Ultraflexible perovskite solar cells (PSCs) have attracted significant attention as lightweight and flexible power sources due to their high efficiency and the ultrathin, lightweight nature of plastic substrates with thicknesses on the order of one micron. Although ultraflexible PSCs offer great potential as high power-per-weight (ppw) energy harvesters, their ppw values are still limited by relatively low device efficiencies. This limitation is primarily attributed to the poor thermal stability of conventional ultrathin plastic substrates and the common use of p-i-n architectures in ultraflexible PSCs, where p-type polymer bottom layers are employed to enable low-temperature fabrication.

In this study, we developed highly efficient ultraflexible PSCs with an n-i-p structure on a newly designed 1.5  μm-thick thermally stable plastic substrate composed of parylene and SU-8. The resulting ultraflexible PSCs achieved a power conversion efficiency of 18.2% while maintaining excellent mechanical flexibility, with stable operation under a bending radius as small as 500  μm.

Furthermore, we fabricated an ultraflexible PSC module by connecting six individual cells in series for energy harvest under indoor lighting conditions. By integrating this PSC module with perovskite nanocrystal LEDs, we successfully demonstrated perovskite LED operation powered solely by the harvested energy from indoor light¹.

Perovskite solar cells have rapidly transitioned from laboratory research to a commercially promising photovoltaic technology within just over a decade, driven by their high power conversion efficiency, low-cost production, and excellent performance in low-light conditions. Hybrid organic-inorganic perovskites combine the solution-processability of organic materials with the robust optoelectronic properties of crystalline inorganic semiconductors, creating a versatile material platform that outperforms conventional photovoltaic technologies in specific applications.

To enable scalable and environmentally responsible production, sustainable and industry-compatible processing methods are essential. This begins with the development of green synthesis routes for perovskite precursors. Solaveni, a German innovator, has introduced sustainable synthesis techniques for organic alkylammonium halides and metal halides using novel green halide chemistry. This presentation evaluates these synthesis routes through a life cycle assessment (LCA), comparing their environmental impacts—resource use, energy consumption, and emissions—against traditional methods. The LCA provides critical insights into the sustainability of these precursors, informing strategies to minimize the ecological footprint of perovskite photovoltaics. Additionally, innovative recycling and upcycling methods for perovskites are introduced, enabling rapid material recovery and fostering a circular economy. These advancements pave the way for sustainable, high-performance perovskite solar technologies with reduced environmental impact.

Perovskite solar cells (PSCs) are at the forefront of next-generation photovoltaics, combining high power conversion efficiency with low-cost and scalable fabrication. Their unique optoelectronic properties and potential for flexible, lightweight applications make them strong candidates for future solar energy systems. However, key challenges, particularly related to long-term stability, scalable manufacturing, and consistent film quality, must be addressed to enable commercial deployment [1,2]. To tackle these issues, we present an automated platform that integrates machine learning (ML) workflows with high-resolution image analysis for real-time process optimization. As illustrated in Figure 1, this platform combines computational tools and data-driven methods to study and impove the crystallization dynamics and morphological quality of PSC films.

Our approach leverages microscopic imaging acquired in situ or post-deposition, which is processed using state-of-the-art segmentation frameworks, including the Segment Anything Model (SAM) and Detectron2. These tools enable the precise identification of morphological features such as crystal domains, grain boundaries, and nuclei formation sites. To further classify and characterize these regions, we employ a ResNet152 convolutional neural network (CNN), which supports detailed recognition of grain size, shape, and orientation.
From the segmented images, we extract a set of quantitative descriptors to assess film homogeneity and microstructural quality. These include crystal size distributions, aspect ratios, and novel information-theoretic metrics such as Shannon entropy and Computable Information Density (CID). These metrics enable a deeper understanding of the crystallization process, revealing correlations between microstructural patterns and device performance. [3].
Applied across multiple fabrication batches, our pipeline captures subtle morphological variations and identifies key trends linked to processing conditions. In particular, we show that entropy and CID serve as sensitive, compact indicators of film homogeneity, complementing physical measurements and aiding in the detection of suboptimal growth regimes.

This methodology provides a scalable and automated framework for image-based quality assessment in PSC fabrication. While real-time control is not yet implemented, the demonstrated analytical capacity lays the groundwork for future integration into closed-loop synthesis platforms, ultimately supporting more consistent and efficient manufacturing.

Perovskite solar cells (PSCs) represent a third-generation solar cell technology and a promising alternative to traditional photovoltaic technologies. One of the key advantages of this technology is solution processability which enables fabrication on flexible substrates using roll-to-roll (R2R) applicable methods such as slot die coating, gravure printing, and rotary screen printing. R2R manufacturing methods offer significant advantages in terms of material utilization and production speed, making them ideal for large-scale, portable, wearable and other applications where lightweight and flexibility are essential [1, 2, 3, 4].

