The photovoltaic performance of new ruthenium complexes in DSSCs based on nanorod ZnO electrode

Three new heteroleptic ruthenium complexes, [Ru(L1)(dcbpy)(NCS)2] RuII(4,7-diphenyl-1,10-phenanthroline-disulfonic acid disodium salt)(4,4′-dicarboxy-2,2′-bipyridyl)-di(thiocyanate) [K28], [RuII(L1)2(NCS)2] RuIIbis(4,7-diphenyl-1,10-phenanthroline-disulfonic acid disodium salt)-di(thiocyanate) [K313], and [Ru(L2)(dcbpy)(NCS)2] RuII(1,10-phenanthroline-5,6-dione)(4,4′-dicarboxy-2,2′-bipyridyl)-di(thiocyanate) [K27], have been synthesized as sensitizers for dye-sensitized solar cells (DSSCs) using ZnO nanorod electrode. The photovoltaic performances of the solar cells based on these sensitizer dyes are studied under AM 1.5 irradiation (100 mW/cm2). Their photophysical and electrochemical properties are also investigated. ZnO nanorod based dye sensitized solar cell sensitized with K28 ruthenium complex bearing bulky sulfoxy groups gives an overall conversion efficiency of 2.51, a short-circuit current of 7.19 mA/cm2, and an open circuit voltage of 550 mV. K28 is firstly designed and synthesized in the literature to increase molar extinction coefficients and enhanced spectral response in the visible light by expanding the π-conjugation, and of course to reduce back electron transfer due to the bulky sulfoxy groups. The vertical excitation energies, corresponding excitation wavelengths and oscillator strengths, predominant orbitals involved in ten singlet–singlet transitions and their characters obtained from the single point TD-DFT calculations have been obtained for K28.