Préparation de couche poreuse de TiO2 par moulage de billes de polymères pour des applications dans des cellules solaires à base de perovskites

The perovskite based solar cells is a new generation solar cell type, the perovskite crystals act as photo-charge-generating materials with organic and inorganic elements more commonly referred to as "halide hybrid perovskite" (ABX3 with A the organic part, B the inorganic part and X an halogen). In addition, they are low-cost materials that are easy to develop, which is a major advantage for this type of cell. There are different types of perovskite-based solar cells (PSC) with different designs. This work focuses on the so-called "monolithic" PSC configuration, which is composed of different porous layers; including TiO2 deposited from commercial pastes by "screen-printing" technique into perovskite crystals infiltrate. In this cell graphite (p type) is used as cathode while FTO (Fluorine Tin Oxide, n type) on glass is used as anode. The aim is to obtain a TiO2 layer with a higher porous volume with respect to the one done commercially, so the quantity of photo-active materials that infiltrates it can be increased and in this sense higher efficiency could be reached. Indeed, up to 9% has been obtained for the optimized cells with the new configuration of porous TiO2 layer obtained by bead molding in comparison with a 6% for reference cells (commercially produced porous layer).Les cellules solaires à base de pérovskite sont considérées comme cellules de nouvelles génération, les cristaux de pérovskite jouent le rôle de matériaux photo-générateurs de charges avec des éléments organiques et inorganiques plus communément appelés « perovskite hybride halogéné » (ABX3 avec avec A la partie organique, B la partie inorganique et X un halogène). De plus, ce sont des matériaux à faible coût et simple à élaborer ce qui présente un avantage majeur pour ce genre de cellule. Il existe différents types de cellules à base perovskite (PSC) avec différentes architectures. Ce travail porte plus particulièrement sur la configuration de PSC dite « monolithique » qui est composée de différentes couches poreuses, dont le TiO2 déposé à partir de pâtes commerciales par « screen-printing » dans lesquelles s’infiltrent les cristaux de perovskite. Dans cette cellule le graphite (type p) est utilisé comme cathode tandis que le FTO (Fluorine Tin Oxide, type n) sur verre est utilisé comme anode. Le but est d’obtenir une couche TiO2 avec un volume poreux plus important par rapport à celui réalisé par voie commerciale, afin d’augmenter la quantité de matériaux photo-actifs qui s’y infiltre et d’atteindre ainsi un rendement supérieur. En effet, jusqu’à 9% a été obtenu pour les cellules optimisées avec la nouvelle configuration de couche poreuse de TiO2 obtenue par moulage de billes contre 6% pour les cellules références (couche poreuse élaboré par voie commerciale)

LACUNARY STATISTICAL CONVERGENCE OF COMPLEX UNCERTAIN SEQUENCE

This study introduces the concepts of lacunary statistical convergence of complex uncertain sequences: lacunary statistical convergence almost surely (S..a.s.), lacunary statistical convergence in measure, lacunary statistical convergence in mean, lacunary statistical convergence in distribution and lacunary statistically convergence uniformly almost surely (S-theta. u.a.s). In addition, decomposition theorems and relationships among them are discussed

ROUGH Delta I-2-STATISTICAL CONVERGENCE OF DOUBLE SEQUENCES IN NORMED LINEAR SPACES

In this paper, we introduce rough Delta I-2-statistical convergence as an extension of rough convergence. We define the set of rough Delta I-2-statistical limit points of a sequence and analyze the results with proofs

Time domain (TD)-NMR relaxometry as a tool to investigate the cell integrity of tomato seeds exposed to osmotic stress (OS), ultrasonication (US) and high hydrostatic pressure (HHP)

NMR relaxometry was used to investigate the proton relaxation distribution of the tomato seeds and analyze the damages of the three different processes on the cell membrane integrity of the tomato seed. Tomato seeds were subjected to osmotic stress (OS) (10, 20, 30% NaCl solutions), ultrasonication (US) (5, 10 and 20 min) and high hydrostatic pressure (HHP) (300, 400 and 500 MPa for 15 min at 20 degrees C). Four peaks were observed in the NMR relaxation spectra of tomato seeds due to multiexponential relation behavior of the plant cell. Each peak corresponds to different water proton compartment within the cell. According to the results, all the three treatments resulted in cell permeabilization and disruption of cellular compartmentalization. Among the treatments, HHP at 500 MPa for 15 min at 20 degrees C resulted in the most detrimental effect in the cell structure and OS treatment with 10% NaCl solution caused the least changes in the cell structure. In order to further analyze the extent of damage to the cell, tomato seeds exposed to OS, US and HHP were also analyzed by scanning electron microscopy (SEM). These results have demonstrated that NMR relaxometry is a useful tool to investigate the cell integrity of tomato seeds subjected to different treatments

Early Stage Detection of Tobacco Mosaic Virus in Tomato Seeds by NMR Relaxometry

Because of rapidly increasing population and limited agricultural areas, it becomes compulsory to fight against viral contamination that disrupts effective agricultural production. In this study, use of NMR Relaxometry is investigated to see the effect of salt diffusion and to detect seeds, which had been infected by virus. Tobacco mosaic virus (TMV) infected tomato is chosen since tomato has a high commercial value in sector. T2 relaxation times were measured by using low resolution NMR Relaxometry. Tomato seeds were diluted with distilled water and with 10%, 20%, 30% NaCI solutions and measurements were done by 15min intervals. T2 values of diluted virus free seeds has dropped to 278 ms from 372 ms after 1 day waiting and has dropped to 189 ms after 2 days. In order to distinguish signals coming from different compartments of seed, relaxation spectra were obtained. At seeds diluted with distilled water, it was observed that T2 of peaks have become closer to each other after 1 day due to diffusion of water into cells and becoming relative water by time. In infected seeds, merging of peaks and decrease in T2 were observed after 1 day. 3 peaks were observed at relaxation spectra after 2 day. Presence of viruses in seeds causes changes in cell structure which can directly be observed by relaxation spectra. Seeds diluted with NaCI solution revealed higher T2 values because of lysis of cell wall and diffusion of more water into cell. These results have proved that NMR Relaxometry can accurately be used in differentiation of infected seeds

Dynamics of unloaded and green tea extract loaded lecithin based liposomal dispersions investigated by nuclear magnetic resonance T-2 relaxation

Liposomes are lipid bilayer vesicles that can be used as encapsulation systems for bioactive agents to provide increased protection against environmental stresses (such as pH or temperature extremes). Time Domain Nuclear Magnetic Resonance (TD-NMR) that is based on differentiation of specimen contents with respect to magnetic relaxation rates provides detailed information on amount, state and distribution of water and oil and provide reproducible results on the samples. These make TD-NMR particularly suitable for time-dependent monitoring of emulsion system dynamics. In this study, spin-spin (T-2) relaxation times and relaxation spectra were used for characterizing green tea extract loaded and unloaded liposornes prepared with soy (S75) and egg lecithins (E80) by different preparation methods (such as homogenization type, pressure and solvent type). Mean particle sizes of liposomes were found to be the most influential factor in shaping mono-exponential T-2 relaxation times. The differences in particle sizes of E80 and S75 samples along with samples with different homogenization pressures could be monitored with T-2 relaxation times. Additionally, T-2 relaxation times were found to be correlated with particle shape irregularity, and chemical instability of samples due to lipid oxidation. With relaxation spectrum analysis, particular components in the sample could be distinguished (internal/external water and lipid bilayers), which gave more elaborate results on mechanisms of instability