Ruthenium(ii) quasi-solid state dye sensitized solar cells with 8% efficiency using a supramolecular oligomer-based electrolyte

Abstract

We have achieved 8% efficiency for the ruthenium(II) dye, SY-04, in quasi-solid state dye sensitized solar cells using a supramolecular oligomer-based electrolyte. The dyes in this study, SY-04 and SY-05, which were synthesized through highly efficient synthetic routes, showed better molar extinction coefficients compared to that of the Z907 dye. In the absorption spectra, SY-04 and SY-05 displayed better red shifted metal ligand charge transfer (MLCT) absorption bands at 533, 382 and 535, 373 nm, respectively, compared with 521, 371 nm of the Z907 dye. Also, SY-04 and SY-05 showed better molar extinction coefficients, 6691, 16 189 M⁻¹ cm⁻¹ and 6694, 16 195 M⁻¹ cm⁻¹ as compared with the Z907 dye, 4308, 4917 M⁻¹ cm⁻¹. When excited into the charge-transfer absorption bands of SY-04 and SY-05 in ethanol at 77 K, broad emission bands for SY-04 and SY-05 with a maximum at 788 nm and 786 nm, respectively, were observed compared to the emission band of Z907 at 797 nm. The current–voltage characteristics of the SY-04 sensitizer gave the best performance data, J_SC = 18.0 mA cm⁻², V_OC = 0.662 V, ff = 0.663, and an η of 8.0%. The increased V_OC value for SY-04 than Z907 is mainly attributed to high charge recombination resistance by effective dye coverage, which is confirmed by impedance spectroscopy.