Search

24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany; 624-626, Spectroscopic ellipsometry (SE) is a well established technique for the study of the properties of thin films. Despite the noticeable and well-known advantages offered by SE in such field, the use of this technique for the characterization of multi-layer polymer solar cells is still scarce. Nevertheless, SE allows getting valuable information for each of the deposited layers of the cells in a reliable and non destructive way. These aspects, as well as the short time needed for the measurement, make ellipsometry a really attracting candidate for the study of organic devices and for in line quality control in the future production process of such devices. In this work we present the results of a systematic optical characterization of multilayer thin films used for bulk heterojunction polymeric solar cells based on the well established donor-acceptor system poly(3-hexylthiophene)/phenyl-C61-butirric acid methyl ester (P3HT:PCBM) as well as on different conjugated polymers, namely poly[9,9-bis(2-ethylhexyl)fluorene-co-4,4’- triphenylamine] (PEFTPA), a material exhibiting a good hole mobility. The polymer solar cell architecture considered is the standard Glass/ITO/PEDOT-PSS/blend multilayer structure. Ellipsometric measurements were also compared with results coming from traditional techniques such as contact profilometry and UV-Vis spectroscopy and a good agreement among the results was shown.

Hydrogenated amorphous silicon carbon films, with relatively low hydrogen content and carbon fraction x, C/(C + Si), ranging from 0.20 to 0.57 have been deposited by RF-plasma enhanced chemical vapor deposition (PECVD) for excimer laser annealing experiments. After the laser treatments all the films show structural modifications. It has been obtained that with increasing, x the crystallinity degree of the Si phase decreases, while that of the SiC phase increases and becomes predominant for x = 0.39. In the overstoichiometric samples only the c-SiC phase has been observed. In all the treated samples 3C-SiC crystallites have been detected. (c) 2005 Elsevier B.V. All rights reserved.

In the present work the use of Spectroscopic Ellipsometry (SE) for a direct and non-destructive optical and structural characterization of opaline photonic crystals is demonstrated. The analysis is performed on self-assembled dye-doped polymer nanospheres deposited on glass substrates. We study two different polymers beads: PMMA (as well-known reference material) and poly[styrene-(co-2- hydroxyethyl metacrylate)] [P(S/HEMA)]. We show that SE allows to obtain information about all the most important optical and geometrical features of the photonic structure as the effective refractive index (neff), the refractive index modulation, the optical anisotropy, the air/sphere filling fraction, the layer distance and the size of nanospheres. Results are in very good agreement with those obtained by Scanning Electron Microscope (SEM) analysis and Bragg reflection spectroscopy. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

We report on the optical characterization of three-dimensional opal-like photonic crystals made by self-organized nanospheres of poly[styrene-(co-2- hydroxyethyl methacrylate)] having a face centred cubic (fcc) structure oriented along the [111] direction. A detailed optical characterization of the samples is presented using angle resolved reflection spectroscopy in specular geometry. The investigated energies are between a/λ=0.5 and a/λ=1.5 (where a is the lattice parameter and λ is the light wavelength), a region in which both first and second-order Bragg diffraction are expected. Some interesting features as branching of the Bragg peak dispersion and high energy reflection peaks are revealed. We compare the experimental data with theoretical calculations using both Bragg diffraction and band structure approach. A comparison with recent results reported in the literature is also presented. © 2008 Optical Society of America.