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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]