Investigation of Regeneration Kinetics in Quantum-Dots-Sensitized Solar Cells with Scanning Electrochemical Microscopy

A fast quantum dots (QDs) regeneration process is necessary for highly efficient QDs-sensitized solar cells. Herein, CdSe and CdS QDs regeneration rates (k(QD)') in three redox electrolytes, which are triiodide and iodide ions (I-3(-)/I-), Co(bpy)(3)(PF6)(2) and Co(bpy)(3)(PF6)(3) (Co3+/Co2+), and 1-methy-1-H-tetrazole-5-thiolate and its dimer (T-2/T-), have been first investigated with scanning electrochemical microscopy (SECM). The results reveal that the kinetics of QDs regeneration depends on the nature of the QDs and the redox shuttles presented in QDSSCs. For QDs of CdSe and CdS, the regeneration rate (k(QD)') in the case of a T-2/T--based electrolyte is about two times larger than that of Co3+/Co2+ and I-3(-)/I-. Additionally, the k(QD)' for CdSe is about two times larger than that of CdS in the same redox shuttle electrolyte, which could be due to a large driving force for the reaction between the exited state quantum dots (QD+) and redox electrolytes.