Enhancing charge extraction in inverted perovskite solar cells contacts via ultrathin graphene:fullerene composite interlayers.

Improving the perovskite/electron-transporting layer (ETL) interface is a crucial task to boost the performance of perovskite solar cells (PSCs). This is utterly fundamental in an inverted (p-i-n) configuration using fullerene-based ETLs. Here, we propose a scalable strategy to improve fullerene-based ETLs by incorporating high-quality few-layer graphene flakes (GFs), industrially produced through wet-jet milling exfoliation of graphite, into phenyl-C61-butyric acid methyl ester (PCBM). Our new composite ETL (GF:PCBM) can be processed into an ultrathin (∼10 nm), pinhole-free film atop the perovskite. We find that the presence of GFs in the PCBM matrix reduces defect-mediated recombination, while creating preferential paths for the extraction of electrons towards the current collector. The use of our GF-based composite ETL resulted in a significant enhancement in the open circuit voltage and fill factor of triple cation-based inverted PSCs, boosting the power conversion efficiency from ∼19% up to 20.8% upon the incorporation of GFs into the ETL.

A fluorescent sensor to detect lead leakage from perovskite solar cells.

Hybrid perovskites have been considered a hot material in the semiconductor industry; included as an active layer in advanced devices, from light emitting applications to solar cells, where they lead as a new strategic solution, they promise to be the next generation high impact class of materials. However, the presence - in most cases - of lead in their matrix, or lead byproducts as a consequence of material degradation, such as PbI2, is currently hindering their massive deployment. Here, we develop a fluorescent organic sensor (FS) based on the Pb-selective BODIPY fluorophore that emits when the analyte - lead in this case - is detected. We carried out a fluorimetric analysis to quantify the trace concentration of Pb2+ released from lead-based perovskite solar cells, exploring different material compositions. In particular, we immersed the devices in rainwater, to simulate the behavior of the devices under atmospheric conditions when the sealing is damaged. The sensor is studied in a phosphate buffer solution (PBS) at pH 4.5 to simulate the pH of acidic rain, and the results obtained are compared with ICP-OES measurements. We found that with fluorometric analysis, lead concentration could be calculated with a detection limit as low as 5 µg l-1, in agreement with ICP-OES analysis. In addition, we investigated the possibility of using the sensor on a solid substrate for direct visualization to determine the presence of Pb. This can constitute the base for the development of a Pb-based label that can switch on if lead is detected, alerting any possible leakage.

Ferroelectricity in Hybrid Perovskites.

Ferroelectric ceramics such as PbZrxTi1-xO3 (PZT) are widely applied in many fields, from medical to aerospace, because of their dielectric, piezoelectric, and pyroelectric properties. In the past few years, hybrid organic-inorganic halide perovskites have gradually attracted attention for their optical and electronic properties, including ferroelectricity, and for their low fabrication costs. In this Review, we first describe techniques that are used to quantify ferroelectric figures of merit of a material. We then discuss ferroelectricity in hybrid perovskites, starting from controversies in methylammonium iodoplumbate perovskites and then focusing on low-dimensional perovskites that offer an unambiguous platform to obtain ferroelectricity. Finally, we provide examples of the application of perovskite ferroelectrics in solar cells, LEDs, and X-ray detectors. We conclude that the vast structure-property tunability makes low-dimensional hybrid perovskites promising, but they have yet to offer ferroelectric figures of merit (e.g., saturated polarization) and thermal stability (e.g., Curie temperature) competitive with those of conventional oxide perovskite ferroelectric materials.

A step beyond in steady-state and time-resolved electro-optical spectroscopy: Demonstration of a customized simple, compact, low-cost, fiber-based interferometer system.

Electro-optical spectroscopy is nowadays a routine approach for the analysis of light induced properties and dynamical processes in matter, whose understanding is particularly crucial for the intelligent design of novel synthetic materials and the engineering and optimization of high-impact optoelectronic devices. Currently, within this field, it is the common choice to rely on multiple commercial setups, often costly and complex, which can rarely combine multiple functions at the same time with the required sensitivity, resolution, and spectral tunability (in both excitation and detection). Here, we present an innovative, compact, and low-cost system based on "three in one" components for the simultaneous electro-optical material and device characterization. It relies on compact fiber-coupled Fourier transform spectroscopy, the core of the system, enabling a fast spectral analysis to acquire simultaneously wavelength and time resolved photoluminescence (PL) maps (as a function of the time and wavelength), PL quantum yield, and electroluminescence signal. Our system bypasses conventional ones, proposing a new solution for a compact, low-cost, and user-friendly tool, while maintaining high levels of resolution and sensitivity.

Manipulating Color Emission in 2D Hybrid Perovskites by Fine Tuning Halide Segregation: A Transparent Green Emitter.

Halide perovskite materials offer an ideal playground for easily tuning their color and, accordingly, the spectral range of their emitted light. In contrast to common procedures, this work demonstrates that halide substitution in Ruddlesden-Popper perovskites not only progressively modulates the bandgap, but it can also be a powerful tool to control the nanoscale phase segregation-by adjusting the halide ratio and therefore the spatial distribution of recombination centers. As a result, thin films of chloride-rich perovskite are engineered-which appear transparent to the human eye-with controlled tunable emission in the green. This is due to a rational halide substitution with iodide or bromide leading to a spatial distribution of phases where the minor component is responsible for the tunable emission, as identified by combined hyperspectral photoluminescence imaging and elemental mapping. This work paves the way for the next generation of highly tunable transparent emissive materials, which can be used as light-emitting pixels in advanced and low-cost optoelectronics.

Tumor desmoide intra-abdominal como recidiva de tumor desmoide de pared abdominal: a propósito de un caso / Intra-abdominal desmoid tumor how relapse of desmoid tumor of abdominal wall: purpose of a case

Se presenta el caso de un paciente masculino de 25 años con diagnóstico por biopsia, de Tumor Desmoide (TD) de pared abdominal, a quien se le practicó excerresis con resección amplia de la lesión en 1995, reingresando en marzo de 1996 con diagnóstico de Tu. Desmoide recidivante intraabdominal, motivo por el cual se practica laparotomia exploradora, encontrándose Tu. Intraabdominal de 30 cm de diámetro, infiltrando asas delgadas, Colon retroperitoneo y grandes vasos