Ligand engineering is an effective method to reduce defects in perovskite solar cells (PSCs) and to enhance efficiency. Likewise, enhancing device stability through ligand engineering is currently emerging as a key focus to suppress the bidirectional migration of halides and silver ions, which otherwise can cause irreversible chemical corrosion to the electrode and perovskite layer. Here, triphenylphosphine oxide (TPPO) is demonstrated to improve the long-term operational stability of PSCs when introduced at the interface between the perovskite and the electron transport layer (ETL). TPPO effectively eliminates uncoordinated Pb2+ and thus reduces surface defects. Accordingly, the target solar cell yields a hero power conversion efficiency (PCE) of 26.01% and a maximum open-circuit voltage (VOC) of 1.23 V, representing the minimum voltage deficit (0.32 V) reported for methylammonium-free (MA-free) PSCs. Moreover, long-term operational analysis reveals that the bidirectional migration of halides and silver ions is significantly suppressed, resulting in enhanced device stability. TPPO-modified PSCs retain 90% of the initial PCE after 1200 hours of operation in maximum power point tracking. Ligand engineering with TPPO marks a significant advancement in enhancing the stability of PSCs and is fully compatible to upscaling scenarios.

Three-dimensional/two-dimensional (3D/2D) heterojunctions in perovskite solar cells exhibit excellent optoelectronic properties and enhanced stability under mild ageing conditions. However, their performance degrades drastically under harsh ageing conditions. This study reveals the intrinsic instability of mono-ammonium based 2D perovskites (2D-mono) under photo-thermal ageing, which decompose into PbI2 and metallic lead (Pb0). The structural collapse promotes vacancy formation and facilitates iodide migration to the anode. As a result, it triggers a redox reaction that reduces the transport layer's mobility and doping concentration, leading to a significant increase in series resistance. Compared to mono-ammonium-2D structure, di-ammonium-2D (2D-di) based interfaces demonstrate superior structural stability and effectively block iodide migration into the transporting layer. However, blocking-induced uneven iodide distribution leads to interstitial defect formation in the 3D layer, exacerbating non-radiative recombination. To address it, we propose a strategical method by incorporating 2D-di in the 3D bulk instead of on the top surface, which effectively confines mobile ions within the grain and suppresses cation phase segregation. This optimization yields stable perovskite solar cells with an extrapolated operational T80 lifetime exceeding 560 hours under harsh conditions (85 degrees C and 2-sun illumination). Three-dimensional/two-dimensional (3D/2D) heterojunctions in perovskite solar cells exhibit excellent optoelectronic properties and enhanced stability under mild ageing conditions.

Perovskite-based tandem solar cells stand at the forefront of photovoltaic innovation due to their exceptional performance and cost-effective fabrication. This study focuses on minimizing energy losses within a 1.80 eV perovskite sub-cell. We demonstrate that the surface treatment of perovskite with binary guanidinium bromide and 4-fluorophenylammonium iodide synergistically reduces defect densities and adjusts interfacial energy-level alignment. The enhanced passivation effect and the formation of a surface dipole significantly reduce nonradiative recombination and transport losses, leading to a notable increase in the open-circuit voltage and fill factor product, thereby achieving an impressive power conversion efficiency (PCE) of 19.0%. The reproducibility of these findings is confirmed by consistent results across different laboratories. Furthermore, integration with a narrow-band-gap perovskite yields an all-perovskite tandem device with a PCE of 27.2%. This comprehensive understanding of the pivotal role of spacer cations in surface treatment significantly advances the pathway toward efficient perovskite photovoltaics.

Formamidinium (FA)-based perovskites exhibit significant potential for highly efficient photovoltaics due to their promising optoelectronic properties and optimal bandgap. However, the undesired inactive phase arises from multiple crystal nucleation pathways formed by various intermediate phases during the film formation process, persistently accompanying it. FA-based perovskites frequently struggle to form uniform, highly crystalline films. This challenge complicates the development of reliable and highly reproducible crystallization processes for perovskites and the establishment of guidelines for controlling the alpha-phase formation. In this work, we investigate the role of poly(acrylonitril-co-methyl acrylate) (PAM) to simultaneously control nucleation and subsequent alpha-phase crystallization. This successfully demonstrates the regulation of oriented crystal growth through the creation of a PAM-PbI2 intermediate. Ultimately, PAM-modified p-i-n architecture devices obtain a promising power conversion efficiency (PCE) of 25.30%, with V-OC (1.211 V), achieving 95% of the detailed balance limit. Additionally, PAM-modified devices maintain >= 90% of the initial efficiency for 1000 h under 1 sun and 65 degrees C operation.

