werbung/Shutterstock.com
Background
MOFs are porous materials made up of metal ions connected by organic molecules. Their large surface area, adjustable pore sizes, and chemical versatility make them useful for enhancing solar cells. These properties help MOFs interact with perovskite materials, potentially leading to smoother films with fewer defects.
Tin halide perovskites are an appealing alternative to lead-based solar cells due to their ideal bandgap and high charge-carrier mobility. However, their practical use is hindered by poor crystal quality and rapid degradation when exposed to air.
Formamidinium tin iodide (FASnI3) is a particularly promising tin-based perovskite, but it remains unstable under environmental stress. To address this, researchers investigated UiO-66, a zirconium-carboxylate MOF known for its stability against moisture and chemicals, as a way to improve the performance and durability of TPSCs.
The Study
In this research, UiO-66 was synthesized with smaller grain sizes (reduced from 200–300 nm to 30–50 nm) to better integrate into the perovskite film. X-ray diffraction confirmed that the MOF maintained its high crystallinity and purity.
UiO-66 was incorporated into FASnI3 using a one-step spin-coating method on a hole transport layer made of PEDOT:PSS. The films were then annealed at 100 °C to complete crystallization. The entire process was carried out in a nitrogen-filled glovebox to maintain controlled conditions.
To assess the device performance, researchers conducted current-voltage (J-V) measurements under standard AM 1.5 sunlight conditions, as well as stability tests to evaluate how long the devices maintained efficiency under ambient exposure.
Results and Discussion
The addition of UiO-66 led to a noticeable increase in power conversion efficiency (PCE), from 11.43 % to 12.64 %. Researchers attributed this improvement to the MOF’s ability to regulate the crystallization of FASnI3, leading to higher-quality films and better electronic properties.
Scanning electron microscopy (SEM) revealed that the UiO-66-enhanced films were denser and more uniform. Optical analysis using UV-vis spectroscopy showed that light absorption was improved, while time-resolved photoluminescence (TRPL) measurements indicated that carrier lifetimes were extended, suggesting a reduction in non-radiative recombination losses. These results confirm that UiO-66 plays a key role in optimizing the structural and optical properties of the perovskite film.
Stability tests showed that TPSCs with UiO-66 maintained over 90 % of their initial efficiency after 100 days in a nitrogen glovebox. In contrast, devices without UiO-66 lost significant efficiency, retaining only 38 % of their initial performance after 144 hours. The improved stability was linked to UiO-66’s ability to reduce defect density and its strong interactions with Sn2+ ions, which helped reinforce the perovskite structure.
Additionally, the porous structure of UiO-66 acted as a protective layer against moisture and oxygen, further extending the lifespan of the solar cells. Theoretical calculations and density functional theory (DFT) simulations confirmed strong interactions between the MOF’s carboxylate groups and tin ions, offering further stability at the molecular level.
Conclusion
This study demonstrates that integrating UiO-66 into tin halide perovskite solar cells significantly enhances efficiency and stability. The incorporation of UiO-66 facilitates improved crystallization kinetics, defect passivation, and superior charge transport properties, resulting in higher power conversion efficiency and extended operational stability.
These findings reinforce the role of MOFs as a viable strategy for addressing the persistent challenges of tin-based perovskites. By optimizing both structural and electronic properties, UiO-66 integration brings TPSCs closer to practical application, offering a promising pathway for advancing lead-free photovoltaic technologies.
Journal Reference
Yin Y., et al. (2025). Enhanced Efficiency and Stability of Tin Halide Perovskite Solar Cells Through MOF Integration. Small. DOI: 10.1002/smll.202411346, https://onlinelibrary.wiley.com/doi/10.1002/smll.202411346