Effet des alcalins sur les propriétés électroniques, thermodynamiques et d’optique non linéaire des phenacenes

Abstract

To study the impact of alkalis (potassium and rubidium) on the electronic, thermodynamic and optical non-linear properties of phenazenes (picene, fulminene and [7]phenacene), we conducted a computational study using ab-initio and DFT methods. We used the base 6-311G and the functional RHF, B3LYP, CAMP-B3LYP and WB97XD to determine the structural properties, and it turns out that the B3LYP gives better results. Therefore, we have opted for DFT/B3LYP/6-311G for our further work. One-atom potassium leads to compound B, two- atom potassium leads to compound C, the one with one rubidium atom leads to compound D and the one with two rubidium atoms leads to compound E. Negative values of different electronic energies of compounds B, C, D and E show that they are stable, but also that compound E is the most stable. The results of the IR and Raman spectroscopic analysis indicate a positive correlation between our values with those of the literature, thus confirming the stability of our pure and impure molecules. In addition, for each of the three molecules, the calculated gap energy is increased from 4.27eV to 2.17eV for picene compound E; from 4.08eV to 2.28eV for fulminene compound E; from 4.07eV to 2.26eV for [7]phenacene compound E. The gap energies of the B, C and D compounds are lower than 5eV, which proves that all molecules obtained after doping are semiconductors. These results show that compound E is more reactive than compounds B, C and D. The results show that compounds B, C, D and E are thermodynamically stable. The maximum first order hyperpolarity of doped molecule derivatives for each of the three molecules is higher than that of urea; this shows that B, C, D and E are potential candidates for NLO applications. Analysis of the UV-visible spectra of different molecules and their derivatives shows that doping shifts the spectra of the compounds B, C, D and E to long wavelengths; this has made it possible to suggest their applications in organic photovoltaic cells. Moreover, this shift is accentuated for compound E.