1,721,029 research outputs found
Highly thermally stable non-fullerene organic solar cells: p-DTS(FBTTh2)2:P(NDI2OD-T2) bulk heterojunction
No full textBecause long-term solar cell stability may be influenced by morphological reorganization, we investigated the effect of thermal annealing on bulk heterojunction solar cells comprised of p-DTS(FBITh2)(2):P(NDI2OD-T2) (3:1). Our results indicate that the p-DTS(FBITh2)(2)) compound with lower diffusion kinetics enables to stabilize the blend morphology at high temperature, leading to high thermal stability of a p-DTS(FBTTh2)2:P(NDI2OD-T2) solar cell device. Therefore, The p-DTS(FBTTh2)(2):P(NDI2OD-T2) solar cell indicates highly thermally stable bulk heterojunction device as retaining 70% of its original power conversion efficiency value after heating at 180 degrees C over 20 h. These results indicate that p-DTS(FBTTh2)(2):P(NDI2OD-T2) is a promising BHJ system for practical use in non-fullerene OSCs. (C) 2015 Elsevier Ltd. All rights reserved.112723Nsciescopu
Reaction synthesis and microstructures of NiAl/Ni micro-laminated composites
No full textThe effects of process parameters on reaction synthesis of NiAl/Ni micro-laminated composite from micro-foils of Ni and Al have been investigated. NiAl/Ni micro-laminated composites were fabricated through diffusion bonding, reaction synthesis and post-heat treatment of alternatively stacked Ni/Al multilayers. DTA analysis showed that the reaction between Ni and Al foils started from the nucleation and growth of NiAl3 at Ni/Al interfaces followed by a diffusional growth of NiAl3 at Ni/NiAb interfaces. The volume fraction of un-reacted Al after reaction was thermodynamically calculated from the initial thickness ratio of Ni:Al and diffusion bonding time before the reaction. As the thickness ratio of Ni:Al increased, the adiabatic temperature and the volume fraction of pure liquid Al decreased. Experimentally measured adiabatic temperature, T-a, was lower than the thermodynamically calculated value, decreased with increasing the thickness ratio of Ni:Al. As the diffusion bonding time increased, the volume fraction of pure liquid Al decreased gradually due to the consumption of Al forming intermetallic at interface of Ni-Al. When initial thickness ratio of Ni:Al during post-heat treatment increased, Al-rich nickel aluminide (Ni0.9Al1.1) was transformed to Ni-rich nickel aluminide (NiAl) so that the final microstructures resulted in a formation of compositionally gradient series of intermetallic phases which consisted of NiAl and Ni3Al. (c) 2005 Elsevier B.V. All rights reserved
Intermixing criteria for reaction synthesis of Ni/Al multilayered microfolls
No full textIntermixing criteria are proposed for determining the microstructure of the reaction products during the reaction synthesis of Ni/Al multilayered microfoils. The critical thickness and thickness ratio for the formation of monolithic intermetallic depend on the conductive heat loss through the Ni layer and are verified by analytical thermophysical modeling. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved
Analysis of moving boundary problem of growth of bismuth germanate crystal by heat exchanger method
No full textTransient two-dimensional model of the growth of BGO crystal by heat exchanger method has been developed. A finite element method with nonorthogonal mapping technique for the solution of the moving boundary problem is developed where the melt/solid interface shape changes from hemispherical to planar. The moving boundary problems for the melt/solid interface location and the temperature field were solved by two mapping rule method which enables the computation of interface shape changing from hemispherical to planar. The maximum deflection of interface is shown when the melt/solid interface meets the corner of crucible. As the excess heating temperature and the heat exchanger temperature were increased, more growth time for whole process is required but the quality of BGO crystal may be improved. The ratio of the height to the radius of crucible hardly affects the deflection of BGO melt/solid interface when it is greater than 1.5. As the cooling zone radius is decreased, maximum deflection is decreased. The heat transfer between the crucible and the heating element should be suppressed to maximize planarity of the interface shape
Guest-induced binding site organization of self-assembled Pd(II) complexes
No full textSelf-assembled Pd(II) complexes derived from a chiral bidentate ligand 1 and (en)Pd(NO3)(2) (2) in D2O showed concentration dependent and guest-induced reorganization behaviour. (C) 1998 Elsevier Science Ltd. All rights reserved.
