2,6-Bis(1-methylbenzimidazol-2-yl)pyridine: a new ancillary ligand for efficient thiocyanate-free ruthenium sensitizer in dye-sensitized solar cell applications

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 (π), or acceptors (A) in D-π-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-π-A configuration can improve the light-harvesting properties and prohibit the charge recombination reactions due to the extension of the π-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 (η) 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 η 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.

Supramolecular photocatalysts constructed with a photosensitizer unit with two tridentate ligands for CO2 reduction

New supramolecular photocatalysts comprising an asymmetric bis-tridentate Ru(ii) complex that functions as a photosensitizer and a Ru(ii) carbonyl complex as the catalyst were designed. The complexes photocatalyzed the reduction of CO₂ to CO or formic acid with high selectivity. The product distribution depended on the catalyst unit. CO and formic acid were the main products when using [Ru(BL)(Clbpy)(CO)]²⁺ (BL = bridging ligand, Clbpy = 4,4′-dichloro-2,2′-bipyridine) and Ru(BL)(CO)₂Cl₂ catalysts, respectively.

Synthesis of multi-donor dyes and influence of molecular design on dye-sensitized solar cells

Multi-donor incorporated organic dyes were designed and synthesized and their structure–property relationship was investigated in dye-sensitized solar cells (DSCs).

Near-infrared unsymmetrical blue and green squaraine sensitizers

Two novel panchromatic asymmetrical squaraine sensitizers (SPSQ1 and SPSQ2) have been synthesized, characterized and effectively used for TiO₂-based dye sensitized solar cells.

High photo-currents with a zwitterionic thiocyanate-free dye in aqueous-based dye sensitized solar cells

A zwitterionic dye shows high photocurrent and incident photon to current efficiency in water based dye sensitized solar cells.

Advanced Cd(II) complexes as high efficiency co-sensitizers for enhanced dye-sensitized solar cell performance

This work reports on two new complexes with the general formula [Cd3(IBA)3(Cl)2(HCOO)(H2O)]n (1) and {[Cd1.5(IBA)3(H2O)6]·3.5H2O}n (2), which can be synthesized by the reaction of Cd(II) with rigid linear ligand 4-HIBA containing imidazolyl and carboxylate functional groups [4-HIBA = 4-(1H-imidazol-1-yl)benzoic acid]. Single-crystal X-ray diffraction analyses indicate that complex 1 is a 2D "wave-like" layer structure constructed from trinuclear units and complex 2 is just a mononuclear structure. Surprisingly, both complexes 1 and 2 appear as a 3D supramolecular network via intermolecular hydrogen bonding interactions. What's more, due to their strong UV-visible absorption, 1 and 2 can be employed as co-sensitizers in combination with N719 to enhance dye-sensitized solar cell (DSSC) performance. Both of them could overcome the deficiency of the ruthenium complex N719 absorption in the region of ultraviolet and blue-violet, and the charge collection efficiency is also improved when 1 and 2 are used as co-sensitizers, which are all in favor of enhancing the performance. The DSSC devices using co-sensitizers of 1/N719 and 2/N719 show an overall conversion efficiency of 8.27% and 7.73% with a short circuit current density of 17.48 mA cm(-2) and 17.39 mA cm(-2), and an open circuit voltage of 0.75 V and 0.74 V, respectively. The overall conversion efficiency is 27.23% and 18.92% higher than that of a device solely sensitized by N719 (6.50%). Consequently, the prepared complexes are high efficiency co-sensitizers for enhancing the performance of N719 sensitized solar cells.

Cyclometalated ruthenium(ii) complexes with bis(benzimidazolyl)benzene for dye-sensitized solar cells

The length of alkyl chains on the benzimidazole rings of cyclometalated ruthenium dyes is critical to the DSSC performance.

Multifunctional Zn(ii)/Cd(ii) metal complexes for tunable luminescence properties and highly efficient dye-sensitized solar cells

Complexes Zn1 and Cd1 exhibit tunable luminescence properties and they can serve as co-sensitizers to enhance the power-conversion efficiency.