Phthalocyanine (H2Pc) and its open-shell copper complex (CuPc) deposited on amorphous gold films have been studied by combining the outcomes of several synchrotron based spectroscopic tools (X-ray photoelectron spectroscopy, UV photoelectron spectroscopy and near-edge X-ray absorption fine structure, NEXAFS, spectroscopy) with those of density functional theory (DFT) calculations. The assignment of experimental evidence has been guided by the results of DFT numerical experiments carried out on isolated molecules. With specific reference to CuPc NEXAFS data collected at the N K-edge, they have been assigned by using the open-shell time-dependent DFT (TDDFT) in the framework of the zeroth order regular approximation (ZORA) scalar relativistic approach. The agreement between theory and experiment has been found to be satisfactory, thus indicating that the open-shell TDDFT (F. Wang and T. Ziegler, Mol. Phys., 2004, 102, 2585) may be used with some confidence to look into the X-ray absorption spectroscopy results pertinent to transition metal complexes. As far as the metal-ligand interaction is concerned, the combined use of NEXAFS spectroscopy and DFT outcomes ultimately testified the significant ionic contribution characterizing the bonding between the metal centre and the nitrogen atoms of the phthalocyanine coordinative pocket.

This work reports an extensive study about the effects of thermal treatments on the performance of TiO 2based dye-sensitized solar cells. The morphologic, structural, luminescence, and electrical properties of the as-prepared TiO 2 electrode are first analyzed by using several diagnostic techniques. In particular, by extensive cathodoluminescence and photocurrent measurements it is possible to determine the energy band diagram of the material intragap levels and to observe their influence in both radiative and photoinduced transport properties. The TiO 2 electrodes have been annealed at 500 °C for 1, 4, and 8 h in argon or in oxygen environment and then used to develop different DSSCs. The oxygen annealed solar cells show a monotonic increase in the efficiency from 6.75 up to 7.30; meanwhile, the argon-annealed solar cells have an efficiency that remains slightly constant around 6.85. By comparing the behavior of all cells parameters with the CL properties of the annealed TiO 2 electrodes, it is possible to determine a correspondence between the short circuit current densities of the DSSCs and the variation of the intragap states in the semiconductor layer induced by annealing.

Hydrogenated nanocrystalline silicon (nc-Si:H) is a multiphase, heterogeneous material, composed of Si nanocrystals embedded in an amorphous matrix. It has been intensively studied in the last few years due to its great promise for photovoltaic and optoelectronics applications. The present paper aims to study the current transport mechanisms in nc-Si:H by mapping the local conductivity at the nanoscale. The role of B doping in nc-Si:H is also investigated. Conductivity maps are obtained by atomic force microscopy using a conductive tip. Differences and similarities between intrinsic and doped nc-Si:H conductivity maps were observed and these are also explained on the basis of recently published computational studies.

Unprecedented room temperature excitonic emissions are achieved from TiO(2) nanocrystals synthesized at 300 K by supersonic cluster beams. Transmission electron microscopy studies show the crystalline nature of the nanoparticles (NPs) with a diameter ranging from 5 to 30 nm. All the samples show mixed rutile and anatase phases as confirmed by Raman spectroscopy. XPS core level analyses evidence an O/Ti ratio of the as-grown nanoparticles of 2.30 ± 0.04. Two room temperature cathodoluminescence excitonic peaks observed at 3.16 and 3.25 eV are ascribed to the coexistence of rutile and anatase crystallographic phases respectively. Subsequent thermal treatments at 450 °C cause the complete quenching of the UV excitonic emissions and result in a more conventional broad visible band centered at 2.5 eV. HRTEM and XPS studies reveal that, after annealing, the NPs remain single crystals in nature with an O/Ti ratio of 2.20 ± 0.04. These results suggest a correlation between the emission properties and the oxygen concentration of our NPs. The achieved ability to tune the optical properties of TiO(2) nanoparticles is very promising for sensing and energy applications.

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