RESUMO
In this paper, we performed theoretical studies on the twelve D-A-π-A type organic dyes (G-1 ~ G-3, M-1 ~ M-3, J-1 ~ J-3, and S-1 ~ S-3) with 9-phenylcarbazole as the electron donor in anticipation of the application of these dyes in dye-sensitized solar cells (DSSCs). DFT and TD-DFT methods are applied to investigate in detail the molecular geometries, frontier molecular orbitals (FMOs), absorption spectra, charge density difference (CDD), and transition density matrix (TDM) of several dyes. The results show that the M-series (M-1 ~ M-3) dyes have the largest dihedral angles between the electron donor and the auxiliary acceptor and also has the largest energy gaps in HOMO-LUMO orbitals, which greatly reduces the charge transfer efficiency. Finally, the UV-Vis absorption spectra inferred that the anchoring groups modified with o-nitrobenzoic acid (G-3, M-3, J-3, S-3) can red-shift the absorption peaks of the dyes, which results in higher light-harvesting efficiency and improves the power conversion efficiency of DSSCs. Overall, all of these dyes contribute to the improvement of photovoltaic power conversion efficiency and have potential for application in DSSCs devices.
RESUMO
Integrated atomistic and molecular dynamic simulations are used to characterize the role hydrogen bonding and interchain interactions on structures and phase transitions of novel bent-core-like mesogenic materials that exhibit new self-assembly features, attractive to the development of functional materials. Multi-step simulations were carried out to model phase transitions and various spectra of two complex mesogenic materials formed from acid functionalized azo compounds, 4-[2,3,4-tri(octyloxy)phenylazo] benzoic acid and 4-[2,3,4- tri(heptyloxy)phenylazo] benzoic acid. The simulations contain three consecutive steps, involving molecular quantum chemistry, molecular crystal packing, and super cell molecular dynamics calculations. These two mesogens are supposed to form phasmidic molecular conformers. However, simulations point to the formation of complex discotic bent-core-like liquid crystals with tetramer mesogenic assemblies, in very good agreement with experimental observations. The wide range agreements between simulations and experimental results include transitions of crystal structures to columnar and uniaxial nematic phases, x-ray diffraction patterns of columnar phases, the structure of the two-dimensional complex bent-core-like tetramers, molecular Raman spectra, Raman depolarization spectra, and order parameters of nematic phases. The multi-step simulation methodology and its results shed light on this unique behaviour of plasmids with flexible side chains for simulation design of novel bent-core-like mesogenic materials.
RESUMO
Taking the degradation mechanism into consideration, inorganic small-molecular H3BO3 was selected for surface coordination of black phosphorus (BP). The successful coordination between BP and H3BO3 not only improves the ambient stability of BP, but also preserves the intrinsic properties of BP without distorting its structure.
