319 research outputs found
On the phase structure of driven quantum systems
Clean and interacting periodically driven quantum systems are believed to
exhibit a single, trivial "infinite-temperature" Floquet-ergodic phase. In
contrast, here we show that their disordered Floquet many-body localized
counterparts can exhibit distinct ordered phases delineated by sharp
transitions. Some of these are analogs of equilibrium states with broken
symmetries and topological order, while others - genuinely new to the Floquet
problem - are characterized by order and non-trivial periodic dynamics. We
illustrate these ideas in driven spin chains with Ising symmetry.Comment: v3 - published version. Discussions expanded/clarified in few place
Employing surfactant-assisted hydrothermal synthesis to control CuGaO2 nanoparticle formation and improved carrier selectivity of perovskite solar cells
Delafossites like CuGaO2 have appeared as promising p-type semiconductor
materials for opto-electronic applications mainly due to their high optical
transparency and electrical conductivity. However, existing synthetic efforts
usually result in particles with large diameter limiting their performance
relevant to functional electronic applications. In this article, we report a
novel surfactant-assisted hydrothermal synthesis method, which allows the
development of ultrafine (~5 nm) monodispersed p-type CuGaO2 nanoparticles
(NPs). We show that DMSO can be used as a ligand and dispersing solvent for
stabilizing the CuGaO2 NPs. The resulting dispersion is used for the
fabrication of dense, compact functional CuGaO2 electronic layer with
properties relevant to advanced optoelectronic applications. As a proof of
concept, the surfactant-assisted hydrothermal synthesized CuGaO2 is
incorporated as a hole transporting layer (HTL) in the inverted p-i-n
perovskite solar cell device architecture providing improved hole carrier
selectivity and power conversion efficiency compared to conventional PEDOT:PSS
HTL based perovskite solar cells
Room Temperature Nanoparticulate Interfacial Layers for Perovskite Solar Cells via solvothermal synthesis
We present a solvothermal synthetic route to produce monodispersed CuO
nanoparticles (NPs) in the range of 5-10 nm that can be used as hole selective
interfacial layer between indium tin oxide (ITO) and perovskite active layer
for p-i-n perovskite solar cells by a spin casting the dispersions at room
temperature. The bottom electrode interface modification provided by spherical
CuO-NPs at room temperature promotes the formation of high quality perovskite
photoactive layers with large crystal size and strong optical absorption.
Furthermore, it is shown that the nanoparticulate nature of the CuO hole
transporting interfacial layer can be used to improve light manipulation within
perovskite solar cell device structure. The corresponding p-i-n
CH3NH3PbI3-based solar cells show high Voc values of 1.09 V, which is
significantly higher compared to the Voc values obtained with conventional
PEDOT:PSS hole selective contact based perovskite solar cells
Marketing in the Hellenic private secondary education during the recession
The purpose of this research, is to investigate whether, during the economic crisis, various private secondary-education organizations in Greece including secondary tutorial schools, private schools, foreign language centers, special course delivery services (private tutorial schools) and study centers, develop and pursue a marketing strategy. Other points covered include demographics, characteristics of organisations, specific strategy focus, amount spent on such strategy and possible changes on both academic and financial level. Possible correlations between specific marketing actions and results were calculated. The statistical analysis of the data, showed that the implementation of a marketing plan (and the amount invested on this project) positively affect students' academic performance, new enrollments, organizations’ earnings and recruitment of new scientific staff. Twenty close-ended questionnaires were used to collect the data. During research period, many private schools had ceased their duties because of summer holiday time. As a result, a small number of the data was collected from these schools and it will not be possible to generalize any results for the ones
3D ultrastructural organization of whole Chlamydomonas reinhardtii cells studied by nanoscale soft x-ray tomography
The complex architecture of their structural elements and compartments is a hallmark of eukaryotic cells. The creation of high resolution models of whole cells has been limited by the relatively low resolution of conventional light microscopes and the requirement for ultrathin sections in transmission electron microscopy. We used soft x-ray tomography to study the 3D ultrastructural organization of whole cells of the unicellular green alga Chlamydomonas reinhardtii at unprecedented spatial resolution. Intact frozen hydrated cells were imaged using the natural x-ray absorption contrast of the sample without any staining. We applied different fiducial-based and fiducial-less alignment procedures for the 3D reconstructions. The reconstructed 3D volumes of the cells show features down to 30 nm in size. The whole cell tomograms reveal ultrastructural details such as nuclear envelope membranes, thylakoids, basal apparatus, and flagellar microtubule doublets. In addition, the x-ray tomograms provide quantitative data from the cell architecture. Therefore, nanoscale soft x-ray tomography is a new valuable tool for numerous qualitative and quantitative applications in plant cell biology
- …