Recently, the diblock co-oligomers concept, a new design method to obtain conjugated organic compounds for varied applications in photovoltaics was proposed. These materials combines the interesting properties of extended systems and the versatility of small molecules, leading to low bandgap materials with improved properties, such as adjustable open circuit voltages and promising optical responses. Aiming to evaluate possible improved routes for the design of such materials, in this report we present a study on the effect of π-bridges incorporation on the properties of diblock co-oligomers. Six different π-bridges were inserted between polythiofene (Th) and polypyrrol (Py) oligomers with five units, following the structure [Th] 5-[π-bridge]-[Py] 5. The geometry optimization and optical absorption studies were carried out in the density functional theory (DFT) and time dependent-DFT (TD-DFT) frameworks, respectively, using the B3LYP correlation-exchange functional and 6-31G(d,p) basis set. The results point out that compounds with improved opto-electronic properties can be obtained by an appropriated choice of the π-bridges. The possible improvements are associated with the higher delocalization of the π-systems on the molecules, reduction of the effective optical/electronic bandgaps, high optical transition probability between the new highest occupied and lowest unoccupied molecular levels (HOMO-LUMO), optimized charge transport properties and reduced exciton dissociation energies.
Carbon-based compounds have been considered materials of great technological interest, mainly due to their high synthesis flexibility, low cost, and unique properties. In particular, graphene-based compounds, such as modified graphene, graphene nanoribbons, and carbon quantum dots (CQD) show improved performance for a variety of applications. CQDs are particularly interesting; such zero dimensional structures usually show strong fluorescence, good water solubility, chemical stability, ease of functionalization and other properties that depend on the CQDs' geometries, sizes, and terminal edges. To better understand the influence of these factors on the electronic and reactivity properties of the CQDs, here we evaluate five different geometries and 11 chemical modifications of this material in a DFT framework using low computational cost electronic descriptors. The results indicate that geometries, edges, and chemical modifications have different roles in the local reactivities of these compounds. For instance, geometric features govern the orbital-based chemical reactivities, while the substituents' nature governs the molecular electrostatic potentials. The evaluation of frontier energy level alignments point out CQDs as potential materials for Cl 2 and SO 2 detection, which is reinforced by simulations via fully atomistic reactive molecular dynamics (FARMD).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.