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Hybrid vapor deposition is one of the most appealing processes for perovskite photovoltaics fabrication, thanks to its versatile nature. By using sequentially different vapor deposition processes tailored to the inorganic and organic perovskite precursors' peculiarities, this type of process gives access to the full potential of vapor deposition. While vapor deposition of metal halides is well understood and mastered, vapor deposition of organohalide species is much more delicate (degradation of vapors, high vapor pressure, setup‐specific constraints). Here, a novel close space sublimation system is reported and in‐depth insights on the conversion into perovskite of a metal halide template are provided. In this evolution of the process, the substrate coated with metal halide template and the organohalide source are loaded together in a dedicated holder, then transferred into a vacuum chamber on a heating element already at temperature setpoint. The system enables a simple, fast, low‐cost, and easy‐to‐reproduce organohalide vapor deposition process. The formation of the perovskite in situ and identification different conversion regimes are studied. Furthermore, the influence of the chemical environment and chamber design on the process are discussed. Compositional tuning and additive engineering in the process are processed and fabricate proof of concept photovoltaic devices reaching high fill factors of 80% and 17% power conversion efficiency for a bandgap of 1.63 eV. [ABSTRACT FROM AUTHOR]

The incorporation of large organic ammonium ions renders the crystallization dynamics and layer formation process of halide perovskites complex, difficult to control, and leads to problems of suppressed charge transport with the formation of tiny‐sized grains. In this paper, the use of methylammonium chloride (MACl) and an excess of PbI2 is introduced as a co‐additives in the precursor solution for the control of phenylmethylammonium or benzylammonium (PMA+ spacer) and formamidinium (FA+)‐based quasi‐2D PMA2FAn−1PbnI3n+1 (n = 5) perovskite layers formation. By this method, the morphology of the layer, the inner phase distribution, and the charge transport properties are improved. By employing glow discharge‐optical emission spectroscopy (GD‐OES) and other techniques, it is revealed that the quasi‐2D perovskites prepared in the presence of co‐additives exhibit uniform removal dynamics of the solvent across the film. Furthermore, the grain growth mode, upon thermal annealing, is lateral. It results in large, monolithic grains with low‐trap state density and excellent substrate coverage. Particularly, co‐additives improve the cations dispersion upon the crystallization process, thus suppressing the low‐n phase formed through the aggregation of spacer cations and accelerating the formation of the high‐n phase. [ABSTRACT FROM AUTHOR]

The transition metal dichalcogenides have been studied for various applications in electronics, sensing, or spintronics. Molybdenum ditelluride, MoTe2, occurs in 3 crystal systems: hexagonal (2H), monoclinic (1T′), and orthorhombic (Td). Here we report on tellurisation of Mo and MoO3 thin films to 2H-MoTe2 and 1T′-MoTe2 thin layers on sapphire substrates, respectively. To study the phases, we employed diffraction patterns using grazing-incidence wide-angle X-ray scattering, conventional X-ray diffraction and transmission electron microscopy (TEM). Measurements of pole figures confirmed the presence of a biaxial texture of both 1T′ and 2H phases. In the hexagonal phase, we found two ensembles of biaxially oriented crystallites offset by 30 degrees between the two groups. On the other hand, in the monoclinic layer, the crystallites follow the six-fold symmetry of the (0001) sapphire surface. [ABSTRACT FROM AUTHOR]

The development of an efficient fabrication route to achieve high‐resolution perovskite pixel array is key for large‐scale flexible image sensor devices. Herein, a high‐resolution and stable 10 × 10 flexible PDs array based on formamidinium(FA+) and phenylmethylammonium (PMA+) quasi‐2D (PMA)2FAPb2I7 (n = 2) perovskite is demonstrated by developing SiO2‐assisted hydrophobic and hydrophilic treatment process on polyethylene terephthalate substrate. By introducing Au nanoparticles (Au NPs), the perovskite film quality is improved and grain boundaries are reduced. The mechanism by which Au NPs upgrade the photoelectric quality of perovskite is mainly revealed by glow discharge‐optical emission spectroscopy (GD‐OES) and grazing‐incidence wide‐angle X‐ray scattering (GIWAXS). To further improve the photoelectric performance of the devices, a post‐treatment strategy with formamidinium chloride (FACl) is used. The optimized flexible PDs arrays show excellent optoelectronic properties with a high responsivity of 4.7 A W−1, a detectivity of 6.3 × 1012 Jones, and a broad spectral sensitivity. The device also exhibits excellent electrical stability even under severe bending and excellent flexural strength, as well as excellent environmental stability. Finally, the integrated flexible PDs arrays are used as sensor pixels in an imaging system to obtain high‐resolution imaging patterns, demonstrating the imaging capability of the PDs arrays. [ABSTRACT FROM AUTHOR]

