Impact of doping with organic dopants and mixed doping with alkali metals and organic dopants on the absorption, electronic, optoelectronic, thermodynamic and nonlinear optical properties of dibenzo[b,def]chrysene in gaseous media: DFT and TD-DFT studies.

CONTEXT: In this study, we evaluate the geometrical, absorption, optoelectronic, electronic, nonlinear optical (NLO) and thermodynamic properties of dibenzo[b,def]chrysene molecule derivatives by means of DFT and TD-DFT simulations. In view of the aim of producing new high-performance materials for non-linear optics (NLO) by doping test, two types of doping were used. We obtained six derivatives by doping with organic dopants (Nitro, amide and ticyanoethenyl) and mixed alkali metal (potassium) and organic dopants. Doping with organic dopants produced molecules A, B and C, respectively when substituting one hydrogen with nitro (NO2), amide (CONH2) and tricyanoethenyl (C5N3) groups, while mixed doping involved considering A, B and C and then substituting two hydrogens with two potassiums to obtain compounds D, E and F respectively. The negative values of the various interaction energies calculated for all the doped molecules show that they are all stable, but also that molecules C and F are the most stable in the case of both dopings. The gap energies calculated at the B3LYP level of theory are all below 3 eV, which means that all the molecules obtained are semiconductors. Better still, compounds C and F, with gap energies of 1.852 eV and 1.204 eV, respectively, corresponding to decreases of 35.67% and 58.18% in gap energy compared with the pristine molecule, are more reactive than the other doped molecules. Mixed doping is therefore a highly effective way of narrowing the energy gap and boosting the semiconducting character and reactivity of organic materials. Optoelectronic properties have also been improved, with refractive index values higher than those of the reference material, glass. This shows that our compounds could be used under very high electric field conditions of the order of 4.164 × 109 V.m-1 for C and 7.410 × 109 V.m-1 for F the highest values at the B3LYP level of theory. The maximum first-order hyperpolarizability values for both types of doping are obtained at the CAM-B3LYP level of theory by C: ß mol = 92.088 × 10-30esu and by F: ß mol = 129.449 × 10-30esu, and second-order values are also given by these same compounds. These values are higher than the reference value, which is urea, making our compounds potential candidates for high-performance NLO applications. In dynamic mode and at a frequency of 1064 nm, at the CAM-B3LYP level of theory, the highest dynamic hyperpolarizability coefficients were obtained by C and F. Hyper-Rayleigh scattering ß HRS , coefficients of the electro-optical Pockel effect (EOPE), EFISHG, third-order NLO-response degree four-wave mixing γ DFWM , quadratic nonlinear refractive index n2 were also calculated. The maximum values of n2 are obtained by C (6.13 × 10-20 m2/W) and F (6.60 × 10-20 m2/W), these values are 2.24 times higher than that of fused silica which is the reference for degenerate four-wave mixing so our molecules could also have applications in optoelectronics as wavelength converters, optical pulse modulators and optical switches. METHODS: Using the DFT method, we were able to determine the optimized and stable electronic structures of doped dibenzo[b,def]chrysene derivatives in the gas phase. We limited ourselves to using the proven B3LYP and CAMB3LYP levels of theory for calculating electronic properties, and non-linear optics with the 6-311G + + (d,p) basis set, which is a large basis set frequently used for these types of compound. Gaussian 09 software was used to run our calculations, and Gauss View 6.0.16 was used to visualize the output files. TD-DFT was also used to determine absorption properties at the B3LYP level of theory, using the same basis set.

Electronic, non-linear optical, optoelectronic, and thermodynamic properties of undoped and doped bis (ethylenedithio) tetraselenafulvalene (BETS) (C10H8S4Se4) molecule: first study using ab initio investigation.

We have performed the ab initio calculation of the undoped and doped molecules bis (ethylenedithio) tetraselenafulvalene (BETS). Carbone (C) atoms have been substituted by Boron (B) to investigate their effects on the electronic structure and nonlinear optical, optoelectronic, and thermodynamic properties of BETS molecule. The RHF and hybrid density functional theories (WB97XD, B3PW91, and B3LYP) methods were applied, using the cc-pVDZ basis set. We found that the energy gap (Egap) of the doped molecules are respectively 2.476 eV and 2.569 eV for C8B2H8S4Se4 and C7B3H8S4Se4 with B3LYP/cc-pVDZ basis set, lower than one of the undoped molecule (3.316 eV). The significant increase values of polarizability (˂α˃) and first order hyperpolarizability (ß) of the doped compounds, especially in C8B2H8S4Se4 (< α > = 4.5315 × 10-23 esu, ß = 22,672.27 × 10-33 esu and < α > = 4.518 × 10-23 esu, ß = 23,657.43 × 10-33 esu respectively for B3LYP and B3PW91) compared to those of the undoped molecule (< α > = 4.3602 × 10-23 esu, ß = 1290.38 × 10-33 esu, and < α > = 4.518 × 10-23 esu) show that the new molecules have a good nonlinear optical property. Results suggest that these molecules doped with boron are a potential candidate as semiconductors compounds and nonlinear optical materials.