X-ray photon detection is important for a wide range of applications. The highest demand, however, comes from medical imaging, which requires cost-effective, high-resolution detectors operating at low-photon flux, therefore stimulating the search for novel materials and new approaches. Recently, hybrid halide perovskite CH3NH3PbI3 (MAPbI3) has attracted considerable attention due to its advantageous optoelectronic properties and low fabrication costs. The presence of heavy atoms, providing a high scattering cross-section for photons, makes this material a perfect candidate for X-ray detection. Despite the already-successful demonstrations of efficiency in detection, its integration into standard microelectronics fabrication processes is still pending. Here, we demonstrate a promising method for building X-ray detector units by 3D aerosol jet printing with a record sensitivity of 2.2 × 108 μC Gyair-1 cm-2 when detecting 8 keV photons at dose rates below 1 μGy/s (detection limit 0.12 μGy/s), a 4-fold improvement on the best-in-class devices. An introduction of MAPbI3-based detection into medical imaging would significantly reduce health hazards related to the strongly ionizing X-rays' photons.

We characterize the opto-mechanical properties of double-layer mechanical devices. These closely spaced photonic crystal membranes can exhibit photonic bound states in the continuum, which could enable the realization of a strongly coupled, integrated op-tomechanical system.

We fabricated and characterized suspended bi-layered photonic crystal slabs in AlGaAs heterostructures. Our approach allows to create integrated, closely spaced membranes, which can exhibit photonic bound states in the continuum to increase light-matter interaction.

The mechanical response of individual titanate nanowires (H2Ti3O7), synthesized in an upscaled production (kg/month) was investigated by means of an Atomic Force Microscope (AFM) in nanomechanical spectroscopic mode. Because of their layered structure, besides the Young's modulus (E) of 66.7 +/- 25 GPa, an important contribution to the mechanical response was identified as coming from the low shear modulus (G) of 1.5 +/- 0.8 GPa between the layers. The mechanical energy loss due to shear is at the origin of the material's fatigue, during which the individual titanate layers crack gradually, until the final failure of the structure. The high-temperature treatment at 800 degrees C transforms the material into anatase (TiO2) nanowires, which have a considerably higher elastic modulus.

The performance of organic-inorganic metal halide perovskites-based (MHPs) photovoltaic devices critically depends on the design and material properties of the interface between the light-harvesting MHP layer and the electron transport layer (ETL). Therefore, the detailed insight into the transfer mechanisms of photogenerated carriers at the ETL/MHP interface is of utmost importance. Owing to its high charge mobilities and well-matched band structure with MHPs, titanium dioxide (TiO2) has emerged as the most widely used ETL material in MHPs-based photovoltaic devices. Here, we report a contactless method to directly track the photo-carriers at the ETL/MHP interface using the technique of low-temperature electron paramagnetic resonance (EPR) in combination with in situ illuminations (Photo-EPR). Specifically, we focus on a model nanohybrid material consisting of TiO2-based nanowires (TiO(2)NWs) dispersed in the polycrystalline methylammonium lead triiodide (MAPbI(3)) matrix. Our approach is based on observation of the light-induced decrease in intensity of the EPR signal of paramagnetic Ti3+ ( S = 1 / 2 ) in non-stoichiometric TiO(2)NWs. We associate the diminishment of the EPR signal with the photo-excited electrons that cross the ETL/MHP interface and contribute to the conversion of Ti3+ states to EPR-silent Ti2+ states. Overall, we infer that the technique of low-temperature Photo-EPR is an effective strategy to study the transfer mechanisms of photogenerated carriers at the ETL/MHP interface in MAPbI(3)-based photovoltaic and photoelectronic systems.

Because of their excellent photoelectric properties, organic-inorganic metal halide perovskites (MHPs), such as methylammonium lead triiodide, CH3NH3PbI3 (MAPbI(3)), and methylammonium lead tribromide, CH3NH3PbBr3 (MAPbBr(3)), are of great interest for the emerging MHPs-based photovoltaic technology. Despite extensive research efforts focused on physicochemical aspects of both MAPbI(3) and MAPbBr(3), the impact of environmental extremes, including various gaseous media, on their photo-electric properties remains poorly understood. In this context, here, the MHPs-based gas-sensing elements were grown by one-step solution process on the outer surface of cylindrical in shape quartz substrates with diameters varying in the range of 80-1100 mu m. The elongated cylinder-shaped geometry and high surface-to-volume ratios of the thus-prepared deposits revealed advantageous for designing miniature, light-transparent gas-flow chambers and made it possible to investigate the photoluminescence (PL) and photocurrent (PC) responses of both MHPs exposed to the precisely controlled recurrent flow of either O-2 or N-2. In addition, we could also collect the PL responses for the deposits of MAPbI(3 )and MAPbBr(3), positioned side-by-side close to each other and therefore simultaneously exposed to identical environmental conditions. Specifically, we found that under exposure to O-2 the PL responses of MAPbI(3) and MAPbBr(3 )were markedly opposite; i.e., the PL decreased for MAPbI(3), whereas it increased for MAPbBr(3). In contrast, under the exposure to N-2, the PL of MAPbI(3 )increased, while it decreased for MAPbBr(3). A considerably differential behavior was also found for the PC responses. In particular, under recurrent exposures to both gaseous media, the PL and PC responses of MAPbBr(3) correlated, whereas for MAPbI(3) they anticorrelated. In conclusion, the distinctly opposite PL and PC responses of polycrystalline deposits of MAPbI(3) and MAPbBr(3 )to O-2 and N-2 reported herein point to markedly contrasting properties of the surface carrier traps and defects for these two MHPs. This study also evidences that a side-by-side arrangement of elongated cylindrically shaped substrates coated with two different MHPs, due to their differential responses to exposure to O-2 or N-2, can function as a simple differential gas detector.

