The performance of QDSCs based on 3D structural counter electrodes of multi-wall carbon nanotubes and nanographite

Abstract

TiO2 photoanode is sensitized with CdS and ZnS quantum dots (QDs) through the successive ionic layer adsorption and reaction (SILAR), and it is assembled into the quantum dot sensitized solar cells (QDSCs) with polysulfide electrolyte and three dimensional (3D) counter electrodes (CEs) of acid-treated multi-wall carbon nanotubes (MWCNTs) mixed with nanographite. According to SEM images and EDS spectrum, CdS and ZnS QDs have been attached to TiO2 photoanode. The infrared spectra of acid-treated MWCNTs can verify that there introduced several oxygenic functional groups in it. The TEM images of carbon CEs show graphite nanoparticles are attached to acid-treated MWCNTs framework to form the 3D structure with the large specific surface area. The photoelectric properties of QDSCs with different CEs (traditional metal Pt and 3D carbon material) are analyzed through EIS, Tafel and J–V curves. The results show that power conversion efficiency (PCE) of QDSCs based on optimized composite CEs is a little lower than that of Pt CE QDSCs, but 3D carbon material CE exhibits excellent corrosion resistance and photovoltaic stability in QDSCs. PCE attenuation rate of QDSCs based on 3D carbon CEs is 3.947%, significantly slower than that of Pt CE QDSCs, 13.118% at the identical conditions of illumination. Especially, the PCE of QDSCs with 3D structure CE (2.482%) is higher than that of Pt CE QDSCs (2.444%) after 12 h illumination.