Structural determination, characterization and computational studies of doped semiconductors base silicon phthalocyanine dihydroxide and dienynoic acids

The chemical doping of silicon phthalocyanine dihydroxide (SiPc(OH)₂), with (2E, 4Z)-5, 7-diphenylhepta-2, 4-dien-6-ynoic acids (DAc) with electron-withdrawing (BrDAc) and electron-donating (MeODAc) substituents is the main purpose of this work. Theoretical calculations were carried out on Gaussian16 software, with geometrical optimization of all involved species, and obtention of the highest occupied molecule orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and the respective energy gaps. The theoretical calculations show two hydrogen bridge formations: the first one as a peripheral interaction between the terminal oxygen atoms from the acid unit and hydrogen atoms from the phthalocyanine aromatic rings. The second one as the interaction at the nitrogen atoms of the phthalocyanine, which are compelled to form a new flat plane far from the original flat phthalocyanine deck. These organic semiconductors were deposited as thin films and characterized by IR spectroscopy, atomic force microscopy (AFM), and the optical parameters were gathered from UV–Vis studies. The indirect and direct optical band gap, the onset gap and the Urbach energy were obtained. In order to compare the effect of the acids as dopants of the silicon phthalocyanine, the SiPc(OH)₂-DAc films were electrically characterized. The SiPc(OH)₂-DAc films exhibit an ambipolar electrical behavior, which is influenced by the incidence of different lighting conditions at voltages above 0.3V. The glass/ITO/SiPc(OH)₂-MeODAc/Ag reaches a maximum current of 5.68 × 10⁻⁵ A for natural light condition, while the glass/ITO/SiPc(OH)₂-BrDAc/Ag, reaches a maximum current of 9.21 × 10⁻⁹ A for white illumination condition.