Highly Efficient Inverted Type-I CdS/CdSe Core/Shell Structure QD-Sensitized Solar Cells

Presynthesized high-quality CdS/CdSe inverted type-I core/shell structure QDs have been deposited onto TiO2 electrodes after first coating with bifunctional linker molecules, mercaptopropionic add (MPA), and the resulting quantum dot sensitized solar cells (QDSCs) exhibited record conversion efficiency of 5.32% (V-oc = 0527 V, J(sc) = 18.02 mA/cm(2), FF = 0.56) under simulated AM 1.5, 100 mW cm(-2) illumination. CdS/CdSe QDs with different CdSe shell thicknesses and different corresponding absorption onsets were prepared via the well-developed organometallic high-temperature injection method. MPA-capped water-dispersible QDs were then obtained via ligand exchange from the initial organic Nand capped oil-dispersible QDs. The QD-sensitized TiO2 electrodes were facilety prepared by pipetting the MPA-capped CdS/CdSe QD aqueous solution onto the TiO2 film, followed by a covering process with a ZnS layer and a postsintering process at 300 degrees C. Polysulfide electrolyte and Cu2S counterelectrode were used to provide higher photocurrents and fill factors of the constructed cell devices. The characteristics of these QDSCs were studied in more detail by optical measurements, incidental photo-to-current efficiency measurements, and Impedance spectroscopy. With the combination of the modified deposition technique with use of linker molecule MPA-capped water-soluble QDs and well-developed inverted type-I core/shell structure of the sensitizer together with the sintering treatment of QD-bound TiO2 electrodes, the resulting CdS/CdSe-sensitized solar cells show a record photovoltaic performance with a conversion efficiency of 5.32%.