Showing papers by "Paolo Giannozzi published in 2014"
TL;DR: In this article, a hybrid ternary model system based on a poly(3-hexylthiophene) (P3HT)/zinc phthalocyanine (ZnPc)/ZnO interface was used to study heterojunction interfaces of hybrid polymer solar cells, with the aim to better understand and precisely predict their photovoltaic properties.
Abstract: Atomistic simulations and experimental investigations are combined to study heterojunction interfaces of hybrid polymer solar cells, with the aim to better understand and precisely predict their photovoltaic properties. The focus is on a hybrid ternary model system based on a poly(3-hexylthiophene) (P3HT)/zinc phthalocyanine (ZnPc)/ZnO interface, in which a ZnPc interlayer is applied to improve the performance of the hybrid interface. Theoretical predictions of the ternary system are validated against the properties of a concrete P3HT/ZnPc/ZnO planar heterojunction device. The theoretical predictions closely agree with the photovoltaic properties obtained in P3HT/ZnPc/ZnO solar cells, indicating the strength of the method for modeling hybrid heterojunction interfaces. The theoretical and experimental results reveal that: i) ZnPc molecules in direct contact with a ZnO surface insert new energy levels due to a strong ZnPc/ZnO coupling, ii) electron injection from these new energy levels of ZnPc into ZnO is highly efficient, iii) the ZnPc/ZnO coupling strongly influences the energy levels of the ZnO and P3HT leading to a reduction of the open circuit voltage, and iv) charge carrier recombination at the P3HT/ZnO interface is reduced by the ZnPc interlayer. The intercalation of ZnPc leads to an increase in photocurrent as well as to an overall increase in power conversion.
44 citations
TL;DR: In this article, the U-corrected density functional theory and time-dependent density functional perturbation theory are used to simulate the photoreduction of dioxygen and photooxidation of methanol catalyzed by model TiO2 nanoparticles.
Abstract: Titanium dioxide and TiO2-based materials are widely used in environmental- and energy-related applications like photocatalysis and photovoltaics, where they are usually employed as nanocrystals or nanostructures. The present contribution is aimed at filling the gap between the vast literature devoted to the simulation of electronic and photochemical properties of TiO2 crystals and surfaces, and the few theoretical studies of photoactivated processes involving instead TiO2 nanostructures. More specifically, photocatalytic and photovoltaic processes promoted by model TiO2 nanoparticles (NPs) have been investigated by using ab initio simulations based on the U-corrected density functional theory, and on the time-dependent density functional perturbation theory. We focus on well-investigated processes like the photogeneration of charge carriers in UV-irradiated NPs, the photoreduction of dioxygen and photooxidation of methanol catalyzed by NPs, and the splitting of photogenerated charge carriers occurring at...
32 citations
TL;DR: In this paper, the authors use an innovative simulation technique to show that rapid molecular rotations explain how a molecule with a three-fold rotational axis crystallizes at room temperature into a form with a four-fold symmetry about the same axis.
Abstract: This papers resolves a long standing experimental paradox in one of the most promising hydrogen storage materials. The authors use an innovative simulation technique to show that rapid molecular rotations explain how a molecule with a three-fold rotational axis crystallizes at room temperature into a form with a four-fold symmetry about the same axis.
6 citations