Most interface materials for organic solar cells (OSCs) were originally optimized for fullerene-based systems and are now being adapted for non-fullerene acceptor (NFA) based solar cells. This reliance on established interface materials results in a limited choice of interface materials for NFA based OSCs. For vacuum processed organic devices, the concept of doped interface materials is exceptionally successful, but has not yet been translated to modern NFA based devices due to solution processing constraints requiring orthogonal solubility. Herein, we report a novel concept for the development of solution-processed HTL in inverted n-i-p architecture OSCs using doped organic nanoparticles (D-NPs), overcoming solvent compatibility limitations and enabling scalable pro-duction processes. We demonstrate that the functional key interface properties of D-NPs HTLs can be tailored independently over a wide regime. Specifically, conductivity and work function can be optimized separately by varying the dopant concentration and the material system. By using D-NPs as HTL in the n-i-p architecture, power conversion efficiencies (PCE) of over 12 % are achieved for PM6:Y6 based devices. The D-NPs HTL concept is successfully applied to a variety of organic semiconductors used in photovoltaics and opens a new class of tailorable interface materials for solution-processed HTL materials.

Crystalline organic semiconducting thin films from the benchmark molecule C8-BTBT-C8 were obtained using physical vapor deposition and various solution-based methods. Utilizing atomic force microscopy and X-ray spectromicroscopy, we illustrate the influence of the underlying growth mechanism and determine the highly preparation-dependent orientation of the thiophene backbone. We observe a continuous trend for crystalline C8-BTBT-C8 thin film domains to extend into the square millimeter-range under near-equilibrium growth conditions. For such well-defined systems, electron diffraction tomography allows us to precisely determine the unit cell directly after film deposition and to reveal an 8° molecular tilt angle with respect to the surface normal. This finding is in almost perfect accordance with the values derived from near-edge X-ray absorption fine structure linear dichroism. Within this work, we shine a light on both the successes and challenges connected to the realization of potent, thiophene-based semiconducting films, paving the way toward square centimeter-sized ultrathin organic crystals and their application in organic circuitry.

Lead-Tin perovskite solar cells (Pb/Sn PSCs) are limited by the intrinsic instability of Sn(II), which tends to oxidize forming Sn vacancies in perovskite films. Herein, a Lewis base beta-guanidinopropionic acid (GUA) and hydrazinium iodide (HAI) are introduced to effectively passivate the perovskite bulk and surface, respectively. The synergistic approach leads to Pb/Sn PSCs with a promising power conversion efficiency of 20.5% owing to the significantly reduced nonradiative recombination and voltage losses. As a result, the V-OC x FF product of PSCs is significantly improved, which is among the highest values documented in the literature, being favorable for perovskite-based tandem applications. Additionally, the strategy demonstrated in this work could also improve the stability of PSCs by enhancing the chemical robustness of the perovskite layer. These results emphasize the significance of bulk and surface passivation in the development of efficient and stable PSCs based on Pb/Sn perovskites.

Two-dimensionally (2D) extended thin films of p-type organic semiconductor C13-BTBT (BTBT = [1]benzothieno[3,2-b]-[1]benzothiophene) were fabricated via self-controlled growth at the liquid-liquid interface. Depicting a compound class originally developed for further functionalization and subsequent realization of self-assembled monolayers (SAMs), the potent BTBT core unit commonly excels in high-quality structure formation as well as charge-transport characteristics. Utilizing a manifold spectromicroscopic toolbox, we observe extraordinarily crystalline C13-BTBT films with an upright standing configuration of the backbone unit accounting for superior intermolecular orbital overlap. The well-defined morphology and internal structure of the film are being underpinned by charge-transport parameters that are in the range of comparable organic electronic devices based on bisubstituted BTBT films from the same processing technique. The inherently favorable membrane-like bilayer molecular arrangement is confirmed by unambiguous representation of the unit cell as derived from electron tomography.

Many European sculptures and altarpieces from the Middle Ages were decorated with Zwischgold, a bilayer metal leaf with an ultra-thin gold face backed by silver. Zwischgold corrodes quickly when exposed to air, causing the surface of the artefact to darken and lose gloss. The conservation of such Zwischgold applied artefacts has been an obstinate problem. We have acquired quantitative, 3D nanoscale images of Zwischgold samples from 15th century artefacts and modern materials using ptychographic X-ray computed tomography (PXCT), a recently developed coherent diffractive imaging technique, to investigate the leaf structure and chemical state of Zwischgold. The measurements clearly demonstrate decreasing density (increasing porosity) of the leaf materials and their corrosion products, as well as delamination of the leaves from their substrate. Each of these effects speak to typically observed issues in the conservation of such Zwischgold applied artefacts. Further, a rare variant of Zwischgold that contains extremely thin multiple gold layers and an overlapping phenomenon of Zwischgold with other metal leaves are observed through PXCT. As supportive data, scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray analysis (EDX) were performed on the medieval samples.

