Exploring Interfacial Phenomena in Photovoltaic Materials Structures Using First-Principles Calculations and Beyond.

[摘要] Photovoltaics are a large part of the global strategy to reduce carbon dioxide emissions. The strict processing requirements of silicon are viewed as economic barriers to larger scale deployment of solar energy.Many of these materials have photocurrents limited by dissociation of bound excited states.The separation between the photo-excited electron and the hole at the interface between the donor and acceptor material is at the core of the functional response of an organic photovoltaic (OPV) device.We therefore examine the effects of interfacial electrostatics in a semi-classical manner on these excited states for both an organic interface and a hybrid organic-inorganic interface. We use boron subphtalocyanine chloride and C60 as our organic interface wherein we also simulate the effects of thermal motion on the excited state energetics using ab initio molecular dynamics. For our hybrid interface, we use pentacene and silicon for which the applicability of our model depends on surface termination. We develop a semi-classical model for the description of dissociation between electron and hole, which takes into account the difference of dielectric constants of the materials juxtaposed at the interface, as well as the potentially polar nature of the interfacial termination.Particularly this latter effect can be exploited for device performance optimization.Using ab intio modeling, we explore possible modifications of boron subphthalocyanine chloride derivatives to control the dipole associated with these molecules and their photonic properties.We substitute the axial boron and chlorine atoms for other trivalent and halogen atoms in our derivatives. We explore boron subphthalocyanine chloride derivatives as possible organic photovoltaic materials. Possible crystal structures are predicted and their electronic and photonic properties for the proposed derivatives.We further refine the semi-classical model, leading to a quantum mechanical model based on the effective mass Schrödinger equation, which utilizes a self-consistent approach for the calculation of excited states.This model reveals that at hybrid organic/inorganic interfaces, excited electron-hole configurations transition from a regime where both reside in the donor phase to a regime where they are separated across the interface, which is controlled by the attraction between electron and hole and the band edge offset.

[发布机构] University of Michigan

[效力级别] DFT

[关键词] Photovoltaics;DFT;Excitons;Solar cells;Heterojunctions;Interfaces;Materials Science and Engineering;Physics;Engineering;Science;Materials Science and Engineering