Effect of carbonaceous counter electrodes on the performance of ZnO-graphene nanocomposites based dye sensitized solar cells

With many advantages like low-cost preparation, excellent electrical properties, and high catalytic activity; carbon allotropes are the most expected carbon materials to substitute the expensive Platinum (Pt) as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). In the present study, the photovoltaic behaviors of DSSCs fabricated with graphene, multiwalled carbon nanotubes (MWCNTs), and Pt films CEs, respectively, were compared. The graphene and MWCNTs CEs films were prepared by doctor blading the graphene and MWCNTs pastes on Indium tin oxides (ITOs) glass substrates. The structural, morphological, and compositional properties of these carbon CEs viz. graphene and MWCNTs were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and energy dispersive X-ray (EDX), respectively. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed for the examination of electrochemical and catalytic properties of Pt as well as carbonaceous CEs. These low-cost graphene and MWCNTs CEs were employed in the sandwich-structured DSSCs having ZnO-graphene nanocomposite films as photoanodes. The photoconversion efficiency (eta) values of as prepared DSSCs were measured under AM 1.5 illumination (100 mW cm(-2)). The DSSCs with graphene CE and MWCNTs CE performed with efficiency values of 2.26% and 2.04%, respectively. The performance of these carbonaceous CEs are comparative to that of Pt CE which indicates the practicability of carbon based nanomaterials in DSSCs as low cost alternatives to the expensive Pt.