Ferroelectric $$\pi $$ π -stacks of molecules with the energy gaps in the sunlight range

Abstract

Ferroelectric p-stacked molecular wires for solar cell applications are theoretically designed in such a way that their energy gaps fall within visible and infrared range of the Sun radiation. Band engineering is tailored by a modification of the number of the aromatic rings and via a choice of the number and kind of dipole groups. The electronic structures of molecular wires and the chemical character of the electron-hole pair are analyzed within the density functional theory (DFT) framework and the hybrid DFT approach by means of the B3LYP scheme. Moreover, it is found that one of the advantageous properties of these systems-namely the separate-path electron and hole transportreported earlier, still holds for the larger molecules, due to the dipole selection rules for the electron-hole generation, which do not allow the lowest optical transitions between the states localized at the same part of the molecule.

Light-Induced EPR Study of Polymorphic Acene-Stipulated Transition in P3DDT:PC61BM Composite

“…Besides, they should consider the influence of possible effects affecting the final result. For example, the value of band gap calculated for isolated benzene molecule by different methods can vary within 5.12−10.5 eV; 16,38,56,57 however, its optical gap was measured to be around 3.6 eV, 58 due to the effect of large exciton binding in small molecules equal, e.g., for this molecule 3.10 eV. 59 Nevertheless, the data obtained allows us to hypothesize a close relationship of electronic properties of a composite with the band structure of an acene.…”

“…Such morphology causes the band dispersions in the direction perpendicular to the layer. This bandwidth broadening, in turn, decreases the energy band gap . The balance of these polymorphs formed in P3AT is governed by polymer structure and conditions of synthesis and can be controlled by their molecular weight, the evaporation rate of solvent, exposure to solvent vapors, and thermal annealing .…”

“…This bandwidth broadening, in turn, decreases the energy band gap. 16 The balance of these polymorphs formed in P3AT is governed by polymer structure and conditions of synthesis and can be controlled by their molecular weight, 17 the evaporation rate of solvent, 18 exposure to solvent vapors, 19 and thermal annealing. 20 When the polymer crystallinity increases, its morphology becomes more planned, its chains form two-dimensional (2D) stacks.…”

Effect of graphene substrate on the spectroscopic properties of photovoltaic molecules: role of the in-plane and out-of-plane π-bonds

“…The optical properties of undoped pentacene were studied with ab initio methods by other authors in relation to the charge transfer between the molecule and a TiO 2 substrate [9]. It has been reported that this molecule has a HOMO-LUMO gap within the range of solar radiation and that the dipole groups do not change much this gap [10]. On the other hand, experimental and theoretical studies about 2D organic networks at highly oriented pyrolytic graphite (HOPG) surface, which is very similar to graphene, reported the possibility to achieve tunable band gaps by a modification of the number of the aromatic rings [11].…”