Key Takeaways & Executive Findings
- •• Replacing NMP with 2-pyrrolidinone (PDI) suppresses crystallization of mixed-halide intermediates, enabling high-quality wide-bandgap perovskite films. • The strategy mitigates phase segregation and reduces defect densities, leading to improved open-circuit voltage and fill factor in perovskite/CIGS tandem solar cells. • The approach is compatible with scalable blade-coating in ambient air, addressing a key bottleneck for commercial deployment. • The work demonstrates a significant efficiency improvement in flexible all-thin-film tandem solar cells, advancing the potential for lightweight photovoltaics.
Abstract
Flexible and lightweight photovoltaics represent a pivotal frontier in renewable energy, offering versatile applications ranging from building-integrated photovoltaics (BIPV) to portable power sources and aerospace systems. Among the various thin-film technologies, all-thin-film tandem solar cells, specifically those pairing metal-halide perovskites with copper indium gallium selenide (CIGS), have garnered considerable attention. This combination is particularly synergistic: CIGS serves as an ideal narrow-bandgap bottom cell (~1.1 eV) with proven stability and flexibility, while perovskites offer a tunable wide bandgap (WBG) top cell. To achieve optimal spectral matching and exceed the Shockley−Queisser limit of single-junction devices, the perovskite top cell requires a wide bandgap (>1.67 eV), which is obtained by increasing the bromide/iodide ratio in the mixed-halide composition. However, the fabrication of high-quality WBG perovskite films, particularly via scalable methods like blade-coating in ambient air, remains a formidable bottleneck. The crystallization kinetics of mixed-halide perovskites are notoriously difficult to control. The rapid evaporation of solvents and the distinct solubility differences between bromide and iodide precursors often drive uncontrollable, rapid crystallization. This leads to severe phase segregation, where iodide-rich and bromide-rich domains form, creating energetic disorder. Furthermore, processing in ambient air introduces moisture, which can act as a nucleation site, further accelerating disordered precipitation. These issues manifest as films with high defect densities, poor coverage (pinholes), and significant non-radiative recombination, which severely compromise the open-circuit voltage (VOC) and fill factor (FF) of the final devices. Zhang et al. address this critical challenge by reporting a crystallization suppression strategy that fundamentally alters the phase transition kinetics (Figs. 1(a) and 1(b), Nat Energy (2026). https://doi.org/10.1038/s41560-026-01975-1). By systematically investigating the coordination strength of solvents, they identified that replacing the traditional N-methyl-2-pyrrolidone (NMP) with 2-pyrrolidinone (PDI) can effectively modulate the nucleation and growth stages. The core innovation lies in the specific interaction between the solvent and perovskite precursors. In conventional NMP-based systems, the coordination...
1. Introduction
Flexible and lightweight photovoltaics represent a pivotal frontier in renewable energy, offering versatile applications ranging from building-integrated photovoltaics (BIPV) to portable power sources and aerospace systems. Among the various thin-film technologies, all-thin-film tandem solar cells, specifically those pairing metal-halide perovskites with copper indium gallium selenide (CIGS), have garnered considerable attention. This combination is particularly synergistic: CIGS serves as an ideal narrow-bandgap bottom cell (~1.1 eV) with proven stability and flexibility, while perovskites offer a tunable wide bandgap (WBG) top cell.
To achieve optimal spectral matching and exceed the Shockley−Queisser limit of single-junction devices, the perovskite top cell requires a wide bandgap (>1.67 eV), which is obtained by increasing the bromide/iodide ratio in the mixed-halide composition. However, the fabrication of high-quality WBG perovskite films, particularly via scalable methods like blade-coating in ambient air, remains a formidable bottleneck. The crystallization kinetics of mixed-halide perovskites are notoriously difficult to control. The rapid evaporation of solvents and the distinct solubility differences between bromide and iodide precursors often drive uncontrollable, rapid crystallization. This leads to severe phase segregation, where iodide-rich and bromide-rich domains form, creating energetic disorder. Furthermore, processing in ambient air introduces moisture, which can act as a nucleation site, further accelerating disordered precipitation. These issues manifest as films with high defect densities, poor coverage (pinholes), and significant non-radiative recombination, which severely compromise the open-circuit voltage (VOC) and fill factor (FF) of the final devices.
Loading authentic research manuscript (Pages 1–5)...
LI Manya, JING Linjing, TAN Hairen (2026). Crystallization suppression of mixed-halide intermediates for perovskite/Cu(In,Ga)Se2 tandem solar cells with improved efficiency. SinoTechIntel Verified Research. https://doi.org/10.1088/1674-4926/26020045
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoTechIntel claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the main challenge addressed in this research?
