Perovskite solar cells (PSCs) have revolutionized the field of photovoltaics with their remarkable power conversion efficiencies and low-cost fabrication processes. Yet, despite these promising attributes, the Achilles’ heel of PSCs remains their operational stability, which has consistently hampered their commercial viability. The problem stems primarily from the intrinsic instability of halide perovskite materials under prolonged illumination, heat, and moisture. In a groundbreaking advance, researchers have now unveiled a novel approach using ionic liquids to fundamentally enhance the longevity and performance of these cells, potentially accelerating their entry into the solar energy mainstream.
A team led by Xu, Shao, Tang, and collaborators introduced an innovative ionic liquid, methoxyethoxymethyl-1-methylimidazole chloride (MEM-MIM-Cl), designed with an ethylene glycol ether side chain tailor-made to govern the complex crystallization dynamics of perovskite films. Unlike conventional additives, MEM-MIM-Cl serves not only as a bulk modifier but also plays a pivotal role in stabilizing buried interfaces within the solar cell architecture. Their work elucidates the molecular design principles behind MEM-MIM-Cl and explores how this compound synergistically interacts with NiOx layers, a common hole transport material, to suppress defect formation and enhance device robustness.
Central to the reported findings is the discovery that MEM-MIM-Cl fosters the creation of a novel intermediate perovskite phase during fabrication. This newly identified phase originates from chelation between the ionic liquid’s molecular structure and undercoordinated Pb(II) ions in the perovskite lattice. This interaction mitigates the typical formation of defects and traps that are usually responsible for accelerated degradation pathways under operational stress. The presence of this intermediate phase effectively acts as a molecular “shock absorber,” protecting the delicate perovskite crystal structure from chemical and environmental damage.
The researchers demonstrated that solar cells incorporating MEM-MIM-Cl consistently achieve unparalleled efficiency benchmarks. Specifically, devices treated with this ionic liquid reached a power conversion efficiency (PCE) of 25.9%, a figure that rivals the highest efficiencies reported for lead halide perovskites. More importantly, this efficiency was maintained under harsh testing regimes simulating real-world conditions. After 1,500 hours of continuous one-sun illumination paired with elevated temperature stress of 90 °C, these cells preserved 90% of their initial performance. Such stability metrics far exceed earlier milestones, which often relied on much milder ageing tests.
Operational resilience was further highlighted by the cells’ response to diurnal cyclic ageing, mimicking day-night temperature and illumination fluctuations. The devices showed unprecedented fatigue resistance, a critical advance given that typical PSCs suffer rapid performance drop-offs during cyclic stress. This enhanced durability directly stems from the dual role of MEM-MIM-Cl: regulating crystal growth to minimize inherent defects while concurrently fortifying interfaces against environmental stressors. This dual-functionality partnership is essential for transforming PSCs from lab curiosities to market-ready energy technologies.
The profound impact of MEM-MIM-Cl on perovskite film quality cannot be overstated. The ionic liquid’s ethylene glycol ether side chain promotes better film uniformity and densification during the spin-coating and annealing stages. These improvements suppress pinholes and grain boundary defects, which traditionally serve as ingress routes for moisture and oxygen—primary culprits of perovskite degradation. The enhanced microstructure not only boosts charge transport properties but also diminishes non-radiative recombination, directly contributing to improved photovoltaic performance.
Additionally, the interaction between MEM-MIM-Cl and NiOx interfaces addresses a critical interface bottleneck in PSCs. NiOx layers often suffer from chemical instability and interface trap states that limit hole extraction efficiency and accelerate device aging. By chemically stabilizing this buried interface through ionic liquid chelation, the researchers successfully extended the operational lifetime of the solar cells under real-world stressors without sacrificing charge transport characteristics. This interfacial engineering represents a paradigm shift in how PSC stability challenges are approached.
The multi-faceted functional role of the ionic liquid was elucidated through advanced characterization techniques, including X-ray diffraction, photoluminescence mapping, and impedance spectroscopy. These methods revealed the subtle formation of the intermediate phase and tracked its evolution during environmental exposure. The detailed mechanistic insights provide valuable guidance for the rational design of future ionic liquids tailored to specific perovskite compositions and device architectures, potentially unlocking new avenues for customized stability enhancement.
Furthermore, the researchers emphasize the scalability and industrial compatibility of their approach. Unlike many exotic stabilization strategies requiring complex fabrication protocols, the incorporation of MEM-MIM-Cl can be seamlessly integrated into existing perovskite solar cell manufacturing workflows. This compatibility lowers barriers to rapid commercialization, an essential factor given the urgent global demand for cost-effective, sustainable energy solutions. The use of ionic liquids with tunable chemical properties opens a versatile toolbox for addressing long-standing challenges in PSC technology.
The implications of this work extend beyond solar cells alone. The concept of utilizing ionic liquids as crystallization regulators and interface stabilizers could be adapted to other optoelectronic devices prone to defect-related failures, such as light-emitting diodes and photodetectors based on perovskite materials. By stabilizing the perovskite lattice at a molecular level, these ionic liquids may pave the way for a new generation of durable, high-performance devices across multiple energy and electronic applications.
Yet, important questions remain concerning the long-term environmental stability of ionic liquids themselves and their potential impacts on the overall lifecycle and recyclability of perovskite photovoltaics. Continued interdisciplinary efforts will be essential to optimize the chemical structure and minimize any side effects related to ionic liquid incorporation. Further exploration into a broader palette of ion combinations could yield even more robust and efficient perovskite solar cells tailored to diverse climatic and operational conditions globally.
This landmark study sets a new benchmark in the perpetual quest for durable, efficient perovskite solar cells by marrying molecular chemistry insights with practical device engineering. The comprehensive understanding and strategic use of ionic liquids represent a critical design paradigm that propels PSCs from promising research prototypes toward sustainable, scalable energy technologies capable of meeting future power needs. If widely adopted, this approach could substantially accelerate the transition to clean energy with solar photovoltaic systems.
In conclusion, the introduction of MEM-MIM-Cl as a functional ionic liquid modifier epitomizes the cutting edge of material science innovation in renewable energy. Achieving simultaneously high efficiency and exceptional operational stability, this discovery offers an inspiring blueprint for future exploration and industrial development. As the solar energy sector intensifies its pursuit of affordable, reliable, and environmentally friendly power sources, breakthroughs such as this herald a new era where perovskite solar cells stand poised to play a transformative role.
Subject of Research: Ionic liquids enhancing the long-term stability and efficiency of halide perovskite solar cells.
Article Title: Ionic liquids improve the long-term stability of perovskite solar cells.
Article References:
Xu, W., Shao, W., Tang, Y. et al. Ionic liquids improve the long-term stability of perovskite solar cells. Nat Energy (2025). https://doi.org/10.1038/s41560-025-01906-6
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41560-025-01906-6
Keywords: Perovskite solar cells, ionic liquids, methylimidazole chloride, stability, power conversion efficiency, NiOx interface, crystallization regulation, defect suppression, operational resilience, photostability.
