Fabrication of quantum dot-sensitized solar cells with multilayer TiO2/PbS(X)/CdS/CdSe/ZnS/SiO2 photoanode and optimization of the PbS nanocrystalline layer

Abstract

In this work, two multilayer photoanode structures of TiO2/PbS(X)/CdS/ZnS/SiO2 and TiO2/PbS(X)/CdS/CdSe/ZnS/SiO2 were fabricated and applied in quantum dot-sensitized solar cells (QDSCs). Then, the effect of PbS QDs layer on the photovoltaic performance of corresponding cells was investigated. The sensitization was carried out by PbS and CdS QDs layers deposited on TiO2 scaffold through successive ionic layer adsorption and reaction (SILAR) method. The CdSe QDs film was also formed by a fast, modified chemical bath deposition (CBD) approach. Two passivating ZnS and SiO2 layers were finally deposited by SILAR and CBD methods, respectively. It was shown that the reference cell with TiO2/CdS/ZnS/SiO2 photoanode demonstrated a power conversion efficiency (PCE) of 3.0%. This efficiency was increased to 4.0% for the QDSC with TiO2/PbS(2)/CdS/ZnS/SiO2 photoelectrode. This was due to the co-absorption of incident light by low-bandgap PbS nanocrystalline film and also the CdS QDs layer and well transport of the charge carriers. For the CdSe included QDSCs, the PbS-free reference cell represented a PCE of 4.1%. This efficiency was improved to 5.1% for the optimized cell with TiO2/PbS(2)/CdS/CdSe/ZnS/SiO2 photoelectrode. The maximized efficiency was enhanced about 25% and 70% compared to the PbS-free reference cells with and without the CdSe QDs layer.