Small Molecules Containing Amphoteric Imidazole Motifs as Sensitizers for Dye-Sensitized Solar Cells: An Overview

Organic dyes, porphyrins and inorganic complexes containing imidazole (IM) motifs have been demonstrated as a new class of sensitizers in dye-sensitized solar cells (DSSCs). Particularly, the amphoteric nature of IM-based motifs allows them to be used as donors (D), auxiliary donors (D-A), linker/branch (pi), or acceptors (A) in D-pi-A-based organic dyes and porphyrins and also employed as cyclometalated heteroleptic and ancillary ligands in the Ru(II) and Ir(III) complexes for DSSCs. It is noteworthy that the introduction of IM chromophores in the dyes of D-pi-A configuration can improve the light-harvesting properties and prohibit the charge recombination reactions due to the extension of the pi-conjugated structures and hydrophobic nature. Similarly, in the case of inorganic complexes, the presence of IM motifs as ligands can improve the light-harvesting ability, give facilely tuned HOMO and LUMO energy levels, increase the charge recombination resistance and photostability. This results in enhanced photocurrent (J(SC)) and photovoltage (V-OC) and consequently solar-to-power conversion efficiency (eta) of DSSC devices based on Ru(II) and Ir(III) complexes. Considering the interesting DSSC applications of IM-derived molecules, in this review, we therefore comprehensively discuss their photophysical, electrochemical and photovoltaic properties reported so far and establish their structure-activity relationship to further advance the eta of DSSCs. To the best of our knowledge, there is no such a review interpreting the importance of molecules possessing IM-motifs for DSSC applications to date. [GRAPHICS] .

Automated summary

Organic dyes, porphyrins, and inorganic complexes containing imidazole (IM) motifs have been used as new sensitizers in dye-sensitized solar cells (DSSCs). The introduction of IM chromophores improves light-harvesting properties and inhibits charge recombination reactions, resulting in enhanced photocurrent and solar-to-power conversion efficiency of DSSC devices. This review comprehensively discusses the photophysical, electrochemical, and photovoltaic properties of IM-derived molecules and establishes their structure-activity relationship.