The Investigation On Quantum Dotssensitized Solar Cells And The Application Of CoS Counter Electrode

Quantum dot-sensitized solar cells(QDSSCs) is a branch of the dye-sensitized solar cells(DSSCs), which is known as the third generation solar cells for easy fabrication and low cost. Duo to the proper advantages of the QDs, such as quantum size effect, multiple excition generation et al., QDSSCs improve the photoelectric conversion characteristics effectively by replacing dye as photosensitizer, and result in a theoretical photoelectric conversion efficiency(PCE) greater than 60%.At present, the PCEs of QDSSCs under 7% are much less than the PCEs of traditional silicon-related solar cells and DSCCs. In this thesis, the regeneration of photo-anode, optimizing of the electrolyte and the application of CoS counter electrode are explored respectively to improve the PCEs and learn more about the inner characteristic of the QDSSCs further.By Scanning Electrochemical Microscopy(SEM),the regeneration of the QDs was measured in polysulfide, iodide/triiodide redox and cobalt-based redox electrolyte, and the fastest regeneration kinetics of CdSe QDs is 5 1 3 16.7 10 mol cm s? ??, which is 4 times higher than dye LD14 measured in the same electrolytes. Then, the optimizing of the sulfide electrolyte used in QDSSCs most commonly, was token to explore the relationship between the electrolyte and the characteristic parameter of the QDSSCs, such as fill factor(FF), PCE, short-circuit current density(JSC) and open-circuit voltage(VOC). Further, CoS counter electrodes on ITO fabricated by electrochemical deposition(ECD) were discussed, which pile into a honeycomb structure and show remarkable electrocatalytic activity for the reduction of polysulfide duo to the high specific surface of the material. The activation energy value and charge-transfer resistance(RCE) were measured to be 0.177 eV and 2 Ω cm2, which are much better than those for CoS counter electrode(0.244 eV, 9.4 Ω cm2) fabricated by chemical bath deposition(CBD) and Pt counter electrode(0.266 eV, 13.5 Ω cm2) sintered. QDSSCs in combination with this type of counter electrode shows appreciated a highest PCE of 5.2% under 1 sun illumination, which is superior than that of CoS(CBD) based cell(4.0%) and Pt based cell(3.6%).