In the relentless pursuit of harnessing solar energy with ever-greater efficiency, recent advancements in perovskite solar cells (PSCs) stand at the forefront of photovoltaic research. Despite substantial progress, fully optimized inverted PSC architectures have struggled to surpass the quasi-steady-state efficiency threshold of 26%. This persistent limitation has largely been ascribed to the intricate interplay between interfacial energy-level mismatches and defect-induced non-radiative recombination phenomena. These factors critically undermine the power conversion efficiency and operational stability of the cells, highlighting the complexity of achieving synergistic improvements in both materials and interface engineering within perovskite photovoltaics.
A groundbreaking study now sheds new light on overcoming these challenges by introducing a novel surface-phase-transformation strategy employing a minimal incorporation of N-methyl pyrrolidone (NMP) into a piperazinium diiodide (PDI)-dissolved isopropanol solution. This innovative approach redefines the perovskite surface treatment protocol during the post-deposition stage, catalyzing a unique crystallization pathway. Unlike the conventional transition via a δ-intermediate phase to the α-phase perovskite, the addition of NMP directs the surface transformation through a solvated intermediate phase, which fundamentally alters the nucleation and growth dynamics at the atomic scale.
The emergence of this distinct crystallization mechanism not only elevates the crystallinity of the perovskite surface but also dramatically reduces interfacial contact losses. Crystallographic integrity is paramount to the optoelectronic behavior of PSCs; thus, the suppression of defects and grain boundary disorders at the interface directly mitigates pathways for non-radiative recombination. Enhanced surface crystallinity also contributes to an optimized energy band landscape, facilitating more efficient charge carrier extraction and transport.
Moreover, NMP’s presence enhances the molecular interaction between PDI and the perovskite layer. This reinforced chemical affinity at the interface seamlessly tunes the interfacial band alignment, thereby reducing energetic barriers that traditionally impede photogenerated charge carrier flow. The concerted effect of improved crystallinity and interface energetics manifests in a significant elevation of device performance metrics.
Empirical validation of this refined processing technique underscores its technological promise. The research reports certified power conversion efficiencies (PCEs) reaching an impressive 26.87% stabilized efficiency for single-junction PSCs. Beyond the lab-scale devices, the strategy has been successfully scaled to fabricate mini-modules achieving PCEs of 23.00%, alongside all-perovskite tandem devices that demonstrate record-setting efficiencies of 29.08%. These figures mark a new milestone in perovskite photovoltaic research, pushing the boundaries of what inverted PSC architectures can achieve.
Durability, often the Achilles’ heel of PSCs, is also critically addressed through this surface-phase-transformation strategy. Under continuous illumination at a standard 1-sun intensity and an elevated temperature of 65°C in ambient air, devices retained 96% of their initial efficiency over 2,500 hours. Such stability metrics signify a substantial leap forward in device longevity, aligning PSCs more closely with the practical requirements for commercial deployment and real-world operating conditions.
The mechanistic insights gleaned from this study underscore the intricate role of solvent-mediated intermediate phases in dictating perovskite lattice organization and surface morphology. By steering the crystal growth pathway away from the conventional δ-intermediate phase, the NMP involvement circumvents defect formation tendencies that act as non-radiative recombination centers. The solvated intermediates provide a dynamic, transient scaffold that promotes uniform crystallite expansion and reduces strain-induced defects—critical factors that traditionally undermine PSC efficiency and longevity.
Intriguingly, the enhanced PDI-perovskite interaction through NMP-facilitated molecular coordination exemplifies how subtle chemical modifications at interfaces can yield outsized effects. By improving electronic coupling and reducing trap densities, the interface acts not merely as a passive boundary but as an active participant in photovoltaic function. This paradigm reflects an evolving understanding that interface engineering holds the key to unlocking perovskite solar cell potential beyond material composition alone.
