Exploration of charge transfer and absorption spectra of porphyrin–polyoxometalate hybrids to search for high performance sensitizers

Abstract

Based on a porphyrin derivative (system 1), Lindqvist-, Keggin-, and Anderson-type polyoxometalate (POM) organic–inorganic hybrids (systems 2–4) were designed with the aim of investigating their charge transfer character and screening them as high performance p-type sensitizers. The electronic structures and absorption spectra of systems 1–4 were systematically investigated by means of density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The results indicate that Lindqvist- and Keggin-type POMs affect the lowest unoccupied molecular orbital (LUMO) energy levels, while the Anderson-type POM does not contribute to the frontier molecular orbitals (FMOs). Furthermore, the absorption spectrum of the Lindqvist-type POM porphyrin derivative (system 2) exhibits strong and broad absorption in the visible region and is red shifted about 100 nm in comparison with system 1. Further studies point out that system 2 can balance the photovoltaic parameters, LHE, HJE, CRE and DRE, indicating that it will be a promising high performance dye sensitizer in p-type dye-sensitized solar cells (DSSCs).