Photo-electrochemical Studies by AC Impedance Spectroscopy on Electrodeposited n-Type PbS

Abstract

Abstract Electrochemical deposition and characterization of PbS nanocrystals on Pb electrodes in alkaline solution containing thiourea are carried out by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods respectively. The diffusion coefficient of electroactive species (Pb+2) at the synthetic potential −0.36 V/SCE is investigated in different alkaline media. The analysis of PbS crystals using X-ray diffraction (XRD) shows that the average of crystalline size and the lattice constant parameter are approximately 39.04 and 0.5948 nm respectively. Also, the morphology of surface was studied by scanning electron microscope (SEM). This work focuses on EIS extraction of Mott–Schottky plots and calculation of several important parameters including Debye length (LD), carrier density (ND), and flat band potential (Efb) for PbS. The parameters are calculated as 3.40 × 10−8 cm, 8.65 × 1019 cm−3, and 0.035 V/NHE respectively in the dark. The comparison of these values in the dark and under light provides some insights into the charge transfer. The increase in the charge transfer resistance (Rct) in the dark with respect to under illumination and the confirmation of the presence of surface states in the n-type PbS are some of the obtained results.