The scalability of this approach to mini-modules and tandem architectures illustrates its versatility and practical relevance. Tandem configurations, which stack multiple absorber layers to capture a broader solar spectrum, particularly benefit from intermediate band alignment optimization to minimize voltage losses and maximize current matching. The researchers’ ability to elevate tandem efficiency beyond 29% demonstrates the critical importance of controlled surface phase transformation in enabling complex device architectures.
From a materials science perspective, this work highlights the synergy between solvent chemistry, crystallography, and electronic structure engineering. The choice of NMP as a polar aprotic solvent fine-tunes the solvation environment during post-treatment, enabling tailored nucleation kinetics and defect passivation processes. This points to broader implications for solvent engineering as a versatile tool for controlling perovskite film quality and interfacial properties in diverse photovoltaic systems.
Looking forward, the implications for this surface-phase-transformation strategy extend beyond the immediate efficiency and stability benefits. The method could act as a benchmark for future perovskite interface modifications, inspiring the exploration of other chemically similar solvents and surface passivation agents. Such innovations might further push the efficiency envelope and enhance environmental robustness, propelling PSCs toward widespread commercial adoption.
Beyond technical achievements, the research contributes to the understanding of how dynamic intermediate phases influence photovoltaic performance, urging reexamination of established processing assumptions. It opens a new frontier in device engineering where transient chemical states are purposefully harnessed to steer crystallization and interface morphology, rather than solely being seen as processing artifacts. This reflects a maturation in perovskite research, emphasizing precision and predictability in fabrication protocols.
The environmental stability observed under operational conditions is particularly striking given the notorious sensitivity of perovskite materials to humidity, heat, and illumination. The improved contact and energy alignment reduce degradation pathways, suggesting that such chemical treatments may also protect perovskite layers from moisture ingress and ion migration. This could underpin the development of more resilient photovoltaic modules capable of withstanding the rigors of outdoor deployment.
In sum, the incorporation of NMP into the PDI-based post-treatment marks a pivotal advancement in perovskite solar cell manufacturing. It reveals how molecular-level modifications enacted through solvent chemistry can redefine crystal growth pathways and interface properties, culminating in unprecedented device performance and stability results. This study serves as a compelling blueprint for the next generation of photovoltaic research and technology development.
Such transformative improvements in PSCs promise to accelerate the penetration of solar photovoltaic technologies into the global energy landscape. The potential for highly efficient, durable, and cost-effective perovskite solar cells invigorates the vision of sustainable energy solutions capable of reducing carbon emissions and mitigating climate change. As research continues to refine these techniques, the prospect of scalable perovskite photovoltaics powering homes and industries worldwide draws ever closer to reality.
In conclusion, the solvated-intermediate-driven surface transformation strategy unveiled here offers a compelling synthesis of chemical ingenuity and materials science. By reimagining how perovskite surfaces evolve during post-treatment, the researchers dramatically elevate efficiency and operational stability, bringing perovskite solar technology closer to commercial viability. This milestone achievement encapsulates the vibrant trajectory of innovation defining the future of renewable energy technologies.
Subject of Research: Advanced surface engineering and interface optimization in lead halide perovskite solar cells
Article Title: Solvated-intermediate-driven surface transformation of lead halide perovskites
Article References:
Liu, S., Miao, T., Wang, J. et al. Solvated-intermediate-driven surface transformation of lead halide perovskites. Nat Energy (2025). https://doi.org/10.1038/s41560-025-01912-8
DOI: https://doi.org/10.1038/s41560-025-01912-8
Tags: advanced materials for solar energyatomic-scale nucleation in perovskitesefficiency challenges in perovskite photovoltaicsenhancingimproving perovskite crystallinityinterfacial energy-level mismatchesN-methyl pyrrolidone in photovoltaicsnon-radiative recombination in solar cellspiperazinium diiodide applicationpost-deposition surface treatment methodssolvated intermediates in perovskite solar cellssurface-phase transformation in PSCs
