Enhanced Energy Conversion Efficiency of La³⁺‐Modified Nanoporous TiO₂ Electrode Sensitized with a Ruthenium Complex

Abstract

The nature of TiO 2 films and sensitizer play significant roles in determining the overall efficiency and mechanical stability of dye sensitized solar cell. In this study, cis-RuL 2 (SCN) 2 , (L＝2,2'-dipyridine-4,4'-dicarboxlic acid) was synthesized from 4-methylpyridine by the procedure of cross-coupling, oxidation, conjugation and ligand substitution. TiO 2 films were obtained by blending P25 and TiO 2 sol. To increase the photoelectric properties of the thin TiO 2 films, La(NO 3 ) 3 with different concentrations (0.1%, 0.3%, 0.5% and 0.7%) were added into the sol. Both undoped and doped samples of the thin films were sensitized by cis-RuL 2 (SCN) 2 and structurally characterized by X-ray diffraction, atomic force microscopy and X-ray photoelectron spectroscopy. In addition, the photoelectric properties of the TiO 2 electrodes were investigated. The results show that doping lanthanum ions made the grain size smaller and surface area larger. When the concentration dopant is 0.5%, the short circuit current and open circuit voltage of the TiO 2 film reach maximum. The short circuit current increases 0.54 mA/cm 2 more than that of undoped film, and the open-circuit voltage increases 30.41 mV more than that of undoped film.

Strong Efficiency Enhancement of Dye-Sensitized Solar Cells Using a La-Modified TiCl4 Treatment of Mesoporous TiO2 Electrodes

“…Recent work suggests that the performance of DSSCs can be improved by doping the TiO 2 nanocrystals during synthesis using lanthanum, , neodymium, gallium, or yttrium ions . For La-doping, it was claimed that an increase in the oxygen vacancy density at the particle surface was responsible for improved dye adsorption, resulting in a higher dye load responsible for an increased photocurrent, which is analogous to our findings.…”

Doping of TiO2for sensitized solar cells

“…75 This theory has been confirmed by EPR analysis, which showed a strong correlation between density of oxygen vacancies, dye loading and device efficiency. 219,220 A post-treatment with an acidic La 3+ solution was shown to drastically increase J SC although no La 3+ was detected in the final particles and no morphology change was observed. An increase in electron density, combined with a down-shifted CB and increased dye adsorption was responsible for the increase in J SC .…”

“…Because many optical conversion studies do not consider the effect of doping on the electron transport rate and lifetime, the exact contribution of conversion is hard to quantify. Lanthanides that have been used to dope TiO 2 are lanthanum, [219][220][221] cerium, 222,223 neodymium, 224 samarium, 225,226 europium, 225,[227][228][229][230] erbium, 229,231-236 thulium 237,238 and ytterbium. 231,232,[234][235][236][237][238][239] 4.6.1 Lanthanum.…”

Thiocyanate-Free Ruthenium(II) Sensitizer with a Pyrid-2-yltetrazolate Ligand for Dye-Sensitized Solar Cells

“…The synthesis involves two steps: (i) preparation of [RuCl 2 (dcbpy) 2 ] (dcbpy = 2,2′-bipyridine-4,4′-dicarboxylic acid); (ii) substitution of the chlorides in [RuCl 2 (dcbpy) 2 ] with 5-(pyrid-2-yl)tetrazole (see the Supporting Information).…”