Studies of Organic Semiconductors for 40 Years—V

The aim of the present paper is limited to a survey of part of the prolonged research activity of the Padova group in Italy on the structural and electronic properties of organic charge transfer (CT) crystals studied by optical spectroscopy methods. The presentation is given in the form of a short review, without attempting to comprehensively cover all the relevant literature. Attention is focused here on semiconducting CT crystals, but it is worthwhile stressing that optical studies of CT organic conductors and superconductors share many of the concepts, experimental methods and theoretical models discussed here.