Cobalt complex dye as a novel sensitizer in dye sensitized solar cells

Abstract

In this study, cobalt metal complex has been introduced as a novel class of sensitizer for more mechanistic consideration of the photovoltaic conversion efficiency (PCE) of dye sensitized solar cells. UV–vis spectroscopy of dye illustrates maximum absorption at wavelengths of dye in 498 and 650 nm. TiO2 was used as the photoanode of the cell whose x-ray diffraction spectrum indicates that its crystal phase is anatase (101). Surface morphology of photoanode was also investigated by scanning electron microscopy (SEM) and obviously showed ∼25 nm TiO2 nanoparticles. The cyclic voltammetry (CV) investigation of Pt-coated fluorine doped tin oxide (FTO) as the counter electrode of the cell indicates redox process on this electrode. Photovoltaic measurements of cobalt complex sensitized solar cell show that the short-circuit current density (JSC), open-circuit voltage (VOC), fill factor (FF%) and photovoltaic conversion efficiency (PCE%) are 48.80 μA.cm−2, 0.7 V, 44% and 0.09% at the air mass 1.5 (100 mW.cm−2) irradiation condition, respectively. The high light harvesting efficiency (LHE) (∼61%) and high molar absorption coefficient of the cobalt complex dye (12,500 M−1.cm−1) were other optical advantages of the cobalt complex sensitized solar cell. The results indicate the quantum yield of electron injection (φing) which depends on dye structure as a parameter influences the JSC. The pyridine rings conformation in donor part of the cobalt complex dye plays a significant role in φing and subsequently PCE. These findings open a new insight about mechanistic aspects of dye sensitized solar cells efficiency.