Elaboration of new semiconductor papers by soft chemistry processes for organic electronics – Scope

The use of organic semiconductors in electronic devices offers interesting prospects, particularly in terms of significant reductions of weight and manufacturing cost. Nevertheless, these materials have several drawbacks, notably the non-reproducibility of the synthesis and the difficulty of purification, besides the toxicity of the used organic solvents. They raise other ecological issues, not only for the semiconductor polymers themselves but also because of the materials used as support, non-recyclable, non-biodegradable or from non-renewable sources (plastic or glass). The SCOPE project is part of a new sustainable perspective oriented towards the development of an environmentally friendly process for the synthesis of new semiconductor molecules, polyimines or polyazomethine, using a simple reaction by condensation of a dialdehyde and a diamine in a green solvent at room temperature. The only by-product formed is water. Among the substrates used, 3 of them are bio-monomers. Several dopants will be considered to modulate the conductivity of the synthesized polymers. All polymers will be characterized to determine their structural, optoelectronic, electrical, and electrochemical properties, and to establish a structure/properties correlation. Measurements combining UV/Visible/Near Infrared spectroscopy and cyclic voltametry will allow experimental determination of the band gap Eg, as well as the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energy levels. The results will allow the selection of the best polymers that will be grafted (as is or after doping) onto paper pulp via a covalent bond. Paper pulp is chosen because it is an eco-material made from renewable and biodegradable resources. The pulp fibers are first oxidized in water before being coupled to the semiconductor polymer by amidation in water without the use of peptide couplers. The influence of the grafting rate and the position of the doping step, before or after the polymer/pulp coupling, on the final conductivity value of the material will be studied. The materials presenting an interesting conductivity will be finely characterized, in terms of mechanical resistance and thermal stability, in a concern of durability, and from the optoelectronic point of view with the determination of their optical gap. Paper sheets will be prepared with these different materials before a complete characterization of their physical properties (conductivity, breaking strength, elongation...). These sheets will be used as supports for printed chemical sensors, which will be produced according to a simple design, before being tested as a proof of concept.