On performance of thin-film meso-structured perovskite solar cell through experimental analysis and device simulation

In the last few years there is an unprecedented progress in the increase of the power conversion efficiency of perovskite solar cells. Evidently, further advances of the efficiency of these devices will depend on the constraints imposed by the optical and electronic properties of their constituents. Quite apparently that during the manufacturing process of a solar cell, there is an inevitable variation in the thicknesses of various functional layers, which affects the optoelectronic characteristics of the final sample. In this work a possible strategy of the analysis of the solar cell performance is suggested, based on statistically averaging procedure of experimental data. We present a case study, in which the optoelectronic properties of the meso-structured perovskite solar cell (with a mesoporous TiO$_2$ layer) are analysed within the method providing a deeper understanding of the device operation. This method enables an assessment of the overall quality of the device, pointing pathways towards the maximum efficiency design of a perovskite solar cell by material properties tuning.Comment: 13 pages, 10 figure

Stability and degradation of organic photovoltaics fabricated, aged, and characterized by the ISOS 3 inter-laboratory collaboration

Trabajo presentado como comunicación al "XIII Organic Photovoltaics" celebrado del 14 al 16 de Agosto del 2012 en San Diego (USA).-- et al.Seven distinct sets (n > 12) of state of the art organic photovoltaic devices were prepared by leading research laboratories in a collaboration planned at the Third International Summit on Organic Photovoltaic Stability (ISOS-3). All devices were shipped to DTU and characterized simultaneously up to 1830 h in accordance with established ISOS-3 protocols under three distinct illumination conditions: accelerated full sun simulation; low level indoor fluorescent lighting; and dark storage with daily measurement under full sun simulation. Three nominally identical devices were used in each experiment both to provide an assessment of the homogeneity of the samples and to distribute samples for a variety of post soaking analytical measurements at six distinct laboratories enabling comparison at various stages in the degradation of the devices. Characterization includes current-voltage curves, light beam induced current (LBIC) imaging, dark lock-in thermography (DLIT), photoluminescence (PL), electroluminescence (EL), in situ incident photon-to-electron conversion efficiency (IPCE), time of flight secondary ion mass spectrometry (TOF-SIMS), cross sectional electron microscopy (SEM), UV visible spectroscopy, fluorescence microscopy, and atomic force microscopy (AFM). Over 100 devices with more than 300 cells were used in the study. We present here design of the device sets, results both on individual devices and uniformity of device sets from the wide range of characterization methods applied at different stages of aging under the three illumination conditions. We will discuss how these data can help elucidate the degradation mechanisms as well as the benefits and challenges associated with the unprecedented size of the collaboration.Peer Reviewe

Materiales híbridos moleculares orgánicos-inorgánicos: síntesis y aplicación como electrodos en baterías recargables de litio

A novel family of molecular hybrid materials based on electroactive inorganic species dispersed in conducting organic polymers is reported as electrodes for energy storage or conversion. Polyaniline and polypyrrole are effectively doped with electroactive polyoxometalates ([PMo12O40]3-) or ferricyanide ([(FeCN)6]3-) anions as the only doping species. The high charge and size of these anions prevents their deintercalation during reduction in most cases. The synthesis of these hybrids can be made by chemical (bulk powders) and electrochemical (films) methods. For [PMo12O40]3-, nine aniline/pyrrole rings by anion are found in each case and the anion stays in the polymer matrix even after reduction at -0.4V (vs Ag/AgCl, 2.6V vs Li). In the case of Polypyrrole-FeCN6 hybrid the pyrrole-ring/Fe(CN)6 ratio was around 10-12 depending on the temperature of synthesis. Temperature also affects the electrical conductivity, with the best values around 60Scm-1 (sample prepared at 0ºC). Fe(CN)6 stays in the polymer matrix when the hybrid material is reduced in organic media. PMo12 hybrids intercalate up to 5.3 h+ during discharge (52 Ah/Kg) whereas the hybrid with Fe(CN)6 intercalates 2.7 lithium ions per formula unit (69Ah/Kg).<br><br>Se describe la síntesis y aplicación como electrodos para el almacenamiento o conversión de energía de materiales híbridos basados en la dispersión de especies inorgánicas electroactivas en el seno de polímeros orgánicos conductores. Polianilina y polipirrol son dopados con polioxometalatos electroactivos ([PMo12O40]3-) o aniones ferricianuro ([(FeCN)6]3-) como únicas especies dopantes. La elevada carga y tamaño de estos aniones evitan, en la mayoría de los casos, su desintercalación durante la reducción. Estos híbridos se han sintetizado por métodos químicos y electroquímicos, siendo la relación anillos de anilina o de pirrol por anión de [PMo12O40]3- de nueve, de manera que el anión permanece en el interior de la matriz polimérica incluso después de reducir el material a -0.4V (vs Ag/AgCl, 2.6V vs Li). En el caso del híbrido Polipirrol/Fe(CN)6 la relación anillos de pirrol/anión oscila entre 10 y 12 dependiendo de la temperatura de síntesis. La temperatura también afecta a su conductividad eléctrica, oscilando los valores más elevados alrededor de 60 Scm-1 (preparado a 0ºC). El anión permanece en el interior de la matriz polimérica cuando se reduce en medio orgánico. Los híbridos con PMo12 pueden intercalar hasta 5.3 Li+ durante la descarga (52Ah/Kg). El híbrido con Fe(CN)6 intercala 2.7 iones litio por fórmula unidad (69Ah/Kg)