Textured silicon wafers used in silicon solar cell manufacturing offer superior light trapping, which is a critical enabler for high‐performance photovoltaics. A similar optical benefit can be obtained in monolithic perovskite/silicon tandem solar cells, enhancing the current output of the silicon bottom cell. Yet, such complex silicon surfaces may affect the structural and optoelectronic properties of the overlying perovskite films. Here, through extensive characterization based on optical and microstructural spectroscopy, it is found that the main effect of such substrate morphology lies in an altering of the photoluminescence response of the perovskite, which is associated with thickness variations of the perovskite, rather than lattice strain or compositional changes. With this understanding, the design of high‐performance perovskite/silicon tandems is rationalized, yielding certified power conversion efficiencies of >28%. [ABSTRACT FROM AUTHOR]

The few-layer transition metal dichalcogenides (TMD) are an attractive class of materials due to their unique and tunable electronic, optical, and chemical properties, controlled by the layer number, crystal orientation, grain size, and morphology. One of the most commonly used methods for synthesizing the few-layer TMD materials is the chemical vapor deposition (CVD) technique. Therefore, it is crucial to develop in situ inspection techniques to observe the growth of the few-layer TMD materials directly in the CVD chamber environment. We demonstrate such an in situ observation on the growth of the vertically aligned few-layer MoS2 in a one-zone CVD chamber using a laboratory table-top grazing-incidence wide-angle X-ray scattering (GIWAXS) setup. The advantages of using a microfocus X-ray source with focusing Montel optics and a single-photon counting 2D X-ray detector are discussed. Due to the position-sensitive 2D X-ray detector, the orientation of MoS2 layers can be easily distinguished. The performance of the GIWAXS setup is further improved by suppressing the background scattering using a guarding slit, an appropriately placed beamstop, and He gas in the CVD reactor. The layer growth can be monitored by tracking the width of the MoS2 diffraction peak in real time. The temporal evolution of the crystallization kinetics can be satisfactorily described by the Avrami model, employing the normalized diffraction peak area. In this way, the activation energy of the particular chemical reaction occurring in the CVD chamber can be determined. [ABSTRACT FROM AUTHOR]

A perovskite solar cell (PSC) featuring a mesoporous architecture can facilitate perovskite layer formation over a large area via increasing the number of heterogeneous nucleation sites. The morphology of the electron transport layer (ETL) and its interface with the perovskite layer is one of the key factors to boost the performance of a PSC. Tin dioxide (SnO2) is considered as a promising ETL in PSCs owing to its high carrier mobility, good transmittance, deep conduction band level, and efficient photoelectron extraction. Generally, the mesoporous SnO2 (m-SnO2) ETL has a higher surface-to-volume ratio compared to a compact SnO2 layer. Herein, we report on an m-SnO2 ETL prepared by anodizing a metallic tin film on a fluorine-doped tin oxide (FTO) substrate in NaOH solution under an ambient atmosphere. In particular, we developed a bilayer architecture of the m-SnO2 ETL based on the fabrication of two consecutive m-SnO2 layers. The morphology of each layer was controlled by varying the anodization voltage and time at a constant solution concentration during the growth process. This unique approach enabled the deposition of an m-SnO2 ETL with sufficient coverage of the FTO substrate, which is difficult to achieve with a single layer of m-SnO2. In particular, the scanning electron and atomic force microscopy analyses confirmed that the m-SnO2 layer covers completely the FTO substrate. The device fabricated with this bilayer m-SnO2 ETL achieved a 27% improvement in power conversion efficiency compared to that with a single layer of m-SnO2. [ABSTRACT FROM AUTHOR]

