Toward the Computational Design of Iron-Based Chromophores
Abstract
The proposed research aims to investigate structure-property relationships in Fe(II)-polypyridines, focusing on their function as chromophores in dye-sensitized solar cells (DSSCs). Iron-based transition metal complexes have recently gained attention as chromophores with potential to replace more traditional ruthenium-based photosensitizers in DSSCs. Visible light excitation in both types of complexes results in the population of photoactive metal-to-ligand charge transfer (MLCT) states that undergo interfacial electron transfer (IET) into the conduction band of the titanium dioxide semiconductor. The MLCT states in Fe(Il)-polypyridines are, however, depopulated via ultrafast intersystem crossing (TSC) into a manifold of photo-inactive metal-centered ligand-field states, which hampers their function as chromophores. The goal of this work is to increase the efficiency of Fe(II)-polypyridines as photosensitizers in DSSCs by tuning their absorption properties, as well as by adjust of Fe(II)-polypyridines the relative rates of the JET and ISC events, so that the interfacial electron transfer occurs at a faster time scale than the intersystem crossing. Strategies to achieve the stated goal include: (1) Use of ligands with high ligand-field strength to increase the lifetime of photoactive MLCT excited states. (2) Cyclometalation of polypyridine ligands to improve the photosensitizer absorption properties. (3) Design of heteroleptic Fe(II)-polypyridines with the aim to induce a faster JET in the chromophore-semiconductor assemblies via directional donor-acceptor effects. To achieve these objectives, we will employ the tools of computational chemistry, such as density functional theory, time-dependent density functional theory, and wavepacket dynamics, to model the initial absorption of visible light by these complexes and JET between the excited chromophores and the semiconductor. Results obtained from this work will lead to a better understanding of how the structure and substituents on the polypyridine ligands impact the light absorption by Fe(II )-polypyridines and subsequent JET into the semiconductor, and have implications for the development of novel photosensitizers based on earth-abundant iron complexes.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 12, 2017
- Source ID
- W911NF1510124
Entities
People
- Elena Jakubikova
Organizations
- Army Contracting Command
- North Carolina State University
- United States Army