Theoretical Study on New Conjugated Compounds of Organic Solar Cell: DFT, TD-DFT and AMPS1D

Une série de nouveaux composés conjugués à faible bande interdite pour les cellules solaires à hétérojonction en vrac ont été étudiées par DFT et TD-DFT. Le programme AMPS-1D a été utilisé pour simuler les performances de nos composés. Ces composés conjugués portent l'unité donneuse triphénylamine, leur pont conjugué est à base de phénylènevinylène, et de différents systèmes π, 3, 4-éthylènedioxythiophène (EDOT), carbazole et thiophène. L'acide -cyanoacrylique a été utilisé comme groupe accepteur d'électrons. Les géométries optimisées calculées indiquent qu'elles ont toutes des structures coplanaires. Les niveaux HOMO (orbitale moléculaire la plus occupée), LUMO (orbite moléculaire inoccupée la plus basse), l'énergie de l'écart (EHOMO-ELUMO) et la longueur d'onde du spectre d'absorption (λmax), ainsi que plusieurs propriétés chimiques quantiques telles que la tension en circuit ouvert Voc, le potentiel d'ionisation ( IP), affinité électronique (EA), ont également été calculés et discutés en détail dans le document. La densité de courant de court-circuit (Jsc), le facteur de forme (FF), le rendement de conversion de puissance (η), la résistance série Rs et les résistances shunt Rsh ont été obtenus à l'aide de l'AMPS-1D. Toutes ces propriétés suggèrent que ces composés sont de bons candidats pour une utilisation dans les cellules solaires organiques. 

Thermal conductivity and latent heat thermal energy storage properties of LDPE/wax as a shape-stabilized composite phase change material

Phase change material (PCM) composites based on low-density polyethylene (LDPE) with paraffin waxes were investigated in this study. The composites were prepared using a meltmixing method with a Brabender-Plastograph. The LDPE as the supporting matrix kept the molten waxes in compact shape during its phase transition from solid to liquid. Immiscibility of the PCMs (waxes) and the supporting matrix (LDPE) is a necessary property for effective energy storage. Therefore, this type paraffin can be used in a latent heat storage system without encapsulation. The objective of this research is to use PCM composite as integrated components in a passive solar wall. The proposed composite TROMBE wall allows daily storage of the solar energy in a building envelope and restitution in the evening, with a possible control of the air flux in a ventilated air layer. An experimental set-up was built to determine the thermal response of these composites to thermal solicitations. In addition, a DSC analysis was carried out. The results have shown that most important thermal properties of these composites at the solid and liquid states, like the "apparent" thermal conductivity, the heat storage capacity and the latent heat of fusion. Results indicate the performance of the proposed system is affected by the thermal effectiveness of phase change material and significant amount of energy saving can be achieved.Scopu

Effect of expanded graphite on the phase change materials of high density polyethylene/wax blends

Phase change materials fabricated from high density polyethylene (HDPE) blended with 40 or 50 wt% commercial wax (melting point of 43.08�C) and up to 15 wt% expanded graphite (EG) were studied. Techniques including scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and an experimental device to measure diffusivity and conductivity (DICO) were used to determine the microstructural, mechanical and thermal properties of the composites. The composites possessed good mechanical properties. Additionally, no leaching was observed during material processing or characterization. Although the Young's modulus increased with the addition of EG, no significant changes in tensile strength were detected. The maximum Young's modulus achieved was 650 MPa for the HDPE/40% wax composite with 15 wt% EG. The EG was well dispersed within the composites and did not affect the melting or crystallization of the HDPE matrix. The incorporation of EG increased the thermal stability of the composites by reducing chain mobility and inhibiting degradation. The intensification of thermal conductivity occurred with increasing fractions of EG, which was attributed to the high thermal conductivity of graphite. The maximum quantity of heat stored by latent heat was found for the HDPE/40% wax composite with EG. The addition of a relatively small quantity of EG enhances the heat conduction in the composite.Scopu

Thermal properties of smart microencapsulated paraffin/plaster composites for the thermal regulation of buildings

Smart plaster composites were manufactured by mixing plaster with different amounts of Micronal? DS5001X microcapsules containing a paraffin mixture with a melting point of 26 �C to develop new construction materials with high thermal energy storage capacity for use in high-comfort constructive systems. Thermal characterization of smart plaster composites was performed using two different experimental techniques: thermal energy storage properties, such as latent heat and heat capacities, were investigated using a Transient Guarded Hot Plate Technique (TGHPT), whereas thermal conductivities and diffusivities were measured using a periodic temperature method. The results revealed an improvement in the latent heat and the heat capacities of the composites with increasing paraffin content in the composite. Furthermore, thermal conductivities and diffusivities decreased with increasing microencapsulated paraffin concentration.Scopu

Concurrrent two-scale analysis of composites embedding phase change particles

International audienc

Computational homogenization for the thermo-mechanical analysis of phase change composite materials

International audienc

The stabilizing effect of expanded graphite on the artificial aging of shape stabilized phase change materials

Artificial aging of Shape Stabilized Phase Change Materials (SSPCM) based on linear low density polyethylene (LLDPE) and paraffin wax (W) modified with various amounts of expanded graphite (EG) was investigated and reported in this paper. It was found that EG not only strongly suppresses leakage of paraffin wax from the material over time but also significantly improves the photo oxidation stability. The increase in the melting point of wax incorporated within LLDPE matrix during aging was observed whereas the specific melting enthalpy of the paraffin wax decreased. This is mainly caused by the leakage of paraffin wax from the blends. The melting of neat LLDPE decreased during aging whereas its specific enthalpy of melting increased. Addition of EG led to the prolonged photo-oxidation stability of materials, as confirmed by Carbonyl Index measurements.Scopu