A compromise between high power conversion efficiency and long-term stability of hybrid organic-inorganic metal halide perovskite solar cells is necessary for their outdoor photovoltaic application and commercialization. Herein, a method to improve the stability of perovskite solar cells under water and moisture exposure consisting of the encapsulation of the cell with an ultrathin plasma polymer is reported. The deposition of the polymer is carried out at room temperature by the remote plasma vacuum deposition of adamantane powder. This encapsulation method does not affect the photovoltaic performance of the tested devices and is virtually compatible with any device configuration independent of the chemical composition. After 30 days under ambient conditions with a relative humidity (RH) in the range of 35-60%, the absorbance of encapsulated perovskite films remains practically unaltered. The deterioration in the photovoltaic performance of the corresponding encapsulated devices also becomes significantly delayed with respect to devices without encapsulation when vented continuously with very humid air (RH > 85%). More impressively, when encapsulated solar devices were immersed in liquid water, the photovoltaic performance was not affected at least within the first 60 s. In fact, it has been possible to measure the power conversion efficiency of encapsulated devices under operation in water. The proposed method opens up a new promising strategy to develop stable photovoltaic and photocatalytic perovskite devices.

Figure 2 . SEM images of the hybrid systems as labeled: a,b) deposited on Ag/Si(100) substrates; c-f) on a SiO 2 nanocolumnar fi lm; g,h) on PDMS. Color photograph in i) was taken for the hybrid system PtOEP/TiO 2 (meso) deposited on the fl exible PDMS substrate. This image is characterized by the intense red coloration of the PtOEP NWs.

Mesoporous tetragonal RE:YPO4 nanophosphors (RE = Eu, Ce, Tb, and Ce + Tb) with a lenticular morphology, narrow size distribution, and high surface area have been prepared by an homogeneous precipitation procedure consisting of aging, at low temperature (80–120 °C) in a microwave oven, ethylene glycol solutions containing only yttrium acetylacetonate and phosphoric acid. This synthesis method involves important advantages such as its simplicity, rapidness (reaction time = 7 min), and high reaction yields. The mechanism of nanoparticle growth has been also addressed finding that the lenticular nanoparticles are formed through an ordered aggregation of smaller entities, which explains their porosity. In all cases, the doping levels were systematically varied in order to optimize the nanophosphors luminescence. All optimum nanophosphors presented a high luminescence quantum yield (QY). In particular, for the Eu and Tb doped systems, the obtained QY values (60% for Eu and 80% for Tb) were the highest so far reported for this kind of nanomaterial. The morphological, microstructural, and luminescent properties of these nanophosphors and their dispersibility in water make them suitable for biomedical applications.

This work reports about the preparation of plasma polymerized thin films of perylene with thicknesses ∼30−150 nm and their characterization by different methods and the analysis of their optical properties. Highly absorbent and fluorescent films have been obtained by this method that combines the sublimation of the perylene molecules and their controlled polymerization by the interaction with remote Ar plasma. The polymeric films are very flat with a root mean square (rms) roughness in the range 0.3−0.4 nm. In contrast with the sublimated layers of perylene that present a high scattering of light, the polymerized films depict the well-defined absorption bands in the region 400−450 nm and fluorescence spectra of the perylene molecule at ∼475 nm. The films are formed by a matrix formed by cross-linked fragments of perylene and intact molecules that confer the observed optical properties to this material. The optical and microstructural characteristics of this type of thin films and the possibility to perform their deposition by using lithographic procedures make them suitable for their integration into photonic components for various applications. A preliminary study of the use of these films as an optical sensor of NO2 is also presented.

The Mexican 3x1 Program for Migrants is a matching fund scheme that seeks to direct the money sent by hometown associations abroad (collective remittances) to productive uses. The federal, state and municipal governments contribute to the program multiplying by three the contributions sent by migrants abroad. Using municipal level data on program participation for the period 2002-2006, we evaluate the program's capacity to target the poorest municipalities. Since migration has a nonlinear relationship with poverty and marginality, a program that unconditionally responds to project initiatives from migrant organizations is bound to be regressive due to self-selection bias. Indeed, poorer municipalities are less likely to participate and they also receive lower amounts and fewer projects than relatively richer localities. Moreover, we find evidence of a partisan bias: states and municipalities ruled by the PAN are significantly more likely to participate in the program, and electoral support for the PAN is associated with more funds or projects awarded. We argue that substantial changes should be implemented for the program to be a truly progressive poverty reduction tool.Please do not cite without authors' permission.

A new kind of visible‐blind organic thin‐film material, consisting of a polymeric matrix with a high concentration of embedded 3‐hydroxyflavone (3HF) dye molecules, that absorbs UV light and emits green light is presented. The thin films can be grown on sensitive substrates, including flexible polymers and paper. Their suitability as photonic active components photonic devices is demonstrated.

Colored and fluorescent thin films are prepared via polymerization of dye molecules by interaction with a remote plasma of Ar while they are sublimated on a substrate. The films are formed by a crosslinked matrix of fragments of the original dye and some unreacted molecules. Films made of Ethyl Red or Rhodamine 6G dyes are characterized and studied with regard to their optical properties. Plasma characterization by optical emission spectroscopy (OES) shows the fragmentation of the evaporated dye molecules by interaction of the dye molecules with the electrons of the plasma. The electron energy seems to be the main parameter controlling the polymerization degree of the films. The process is very interesting for the deposition of thin films containing functional molecules.

Luminescent organic-thin-films transparent in the visible region have been synthetized by a plasma assisted vacuum deposition method. The films have been developed for their implementation in photonic devices and for UV detection. They consist in a plasma polymeric matrix that incorporates 3-hydroxyflavone molecules characterized by absorbing UV radiation and emitting green light. The present work studies in detail the properties and synthesis of this kind of transparent and luminescent materials. The samples have been characterized by X-ray photoemission (XPS), infrared (FT-IR) and secondary ion mass (ToF-SIMS) spectroscopies; and their optical properties analysed by UV-Vis absorption, fluorescence and ellipsometry (VASE) spectroscopies. The key factors controlling the optical and luminescent properties of the films are also discussed. Indeed, our experimental results show how the optical properties of the films can be adjusted for their integration in photonic devices. Moreover, time resolved and steady state fluorescence analyses, including quantum yield determination, indicate that the fluorescence efficiency is a function of the deposition parameters. An outstanding property of these materials is that, even for high UV absorption values (i.e. large layer thickness and/or dye concentration), the emitted light is not reabsorbed by the film. Such a highly UV absorbent and green emitting films can be used as UV photodetectors with a detection threshold smaller than 10 μW cm -2 , a value similar to the limit of some commercial UV photodetectors. Based on these properties, it is also proposed the use of the films as visual tags for the detection of solar UV irradiation.