Cu2S Counter Electrode Prepared by Various Methods Enhanced the Efficiency of CdS/CdSe Quantum Dot Sensitized Solar Cells

CdS/CdSe co-sensitized TiO2 photoanodes for QDSSCs were prepared by successive ionic layer adsorption and reaction (SILAR), spray pyrolysis and zinc-copper alloy processes. The TEM, SEM, EDS, XRD, UV-Vis and J-V curve analyses were performed to investigate the surface and structural properties of the prepared electrodes and the efficiencies of the fabricated QDSSs. Employing different methods for preparation of Cu2S counter electrode affected the performance of QDSSCs under one illumination of sun (100 mW/cm2) so that various conversion efficiencies (μ) of 3.18, 0.341 and 0.266% were measured in alloy, SILAR and spray pyrolysis methods, respectively. Therefore, among these methods, the zinc-copper alloy process with higher efficiency is preferred that gives fill factor (ff) and short circuit density (JSC) values of 0.44 and 11.69 mA/cm2. The TEM images showed that CdS and CdSe QDs are in close contact with TiO2 nanoparticles and the sizes of CdS and CdSe QDs are about 5 and 6nm, respectively. The energy-dispersive X-ray spectroscopy (EDS) measurement confirmed that CdS and CdSe QDs are successfully deposited on the surface of the TiO2 film. The band gaps estimated from Tauc plots using UV-Vis spectra vary from 3.1 eV (without CdS and CdSe, bare TiO2) to 2.38 eV (TiO2/CdS (3)/CdSe).

Keywords:

Quantum dot sensitized solar cells , TEM , Photocurrent , Photovoltaic performance , Cu2S counter electrode