Organic-inorganic metal-halide perovskites (e.g. CH3NH3PbI3-xClx) emerged as a promising opto-electronic material. However, the Shockley-Queisser Limit for the power conversion efficiency (PCE) of perovskite-based photovoltaic devices has still not been reached, which was attributed to non-radiative recombination pathways, as suggested by photoluminescence (PL) inactive (or dark) areas on perovskite films. Although these observations have been related to the presence of ions/defects, the underlying fundamental physics and detailed microscopic processes, concerning trap/defect status, ion migration, etc., still remain poorly understood. Here we utilize correlated wide-field PL microscopy and impedance spectroscopy (IS) on perovskite films to in-situ investigate both the spatial and temporal evolution of these PL inactive areas under external electrical fields. We attribute the formation of PL inactive domains to the migration and accumulation of iodine ions under external fields.Hence we are able to characterize the kinetic processes and determine the drift velocities of these ions. In addition, we show that I2 vapor directly affects the PL quenching of a perovskite film, which provides evidence that the migration/segregation of iodide ions plays an important role in the PL quenching and consequently limits the PCE of organometal halide based perovskite photovoltaic devices.

Inorganic-organic halide organometal perovskites have demonstrated very promising performance for opto-electronic applications, such as solar cells, light-emitting diodes, lasers, single-photon sources, etc. However, the little knowledge on the underlying photophysics, especially on a microscopic scale, hampers the further improvement of devices based on this material. In this communication, correlated conventional photoluminescence (PL) characterization and wide-field PL imaging as a function of time are employed to investigate the spatially-and temporally-resolved PL in CH 3 NH 3 PbI 3−x Cl x perovskite films. Along with a continuous increase of the PL intensity during light soaking, we also observe PL blinking or PL intermittency behavior in individual grains of these films. Combined with significant suppression of PL blinking in perovskite films coated with a phenyl-C61-butyric acid methyl ester (PCBM) layer, it suggests that this PL intermittency is attributed to Auger recombination induced by photoionized defects/traps or mobile ions within grains. These defects/traps are detrimental for light conversion and can be effectively passivated by the PCBM layer. This finding paves the way to provide a guideline on the further improvement of perovskite opto-electronic devices.

Organolead halide perovskite solar cells (PSCs) have generated extensive attention recently with power conversion efficiency (PCE) exceeding 23%. However, these PSCs exhibit photoinduced instability in the course of their current-voltage measurements. In this work, we study the light-induced behavior in CH3NH3PbI3−xClx films in situ, by employing wide-field photoluminescence (PL) microscopy to obtain both the spatially and temporally resolved PL images simultaneously. Along with the increase in the PL intensity under continuous illumination, some areas render PL inactive. By characterizing the excitation energy dependent long-time PL decay behavior, we suggest that the PL quenching can be ascribed to a localized accumulation of iodide ions driven by the optical field. This ion localization leads to an enhancement of non-radiative recombination. The appearance of the PL inactive areas in the perovskite film impedes its photovoltaic device performance approaching the theoretical maximum PCE. Therefore, the herein presented real-time investigation of the light soaking of perovskite films is a versatile and adaptable method providing more details to improve the performance of PSCs.

Game theory is a well established branch of mathematics whose formalism has a vast range of applications from the social sciences, biology, to economics. Motivated by quantum information science, there has been a leap in the formulation of novel game strategies that lead to new (quantum Nash) equilibrium points whereby players in some classical games are always outperformed if sharing and processing joint information ruled by the laws of quantum physics is allowed. We show that, for a bipartite non zero-sum game, input local quantum correlations, and separable states in particular, suffice to achieve an advantage over any strategy that uses classical resources, thus dispensing with quantum nonlocality, entanglement, or even discord between the players’ input states. This highlights the remarkable key role played by pure quantum coherence at powering some protocols. Finally, we propose an experiment that uses separable states and basic photon interferometry to demonstrate the locally-correlated quantum advantage.

Push-Pull functional compounds consisting of dicyanorhodanine derivatives have attracted a lot of interest because their optical, electronic, and charge transport properties make them useful as building blocks for organic photovoltaic implementations.The analysis of the frontier molecular orbitals shows that the vertical transitions of electronic absorption are characterized as intramolecular charge transfer; furthermore, we show that the analyzed compounds exhibit bathochromic displacements when comparing the presence (or absence) of solvent as an interacting medium. In comparison with materials defined by their energy of reorganization of electrons (holes) as electron (hole) transporters, we find a transport hierarchy whereby the molecule (Z)-2-((1,1-Dicyanomethylene)-5-(4-dimethylamino)benzylidene)-1,3-thiazol-4 is better at transporting holes than molecule (Z)-2-((1,1-Dicyanomethylene)-5-(tetrathiafulvalene-2-ylidene)-1,3-thiazol-4.

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Emergent technologies that make use of novel materials and quantum properties of light states are at the forefront in the race for the physical implementation, encoding and transmission of information. Photonic crystals (PCs) enter this paradigm with optical materials that allow the control of light propagation and can be used for optical communication, and photonics and electronics integration, making use of materials ranging from semiconductors, to metals, metamaterials, and topological insulators, to mention but a few. Here, we show how designer superconductor materials integrated into PCs fabrication allow for an extraordinary reduction of electromagnetic waves damping, making possible their optimal propagation and tuning through the structure, below critical superconductor temperature. We experimentally demonstrate, for the first time, a successful integration of ferroelectric and superconductor materials into a one-dimensional (1D) PC composed of (BTO/YBCO) N /STO bilayers that work in the whole visible spectrum, and below (and above) critical superconductor temperature T C = 80 K. Theoretical calculations support, for different number of bilayers N, the effectiveness of the produced 1D PCs and may pave the way for novel optoelectronics integration and information processing in the visible spectrum, while preserving their electric and optical properties. The use of electromagnetic (EM) waves as information carriers for communication systems has been in place for many years 1,2 ; as such, EM wavelengths make possible the transmission over large distances but, at the same time, they limit the amount of information they can convey by their frequency: the larger the carrier frequency, the larger the available transmission bandwidth and thus the information-carrying capacity of the communication system 3. For this reason, quantum artificial nanostructured materials such as photonic crystals that are able to transmit at high frequencies and that concentrate the available power within the transmitted electromagnetic wave, thus giving an improved system performance, are desired 4. PCs are artificial periodic structures characterised by a periodic variation of the refractive index with a consequent periodic spatial variation of the dielectric constant, which may be tailored to control light properties 4. They, therefore, allow the appearance of defined frequency ranges and address the issue of forbidden/allowed propagation of electromagnetic waves. As a consequence, the control and tunability of PCs opens a new perspective for information processing and technological

The study of vegetable tissue is essential in plant growth analysis. The elasticity is an important characteristic when firmness is studied in fruits or when turgidity is tested in plant leaves. This property gives information about the ripeness of fruits, the water content in leaves, and, in general, the morphological and physiological state of plants. Hence, the propagation of elastic waves in these media is a useful tool that gives information about the developmental stage of the plant. In this sense, laser ultrasonics is a promising method in the characterization of composite materials. In a certain way, vegetable tissues can be thought of as a kind of biological composite abstracted as a stratified plate of several layers. In this work, as a first approximation, we propose a methodology to generate guided waves in vegetable tissues by using laser ultrasonics techniques. We implement a pulsed laser system to induce ultrasonic waves without damage on the samples. Besides, we develop a methodology for processing the propagated acoustic waves. This analysis allows us the assessment of dispersive properties, a useful tool when determining important descriptors such as firmness index, water content, and provide useful information to feed biophysical models, among others.