Study On The Relationship Between Work Electrode Crystal And Cell Performance In TiO₂/CdS/CdSe Quantum Dot Sensitized Solar Cells

Due to their potential applications in solar energy utilization, quantum-dot-sensitized solar cells (QDSSCs) has attracted a great deal of research interest. As a core part of QDSSC, the structure of quantum dot sensitized semiconductor nanocrystalline film plays a decisive role in determining the cell performance of a QDSSC. In this thesis, using the CdS/CdSe cosensitized QDSSC as a example, we studied the effect of lattice matching between the oxide semiconductor and quantum dots (QDs), quantum dots and passivation on the cell performance. The main content of the research are as follows:1. dual post-treatments was performed for CdS/CdSe sensitized QDSSC by introducing a CdS lattice transition layer between CdS/CdSe QDs and ZnS passivation layer through a successive ionic layer adsorption and reaction (SILAR) method.. EIS analysis shows that the introduction of CdS leads to a large decrease of the charge recombination and improvement of charge transport whitin the photoanode film. IMPS and IMVS reveals electron collection efficiency is increased due to the introduction of CdS. As a result, a20%increment in photocurrent was observed when CdS/ZnS post-treatment is compared to that of ZnS post-treatment. With post-treated by CdS/ZnS, a high energy conversion of5.47%for CdS/CdSe cosensitized QDSSC was achieved.2. Anatase TiO2nanoparticles were prepared through a hydrothermal route using C12H28O4Ti as the titanium source, while rutile TiO2nanoparticles were prepared using TiCl4as titanium source. The TiO2crystals were characterized by XRD, SEM, BET analyses. Moreover, the TiO2crystals were used to fabricate CdS/CdSe sensitized QDSSCs. Cell performance investigations show that the cell efficiency of the rutile TiO2based QDSSCs is of3.71%, which is much higher than that of the anatase TiO2based cell. This is ascribed to its better light scattering, larger loading of CdS/CdSe QDs as well as higher charge separation efficiency of rutile TiO2as proved by the light scatering, EIS, IMPS/IMVS investigations.