Dye-sensitized semiconductors are promising materials for applications in Grätzel solar cells. Here we are interested in the electron injection into the semiconductor and the initial phase of the electron transport towards the anode. We show that the charge transport in the nanostructured active solar cell material can be very different from that in nonsensitized semiconductors. For ZnO an electron-cation complex is formed within 5 ps which causes fast charge recombination.
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Significant results of scientific activity in year 2010
The paper provides first systematic analysis of properties of all mechanically compatible and electrically neutral domain walls in tetragonal, orthorhombic, and rhombohedral ferroelectric phases of BaTiO3. Polarization and strain profiles within domain walls are calculated. Domain-wall thicknesses and energy densities are estimated for all mechanically compatible and electrically neutral domain-wall species in the entire temperature range of ferroelectric phases.
We suggested using strong internal electric field in multiferroic Eu0.5Ba0.5TiO3 for the search of permanent electric dipole moment (EDM) of the electron. According to standard model of particles its value should be of order of 10–40 e.cm. Recently it has been shown that spontaneous violation of charge parity symmetry is much larger then it follows from the standard model, therefore this model needs an extension. New particle theories propose EDM of electrons 8 or 12 orders of magnitude larger then the standard model.
We analyzed microscopically the valence and impurity band models of ferromagnetic (Ga,Mn)As. We found that the tight-binding Anderson approach with conventional parametrization and the full potential local−density approximation+U calculations give a very similar band structure whose microscopic spectral character is consistent with the physical premise of the k⋅p kinetic-exchange model. On the other hand, the various models with a band structure comprising an impurity band detached from the valence band assume mutually incompatible microscopic spectral character.
We report on a systematic study of optical properties of (Ga,Mn)As epilayers spanning the wide range of accessible MnGa dopings. The material synthesis was optimized for each nominal Mn doping in order to obtain films which are as close as possible to uniform uncompensated (Ga,Mn)As mixed crystals. We observe a broad maximum in the mid-infrared absorption spectra whose position exhibits a prevailing blueshift for increasing Mn doping. In the visible range, a peak in the magnetic circular dichroism also shifts with increasing Mn doping.
Any attempt to study matter in extreme conditions encounters severe issues connected with non-linear intensity-dependent phenomena naturally occurring in the interaction process. For the purposes of such fundamental experiments, the laser beam must be well pre-defined before and/or rather well characterized after the irradiation since the non-Gaussian nature of almost all the XUV/X-ray laser beams is responsible for parasitic non-linear effects in the experimental results.
Stochastic quasi-phase-matching of the process of spontaneous parametric down-conversion is analyzed. It is shown that spectral, temporal and spatial properties of photon pairs generated in randomly poled crystals are similar to those generated in chirped periodically-poled crystals. Especially, randomly poled crystals are capable to emit photon pairs with ultra-broad spectra. For possible applications, the production of randomly poled nonlinear crystals would be much cheaper than chirped, while their properties are very similar.
Diamond is recognized as an attractive material for merging solid-state and biological systems. The advantage of diamond field-effect transistors (FET) is that they are chemically resistant, bio-compatible, and can operate without gate oxides. Solution-gated FETs based on H-terminated nanocrystalline diamond films exhibiting surface conductivity are employed here for studying effects of fetal bovine serum (FBS) proteins and osteoblastic SAOS-2 cells on diamond electronic properties.
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Technologické centrum AV ČR, 11.10.2018.
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