A Simple Synthetic Route to Obtain Pure Trans‐Ruthenium(II) Complexes for Dye‐Sensitized Solar Cell Applications

Abstract

We report a facile synthetic route to obtain functionalized quaterpyridine ligand and its trans-dithiocyanato ruthenium complex, based on a microwave-assisted procedure. The ruthenium complex has been purified using a silica chromatographic column by protecting carboxylic acid groups as iso-butyl ester, which are subsequently hydrolyzed. The highly pure complex exhibits panchromatic response throughout the visible region. DFT/time-dependent DFT calculations have been performed on the ruthenium complex in solution and adsorbed onto TiO2 to analyze relative electronic and optical properties. The ruthenium complex endowed with the functionalized quaterpyridine ligand was used as a sensitizer in dye-sensitized solar cell yielding a short-circuit photocurrent density of more than 19 mA cm(-2) with a broad incident photon to current conversion efficiency spectra ranging from 400 to 900 nm, exceeding 80 % at 700 nm.

Terpyridine and Quaterpyridine Complexes as Sensitizers for Photovoltaic Applications

“…The poorer efficiency with respect to N886 was ascribed to a lower driving force for electron injection, that limits the open circuit potential. The same drawback was also reported for a qtpy substituted with four COOH anchoring moieties ( 18 , Figure 13) [68] but its high charge injection and an optimization of the electrolyte composition led to a record efficiency for qtpy Ru-complexes of 6.53% (TiO 2 : 12 + 5 μm, dye: 0.18 mM t -butanol / CH 3 CN 1:1 with 10% DMF, electrolyte: 1.0 M dimethylimidazolium iodide, 0.03 M I 2 , 0.1M CDCA, 0.1M GuSCN, 0.23 M LiI in valeronitrile / CH 3 CN 15:85). Co-sensitization with D35, in order to enhance conversion at higher frequencies, was also reported.…”

“…Exploiting microwave-assisted synthesis, a facile procedure to obtain a functionalized qtpy ligand and its trans -dithiocyanato ruthenium complex has been reported [68] (Scheme 3). …”

Polymethine Dyes in Hybrid Photovoltaics: Structure–Properties Relationships

“…As result, a lower recombination of injected electrons with electrolyte and less self quenching of excited states is observed. These features led to an overall increase in charge injection and to better J SC , which is commonly low for organic dyes compared with those of Ru complexes 24. Notably, improved efficiencies are correlated with better IPCE in the same spectral region, in fact (as reported in Section 3.3.3) the chromogen core has not been modified.…”

“…However, it is difficult to find a sensitizer that fulfills all the above requirements. For examples, metal–organic complexes generally show panchromatic absorptions but low molar extinction coefficients,24 whereas the well‐studied D–π–A organic dyes25 have the opposite characteristics, with narrower absorptions in the visible region. Therefore, in this scenario, polymethine dyes can play an important role because of their intense absorption in the far‐red/NIR region 26…”

Can nitro groups really anchor onto TiO2? Case study of dye-to-TiO2adsorption using azo dyes with NO2substituents

“…[1][2][3][4][5][6] A photosensitizer, which absorbs light (solar energy) and converts it into electrical energy, is one of the most important device components of a DSSC. 5,7,8 Both metal-organic complexes (usually based on rutheniumpyridyl or zinc-porphyrin) and organic dyes have been successfully incorporated into DSSCs. [9][10][11][12][13] The structures of organic dyes generally consist of an electron-rich donor, a conjugated π-bridge, an electron-deficient acceptor and an anchoring group.…”