Structure Conturoll And The Application In Solar Cells Of Cdte Quantum Dots

At present, semiconductor quantum dots sensitized solar cells (QDSSCs) are receiving more and more attention comparing with other sensitizers, such as dye sensitized solar cells (DSSCs). QDSSCs constitute one of the most promising low-cost candidates for the third generation photovoltaic cells due to the QDs possessing potential advantages of high extinction coefficients, tunable band gaps by size control(due to quantum confinement), which can be used to match the absorption spectrum to the spectral distribution of solar light, their photoelectric properties can be tailored in the nanoscale region, and large intrinsic dipole moment leading to rapid charge separation. The application in solar cells of QDs has attracted more and more attention for researchers. CdTe QDs were synthesized in water-soluble, and CdTe/CdS QDs were obtained via anion exchange in which Te2-was replaced by S2-.CdTe QDSSCs and CdTe/CdS core/shell QDSSCs had been investigated.1、Synthesis of CdTe QDs and CdTe core/shell QDs. CdTe QDs with different size were synthesized through an aqueous route. Core/shell QDs with controlled structure and properties were obtained by controlling the reaction conditions. UV-Vis spectroscopy indicated that the size of CdTe QDs was increased when prolonging the refluxing time. As for CdTe/CdS QDs, at lower temperature, the UV-Vis of the obtained QDs was blue shifted swiftly or almost maintained invariable while prolonging the reaction time, however, which was red shifted apprarently at higher temperature.2、The optimization of sensitization conditions of working electrode.CdTe QDs and CdTe/CdS QDs was deposited onto the porous nanostructure TiO2film successfully. The QDs sensitized TiO2electrodes were facilely prepared by immersing the TiO2film into the TGA-capped QDs aqueous solution, followed by a covering process with a ZnS layer. The influencing factors to conversion efficiency, which includes pH value of QDs solution, additive agent, sensitized temperature, sensitized time, the thickness of TiO2substrate, and so on, are studied. The optimal sensitization conditions of working electrode were improved through the handling of QDs solution and TiO2substrate.3、Characterization of working electrod and photovoltaic performance of QDSSCs.The resulted electrod were characterized by UV-Vis spectroscopy, XRD, SEM and HRTEM. The photovoltaic performance of QDSSCs with different structure were investigated systematacally. It turned out that CdTe/CdS core/shell QDs as sensitizer can enhance the properties of the devices tremendously contrast to CdTe QDs. The conversion efficiency of CdTe/CdS QDSSCs was achieved to2.44%(Jsc=6.73mA/cm2,Voc=505mV, FF=0.72)), which was14times to that of CdTe QDSSCs. Polysulfide electrolyte and Cu2S counter electrode were used to provide higher photocurrents and fill factors of the constructed cell devices.