The commercialization of PSCs hinges on the development of scalable, low-temperature, and solution-processable materials compatible with high-throughput R2R fabrication techniques. The R2R manufacturing methods require specific ink compositions and rheological properties, which our research has addressed previously. Tin dioxide (SnO₂) is a leading candidate for the electron transport layer (ETL) in PSCs due to its excellent electronic properties, transparency, and chemical robustness. Yet conventional colloidal SnO₂ dispersions designed for laboratoryspin‑coating translate poorly to industrial processes because of inadequate viscosity which causes uncontrollable ink spreading. We have demonstrated that transferring SnO2 deposition from laboratory to larger scale is achievable through ink formulation [2].

In this work, we present the development of a R2R-compatible SnO₂ ink for gravure printing. The formulation is based on a solvent blend containing water and alcohol. Alcohol is introduced as a rheology modifier to ensure suitable particle size distribution and viscosity leading to shear-thinning behavior that ensures clean ink release from the gravure cells and prevents ink bleeding after printing. This resulted in uniform deposition and film formation at low annealing temperatures (<140 °C) in ambient conditions, suitable for flexible substrates. The resulting SnO₂ layers demonstrate high optical quality, low surface roughness, and compatibility with perovskite absorbers. Devices fabricated using R2R printed SnO₂ ETLs in an n-i-p architecture with printed perovskite layer achieved power conversion efficiencies up to 11 % with excellent reproducibility and operational stability under continuous illumination (nearly 10 % PCE). This work highlights the importance of ink rheology and process compatibility in transitioning PSCs toward industrial-scale production via roll-to-roll manufacturing.

Halide perovskites (HPs) continue to revolutionize optoelectronics due to their outstanding properties—tunable bandgaps, high absorption coefficients (10⁴–10⁵ cm⁻¹), and remarkable defect tolerance. These features have enabled advances in photodetectors (PDs) and light-emitting diodes (PeLEDs), with recent external quantum efficiencies (EQE) in PeLEDs exceeding 26%, surpassing those of planar OLEDs [1-4]. Nevertheless, the field demands scalable, material-efficient, and environmentally responsible manufacturing processes.

Inkjet printing has emerged as a transformative technology for perovskite optoelectronics, offering digital patterning, low material waste, and compatibility with flexible substrates. Since early implementations yielded modest efficiencies below 10% [3,4], the technique has matured toward fully inkjet-printed PeLEDs [5], integration with sustainable solvent systems [6], and novel device functionalities. Recent efforts by our group include:

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(i) Fully inkjet-printed green PeLEDs using CsPbBr₃ nanocrystal inks, where post-print annealing was found to modulate structural dimensionality and increase photoluminescence by over 70-fold [5].

(ii) Red-emitting TEA₂SnI₄ and PEA₂SnI₄ PeLEDs fabricated with eco-friendly DMSO inks, demonstrating excellent emission stability and environmental compliance with EU RoHS directives [6].

(iii) Photodetectors based on 2D/3D tin perovskite (PEA₀.₅BA₀.₅)₂FA₉Sn₁₀I₃₁, showing high responsivity (up to 50 A/W), broadband detection from UV to near-infrared, and improved performance over time under effective encapsulation strategies [7].

(iv) Single-mode random lasing in inkjet-printed FASnI₃ integrated into vertical cavities, reaching Q-factors up to 1000 and demonstrating low-threshold, spectrally stable lasing [8].

This body of work underscores the convergence of scalable inkjet printing with advanced functional materials, offering new opportunities in optoelectronic design. Detailed evaluation of ink formulation, printing parameters, and annealing protocols reveals pathways to control crystallization dynamics, mitigate printing artifacts (e.g., coffee-ring effects), and optimize film morphology. Additionally, green chemistry approaches—including the replacement of lead with tin and DMF with DMSO—are shown to substantially reduce environmental impact without compromising device performance.

The integration of light emission and photodetection capabilities in similar material platforms further supports the vision of multifunctional, monolithically integrated perovskite optoelectronics. These advances position inkjet printing as a key enabling technology for future applications in wearable electronics, flexible photonics, smart displays, and sustainable photonic systems.

[1] Zhao, B. et al., Nature Nanotechnology 18, 981–992 (2023).

[2] Wenger, B. et al., Nat Commun 8, DOI 10.1038/s41467-017-00567-8 (2017).

[3] Shen, W. et al., ACS Appl. Mater. Interfaces 14, 5682-5691 (2022).

[4] Hermerschmidt, F. et al., Mater. Horizons 7, 1773-1781 (2020).

[5] Vescio, G. et al., Adv. Eng. Mater. 25 (2023).

[6] Vescio, G. et al., ACS Energy Lett. 7, 3653-3655 (2022).

[7] Vescio, G. et al., Small Science (2025).