The photovoltaic perovskite, methylammonium lead triiodide [CH3NH3PbI3 (MAPbI3)], is one of the most efficient materials for solar energy conversion. Various kinds of chemical and physical modifications have been applied to MAPbI3 towards better understanding of the relation between composition, structure, electronic properties and energy conversion efficiency of this material. Pressure is a particularly useful tool, as it can substantially reduce the interatomic spacing in this relatively soft material and cause significant modifications to the electronic structure. Application of high pressure induces changes in the crystal symmetry up to a threshold level above which it leads to amorphization. Here, a detailed structural study of MAPbI3 at high hydrostatic pressures using Ne and Ar as pressure transmitting media is reported. Single-crystal X-ray diffraction experiments with synchrotron radiation at room temperature in the 0-20 GPa pressure range show that atoms of both gaseous media, Ne and Ar, are gradually incorporated into MAPbI3, thus leading to marked structural changes of the material. Specifically, Ne stabilizes the high-pressure phase of NexMAPbI3 and prevents amorphization up to 20 GPa. After releasing the pressure, the crystal has the composition of Ne0.97MAPbI3, which remains stable under ambient conditions. In contrast, above 2.4 GPa, Ar accelerates an irreversible amorphization. The distinct impacts of Ne and Ar are attributed to differences in their chemical reactivity under pressure inside the restricted space between the PbI6 octahedra.

Optoelectronic devices and solar cells based on organometallic hybrid perovskites have to operate over a broad temperature range, which may contain their structural phase transitions. For instance, the temperature of 330 K, associated with the tetragonal–cubic transformation, may be crossed every day during the operation of solar cells. Therefore, the analysis of thermal cycling effects on structural and electronic properties is of significant importance. This issue is addressed in the case of methylammonium lead iodide (CH 3 NH 3 PbI 3 ) across both structural phase transitions (at 160 and 330 K). In situ synchrotron radiation X‐ray diffraction (XRD) data recorded between 140 and 180 K show the emergence of a boundary phase between the orthorhombic and tetragonal phases, which becomes more abundant with successive thermal cycles. At high temperatures, around 330 K, an incommensurately modulated tetragonal phase is formed upon repeated crossings of the phase boundary between tetragonal and cubic phases. These alterations, which indicate a gradual evolution of the material under operating conditions of photovoltaic devices, are further documented by electrical resistivity and heat capacity measurements.

We report the synthesis and crystal structure of an organic-inorganic compound, ethylenediammonium lead iodide, NH3CH2CH2NH3PbI4. Synchrotron-based single crystal X-ray diffraction experiments revealed that the pristine and thermally treated crystals differ in the organic cation behaviour, which is characterized by a partial disorder in the thermally treated crystal. Based on current-voltage measurements, increased disorder of the organic cation is associated with enhanced photoconductivity. This compound could be a potential candidate for interface engineering in lead halide perovskite-based optoelectronic devices.

Organic-inorganic metal halide perovskites have recently attracted increasing attention as highly efficient light harvesting materials for photovoltaic applications. However, the precise control of crystallization and morphology of organometallic perovskites deposited from solution, considered crucial for enhancing the final photovoltaic performance, remains challenging. In this context, here, we report on growing microcrystalline deposits of CH3NH3PbI3 (MAPbI3), by one-step solution casting on cylinde-shaped quartz substrates (rods). We show that the substrate curvature has a strong influence on morphology of the obtained polycrystalline deposits of MAPbI3. Although the crystalline width and length markedly decreased for substrates with higher curvatures, the photoluminescence (PL) spectral peak positions did not significantly evolve for MAPbI3 deposits on substrates with different diameters. The crystalline size reduction and denser coverage of microcrystalline MAPbI3 deposits on cylinder-shaped substrates with higher curvatures were attributed to two major contributions, both related to the annealing step of the MAPbI3 deposits. In particular, the diameter-dependent variability of the heat capacities and the substrate curvature-enhanced solvent evaporation rate seemed to contribute the most to the crystallization process and the resulting morphology changes of MAPbI3 deposits on cylinder-shaped quartz substrates with various diameters. The longitudinal geometry of cylinder-shaped substrates provided also a facile solution for checking the PL response of the deposits of MAPbI3 exposed to the flow of various gaseous media, such as oxygen, nitrogen and argon. Overall, the approach reported herein inspires novel, cylinder-shaped geometries of MAPbI3 deposits, which can find applications in low-cost photo-optical devices, including gas sensors.

We discuss the known construction of two interacting superconducting circuits based on Josephson junctions, which can be precisely engineered and easily controlled. In particular, we use the parametric excitation of two circuits realized by an instant change of the qubit coupling to study entropic and information properties of the density matrix of a composite system. We obtain the density matrix from the initial thermal state and perform its analysis in the approximation of small perturbation parameter and sufficiently low temperature. We also check the subadditivity condition for this system both for the von Neumann entropy and deformed entropies and check the dependence of mutual information on the system temperature. Finally, we discuss the applicability of this approach to describe the two coupled superconducting qubits as harmonic oscillators with limited Hilbert space.

We verify the new entropic and information inequalities for noncomposite systems using an experimental 5×5 density matrix of the qudit state measured by the tomographic method in a multilevel superconducting circuit. These inequalities are well known for bipartite and tripartite systems but have never been tested for superconducting qudits. Entropic inequalities can also be used to evaluate the accuracy of experimental data and the value of mutual information deduced from them and characterize correlations between different degrees of freedom in a noncomposite system.