Influence of TCNQ acceptor on optical and electrical properties of tetrasubstituted allenes films fabricated by vacuum thermal evaporation

In this work, the synthesis and characterization of organic semiconductors formed from allenes and TCNQ salts are reported. These materials have been utilized to prepare thin films by thermal evaporation at high temperature. The chemical structure and morphology of the deposited films were analyzed by IR spectroscopy, fast atomic bombardment mass and scanning electron microscopy. The optical band gap of these semiconductors films was evaluated from optical absorption measurements. Theoretical calculations (DFT with dispersion forces analysis included) were carried out in order to simulate molecular interaction and to establish the nature of the bonds between both fragments. This has resulted in finding some intermolecular and some intramolecular hydrogen bonds and their formation is discussed. Finally the direct current electrical properties of the glass/ITO/allene-TCNQ/Ag sandwich structures were also investigated. The conductivity behaviour of these materials was achieved by means of electrical measurements; the materials show semiconductor characteristics and all the conductivity values are found around 10⁻⁸–10¹ Ω⁻¹ cm⁻¹.