Efficient dye-sensitized solar cell with a pure thin film of a hybrid polyoxometalate covalently attached organic dye as a working electrode in a cobalt redox mediator system

• Published in: RSC advances 2015-09, Vol.5 (94), p.76875-76882
• Main Authors: Karimian, Davud, Yadollahi, Bahram, Zendehdel, Mahmoud, Mirkhani, Valiollah
• Format: Article
• Language: English
• Subjects: Cobalt; Dyes; Electric potential; Electrodes; Polyoxometallates; Semiconductors; Thin films; Titanium dioxide; Voltage
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C5RA09104G

Polyoxometalates (POMs) are a class of inorganic metal–oxygen clusters comprising many elements, with unique structures and molecular weights, which possess similar energy band structures to metal oxides. In this research, for the first time, a Keggin-type hybrid polyoxometalate [SiW 11 O 39 (Si(CH 2 ) 3 NH 2 ) 2 O] (Hybrid-POM) is used as a pure semiconductor thin film in the working electrode of an efficient dye-sensitized solar cell (DSC) which was fabricated with a D35 organic dye as the sensitizer and a one-electron fast redox mediator cobalt complex. The D35 dye is attached to the surface of the POM by a strong amide bond (D35@Hybrid-POM). For comparison, two DSCs were also fabricated with mesoporous anatase TiO 2 , with and without a titania blocking layer, under the same conditions of electrolyte, sensitizer and counter electrode. J – V measurements of the DSCs were obtained under AM1.5G irradiation and photoelectrochemical parameters like open-circuit voltage ( V oc ), short-circuit current density ( J sc ), fill factor (FF), voltage decay and the overall efficiency were measured and compared to the mesoporous titania cells. The J – V curves show a promising enhancement overall in the DSC with the D35@Hybrid-POM structure in comparison with other prevalent mesoporous titania cells. Incident photon to current conversion efficiency spectra of the D35@Hybrid-POM DSCs and mesoporous titania with TBL (titania blocking layer) working electrodes were also obtained. A maximum IPCE of about 91% was found for the DSC employing D35@Hybrid-POM which is about 30% higher than the DSC with the mesoporous titania layer. The voltage decay measurements, calculated electron lifetime and effective recombination order ( β ) showed that the electron lifetime becomes promisingly longer when we use the Hybrid-POM structure in the photoanode. Thus, these results show that the rates of recombination and electron transfer of the cobalt mediator system at the surface of Hybrid-POM are very slow.