High-Efficiency Cycloruthenated Sensitizers for Dye-Sensitized Solar Cells

Abstract

Four thiocyanate-free ruthenium sensitizers (DUY24-DUY27) containing 2-thienylpyridine moiety as cyclometalating core were synthesized for dye-sensitized solar cell (DSC) application. To the best of our knowledge, DUY24-DUY27 are four best-efficiency sensitizers having 42%-65% higher efficiencies compared to those of the published sensitizers comprising the same type of the cyclometalating ancillary ligands. The significant characteristic of DUY24-DUY27 is their β-lowest unoccupied spin orbital (β-LUSO) distributes remarkably on the cyclometalating ligands, especially on the soft sulfur atom, which strengthens the interaction between the oxidized dye and iodide ion for efficient dye regeneration. The photovoltaic performance of DUY24-DUY27-based DSCs supports that the dye regeneration (therefore the short-circuit photocurrent density (J) of the cell) can be improved by not only lowering the highest occupied molecular orbital energy level of the dye molecule but also distributing the β-LUSO properly on the soft atoms. The study provides an important new guide for designing high-efficiency ruthenium-based dyes for DSC application.

Recent Investigations on Thiocyanate-Free Ruthenium(II) 2,2′-Bipyridyl Complexes for Dye-Sensitized Solar Cells

“…Table 2 lists all detailed data for these dyes. Another paper with four new dyes was published in 2018 by the same group [32], this time choosing as only anchoring ligands the tetrabutylammonium salts of dcbipy and as N^C ligand a thienyl-or thienothienyl-pyridine, bearing a 5-Hex-thienyl moiety in the 4 position of the pyridine and different alkyl chains on the cyclometalating ring. Figure 6 shows the structures of the novel compounds 11a-11d, through which the authors explored the effect of having a simple thiophene or a thienothiophene on the pyridine, and also the influence of the presence of a sulfur atom between the ring and the hexyl chain.…”

The function of Chalcogenophene in the Cyclomatelated Ring of the Cycloruthenated Dyes applied in Dye-Sensitized Solar Cell

“…The new complexes DUY24-O and DUY24-Se were synthesized by a cyclometalation reaction similar to the procedure for preparing DUY24 reported previously. 21 The detailed synthesis steps and structure characterization can be found in Scheme S1, Supporting Information.…”

“…24−26 Recently, we have reported a good-efficiency NCS-free cycloruthenated dye (DUY24) with thiophene as a part of the cyclometalated ring in the ancillary ligand. 21 It was also shown that an organic dye containing a selenophene π-bridge has higher absorption coefficient and longer λmax compared to that containing the thiophene ring. 27−29 NCS-containing ruthenium (not the NCS-free cyclometalated structure) dye with selenophene as the substitute in the bipyridine ancillary ligand also shows higher absorption coefficient and lower MLCT energy compared to its thiophene analogue.…”

First cycloruthenation of 2-alkenylpyridines: synthesis, characterization and properties

“…Cyclometalated ruthenium complexes have been investigated for their significantly improved absorptions in the visible region especially when compared with the classic Ru(bpy) 3 2+ . 10,11 To date, many cycloruthenated complexes have been synthesized and used as energy acceptors, 12 electron transfer sensitizers in dyads, 13 redox mediators in oxidase chemistry, 14 sensitizers for dye sensitized solar cells, 15 chemosensors, 16 and PDT sensitizers 17 by personalized modifications of cyclometalated ligands such as expanding π-systems, 13,15 and grafting photosensitive groups. 16 b ,17 However, most of ligand frameworks used in these complexes have been based on 2-arylpyridine derivatives 11–17 and N -heterocyclic carbenes 18 with rare examples with 2-phenylimidazole, 19 and N , N -dimethylbenzylamine.…”