Perovskite solar cells are well‐known for their high energy conversion efficiency, low‐temperature processing, and cost‐effective production. Flash infrared annealing (FIRA) of slot‐die cast perovskite precursors offers an attractive manufacturing route using high‐throughput roll‐to‐roll technology. Despite the recent progress in FIRA perovskite annealing, the optimal composition of the perovskite precursor is yet to be developed. Here, the effect of methylammonium chloride (MACl) on the perovskite structure and trap‐state density as a function of the FIRA annealing time is investigated. In situ real‐time grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) is employed to monitor the perovskite layer formation during FIRA annealing with millisecond temporal resolution. In addition, the density of states in the bandgap is estimated using ex situ energy‐resolved electrochemical impedance spectroscopy. Evidence is found that adding 10% MACl into the perovskite precursor solution significantly improves the crystallographic orientation of the perovskite layers while reducing the trap‐state density by one order of magnitude. In addition, using time‐resolved GIWAXS, the most favorable time window for the FIRA processing of perovskite films with the lowest mosaicity and trap‐state density is identified. The results are of general importance for elucidating the appropriate temporal windows in complex and fast‐evolving crystallization processes. [ABSTRACT FROM AUTHOR]

Few-layer films of transition metal dichalcogenides have emerged as promising candidates for applications in electronics. Within this group of 2D materials, platinum diselenide (PtSe2) was predicted to be a compound with one of the highest charge carrier mobility. Recently, the successful integration of group III–V nitride semiconductors with NbNx-based superconductors was reported with a semiconductor transistor grown directly on a crystalline superconductor. This opens up the possibility of combining the macroscopic quantum effects of superconductors with the electronic, photonic, and piezoelectric properties of the semiconducting material. Here, we report on the fabrication of a few-layer PtSe2 film on top of an NbN substrate layer by selenization of pre-deposited 3 nm thick Pt layers. We found the selenization parameters preserving the chemical and structural integrity of both the PtSe2 and NbN films. The PtSe2 film alignment can be tuned by varying the nitrogen flow rate through the reaction chamber. The superconducting critical temperature of NbN is only slightly reduced in the optimized samples compared to pristine NbN. The carrier mobility in PtSe2 layers determined from Hall measurements is below 1 cm2/V s. [ABSTRACT FROM AUTHOR]

2D hybrid organic–inorganic perovskites are valued in optoelectronic applications for their tunable bandgap and excellent moisture and irradiation stability. These properties stem from both the chemical composition and crystallinity of the layer formed. Defects in the lattice, impurities, and crystal grain boundaries generally introduce trap states and surface energy pinning, limiting the ultimate performance of the perovskite; hence, an in‐depth understanding of the crystallization process is indispensable. Here, a kinetic and thermodynamic study of 2D perovskite layer crystallization on transparent conductive substrates are provided—fluorine‐doped tin oxide and graphene. Due to markedly different surface structure and chemistry, the two substrates interact differently with the perovskite layer. A time‐resolved grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) is used to monitor the crystallization on the two substrates. Molecular dynamics simulations are employed to explain the experimental data and to rationalize the perovskite layer formation. The findings assist substrate selection based on the required film morphology, revealing the structural dynamics during the crystallization process, thus helping to tackle the technological challenges of structure formation of 2D perovskites for optoelectronic devices. [ABSTRACT FROM AUTHOR]

An x-ray phase tomographic microscope has been developed by optimizing the optical system for 9-keV synchrotron x rays at BL37XU, SPring-8, Japan. The system consists of a full-field x-ray imaging microscope and a Talbot interferometer. In contrast with our previous system, a Fresnel zone plate for the microscope objective and transmission gratings of the interferometer was designed to improve the refraction sensitivity, with a larger field of view and a higher spatial resolution, utilizing a 28-m space available at BL37XU. An x-ray phase tomographic microscope with a field of view of 375 µm and a spatial resolution of 560 nm was thus constructed, even with a considerably low x-ray dosage. By applying this tomographic microscope to auditory bone specimens of young mice, it was shown that soft tissues in addition to bone tissue could be observed simultaneously without serious radiation damage. [ABSTRACT FROM AUTHOR]

