Photoluminescence spectroscopy evaluation

Finally, we will concentrate on the chemical reactivity of silyl derivatives of thiophene. The oxidative polymerization of various silyl monomers lead to polythiophene. The evaluation of this new polymerization reaction implies a precise characterization of the produced conjugated materials. Knowledge and the control of the pertinent parameters which direct the properties of the conjugated systems are essential. Also required is the development of methods which allow a precise characterization of the samples. The role of vibrational infrared and Raman spectroscopy is of fundamental importance in this field. Optical spectroscopy is one of the few tools for unravelling the structure of these materials and understanding their properties. First, new criteria based on infrared, Raman and photoluminescence spectroscopy which allow precise estimates of the conjugation properties will be reported. Then the synthesis and characterization of polythiophene samples arising from the oxidative polymerization of silyl thiophene will be presented. 

Band gaps in semiconductors can be investigated by other optical methods, such as photoluminescence, cathodoluminescence, photoluminescence excitation spectroscopy, absorption, spectral ellipsometry, photocurrent spectroscopy, and resonant Raman spectroscopy. Photoluminescence and cathodoluminescence involve an emission process and hence can be used to evaluate only features near the fundamental band gap. The other methods are related to the absorption process or its derivative (resonant Raman scattering). Most of these methods require cryogenic temperatures. 

Presentations of Jablohski s contribution to spectroscopy in the frame of the evolution of science and political situation in the 1930s and 1940s have been published [14, 15]. The contribution of Jacques and Francis Perrin, Jablonski, Vavilov, Levshin, Lewis, and Kasha to the definition of state diagram has been critically evaluated and the originality of each one commented by Nickel [16, 17]. The topic was discussed at the first congress on photoluminescence in Warsaw, May 20-25, 1936 (Pringsheim president, Jablonski secretary). The lively discussion that took place on that occasion has been retraced in detail by Nickel [18]. 

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