Exciton energy and charge transfer in porphyrin aggregate/semiconductor (TiO₂) composites

Abstract

A porphyrin aggregate is reported that exhibits novel exciton state properties for light-harvesting applications. This porphyrin aggregate enables control of energy dissipation of coherent excited states by changing the self-assembly pattern. New exciton spectral features create a new route of energy transfer in this porphyrin aggregate. The kinetic model of exciton state decay is addressed in this Perspective by reporting steady-state and transient emission and absorption studies of porphyrin J- and H-aggregates. The porphyrin J-aggregate emerges with better spectral coverage and exciton dynamics, which are suitable for light-harvesting antenna functions. This motif is explored in a photosensitization study of TiO₂ semiconductor materials. The transient absorption studies show that the J-aggregate improves the photoinduced charge separation at the porphyrin/TiO₂ interface. The higher charge separation is attributed to exciton-coupled charge-transfer processes in porphyrin J-aggregate/TiO₂ hybrid materials. It represents the potential of porphyrin aggregates in biomimetic artificial antenna activity.