Infoscience

Journal article

Photoelectrochemical studies of ionic liquid-containing solar cells sensitized with different polypyridyl-ruthenium complexes

The efficiency of dye-sensitized nanocryst. solar cells contg. ionic liqs., composed of org. sulfonium or imidazolium iodides, or a std. org. liq.-based electrolyte was studied, using sensitizers based on different polypyridyl-Ru complexes. The dyes N-719, [cis-Ru(II)(H2dcbpy)2(NCS)2(TBA)2] and Z-907, [cis-Ru(II)(H2dcbpy)(dnbpy)(NCS)2], with Z-907 having a more hydrophobic character, as well as the bidentate β-diketonato complex, [(dcbpy)2Ru(acetylacetonate)]Cl-, was studied. Solar cells sensitized with N-719 were more efficient than the Z-907 cells for all electrolytes studied. Adding a co-adsorbent, the amphiphilic hexadecylmalonic acid (HDMA), to Z-907 solar cells contg. an org.-liq. electrolyte resulted in increased overall light-to-electricity conversion efficiencies from 3.7% to 4.0%, (100 W/m2, AM 1.5). Possibly this is caused by an insulating hydrophobic barrier formed to suppress unwanted electron losses. By applying TiO2 (P25) nanoparticles, assumed to support electron transfer reactions, to the org.-liq. electrolyte, the conversion efficiency increased from 4.1% to 4.6% (100 W/m2, AM 1.5). In 1000 W/m2 illumination, the highest overall short-circuit c.d., 9.3 mA/cm2, was achieved with the N-719 sensitized cells, with the TiO2 nanocomposite-contg. org. liq. electrolyte. For solar cells sensitized with N-719, Z-907 or the β-diketonato complex, and contg. imidazolium or sulfonium iodide ionic liqs., no improvement of the overall conversion efficiency was noticed on addn. of HDMA to the dye or nanoparticles to the electrolyte.

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