143 research outputs found
Etude des propriétés électrochromes des films anodiques de trioxyde de tungstène.
No full textStudy of the absorption that appears in this material during its colouring and the possibilities of use for the realization of display systems. It is shown that the layers formed by anodic oxidation present a progressive crystallization according to the anodic tension. For low voltages, these layers are amorphous. Calculation of refractive and absorption indices from spectroreflectrometric data. During electrostaining with H**(+), Li**(+), Na**(+), a decrease in Raman peaks of W-O bonds vibrations and an appearance of W=O bonds vibration peaks are observed. .Étude de l'absorption qui apparait dans ce matériau au cours de sa coloration et des possibilités d'utilisation pour la réalisation des systèmes d'affichage. On montre que les couches formées par oxydation anodique présentent une cristallisation progressive en fonction de la tension anodique. Pour de faibles tensions, ces couches sont amorphes. Calcul des indices de réfraction et d'absorption à partir des données spectroreflectrométriques. Au cours de l'électrocoloration avec des ions H**(+), Li**(+), Na**(+), une diminution des pics Raman des vibrations des liaisons W-O et une apparition des pics des vibrations des liaisons W=O sont observées.
Minimizing Energy Losses in Dye‐Sensitized Solar Cells Using Coordination Compounds as Alternative Redox Mediators Coupled with Appropriate Organic Dyes
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Solution-processed hydrogen molybdenum bronzes as highly conductive anode interlayers in efficient organic photovoltaics
No full textHighly efficient and stable organic photovoltaic (OPV) cells are demonstrated by incorporating solution-processed hydrogen molybdenum bronzes as anode interlayers. The bronzes are synthesized using a sol-gel method with the critical step being the partial oxide reduction/hydrogenation using an alcohol-based solvent. Their composition, stoichiometry, and electronic properties strongly correlate with the annealing process to which the films are subjected after spin coating. Hydrogen molybdenum bronzes with moderate degree of reduction are found to be highly advantageous when used as anode interlayers in OPVs, as they maintain a high work function similar to the fully stoichiometric metal oxide, whereas they exhibit a high density of occupied gap states, which are beneficial for charge transport. Enhanced short-circuit current, open-circuit voltage and, fill factor, relative to reference devices incorporating either PEDOT-PSS or a solution processed stoichiometric molybdenum oxide, are obtained for a variety of bulk heterojunction mixtures based on different polymeric donors and fullerene acceptors. In particular, high power conversion efficiencies are obtained in devices that employed the s-HxMoO2.75 as the hole extraction layer. The incorporation of solution-processed hydrogen molybdenum bronzes as anode interlayers in organic photovoltaic cells is presented. High power conversion efficiencies are observed in devices based on polymeric donors and fullerene acceptors that include a bronze with a moderate degree of reduction, namely the s-HxMoO2.75, as the anode interlayer.</p
A Review on Emerging Efficient and Stable Perovskite Solar Cells Based on g-C3N4 Nanostructures
No full textPerovskite solar cells (PSCs) have attracted great research interest in the scientific community due to their extraordinary optoelectronic properties and the fact that their power conversion efficiency (PCE) has increased rapidly in recent years, surpassing other 3rd generation photovoltaic (PV) technologies. Graphitic carbon nitride (g-C3N4) presents exceptional optical and electronic properties and its use was recently expanded in the field of PSCs. The addition of g-C3N4 in the perovskite absorber and/or the electron transport layer (ETL) resulted in PCEs exceeding 22%, mainly due to defects passivation, improved conductivity and crystallinity as well as low charge carriers’ recombination rate within the device. Significant performance increase, including stability enhancement, was also achieved when g-C3N4 was applied at the PSC interfaces and the observed improvement was attributed to its wetting (hydrophobic/hydrophilic) nature and the fine tuning of the corresponding interface energetics. The current review summarizes the main innovations for the incorporation of graphitic carbon nitride in PSCs and highlights the significance and perspectives of the g-C3N4 approach for emerging highly efficient and robust PV devices
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