Search

The effect of biaxial strain on O-doped monolayers MoS2 has been systematically studied by the first-principles calculations. It is shown that the strain decreases the structural stability of O-doped monolayer MoS2. Between 0% and 12% tensile strains, the bandgap steadily narrows. At different compression strains, the bandgap increases and then decreases. The optical properties analysis shows that the strain causes the peaks of both the real and imaginary parts of the dielectric function to appear in the low energy region. And it affects the absorption and reflection peaks of the doping system so that it has a strong absorption of photons in the ultraviolet region. The doping system shows resonance in the range of 0–10 eV. The results of this study verify that strain can properly regulate the electronic and optical properties of O-doped monolayer MoS2, and provide a theoretical reference for the implementation of MoS2 in optoelectronic devices. [ABSTRACT FROM AUTHOR]

SrAl 2 O 4 :Eu 3+ down-conversion (DC) nanocrystals were synthesized by a sol–gel method and then doped in TiO 2 as a photoanode in dye-sensitized solar cells (DSSCs). Differential thermal analysis, fourier transform infrared spectroscopy, X-ray diffraction and Brunauer–Emmet–Teller analysis confirmed the formation of SrAl 2 O 4 :Eu 3+ nanocrystals with diameters of ∼47 nm, pore size of ∼25 nm, sintering temperature of 1300 °C. The photoluminescence and UV–vis absorption spectra of the SrAl 2 O 4 :Eu 3+ revealed a DC from ultraviolet light to visible light which matched the strong absorbing region of the N719 dye. The photoelectric conversion efficiency of the DSSCs with a TiO 2 photoanode doped with 3 wt% SrAl 2 O 4 :Eu 3+ was 20% higher than that with a pure TiO 2 photoanode. This phenomenon could be mainly explained by SrAl 2 O 4 :Eu 3+ nanocrystals’ ability of DC and increased the short-circuit current density. It could be minorly due to the p-type doping effect and slightly improved the open-circuit voltage. [ABSTRACT FROM AUTHOR]

SrTiO 3 :Sm 3+ @SiO 2 (STS@SiO 2 ) core–shell nanoparticles were fabricated by Stöber method after a simple hydrothermal process and then being introduced into the TiO 2 photoanode to assemble dye–sensitized solar cells (DSSCs). X–ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM) analysis confirmed the formation of core–shell nanoparticles with cubic structured SrTiO 3 :Sm 3+ (STS) as core, SiO 2 as shell. The photo–fluorescence (PL) and ultraviolet–visible (UV–Vis) absorption spectra of photoanodes with different STS@SiO 2 content indicate a down–conversion from ultraviolet light to visible light which matched the strong absorbing region of the N719 dye. Compared with the pure TiO 2 and STS doped TiO 2 photoanode, STS@SiO 2 doped TiO 2 photoanode showed a greater photovoltaic efficiency. The photoelectric conversion efficiency ( η ) of 5.07% for 10 wt% STS@SiO 2 doped TiO 2 –based DSSC was higher than that of 3.72% for pure TiO 2 –based DSSC and 4.29% for 10 wt% STS doped TiO 2 –based DSSC. This phenomenon could be explained by STS@SiO 2 core–shell nanoparticles’ triple ability to extend spectral response range to the ultraviolet region, suppress the recombination of electron–electrolyte and lengthen the light traveling distance in the photoanode by the scattering. [ABSTRACT FROM AUTHOR]

Functional ferromagnetic (Fe 2 O 3 ) x :(CeO 2 ) 1− x vertically aligned nanocomposite (VAN) layers were deposited as either buffer or cap layers for YBa 2 Cu 3 O 7−δ (YBCO) thin films. The composition of Fe 2 O 3 dopants in the VAN nanolayers is controlled at 10%, 30% and 50% in order to create different arrangements of Fe 2 O 3 and CeO 2 nanopillars and therefore to tune the flux pining landscapes. The composition variation provides tunable and ordered arrangements of magnetic nanodopants and interfacial defects as pinning centers in the YBCO thin films. The superconducting property measurements show that most doped samples obtain a T c above 90 K and the J c sf measured at 75 K and 65 K maximized at 3.07 MA/cm 2 and 9.2 MA/cm 2 for 30% Fe 2 O 3 VAN doped sample. As the temperature decreased to 5 K, the sample with 50% Fe 2 O 3 VAN doped sample show the best pinning effect due to pronounced magnetic pinning effects. This work demonstrates the tunable density of magnetic pinning centers can be achieved by VAN to meet the specific pinning requirement. [ABSTRACT FROM AUTHOR]