The main challenge is controlling the crystallization of mixed-halide wide-bandgap perovskite films, which often leads to phase segregation and defects, especially when fabricated via scalable methods like blade-coating in ambient air.
How does the proposed crystallization suppression strategy work?
The strategy replaces the traditional solvent N-methyl-2-pyrrolidone (NMP) with 2-pyrrolidinone (PDI). The stronger coordination of PDI with perovskite precursors modulates nucleation and growth, suppressing uncontrolled crystallization and phase segregation.
What are the benefits of using PDI instead of NMP?
Using PDI results in perovskite films with lower defect densities, better coverage, and reduced non-radiative recombination, leading to improved open-circuit voltage and fill factor in tandem solar cells.
Is this method compatible with industrial-scale production?
Yes, the method is compatible with scalable blade-coating in ambient air, making it promising for commercial manufacturing of flexible tandem solar cells.
What is the significance of this work for the field?
This work provides a simple yet effective solvent engineering approach to overcome a key bottleneck in perovskite/CIGS tandem solar cells, potentially accelerating their deployment in lightweight and flexible photovoltaic applications.
Related Technical Papers & Translations
A Novel Approach for Enhanced Brain Tumor Segmentation Using Multimodal MRI and Deep Learning
Brain tumor segmentation from multimodal MRI is crucial for diagnosis and treatment planning. In this study, we propose a novel deep learning framework that integrates structural and functional imaging modalities to improve segmentation accuracy. Our method employs a multi-scale attention mechanism and a hybrid loss function to handle class imbalance and boundary ambiguity. Evaluated on the BraTS benchmark, our approach achieves state-of-the-art performance, with Dice scores of 0.91, 0.87, and 0.84 for whole tumor, core, and enhancing tumor, respectively. Furthermore, we demonstrate the generalizability of our model across different scanners and protocols. Our findings suggest that the proposed method can significantly aid clinical decision-making and surgical planning.
Investigation of coupled acoustic and electrical responses and early warning approaches during re-loading of damaged coal
Initial damage from engineering disturbances in deep coal mining degrades mechanical properties and heightens dynamic-hazard risks, challenging conventional monitoring. This study probes the coupled acoustic-electrical responses of initially damaged coal under reloading and develops a multi-parameter, multi-level dynamic integrated early-warning model. Using a true-triaxial Split Hopkinson Pressure Bar (SHPB) system, we prepared specimens with graded damage by varying static deviatoric stresses and dynamic impacts. Uniaxial compression reloading was conducted with synchronous acoustic emission (AE) and resistivity monitoring. Joint time-domain responses of force, acoustics, and electricity delineated distinct loading stages. Time-frequency features were extracted via Fourier and wavelet transforms; crack architecture was quantified by 3D AE localization and fractal-dimension analysis. Initial damage markedly reduced load-bearing capacity. Resistivity decreased sharply with increasing deviatoric stress, while cumulative AE counts increased strongly. The AE spectrum evolved from bimodal to broadband with low- and high-frequency enhancement. The resistivity spectrum showed progressive bandwidth broadening, energy amplification, and high-frequency advancement. The AE spatial fractal dimension rose significantly during compaction. An integrated warning system combining multiscale entropy fusion, Temporal Convolutional Network (TCN)-Transformer forecasting, recurrence-network analysis, and a Bayesian framework yielded a 28.4 s lead time, offering a theoretical basis and technical pathway for intelligent prevention of dynamic hazards.
Influence of aggregate particle size on fracture behavior and energy evolution of cemented rockfill in the post-peak stage
Cemented rockfill (CRF) combines structural support with sustainable reuse of coal-derived solid waste. This study integrates digital image correlation, acoustic emission monitoring, and finite–discrete element simulations to investigate mechanical behavior, fracture development, and energy evolution of CRF containing 54% aggregate content with three grain-size distributions (5–10, 10–20, and 20–30 mm). Results indicate finer aggregates raise compressive strength and elastic modulus, and increase post-peak softening and residual stiffness. Fracture patterns transition from dominantly unidirectional failure in coarse specimens to pronounced X-shaped conjugate shear in fine specimens, with cracks initiating at boundaries and propagating inward. The proportion of failed joints at comparable strains decreases markedly with finer gradation, reflecting a more homogeneous crack network that enhances post-peak load retention and produces frequent minor stress fluctuations. Energy analyses reveal a coarse > medium > fine ordering in cumulative dissipation; however, finer aggregates delay rapid kinetic and dissipative energy release, promoting slower energy redistribution and improved load resistance. These findings quantify how aggregate gradation controls deformational mechanisms, crack topology, and energy partitioning, and provide design guidance for optimizing aggregate size and cementitious composition to enhance ductility, energy absorption, and structural reliability of CRF in underground engineering.