Graphene Based Nanomaterials for DSSC Counter Electrode Applications

Abstract

Dye sensitized solar cells (DSSCs) are a unique class of promising photovoltaic technologies due to its favorable advantages such as simple fabrication process, low cost and efficient harvesting of solar energy at both low and high light intensities compared to that of Si-based solar cells. Recently, there has been interest from all around the world to make breakthroughs in progress on every component of DSSC to enhance the efficiency, stability and commercialization. Among the component of DSSC, the counter electrode (CE) plays a crucial role in determining the power conversion efficiency as well as commercialization, which functions as intermediate for the catalytic reduction of triiodide species of Iand#8254; / I3and#8254; redox electrolyte by collecting electrons from the external circuit.This thesis focusses on developing alternative CE materials to replace the noble metal platinum and achieving high power conversion efficiency (PCE) of the DSSC at the device level. The research work described in this thesis covers the synthesis, characterization and performance analysis of four different materials used as DSSC counter-electrode materials namely (1) Low temperature thermally reduced graphene oxide (TrGO) (2) MoS2 directly grown on a conducting substrate through a hydrothermal process (3) Stabilizer-free MoS2-rGO hybrids through a one-step hydrothermal method (4) CoxMo(1-x)S2atrGO hybrids by a one-step hydrothermal method. These four material systems are briefly described below. newlineThe first system is TrGO which was synthesized by a low temperature thermal reduction of graphene oxide under an argon-hydrogen (Ar-H2) gas atmosphere. These nanostructured materials were characterized by X-ray diffraction, Raman spectroscopy, TEM analysis, X-ray photoelectron spectroscopy and FTIR analysis. The redox behavior and interfacial charge transfer kinetics of these TrGO counter electrodes (TrGO-CE) were analyzed through cyclic voltammetry (CV),electrochemical impedance spectroscopy (EIS) and Tafel polarization.The TrGO CEs in DSSC showed..