Comparative Study of Edge-Functionalized Graphene Nanoplatelets As Superior Metal-Free Counter Electrodes for Dye-Sensitized Solar Cells

Abstract

Dye-sensitized solar cells (DSSCs) have aroused intense interest and been regarded as one of the most prospective solar cells, due to low-cost, flexibility, simple device fabrication and high conversion efficiency under weak light, in comparison to the conventional photovoltaic devices. Very recently, G2E in Swiss and G24i in UK including Korean and Japan companies have demonstrated commercial and prototyped components based on DSSC technology with liquid electrolytes. However, the unit costs, long-term device stability and power conversion efficiency must be further improved for real-life applications. For this purpose, considerable efforts have been devoted to the search for low cost Pt-free catalysts that exhibit high electrochemical activity and fast electron transfer kinetics, while a platinum (Pt) catalyst is still the most efficient and widely used counter electrode (CE) in DSSCs, but it has some problems that make it unsatisfactory, such as its high manufacturing cost, due to scarcity, and poor long-term stability for the iodide/triiodide redox couple in a DSSC. As a result, significant efforts have been devoted to finding possible alternatives to Pt, including carbon blacks, carbon nanotubes, functionalized graphene, and heteroatom-doped GnPs as efficient metal-free electrocatalysts. One of the most promising candidates as CE materials is non-metallic heteroatom-doped graphene nanoplatelets (GnPs). Heteroatom-doped GnPs gave high power conversion efficiency (PCE) of DSSCs employing cobalt electrolytes. However, they are not sufficiently active in iodidde electrolytes, which are more common and desirable electrolytes. Thus, the better elcetrocatalytical ability and electrochemical stability of carbon-basedmaterials toward the redox couples still need to be significantly improved for the practical applicationof DSSCs. Very recently, a series of edge-fuctionalized heteroatom-doped and metalliod-doped graphene nanoplatelets (GnPs) have been prepared through a simple mechanochemical ball-milling process. In this presentation, comparative study of edge-functionalized heteroatom-doped and metalloid-doped graphene nanoplatelets as metal-free counter electrodes for highly efficient dye-sensitized solar cells employong bothe redox shuttles will be described to understand and establish the structure-property relationship between sort of fuctionalization and cell performance with regard to the present GnPs through the same fabrication process under the same experimental condition.