A Series of Iron(II)-NHC Sensitizers with Remarkable Power Conversion Efficiency in Photoelectrochemical Cells*

Abstract

A series of six new Fe(II)NHC-carboxylic sensitizers with their ancillary ligand decorated with functions of varied electronic properties have been designed with the aim to increase the metal-to- surface charge separation and light harvesting in iron-based dye-sensitized solar cells (DSSCs). ARM130 scored the highest efficiency ever reported for an iron-sensitized solar cell (1.83 %) using Mg²⁺ and NBu₄ I-based electrolyte and a thick 20 μm TiO₂ anode. Computational modelling, transient absorption spectroscopy and electrochemical impedance spectroscopy (EIS) revealed that the electronic properties induced by the dimethoxyphenyl-substituted NHC ligand of ARM130 led to the best combination of electron injection yield and spectral sensitivity breadth.

Keywords: DSSC; NHC; iron complexes; light harvesting; sensitizers.