The excellent craftsmanship of ancient Oriental and Central Asian textile dyers is already demonstrated in the remarkable brilliance and fastness of the colours of the so-called Pazyryk carpet, the by far oldest pile carpet found to date. This specimen resembles the advanced craftsmanship of Iron Age Central Asian textile production. We have employed synchrotron-based µ -XRF imaging to detect the distribution of metal organic pigments within individual fibres of the Pazyryk carpet (about 2500 years old) and compare the results to wool fibres, which we prepared according to traditional Anatolian dyeing recipes. We observe congruent pigment distribution within specimens from the Pazyryk carpet and natural wool fibres that we have fermented prior to dyeing. Therefore, we conclude that the superior fermentation technique has been utilized about 2000 years earlier than known so far.

Photodynamic inactivation (PDI) of pathogenic bacteria is a promising technology in different applications. Thereby, a photosensitizer (PS) absorbs visible light and transfers the energy to oxygen yielding reactive oxygen species (ROS). The produced ROS are then capable of killing microorganisms via oxidative damage of cellular constituents. Among other PS, some flavins are capable of producing ROS and cationic flavins are already successfully applied in PDI. When PDI is used for example on tap water, PS like flavins will encounter various ions and other small organic molecules which might hamper the efficacy of PDI. Thus, the impact of carbonate and phosphate ions on PDI using two different cationic flavins (FLASH-02a, FLASH-06a) was investigated using Staphylococcus aureus and Pseudomonas aeruginosa as model organisms. Both were inactivated in vitro at a low light exposure of 0.72 J cm - 2 . Upon irradiation, FLASH-02a reacts to single substances in the presence of carbonate or phosphate, whereas the photochemical reaction for FLASH-06a was more unspecific. DPBF-assays indicated that carbonate and phosphate ions decreased the generation of singlet oxygen of both flavins. Both microorganisms could be easily inactivated by at least one PS with up to 6 log 10 steps of cell counts in low ion concentrations. Using the constant radiation exposure of 0.72 J cm -2 , the inactivation efficacy decreased somewhat at medium ion concentrations but reached almost zero for high ion concentrations. Depending on the application of PDI, the presence of carbonate and phosphate ions is unavoidable. Only upon light irradiation such ions may attack the PS molecule and reduce the efficacy of PDI. Our results indicate concentrations for carbonate and phosphate, in which PDI can still lead to efficient reduction of bacterial cells when using flavin based PS.

The availability of intense soft x-ray beams with tunable energy and polarization has pushed the development of highly sensitive, element-specific, and noninvasive microscopy techniques to investigate condensed matter with high spatial and temporal resolution. The short wavelengths of soft x-rays promise to reach spatial resolutions in the deep single-digit nanometer regime, providing unprecedented access to magnetic phenomena at fundamental length scales. Despite considerable efforts in soft x-ray microscopy techniques, a two-dimensional resolution of 10 nm has not yet been surpassed in direct imaging. Here, we report on a significant step beyond this long-standing limit by combining newly developed soft x-ray Fresnel zone plate lenses with advanced precision in scanning control and careful optical design. With this approach, we achieve an image resolution of 7 nm. By combining this highly precise microscopy technique with the x-ray magnetic circular dichroism effect, we reveal dimensionality effects in an ensemble of interacting magnetic nanoparticles. Such effects are topical in current nanomagnetism research and highlight the opportunities of high-resolution soft x-ray microscopy in magnetism research and beyond.

The top-down lithographic fabrication of functional metal oxide nanostructures enables technologically important applications such as catalysis and electronics. Here, we report the use of molecular vanadium oxides, polyoxovanadates, as molecular precursors for electron beam lithography to obtain functional vanadium oxide nanostructures. The new resist class described gives access to nanostructures with minimum dimensions close to 10 nm. The lithographically prepared structures exhibit temperature-dependent switching behaviour of their electrical resistivity. The work could lay the foundation for accessing functional vanadium oxide nanostructures in the sub-10-nm domain using industrially established nanolithographic methods.

