The Optical and Electrochemical Properties of ZnS/CdSe Qds/CdS co-Sensitized TiO2 Photoanode for Quantum Dot Solar Cells

Q.V. Lam, T.H. Nguyen, T.P.T. Nguyen
Vietnam National University - Ho Chi Minh City, VN

Keywords: co-sensitized solar cell, quantum dots, thin film, titanium dioxide

Summary:

Quantum dots (QDs) - sensitized nanocrystalline TiO2 solar cells (QDSCs) are promising third-generation photovoltaic devices. Due to the tunable bandgap, the conduction bands (CB) of QDs can match the CB of TiO2 and thereby ensure effective electron transfer from QDs to TiO2. Moreover QDs may improve the efficiency of solar cells due to their multiple-exciton effect. In our work, the inhomogeneous across distribution of QDs in the TiO2 film was found, with the concentration at the upper layer. As a result, the simple film-thickness increase would not make significant contribution in improvement of solar cell efficiency. In this study CdSe quantum dots have been prepared via a colloidal with an organic ligand layer trioctylphosphine (TOP) and oleic acid as a capping agent, The photoanode composed of CdS/CdSe QDs/ZnS thin films deposited on TiO2 electrode was prepared by successive ionic layer adsorption and reaction method. The materials structure, as well as the optical, morphological and photoelectrochemical properties of ZnS/CdSeQDs/CdS//TiO2 thin films was investigated by optical spectrum, TEM, SEM, Raman spectroscopy and XRD. Sequentially assembled CdS/CdSe/ZnS quantum dots exhibited significantly improved light-harvesting ability and photocurrent efficiency, which led to a high energy conversion efficiency of 1.5 % obtained for the corresponded QDSCs.