[8] H. P. Adl et al. Advanced Materials 36 (2024).

Halide perovskite solar cells combine record‐high power conversion efficiencies with low‐cost, solution‐based processing. and have rapidly emerged as a leading candidate in next-generation photovoltaics also in combination with silicon photovotlaics. However, their commercial viability remains challenged by environmental and stability concerns. In this work, we present a comprehensive approach to the sustainable development of halide perovskite photovoltaics through environmentally conscious materials and processes on both glass and flexible sustrates. Key strategies include the use of green solvents for perovskite film deposition, enabling safer and more scalable fabrication routes. We demonstrate the fabrication of fully flexible perovskite solar cells under ambient air conditions using low-toxicity, eco-friendly solvents via scalable printing technologies. Additionally, we replace conventional noble metal electrodes with carbon-based back contacts, offering a cost-effective and sustainable alternative with good conductivity and stability, showcasing potential for full roll-to-roll production. Finally, we address the critical issue of lead toxicity by partially substituting lead with tin in mixed Pb-Sn perovskite compositions, achieving reduced environmental impact while maintaining promising photovoltaic properties as single junction as well as in perovskite/perovkite tandem. Together, these innovations mark significant progress toward greener, safer, and more sustainable perovskite solar technologies suitable for widespread deployment.

In 2025, certified efficiency up to 27% has been demonstrated using Perovskite Solar Cells.[1] Also, many progresses have been done on encapsulation to improve their stability.[2] These results are showing their potential for the next generation of photovoltaic device.  This explain why some industrials are now investigating this field and start to build their pilot and fabrication lines. So far most of high efficiency devices have been achieved using the DMF / DMSO solvent system with an antisolvent step using chlorobenzene.[3] This approach is very sensitive to the antisolvent step and has a narrow processing window which might make it difficult to scale up. Other approaches rely on the use of nitrogen or vacuum quenching which might be costly due to the high amount of high purity gas use during the nitrogen quenching step and the slow speed of the vacuum quenching respectively.[4] Here we present our work on inkjet printed perovskite using a relatively unexplored solvent with low toxicity, 1-methoxy-2-propanol. By using different additive we show that we can control the crystallization kinetic to make compact perovskite layer without any quenching and achieve device efficiency over 20%.

The highly sought after optoelectronic properties of metal halide perovskites and their straightforward solution-processability offers a promising way ahead to realizing high-performance devices through additive approaches like printing.[1,2] The composition of inks used in printing plays a vital role in functional thin film formation which is critical for optical conversion and electrical transport in devices. However, understanding and controlling crystallization of perovskite layers from printed wet films on substrates for device applications remains largely elusive. In this study, the influence of graphene nanosheets on the crystallization dynamics of inkjet-printed methyl ammonium lead bromide (MAPbBr₃) thin films is presented and leveraged for device application in photodetection.  

The centers of heterogeneous nucleation could be ascribed to graphene nanosheets, resulting in highly textured films while retaining optical properties such as the absorption and emission features of the MAPbBr₃. Stark differences in morphology ranging from poorly connected island films to dendritic networks were observed through a variety of microscopic techniques and correlated to the crystalline orientation from x-ray diffraction studies. Additionally, a correlation with time resolved photoluminescence exhibited an interesting evolution in the decay profile that could be linked to the crystallinity of the films, as well as with electrical measurements. To profit from the control on crystallinity to the electro-optical characteristics of these films, printed photodetectors were investigated and found to exhibit strong selective photoresponse above 2.3 eV without the use of external filtering. Benefitting from the influence of graphene on the optoelectronic properties of the films, devices with responsivities of 2 A W^-1 and detectivities of nearly 1.9×10¹⁰ Jones were obtained. Similarly, flexible devices were also fabricated on polymer substrates and found to have good retention of photoresponse to cyclical mechanical stress. These findings point to the crucial role of tuning ink composition with nano-additives such as graphene, its impact on film formation, and implication in the optoelectronic performance of printed devices.  

Perovskite and inkjet printing offer a promising combination for the realization of novel X-ray detectors. Perovskite semiconductors combine excellent X-ray absorption properties with high photon-to-charge conversion efficiencies in direct detectors. Moreover, they offer equally promising properties for novel scintillator materials with high photon-to-photon efficiencies for indirect detectors [1]. We have investigated different device architectures for efficient charge collection based on perovskite active layers. Due to the perovskite’s processability at low temperatures, perovskite-based X-ray absorbers can also be realized on polymeric substrates and are therefore particularly attractive for the realization of mechanically flexible and curved detectors [2]. We have elaborated on the design, fabrication, and characterization of suitable device architectures and have demonstrated the use of digital inkjet printing to realize triple cation perovskite X-ray detectors on mechanically flexible substrates. Mechanical flexibility opens a pathway towards folded (“origami-type”) devices that bring 2D printing into 3D devices [3].