| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Tuesday Sessions |
| Session TF-TuM |
| Session: | Nanostructured Surfaces & Thin Films II |
| Presenter: | Michal Novotny, Institute of Physics of the Czech Academy of Sciences, Czech Republic |
| Authors: | E. Maresova, Institute of Physics of the Czech Academy of Sciences, Czech Republic M. Novotny, Institute of Physics of the Czech Academy of Sciences, Czech Republic P. Fitl, University of Chemistry and Technology Prague, Czech Republic J. Vlcek, University of Chemistry and Technology Prague, Czech Republic M. Vondracek, Institute of Physics of the Czech Academy of Sciences, Czech Republic P. Hubik, Institute of Physics of the Czech Academy of Sciences, Czech Republic L. Fekete, Institute of Physics of the Czech Academy of Sciences, Czech Republic M. Vrnata, University of Chemistry and Technology Prague, Czech Republic J. Bulir, Institute of Physics of the Czech Academy of Sciences, Czech Republic B. Paruzel, Institute of Macromolecular Chemistry of the Czech Academy of Sciences, Czech Republic J. Pfleger, Institute of Macromolecular Chemistry of the Czech Academy of Sciences, Czech Republic R. Slota, Faculty of Chemistry, Opole University, Poland J. Sebera, Institute of Physics of the Czech Academy of Sciences, Czech Republic I. Pis, Elettra - Sincrotrone Trieste S.C.p.A., Italy I. Kratochvilova, Institute of Physics of the Czech Academy of Sciences, Czech Republic J. Lancok, Institute of Physics of the Czech Academy of Sciences, Czech Republic |
| Correspondent: | Click to Email |
Phthalocyanines (Pcs) exhibit unique properties, i.e. semiconductivity, photoconductivity, chemical stability and optical absorption in the UV-VIS-NIR region. These properties make the Pcs suitable candidates for optoelectronic devices, small molecular organic solar cells, laser printers or chemiresistive gas sensors. Pcs belong in the most efficient class of organic semiconductors for solid state photovoltaic conversion. Metal 'mono'-Pc compounds, i.e. ZnPcs, CuPcs, are most commonly utilized. Lanthanide bis-phthalocyanines (LnPc2) based on two macrocycles coordinated by the rare earth metal offer additional possibilities since their arrangement allows changing the distribution of electronic density within the cores of the particular phthalocyanine moieties whereas the molecular structure of the sandwich complex remains intact.
Bis-phthalocyanine thin films of GdPc2 and EuPc2 were grown by vacuum evaporation from effusion cell. The optical properties were characterized by spectrophotometry and spectral ellipsometry. The spectra exhibited well pronounced Q, B, N and C bands and a band around 460 nm that could be attributed to radical band (X band) – transition [2eg(π)-2a1u(π)] suggesting Ln3+Pc2. Relatively high values of conductivity (1.3·10-5 S.cm-1 for EuPc2 and 6.1·10-5 S.cm-1 for GdPc2) were obtained in open air at room temperature with interdigital surface Au electrodes arrangement. The conductivity was found to be sensitive to the thermal annealing and ambient conditions. Electronic structure was analyzed by XPS, resonant PES and NEXAFS. Well pronounced individual components of core level spectra of C 1s, N 1s, Eu 4d and Gd 4d and resonating lanthanide 4f levels in valence band were obtained and analyzed. The analyses confirmed Ln3+ ionic state. NEXAFS measurement supported by density functional theory calculations revealed rather inclined orientation of LnPc2 molecules on the substrate. The molecular orientation could be manipulated by deposition pressure and depends on the film thickness. Morphology was studied by SEM and AFM. The surface roughness was found to be lower than 1 nm. FTIR characterization suggested low deterioration of LnPc2 in the films.
The obtained results suggest both GdPc2 and EuPc2 as promising candidates for application in photovoltaics.