Creative Method of Electron Exchange Magnitude (EEM) for Determination of Band Edges in PbS QDs

Determining the band edges of Quantum Dots (QDs) in electrolytes with different redox is still a serious challenge for many researchers. A new and innovative method to trace Valence Band (VB) and Conduction Band (CB) edges is Electron Exchange Magnitude (EEM) determination with logarithmic scaling in Cyclic Voltammetry (CV) curves. The EEM method is an adaptation of the Tafel method, which determines the equilibrium currents in the logarithmic scale in the potential current curves. Accordingly, the equilibrium currents on the surface of QDs can be related to the currents occurring at the band edges. Since the band gap varies with the size of the QDs, the shift of the band edges occurs as the size of the QDs changes. In this study, PbS QDs were deposited on ITO/ZnO by the SILAR method and considered as a photoanod. The band edges were investigated by EEM method in electrolytes with and without Sulfide polysulfide redox. In this way, the minimum value of EEM in the anodic and cathodic range was considered as the VB and CB edges, respectively. Investigations show that some results of this research are in good agreement with the observations and results of others in matters such as determining the PbS QDs bandgap, although there are significant differences in determining the exact position of the band edges.