Doping of molecular materials based on ferrocene and the study of their properties as organic semiconductors for their application in optoelectronic devices

Abstract 
The present study refers to the chemical doping of ferrocene materials from the reaction with 2,6-Dihydroxyanthraquinone and 2,6-Diaminoanthraquinone. Thin films of the doped molecular materials were prepared by vacuum evaporation and the morphology and structure of films were studied using SEM, EDS and IR spectroscopy. Theoretical calculations were carried out by means Gaussian16 software and all the involved species were geometrically optimized. The IR spectrum, the HOMO-LUMO energy and the bandgaps from these calculations were achieved. The theoretical and experimental IR spectra were compared in order to verify the presence of the main functional groups of the molecular materials. The theoretical bandgap of each film was also compared with that obtained by UV–vis spectroscopy, showing similar results in the range of 2–2.9 eV. These bandgap values place the synthesized materials within the so-called organic semiconductors. Additionally from the calculations of HOMO-LUMO and bandgap results, it has been suggested that the synthesized materials can be used as a semiconductor p-type. The films were evaluated in their p-type semiconductor behavior by means of unipolar devices. In the material synthesized from ferrocene and 2,6-Dihydroxyanthraquinone a virtually ohmic I-V ratio was obtained, while the compound constituted by 2,6-Diaminoanthraquinone behaved as an insulator. In order to improve the p-type behavior of the synthesized semiconductors, unipolar devices were given a hole-injecting layer between the anode and the synthesized materials: glass/ITO/CuPc/synthesized material/Ag. Its I-V electrical behavior was evaluated by the effect of influencing electromagnetic radiation in the range of the electromagnetic spectrum between the IR and the UV passing through the visible spectrum. The results for both devices have shown that the one manufactured from ferrocene and 2,6-Dihydroxyanthraquinone exhibited a behavior similar to that of a Schottky diode, while the one prepared from ferrocene and 2,6-Diaminoanthraquinone behaves like a resistor.