An original diffraction model for the evaluation of the grazing-incidence small-angle X-ray scattering (GISAXS) of the three-dimensional (3D) supported self-assembled nanoparticle crystals is presented. The model utilizes the formalism of traditional crystallography that is applied to nanoparticles as scattering entities. The infinite paracrystal concept was adopted in order to include cumulative disorder that is typical for the self-assembled nanoparticle structures. Azimuthal averaging around a chosen crystallographic direction allows incorporation of texture effects. A transformation of the SAXS paracrystal equations to comply with the GISAXS geometry was employed to describe the scattering process in the limit of the kinematical approximation which facilitates calculations. The model was developed for the face-centered cubic (FCC) symmetry, however, its extension to any other cubic symmetry is straightforward. The model was tested on a 3D nanoparticle assembly formed on silicon from a dried drop-cast colloidal solution of monodisperse silver nanoparticles of 5.8 ± 0.6 nm diameter. Presence of the FCC nanoparticle crystal with the [111] texture along the substrate normal was evidenced from evaluation of the synchrotron GISAXS data. The degree of paracrystal disorder is 2.5% and 3.6% parallel and perpendicular to the substrate, respectively, suggesting the anisotropic character of the self-assembling process. A SAXS measurement of the nanoparticle crystal formed from the same solution in a capillary revealed a randomly oriented FCC structure with a slightly larger paracrystal disorder of 4%. Obviously, different conditions of the nanoparticle crystal formation affect its azimuthal and translational disorder. [ABSTRACT FROM AUTHOR]

The 2D transition metal dichalcogenides attract high research interest due to their electronic properties, and MoS2 is likely the most explored compound of this group. The fabrication of MoS2 thin films by the sulfurization of predeposited MoO3 layers on a c‐plane sapphire substrate by radio frequency magnetron sputtering from stoichiometric MoO3 target is reported. The structure and properties of as‐grown MoO3 and MoS2 layers are characterized by several methods including X‐ray diffraction, grazing‐incidence wide‐angle X‐ray scattering, photoelectron spectroscopy, Raman spectroscopy, and atomic force microscopy. Furthermore, the influence of the crystallographic structure of MoO3 layers on the final MoS2 films is studied. The influence of the crystallographic structure of MoO3 on the resulting MoS2 films is focused. A strong texturation in the c‐axis direction and an indication of a high degree in‐plane orientation of MoS2 thin films on the c‐sapphire substrate is observed. [ABSTRACT FROM AUTHOR]

At present, the power conversion efficiency of single-junction perovskite-based solar cells reaches over 26%. The further efficiency increase of perovskite-based optoelectronic devices is limited mainly by defects, causing the nonradiative recombination of charge carriers. To improve efficiency and ensure reproducible fabrication of high-quality layers, it is crucial to understand the perovskite nucleation and growth mechanism along with associated process control to reduce the defect density. In this study, we investigate the growth kinetics of a promising narrow bandgap perovskite, formamidinium methylammonium lead iodide (FAMAPbI 3 ), for high-performance single-junction solar cells. The temporal evolution of structural and optoelectronic properties during FAMAPbI 3 vacuum codeposition was inspected in real time by grazing-incidence wide-angle X-ray scattering and photoluminescence. Such a combination of analytical techniques unravels the evolution of intrinsic defect density and layer morphology correlated with lattice strain from the early stages of the perovskite deposition.

