Earth-Abundant Materials as Photosensitizers in the Molecular Assemblies for Solar Energy Conversion

Abstract

Abstract : We investigate the applicability of the B3LYP functional to the ground state determination of first row transition metal complexes, focusing mainly on Fe(II)-polypyridine complexes with ligands of varying ligand field strength. We find that the error in the energy differences between the low-spin (singlet) and high-spin (quintet) states is systematic for structurally related complexes that undergo similar distortion in the metal-ligand coordination environment between the high-spin and low-spin states. This systematic behavior can be exploited and the ground state of an arbitrary Fe(II) complex can be determined by comparing the calculated energy differences between the singlet and quintet electronic states of a complex to the energy differences of structurally related complexes with a known, experimentally-determined ground state. Furthermore, we apply DFT and TD-DFT to study ground and excited state properties of Fe(II)-polypyridine sensitizers. Quantum dynamics simulations are further used to investigate the interfacial electron transfer (IET) between the excited Fe(II) dyes and titanium dioxide nanoparticle. All three complexes investigated display band-selective sensitization, whose origin is attributed to the poor alignment of the lowest energy excited states with the conduction band of the titanium dioxide semiconductor.