X-ray tomography has become an indispensable tool for studying complex 3D interior structures with high spatial resolution. Three-dimensional imaging using soft X-rays offers powerful contrast mechanisms but has seen limited success with tomography due to the restrictions imposed by the much lower energy of the probe beam. The generalized geometry of laminography, characterized by a tilted axis of rotation, provides nm-scale 3D resolution for the investigation of extended (mm range) but thin (μm to nm) samples that are well suited to soft X-ray studies. This work reports on the implementation of soft X-ray laminography (SoXL) at the scanning transmission X-ray spectromicroscope of the PolLux beamline at the Swiss Light Source, Paul Scherrer Institut, which enables 3D imaging of extended specimens from 270 to 1500 eV. Soft X-ray imaging provides contrast mechanisms for both chemical sensitivity to molecular bonds and oxidation states and magnetic dichroism due to the much stronger attenuation of X-rays in this energy range. The presented examples of applications range from functionalized nanomaterials to biological photonic crystals and sophisticated nanoscaled magnetic domain patterns, thus illustrating the wide fields of research that can benefit from SoXL.

Focused soft X-ray beam induced deposition (FXBID) is a novel technique for direct-write nanofabrication of metallic nanostructures from metal organic precursor gases. It combines the established concepts of focused electron beam induced processing (FEBIP) and X-ray lithography (XRL). The present setup is based on a scanning transmission X-ray microscope (STXM) equipped with a gas flow cell to provide metal organic precursor molecules towards the intended deposition zone. Fundamentals of X-ray microscopy instrumentation and X-ray radiation chemistry relevant for FXBID development are presented in a comprehensive form. Recently published proof-of-concept studies on initial experiments on FXBID nanolithography are reviewed for an overview on current progress and proposed advances of nanofabrication performance. Potential applications and advantages of FXBID are discussed with respect to competing electron/ion based techniques.

Focal stack (FS) is an effective technique for fast 3D imaging in high-resolution scanning transmission X-ray microscopy. Its crucial issue is to assign each object within the sample to the correct position along the optical axis according to a proper focus measure. There is probably information loss with previous algorithms for FS reconstruction because the old algorithms can only detect one focused object along each optical-axial pixel line (OAPL). In this study, we present an improved FS algorithm, which utilizes an elaborately calculated threshold for normalized local variances to extract multiple focused objects in each OAPL. Simulation and experimental results show its feasibility and high efficiency for 3D imaging of high contrast, sparse samples. It is expected that our advanced approach has potential applications in 3D X-ray microscopy for more complex samples.

Journal Article 7 nm Spatial Resolution in Soft X-ray Microscopy Get access Benedikt Rösner, Benedikt Rösner Paul Scherrer Institut, 5232 Villigen PSI, Switzerland Benedikt Rösner, benedikt.roesner@psi.ch Search for other works by this author on: Oxford Academic Google Scholar Frieder Koch, Frieder Koch Paul Scherrer Institut, 5232 Villigen PSI, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Florian Döring, Florian Döring Paul Scherrer Institut, 5232 Villigen PSI, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Vitaliy A Guzenko, Vitaliy A Guzenko Paul Scherrer Institut, 5232 Villigen PSI, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Markus Meyer, Markus Meyer Department Chemistry and Pharmacy, FAU Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany Search for other works by this author on: Oxford Academic Google Scholar Joshua L Ornelas, Joshua L Ornelas Department Chemistry and Pharmacy, FAU Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany Search for other works by this author on: Oxford Academic Google Scholar Andreas Späth, Andreas Späth Department Chemistry and Pharmacy, FAU Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany Search for other works by this author on: Oxford Academic Google Scholar Rainer H Fink, Rainer H Fink Department Chemistry and Pharmacy, FAU Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany Search for other works by this author on: Oxford Academic Google Scholar Stefan Stanescu, Stefan Stanescu Synchrotron SOLEIL, L’ormes des Merisiers, Saint Aubin BP-48, 91192, Gif-Sur-Yvette Cedex, France Search for other works by this author on: Oxford Academic Google Scholar Sufal Swaraj, Sufal Swaraj Synchrotron SOLEIL, L’ormes des Merisiers, Saint Aubin BP-48, 91192, Gif-Sur-Yvette Cedex, France Search for other works by this author on: Oxford Academic Google Scholar ... Show more Rachid Belkhou, Rachid Belkhou Synchrotron SOLEIL, L’ormes des Merisiers, Saint Aubin BP-48, 91192, Gif-Sur-Yvette Cedex, France Search for other works by this author on: Oxford Academic Google Scholar Benjamin Watts, Benjamin Watts Paul Scherrer Institut, 5232 Villigen PSI, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Jörg Raabe, Jörg Raabe Paul Scherrer Institut, 5232 Villigen PSI, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Christian David Christian David Paul Scherrer Institut, 5232 Villigen PSI, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 24, Issue S2, 1 August 2018, Pages 270–271, https://doi.org/10.1017/S1431927618013697 Published: 10 August 2018

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