Molybdenum disulfide (MoS 2 ) few-layer films have gained considerable attention for their possible applications in electronics and optics and also as a promising material for energy conversion and storage. Intercalating alkali metals, such as lithium, offers the opportunity to engineer the electronic properties of MoS 2 . However, the influence of lithium on the growth of MoS 2 layers has not been fully explored. Here, we have studied how lithium affects the structural and optical properties of the MoS 2 few-layer films prepared using a new method based on one-zone sulfurization with Li 2 S as a source of lithium. This method enables incorporation of Li into octahedral and tetrahedral sites of the already prepared MoS 2 films or during MoS 2 formation. Our results discover an important effect of lithium promoting the epitaxial growth and horizontal alignment of the films. Moreover, we have observed a vertical-to-horizontal reorientation in vertically aligned MoS 2 films upon lithiation. The measurements show long-term stability and preserved chemical composition of the horizontally aligned Li-doped MoS 2 ., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Few-layer MoS 2 films are promising candidates for applications in numerous areas, such as photovoltaics, photocatalysis, nanotribology, lithium batteries, hydro-desulfurization catalysis and dry lubricants, especially due to their distinctive electronic, optical, and catalytic properties. In general, two alignments of MoS 2 layers are possible - the horizontal and the vertical one, having different physicochemical properties. Layers of both orientations are conventionally fabricated by a sulfurization of pre-deposited Mo films. So far, the Mo thickness was considered as a critical parameter influencing the final orientation of MoS 2 layers with horizontally and vertically aligned MoS 2 grown from thin (1 nm) and thick (3 nm) Mo films, respectively. Here, we present a fabrication protocol enabling the growth of horizontally or vertically aligned few-layer MoS 2 films utilizing the same Mo thickness of 3 nm. We show that the sulfur vapor is another parameter influencing the growth mechanism, where a sulfurization with higher sulfur vapor pressure leads to vertical MoS 2 layers and slow sulfur evaporation results in horizontally aligned layers for a thicker Mo starting layer., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Few-layer MoS 2 films stay at the forefront of current research of two-dimensional materials. At present, continuous MoS 2 films are prepared by chemical vapor deposition (CVD) techniques. Herein, we present a cost-effective fabrication of the large-area spatially uniform films of few-layer MoS 2 flakes using a modified Langmuir-Schaefer technique. The compression of the liquid-phase exfoliated MoS 2 flakes on the water subphase was used to form a continuous layer, which was subsequently transferred onto a submerged substrate by removing the subphase. After vacuum annealing, the electrical sheet resistance dropped to a level of 10 kΩ/sq, being highly competitive with that of CVD-deposited MoS 2 nanosheet films. In addition, a consistent fabrication protocol of the large-area conductive MoS 2 films was established. The morphology and electrical properties predetermine these films to advanced detecting, sensing, and catalytic applications. A large number of experimental techniques were used to characterize the exfoliated few-layer MoS 2 flakes and to elucidate the formation of the few-layer MoS 2 Langmuir film.

Solvent annealing is an efficient way of phase separation in polymer-fullerene blends to optimize bulk heterojunction morphology of active layer in polymer solar cells. To track the process in real time across all relevant stages of solvent evaporation, laboratory-based in situ small- and wide-angle X-ray scattering measurements were applied simultaneously to a model P3HT:PCBM blend dissolved in dichlorobenzene. The PCBM molecule agglomeration starts at ∼7 wt % concentration of solid content of the blend in solvent. Although PCBM agglomeration is slowed-down at ∼10 wt % of solid content, the rate constant of phase separation is not changed, suggesting agglomeration and reordering of P3HT molecular chains. Having the longest duration, this stage most affects BHJ morphology. Phase separation is accelerated rapidly at concentration of ∼25 wt %, having the same rate constant as the growth of P3HT crystals. P3HT crystallization is driving force for phase separation at final stages before a complete solvent evaporation, having no visible temporal overlap with PCBM agglomeration. For the first time, such a study was done in laboratory demonstrating potential of the latest generation table-top high-brilliance X-ray source as a viable alternative before more sophisticated X-ray scattering experiments at synchrotron facilities are performed.

We report on an in-situ observation of the colloidal silver nanoparticle self-assembly into a close-packed monolayer at the air/water interface followed by a 2D to 3D transition. Using the fast tracking GISAXS technique, we were able to observe the immediate response to the compression of the self-assembled nanoparticle layer at the air/water interface and to identify all relevant intermediate stages including those far from the equilibrium. In particular, a new nonequilibrium phase before the monolayer collapse via the 2D to 3D transition was found that is inaccessible by the competing direct space imaging techniques such as the scanning and transmission electron microscopies due to the high water vapor pressure and surface tension.

Real-time reassembly of an ordered nanoparticle monolayer due to UV-photolysis of the surfactant shell of nanoparticles was observed. The technique of grazing-incidence small-angle X-ray scattering provided the possibility to track in situ the nanoparticle pair correlation function of the sample processed in a UV-ozone reactor. The analysis revealed a total shift of approximately 1 nm of the nanoparticle nearest-neighbor distance. The temporal evolution of the interparticle distance proved to be the first-order process governed by the UV-photolysis and described by a single-exponential decay function. The nanoparticles tend to agglomerate into a labyrinth-like structure with a typical length scale of some 30 nm.