RESUMEN
In recent times, considerable attention has been given to examining the impact of micro/nanostructure on the thermoelectric characteristics of nonstoichiometric AgSbTe2. The present investigation employed direct melting of elements that produced p-type AgSbTe2 with spontaneous nanostructuring due to cation ordering. The product predominantly features an Ag-deficient Ag0.927Sb1.07Te2.005 phase with monoclinic Ag2Te nanoprecipitates and exhibits a degenerate semiconductor-like behavior with an energy band gap of 0.15 eV. A Seebeck coefficient of 251 µV K-1 and a power factor of 741 µW m-1 K-2 at near ambient temperature are attained with this composition. The variable range hopping (VRH) and linear magnetoresistance (LMR) confirmed that the low-temperature transport followed a VRH between the localized states. The composition also exhibited glass like thermal conductivity of 0.2 W m-1 K-1 arising from phonon scattering at all-scale hierarchical structures that led to a high ZT of 1.1 at room temperature. The direct melted ingots show a high relative density of â¼97%, Vickers hardness Hv of â¼108.5 kgf mm-2, and excellent thermal stability, making them an attractive choice for TEGs.
RESUMEN
Designing surface-confined molecular systems capable of expressing changes in functional properties as a result of slight variations in chemical structure under the influence of an external stimulus is of contemporary interest. In this context, we have designed three tetraterpyridine ligands with variations in their core architecture (phenyl vs tetraphenylethynyl vs bithiophene) to create spray-coated electrochromic assemblies of iron(II)-based metallosupramolecular polymer network films on transparent conducting oxide substrates. These assemblies exhibited molecular permeability and spectroelectrochemical properties that are in turn dictated by the ligand structure. Electrochromic films with high coloration efficiencies (up to 1050 cm2/C) and superior optical contrast (up to 76%) with a concomitant color-to-color redox transition were readily achieved. These functional switching elements were integrated into sandwich-type electrochromic cells (CE up to 641 cm2/C) that exhibited high contrast ratios of up to 56%, with attractive ON-OFF ratios, fast switching kinetics, and high operational stability. Every measurable spectroelectrochemical property of the films and devices is an associated function of the ligand structure that coordinates the same metal ion to different extents. While exhibiting a ligand-structure induced differential metal coordination leading to porosity and spectroelectrochemical diversification, these assemblies allow the creation of electrochromic patterns and images by a simple spray-coating technique.
RESUMEN
The synthesis, optoelectronic characterization and device properties of a cross-linkable fullerene derivative, [6,6]-phenyl-C61 -butyric benzoxazine ester (PCBB) is reported. PCBB shows all the basic photophysical and electrochemical properties of the parent compound [6,6]-phenyl-C61 -butyric methyl ester (PCBM). Thermal cross-linking of the benzoxazine moiety in PCBB resulted in the formation of cross-linked, solvent resistive adhesive films (C-PCBB). Atomic force microscopy (AFM) and optical microscopic studies showed dramatic reduction in the roughness and aggregation behaviour of P3HT-PCBM polymer blend film upon incorporation of C-PCBB interlayer. An inverted bulk heterojunction solar cell based on the configuration ITO/ZnO/C-PCBB/P3HT-PCBM/V2 O5 /Ag achieved 4.27 % power conversion efficiency (PCE) compared to the reference device ITO/ZnO/P3HT-PCBM/V2 O5 /Ag (PCE=3.28 %). This 25 % increase in the efficiency is due to the positive effects of C-PCBB on P3HT/C-PCBB and PCBM/C-PCBB heterojunctions.
RESUMEN
Multicolor electrochromic systems based on heat cross-linkable arylamine-substituted fluorene derivatives, FD and FDOMe, are reported. These derivatives with pendant vinyl groups have been synthesized by the Buchwald-Hartwig amination reaction and were well-characterized using various analytical and spectroscopic techniques such as NMR, ESI-MS, and single-crystal X-ray diffraction analysis. FD and FDOMe exhibited thermally activated cross-linking above their melting temperatures, which was confirmed through absorption, differential scanning calorimetry (DSC), FT-IR, and wide-angle X-ray diffraction (WAXD) techniques. Cross-linked FD films (FD-X) on ITO showed two reversible redox peaks at 0.74 and 0.91 V (versus Ag/AgCl) that correspond to the formation of radical cations and dications, respectively. The corresponding redox peaks were observed at 0.6 and 0.8 V for cross-linked FDOMe films (FDOMe-X). Spectroelectrochemical studies of the electrochromic films on ITO revealed multicolor electrochromism of FD-X (colorless-yellow-dark cyan) and FDOMe-X (colorless-brick red-blue) with a color contrast of â¼44% at 485 nm for FD-X and â¼63% at 500 nm for FDOMe-X and good switching stability between the neutral and oxidized states (>300 cycles) with low switching voltages (<0.9 V for the first oxidation and <1.3 V for the second oxidation). Furthermore, fabrication of electrochromic devices using FD-X and FDOMe-X on FTO substrate with PMMA-based solid electrolyte was demonstrated, where the devices exhibited reasonably low switching time between the redox states (<30 s) with good optical contrast.
RESUMEN
A scalable and versatile method for the large-scale synthesis of tungsten trioxide nanowires and their arrays on a variety of substrates, including amorphous quartz and fluorinated tin oxide, is reported. The synthesis involves the chemical-vapor transport of metal oxide vapor-phase species using air or oxygen flow over hot filaments onto substrates kept at a distance. The results show that the density of the nanowires can be varied from 10(6)-10(10) cm(-2) by varying the substrate temperature. The diameter of the nanowires ranges from 100-20 nm. The results also show that variations in oxygen flow and substrate temperature affect the nanowire morphology from straight to bundled to branched nanowires. A thermodynamic model is proposed to show that the condensation of WO(2) species primarily accounts for the nucleation and subsequent growth of the nanowires, which supports the hypothesis that the nucleation of nanowires occurs through condensation of suboxide WO(2) vapor-phase species. This is in contrast to the expected WO(3) vapor-phase species condensation into WO(3) solid phase for nanoparticle formation. The as-synthesized nanowires are shown to form stable dispersions compared to nanoparticles in various organic and inorganic solvents.