Alexandre Marletta

By Eralci M. Therézio, Maria L. Vega, Roberto M. Faria and Alexandre Marletta

Part of the book: Scanning Probe Microscopy

By Sankler Soares de Sá, Fernando Costa Basílio, Henrique de Santana, Alexandre Marletta and Eralci Moreira Therézio

Poly(3‐alkylthiophene) (P3ATs) have been extensively used in photovoltaic devices such as a p‐type organic Semiconductors. However, several electronic properties of P3ATs present energy transfer inter- and intra-chains that have direct consequences on the performance of optoelectronic devices. Traditionally electrochemical techniques, such as cyclic voltammetry, chronoamperometry and chronocoulometry, have been applied to process polymer thin films and unconventional spectroscopy techniques are used to characterize the electronic properties. In the present work, we used an innovative technique called ellipsometry emission to investigate the optical properties of P3AT films. We propose a new approach to study the electrochemical synthesize and unintentional doping processes of polymeric systems. We showed a strong correlation between the electrochemical synthesis and the optical properties controlling the film growth conditions for P3ATs. The results obtained in the present study can be potentially utilized for applications in organic devices, mainly in photovoltaic cells when the film deposition and the optical properties control are relevant.

Part of the book: Modern Technologies for Creating the Thin-film Systems and Coatings

By Eralci Moreira Therézio, Gustavo G. Dalkiranis, André A. Vieira, Hugo Gallardo, Ivan H. Bechtold, Patricia Targon Campana and Alexandre Marletta

In the present chapter, the theory and some applications of Achromatic Ellipsometry, including transmittance, absorbance, and emission, are presented. The new methodology introduced here comprises the calculation of Stokes parameters using Fourier series analysis. Light polarization was determined by calculating the polarization degree, anisotropy, asymmetry parameters, and rotational and ellipsometry angles. The nematic liquid crystal E7™ doped with 4,7-bis{2-[4-(4-decylpiperazin-1-yl) phenyl]ethynyl}-[2,1,3]-benzothiadiazole (5A) within twisted and parallel structures, was used to illustrate the applications for this technique, that has been shown to be an innovative and versatile tool to correlate the photophysics with materials structure.

Part of the book: Ellipsometry