Investigation of the thermo-reversible properties of different poly(N-isopropyl acrylamide) samples, including microgels and block copolymers, with a combination of methods such as electron microscopy, dynamic light scattering, analytical ultracentrifugation, electrophoresis and ultrasound resonator technology allows comprehensive characterisation of the phase transition. By the combination of methods, it was possible to show that the precipitated polymer phase contains at 40°C between 40 and 50 vol.% of water. Besides free bulk water, there is also bound water that strongly adheres to the N-isopropyl acrylamide units (about 25 vol.%). Ultrasound resonator technology, which is a non-sizing characterisation method, revealed for the microgel particles two more temperatures (at about 35 and between 40°C and 50°C depending on the chemical nature) where characteristic changes in the ultrasound attenuation take place. Moreover, the experimental data suggest that the phase transition temperature is related to surface charge density of the precipitated particles.

In this work we report a simple and cost-effective CsPbBr 3based solar cell without ordinary selective contacts. To do so we follow an electrochemical approach consisting of three successive steps: (1) electrodeposition of PbO 2 directly on top of FTO substrates, (2) heterogeneous phase reaction with gaseous HBr and (3) spin-coating of methanolic CsBr solutions followed by annealing. This method is more adequate for largescale environmentally friendly production as it reduces chemical waste, particularly toxic lead. The resulting films were structurally and optically characterized showing good coverage of the FTO substrates, absence of defects such as pinholes and orthorhombic structure. Photovoltaic and impedance characterization was carried out by pressing a carbon coated metal spring onto the CsPbBr 3 film until obtaining maximized opencircuit potential (V oc) and short-circuit photocurrent density (j sc) under simulated sunlight. The stabilized current at fixed voltage (SCFV) technique gave a maximum PCE value of 2.70 % close to devices with similar configuration. Impedance measurements demonstrated analogous behavior to that of state-of-art CsPbBr 3 based solar cells, comprising a recombination arc at mid-high frequencies, geometrical capacitance and ideality factors closed to 2, typical of SRH recombination in the perovskite bulk.

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The optical properties of bare ZnO nanorods and sensitized nanostructures, with Cu 2 O and CdS, are comparatively studied. These nanostructures may show improved photovoltaic performance compared to planar ones. ZnO nanorod arrays were grown by electrochemical deposition. In a second step, Cu 2 O was also deposited electrochemically, while for CdS successive ion layer adsorption and reaction techniques were used. The experimental results are interpreted using numerical simulation based on an effective medium theory. Bare nanorod samples reveal mainly the direct ultraviolet absorption edge of ZnO (between 3.25 and 3.30 eV) and a monotonically increasing transmittance from the ultraviolet into the red. This increase is originated in light scattering, probably by the nanometric structure of the samples. For the sensitized samples reduced transmittance in the solar spectrum region is observed and several well-defined absorption edges appear. Spectral absorption edge shifts are interpreted comparing with numerical simulations. For CdS the measured shifts are larger than the ones obtained from numerical simulations. The difference may be due to the combined influence of sub-bandgap absorption, light scattering in the nanorod array and quantum confinement in the nanocrystalline structure of sensitizer layers. For Cu 2 O its more complex electronic structure gives larger dispersion in the results although major absorption edges are clearly observed.