Tensile and fracture properties of NiAl/Ni micro-laminated composites prepared by reaction synthesis
Full text linkThe mechanical properties of NiAI/Ni micro-laminated composites with highly gradient microstructure have been investigated. Two types of composites with different gradient microstructures were prepared by reaction synthesis. Intermetallics of type I and type 11 composites mainly consisted of Al-rich Ni0.45Al0.55 with variable thickness and Ni-rich Ni0.58Al0.42 with similar thickness, respectively. As intermetallic volume fraction increased, yield strength of type II followed the rule-of-mixture well, while that of type I deviated due to the composition variation of intermetallic phases. Fracture toughness of type 11 was higher than that of type I, and all showed K-R curves with upward curvature by large-scale bridging. Even though the relative strength of constituent phases in intermetallic/metal laminates was not constant due to the gradient microstructure, the fracture mode transition showed similar behavior to that of metal/ceramic laminates
Fabrication of high-performance composite electrodes composed of multiwalled carbon nanotubes and glycerol-doped poly(3,4-ethylenedioxythiophene):polystyrene sulfonate for use in organic devices
No full textIn this study, composite films composed of highly conductive multiwalled carbon nanotubes (MWCNTs) and poly(3,4-ethylenedioxythiophene) polymerized with poly(4-styrenesulfonate) (PEDOT:PSS) were fabricated via additional organic-compound doping. The effects of glycerol (GL) or dimethyl sulfoxide (DMSO) doping on the film properties, such as surface roughness, work function (Phi), and conductivity, were studied for both PEDOT: PSS and MWCNT/PEDOT: PSS composite systems. The interactive couplings between the PEDOT and PSS molecules became disordered upon doping with GL or DMSO, which altered the conjugated structure between the PEDOT and PSS chains. Therefore, the electrical conductivity of the PEDOT: PSS and MWCNT/PEDOT: PSS films was enhanced by the addition of GL or DMSO molecules. The GL-doped PEDOT: PSS (PEGL) and ultraviolet (UV)-oxidized MWCNT/PEDOT: PSS (0.2-UVGL) films exhibited comparable work functions (PEGL = 4.87 eV, 0.2-UVGL = 5.0 eV). They also had lower sheet resistances (R-s; PEGL = 806.7 +/- 50 Omega square(-1), 0.2-UVGL = 613 +/- 120 Omega square(-1)) as compared to those of the undoped PEDOT: PSS (Phi = 4.92 eV, R-s = 1.03 +/- 0.10 M Omega square(-1)) and MWCNT/PEDOT: PSS composites (Phi = 4.7 eV, R-s = 2184 +/- 244 Omega square (1)). Furthermore, because of these excellent electrical properties, the doped MWCNT/PEDOT: PSS films showed great potential as the source/drain electrode in an organic thin-film transistor and as the catalytic counter electrode in a dye-sensitized solar cell. In conclusion, devices with 0.2-UVGL electrodes performed better than the corresponding devices with other MWCNT/PEDOT: PSS composite electrodes and the device characteristics were comparable to that of standard devices with platinum/fluorine-doped tin oxide electrodes.111613Nsciescopu
A push-pull organic semiconductor with efficient intramolecular charge transfer for solution-processed small molecule solar cells
No full textA new push-pull organic semiconductor, DMF-BP-T-MMN, containing a functionalized amine donor and a methylene malononitrile (MMN) acceptor has been designed and synthesized for use in solutionprocessable small molecule solar cells. This material exhibits superior intramolecular charge transfer from the functionalized amine group to MMN, which produces an electron-rich MMN group that facilitates electron transfer into the active layer constituent phenyl-C-71-butyric acid methyl ester in a solar cell. As a result, DMF-BP-T-MMN was found to exhibit excellent p-type semiconductor performance in an optimized organic solar cell: a power conversion efficiency of 3.40% with a high photocurrent density of 8.2 mA cm (2).open111212Nsciescopu
Structure-Property Relationships: Asymmetric Alkylphenyl-Substituted Anthracene Molecules for Use in Small-Molecule Solar Cells
No full textTwo asymmetric anthracene-based organic molecules, NDHPEA and TNDHPEA, were prepared without or with a thiophene spacer between the anthracene and naphthalene units. These asymmetric oligomers displayed different degrees of coplanarity, as evidenced by differences in the dihedral angles calculated by using DFT. Differential scanning calorimetry and XRD studies were used to probe the crystallization characteristics and molecular packing structures in the active layers. The coplanarity of the molecules in the asymmetric structure significantly affected the crystallization behavior and the formation of crystalline domains in the solid state. The small-molecule crystalline properties were correlated with the device physics by determining the J-V characteristics and hole mobilities of the devices.X1133Nsciescopu
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