Enhancement of TiO2 nanoparticle properties and efficiency of dye-sensitized solar cells using modifiers

A low-temperature hydrothermal process developed to synthesizes titania nanoparticles with controlled size. We investigate the effects of modifier substances, urea, on surface chemistry of titania (TiO2) nanopowder and its applications in dye-sensitized solar cells (DSSCs). Treating the nanoparticles with a modifier solution changes its morphology, which allows the TiO2 nanoparticles to exhibit properties that differ from untreated TiO2 nanoparticles. The obtained TiO2 nanoparticle electrodes characterized by XRD, SEM, TEM/HRTEM, UV–VIS Spectroscopy and FTIR. Experimental results indicate that the effect of bulk traps and the surface states within the TiO2 nanoparticle films using modifiers enhances the efficiency in DSSCs. Under 100-mW cm−2 simulated sunlight, the titania nanoparticles DSSC showed solar energy conversion efficiency = 4.6 %, with Voc = 0.74 V, Jsc = 9.7324 mA cm−2, and fill factor = 71.35

Littérature et politique en Somalie

Hawshan waxay muujinaysa in daraasaadka suugaanta soomaaliyeed loo adeegsado baaritaanka astamo saadaalinaya dagaalka sokeeye iyo burburka Soomaaliya.Questo lavoro suggerisce lo studio della letteratura somala come mezzo per indagare sui segni premonitori della guerra civile e della distruzione della Somalia.This work suggests the study of Somali literature as a means to find the signs the were forerunners of the civil war and the destruction of Somalia

Metal oxides in photovoltaics: All-oxide, ferroic and perovskite solar cells

Semiconductor oxides have been applied in photovoltaic technologies for many years. The remarkable versatility of their properties and the feasibility to be fabricated by simple, low-cost and easily scalable fabrication methods confers oxides a unique place in next generation photovoltaics (NGPVs). Their outstanding ability to preserve or improve device characteristics, even as a noncrystalline (amorphous) material, allows their application in flexible and semitransparent PVs devices and printed electronics. Basic (doped and undoped) semiconductor oxides have demonstrated to provide enhanced lifetime stability to state-of-the-art PVs such as Organic (OPV) and halide perovskite solar cells (PSCs), which is a significant step toward NGPVs industrialization and commercialization. But semiconductor oxides, in their more complex form, can also provide properties like magnetism, ferroelectricity, or pyroelectricity (among others), that collectively with the most classical materials, can deliver novel and innovative features. This chapter documents the most recent results observed when semiconductor oxides are applied in different NGPVs technologies. The chapter covers technologies like all-oxide solar cells where the oxide is not only part of the device but also acts as the main light harvesting material. The chapter also describes the application of oxides as part of OPV and PSCs where semiconductor oxides are mostly applied as barrier layers eliminating the use of expensive and unstable organic semiconductors, enhancing device lifetime.A.P.T. acknowledges Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) under contract ENE2015-74275-JIN. To the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grant SEV-2013-0295 for the predoctoral contract to A.M; for the grant ENE2013-48816-C5-4-R, ENE2016-79282-C5-2-R and the Nanoselect Excelence Network MAT2015-68994-REDC. To the Agència de Gestiód'Ajuts Universitaris i de Recerca for the support to the consolidated Catalonia research group 2014SGR-1212 and the Xarxa de Referència en Materials Avançats per a l'Energia (Xarmae). To the COST Action StableNextSol project MP1307.Peer Reviewe